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Novel compounds bearing acetal groups in their biphenylmethane skeletons were synthesized in moderate yields from benzophenone derivative. Compound 1 did not exhibit antagonistic activity against the ERα estrogen receptor; however, compounds 2, 3, and 4 exhibited potent ERα antagonistic activities. A small difference in the ERα antagonistic activities of the stereoisomers was observed. It was suggested that the methyl groups on the acetal moieties were responsible for the observed ERα antagonistic activities of the compounds. These results could be attributed to interactions of the methyl groups of the acetal functional groups with the hydrophobic binding residues of the binding site.

l?Leu-based heteropeptides having (R)- or (S)-chiral five-membered carbocyclic ring amino acids (Ac5c3EG) with an ethylene acetal moiety were prepared. A conformational analysis using FT-IR absorption, 1H NMR, and circular dichroism (CD) spectra revealed that l?Leu-based hexapeptides and nonapeptides having (R)- or (S)-Ac5c3EG formed right-handed (P) helical structures in solution. An X-ray crystallographic analysis of nonapeptides 5 a and 5 b showed similar right-handed (P) α-helical structures, without an intramolecular hydrogen bond of the peptide N?H????O? (acetal) type., ChemistrySelect, 2(26), pp.8108-8114; 2017

Lysine-based amphipathic nonapeptides, including homochiral peptides [Ac-(l-Lys-l-Lys-Xaa)3-NH2 (Xaa=Gly, Ala, Aib, Ac5c, or Ac6c) and Ac-(d-Lys-d-Lys-Aib)3-NH2], a heterochiral peptide [Ac-(l-Lys-d-Lys-Aib)3-NH2], and a racemic mixture of diastereomeric peptides [Ac-(rac-Lys-rac-Lys-Aib)3-NH2] were designed and synthesized to investigate the relationship between their preferred secondary structures and their antimicrobial activity. Peptide 5, [Ac-(l-Lys-l-Lys-Ac6c)3-NH2] formed a stable α-helical structure and exhibited strong activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa).

We developed a novel methodology using cyclic α,α-disubstituted α-amino acids (dAAs) with an acetal-side chain to control peptide secondary structures. The introduction of cyclic dAAs into peptides contributed to the stabilization of peptide secondary structures as a helix, while an acidic treatment of peptides resulted in a marked conformational change., Organic and Biomolecular Chemistry, 15(30), pp.6302-6305; 2017

Here we report the synthesis of new PNA monomers for pseudocomplementary PNA (pcPNA) that are fully compatible with standard Fmoc chemistry. The thiocarbonyl group of the 2-thiouracil (sU) monomer was protected with the 4-methoxy-2-methybenzyl group (MMPM), while the exocyclic amino groups of diaminopurine (D) were protected with Boc groups. The newly synthesized monomers were incorporated into a 10-mer PNA oligomer using standard Fmoc chemistry for solid-phase synthesis. Oligomerization proceeded smoothly and the HPLC and MALDI-TOF MS analyses indicated that there was no remaining MMPM on the sU nucleobase. The new PNA monomers reported here would facilitate a wide range of applications, such as antigene PNAs and DNA nanotechnologies.

Steroids are important components of cell membranes and are involved in several physiological functions. A diphenylmethane (DPM) skeleton has recently been suggested to act as a mimetic of the steroid skeleton. However, difficulties are associated with efficiently introducing different substituents between two phenyl rings of the DPM skeleton, and, thus, further structural development based on the DPM skeleton has been limited. We herein developed an efficient synthetic method for introducing different substituents into two phenyl rings of the DPM skeleton. We also synthesized DPM-based estrogen receptor (ER) modulators using our synthetic method and evaluated their ER transcriptional activities.

We report the synthesis of a peptide nucleic acid (PNA) monomer containing preQ1, a positively charged guanine analogue. The new monomer was incorporated into PNA oligomers using standard Fmoc-chemistry-based solid-phase synthesis. The preQ1 unit-containing PNA oligomers exhibited improved affinity for their complementary DNA through electrostatic attraction, and their sequence specificity was not compromised. It could be beneficial to incorporate preQ1 into PNA oligomers instead of guanine when creating antisense/antigene agents or research tools.

A dodecapeptide, Boc-(L-Leu-L-Leu-Aib-L-Leu-D-Leu-Aib)2-OMe (2), was designed and synthesized to investigate the influence of L-Leu to D-Leu residue replacement on the helical secondary structure of L-Leu-Aib-based dodecapeptides. Its preferred conformation was analyzed based on its Fourier transform infrared spectra, CD spectra, and X-ray diffraction. It was revealed that peptide 2 formed a mixture of right-handed (P) 310- and α-helical structures in solution, and eight helical molecules were assembled in the crystalline state.

The chiral deuterium- and 13C-isotope-labeled α-aminoisobutyric acids CD3-Aib and 13CH3-Aib were enantioselectively synthesized from L-Ala aldimine using simplified Maruoka chiral phase-transfer catalysts. Homo-chiral (S)-CD3-Aib homopeptides, up to decamers, were prepared. A (R)-CD3-Aib polymer and (S)-13CH3-Aib polymer were also prepared. Conformational studies on homopeptides using CD spectra and an X-ray crystallographic analysis revealed that the preferred conformations were 310-helical structures comprising equal amounts of right-handed (P) and left-handed (M) helical-screw structures. The α-carbon chiral centers induced by the D- or 13C-isotope substitution of Aib were incapable of controlling the helical-screw directions of their oligopeptides and short polymers., Tetrahedron, 72(39), pp.5864-5871; 2016

A single chiral cyclic α,α-disubstituted amino acid with side-chain methoxymethyl (MOM) protecting groups, (3S,4S)-1-amino-(3,4-dimethoxymethoxy)cyclopentanecarboxylic acid [(S, S)-Ac5 c(dOMOM) ], or side-chain hydroxy groups, (3S,4S)-1-amino-(3,4-dihydroxy)cyclopentanecarboxylic acid [(S, S)-Ac5 c(dOH) ], was attached to the N-terminal or C-terminal position of α-aminoisobutyric acid (Aib) tetrapeptide segments; i.e., we designed and synthesized four pentapeptides, Cbz-[(S, S)-Ac5 c(dOMOM) ]-(Aib)4 -OEt (1), Cbz-[(S, S)-Ac5 c(dOH) ]-(Aib)4 -OEt (2), Cbz-(Aib)4 -[(S, S)-Ac5 c(dOMOM) ]-OMe (3), and Cbz-(Aib)4 -[(S, S)-Ac5 c(dOH) ]-OMe (4). We then analyzed the peptides' structures in the crystalline state. The four peptides all folded into 310 -helical structures; 1 formed a left-handed (M) 310 -helix, 2 formed a mixture of right-handed (P) and (M) 310 -helices, 3 formed a mixture of (P) and (M) 310 -helices, and 4 formed a (P) 310 -helix, respectively. In packing mode, the molecules of peptides 1 and 3, which both possessed an Ac5 c(dOMOM) residue, were connected by intermolecular hydrogen bonds along the peptide backbone (NH···O type). On the other hand, the packing of peptides 2 and 4, which both contained an Ac5 c(dOH) residue, was based on intermolecular hydrogen bonds derived from both the peptide backbone and the side-chain hydroxy groups of the amino acid Ac5 c(dOH) (OH···O type). © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 757-768, 2016.

Chiral five-membered carbocyclic ring amino acids bearing various diol acetal moieties were synthesized starting from l-malic acid, and homo-chiral homopeptides composed of cyclic amino acid (S)-Ac5 c(3EG) bearing an ethylene glycol acetal, up to an octapeptide, were prepared. A conformational analysis revealed that (S)-Ac5 c(3EG) homopeptides formed helical structures. (S)-Ac5 c(3EG) homopeptides, up to hexapeptides, formed helical structures without controlling the helical screw direction, while (S)-Ac5 c(3EG) hepta- and octapeptides formed helical structures with a preference for the left-handed (M) helical-screw direction. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 555-562, 2016.

A homochiral L-Leu-L-Leu-Aib segment was incorporated into the N- or C-termini of left-handed (M) helical peptides (D-Leu-L-Leu-Aib)n. We then investigated the preferred conformations of two sets of three peptides; i.e., Boc-L-Leu-L-Leu-Aib-(D-Leu-L-Leu-Aib)n-OMe (n = 1: 1; 2: 2; 3: 3) and Boc-(D-Leu-L-Leu-Aib)n-L-Leu-L-Leu-Aib-OMe (n = 1: 4; 2: 5; 3: 6), in solution and in the crystalline state. Nonapeptide 2 and dodecapeptide 3, each containing an N-terminal L-Leu-L-Leu-Aib segment, formed left-handed (M) helices as the preferred secondary structures in solution. In the crystalline state, nonapeptide 2 folded into an (M) -helical structure. Peptides 4–6, each containing a C-terminal L-Leu-L-Leu-Aib segment, formed roughly equivalent amounts of right-handed (P) and (M) helices.

Non-secosteroidal VDR ligands without any assymmetric carbon were designed and synthesized based on the structure of the previously reported non-secosteroidal VDR agonist LG190178. The VDR-agonistic activity of all synthesized compounds was evaluated, and 7b emerged as a potent agonist activity with an EC50 value of 9.26 nM. Moreover, a docking simulation analysis was also performed to determine the binding mode of 7b with VDR-LBD.

We designed and synthesized two dodecapeptides, Boc-(l-Leu-l-Leu-Aib-d-Leu-d-Leu-Aib)2-OMe (5) and Boc-l-Leu-l-Leu-Aib-(d-Leu-d-Leu-Aib)2-l-Leu-l-Leu-Aib-OMe (6), that contain equal amounts of l-Leu, d-Leu, and achiral Aib residues. The conformations of peptides 5 and 6 in the crystalline state were studied using X-ray crystallographic analysis. Peptide 5 formed a left-handed (M) α-helical structure, whereas peptide 6 was composed of a combination of fused (M) α-helical and right-handed (P) 310-helical structures. In solution, roughly equivalent amounts of (P) and (M) helices were present in 5, whereas the (M) α-helix was present in 6 as its dominant conformation.

Estrogen receptors (ERs) play a major role in the growth of human breast cancer cells. An antagonist that acts as not only an inhibitor of ligand binding but also an inducer of the down-regulation of ER would be useful for the treatment for ER-positive breast cancer. We previously reported the design and synthesis of a selective estrogen receptor down-regulator (SERD), (E/Z)-4-(1-{4-[2-(dodecylamino)ethoxy]phenyl}-2-phenylbut-1-en-1-yl)phenol (C12), which is a tamoxifen derivative having a long alkyl chain on the amine moiety. This compound induced degradation of ERα via a proteasome-dependent pathway and showed an antagonistic effect in MCF-7 cells. With the aim of increasing the potency of SERDs, we designed and synthesized various tamoxifen derivatives that have various lengths and terminal groups of the long alkyl side chain. During the course of our investigation, C10F having a 10-fluorodecyl group on the amine moiety of 4-OHT was shown to be the most potent compound among the tamoxifen derivatives. Moreover, computational docking analysis suggested that the long alkyl chain interacted with the hydrophobic region on the surface of the ER, which is a binding site of helix 12 and coactivator. These results provide useful information to develop promising candidates as SERDs.

Chiral cyclic α,α-disubstituted α-amino acids with four chiral centers at their acetal moieties were synthesized. An X-ray crystallographic analysis of homo-chiral tripeptide with (2R,3R)-butane-2,3-diol acetal moieties revealed that the tripeptide formed both (P) and (M) helical structures, and all peptide main-chain N(i)-H were intramolecularly hydrogen-bonded with the side-chain acetal -O- of the same amino acid residues (i). The effect of the four chiral centers in the amino acid residue on the peptide backbone helical-screw control was very weak., Tetrahedron, 71(23), pp.3909-3914; 2015

Two diastereomeric six-membered ring α,α-disubstituted α-amino acids (1R,3R)- and (1S,3R)-1-amino-3-methylcyclohexanecarboxylic acids (Ac6c3M); side-chain restricted leucine analogs, were stereoselectively synthesized from (3R)-3-methylcyclohexanone by a Bucherer–Bergs or Strecker reaction. Two series of homo-chiral homopeptides Cbz-[(1R,3R)- and (1S,3R)-Ac6c3M]n-OMe, up to hexapeptides (n=6), were prepared, respectively, and the preferred conformations of cyclohexane rings of amino acid residues and the peptide-backbones were studied. In solution, these peptides formed helical structures, but the helical-screw control to one-handedness was not possible for the hexapeptide length. In the crystal state, all (1R,3R)-Ac6c3M residues formed cyclohexane chair form conformations with a 3-methyl substituent at equatorial orientation and an amino group at the axial position, whereas all (1S,3R)-Ac6c3M residues assumed cyclohexane chair forms with the 3-methyl and amino groups at equatorial orientations. The preferred peptide-backbone structure of (1R,3R)-Ac6c3M hexapeptide had (P) and (M) 310-helices, and that of (1S,3R)-Ac6c3M hexapeptide had (P) and (M) α-helices in the crystal state.

A new bis-cationic cyclic amino acid, 9-amino-3,7-diazabicyclo[3.3.1]nonane-9-carboxylic acid (9- a mino- b is p idine-9-carboxylic acid; Abp), which is available for both solution phase and solid phase peptide synthesis, was designed and synthesized. Furthermore, a heterotripeptide Cbz-Leu-Abp-Ala-OMe (9) containing Abp was prepared, and its dominant conformation was analyzed by examining its nuclear magnetic resonance and infrared spectra and performing molecular modeling. The tripeptide 9 formed a β-turn structure as its preferred conformation in solution.

We developed several stabilized helical heptapeptides (DPI-01-10) composed of l-leucine residues, an α,α-disubstituted α-amino acid (α-aminoisobutyric acid [Aib] or hydroxymethylserine [Hms]), and a stapled side chain as inhibitors of vitamin D receptor (VDR)-coactivator interactions. The inhibitory activity of these peptides against VDR-coactivator interactions was evaluated using a receptor cofactor assay system, and DPI-08 demonstrated strong activity (IC50: 3.2μM).

We designed and synthesized hybrid molecules for a protein knockdown method based on the recognition of a His-tag fused to a protein of interest (POI). The synthesized target protein degradation inducers contained three functional moieties: a His-tag ligand (nickel nitrilotriacetic acid [Ni-NTA]), an E3 ligand (bestatin [BS] or MV1), and a carrier peptide (Tat or nonaarginine [R9]). The designed hybrid molecules, BS-Tat-Ni-NTA, MV1-Tat-Ni-NTA, BS-R9-Ni-NTA, and MV1-R9-Ni-NTA, efficiently degraded His-tagged cellular retinoic acid binding protein 2 via the ubiquitin-proteasome system (UPS). This system will become a useful tool for research into selective protein degradation inducers that act via the UPS.

A chiral five-membered ring α,α-disubstituted α-amino acid (R,R)-Ac5c(dN3) having two azido functional groups has been designed and synthesized. The cyclic amino acid (R,R)-Ac5c(dN3) could be efficiently converted into several cyclic amino acids with various two 1,2,3-triazole functional groups. (R,R)-Ac5c(dN3) homochiral peptides (up to hexapeptide) and (R,R)-Ac5c(dN3)-containing l-Leu-based peptides were prepared, and their conversion of azido functional groups into triazole groups was completed. The preferred conformation of oligomers, before and after the "click reaction", together with the azido gauche effect of amino acid residues were studied using FT-IR absorption, CD, (1)H NMR, and X-ray crystallographic analysis. The cyclic amino acid (R,R)-Ac5c(dN3) could be used as a helical conformation controlling residue and also has a versatile functionalizing site in its oligopeptides.

A new amino acid-sesquiterpene adduct, isoheleproline (1), was isolated from the roots of Inula helenium (elecampane), together with four known sesquiterpene lactones (2-5). The planar configuration of 1 was elucidated on the basis of spectroscopic data analysis, and the relative configuration of 1 was determined by performing a detailed analysis of NOESY correlations and comparing its physicochemical data with the D- and L-proline adducts of 2 obtained by Michael addition. This is the first report of a new amino acid-sesquiterpene adduct from Inula plants.

(R,R)-Ac6c4BD homopeptides form helical structures with slight control of the helical screw sense to the right-handed form. The chiral acetal moieties in (R,R)-Ac6c4BD are changeable in the peptide state.

A novel series of uracil derivatives with a 3,5-dimethylbenzyl group at the N(3)-position were synthesized and evaluated as non-nucleoside HIV-1 reverse transcriptase inhibitors. Some of these compounds showed good-to-moderate activity with EC50 values in the submicromolar range. Among them, compound 10c showed significant potency against HIV-1 activity with an EC50 value of 0.03 μM and a high selectivity index of 2863. Preliminary structure-activity relationships and molecular modeling analyses were used to explore the major interactions between HIV-1 reverse transcriptase and the potent inhibitor 10c, which may serve as an important lead for further optimization.

This paper reports the synthesis of new β-Lys peptide nucleic acid (PNA) monomers and their incorporation into a 10-residue PNA sequence. PNA containing β-Lys PNA units formed a stable hybrid duplex with DNA. However, incorporation of β-Lys PNA units caused destabilization of PNA-DNA duplexes to some extent. Electrostatic attractions between β-PNA and DNA could reduce this destabilization effect. Subsequently, bipyridine-conjugated β-Lys PNA was prepared and exhibited sequence selective cleavage of DNA. Based on the structures of the cleavage products and molecular modeling, we reasoned that bipyridine moiety locates within the minor groove of the PNA-DNA duplexes. The lysine side chain of β-PNA is a versatile handle for attaching various functional molecules.

Chiral bicyclic α-amino acid (R,R)-Ab5,6=c with stereogenic centers at the γ-position of fused-ring junctions, and its enantiomer (S,S)-Ab5,6=c, were synthesized. The CD spectra of (R,R)-Ab5,6=c oligomers indicated that the (R,R)-Ab5,6=c hexapeptide formed a mixture of right-handed (P)- and left-handed (M)-310-helices, while, in the (R,R)-Ab5,6=c nonapeptide, a right-handed (P)-310-helix slightly dominated over the (M)-helix. X-Ray crystallographic analyses of (S,S)-tripeptide and (R,R)-hexapeptide revealed that both the tripeptide and hexapeptide formed a mixture of (P)- and (M)-310-helices, respectively. These results indicated that the side-chain environments around the stereogenic centers are particularly important to control the helical-screw handedness of foldamers.

A pair of L-leucine (L-Leu) and D-leucine (D-Leu) was incorporated into a-aminoisobutyric acid (Aib) peptide segments. Thedominant conformations of four hexapeptides, Boc-L-Leu-Aib-Aib-Aib-Aib-L-Leu-OMe (1a), Boc-D-Leu-Aib-Aib-Aib-Aib-L-Leu-OMe(1b), Boc-Aib-Aib-L-Leu-L-Leu-Aib-Aib-OMe (2a), and Boc-Aib-Aib-D-Leu-L-Leu-Aib-Aib-OMe (2b), were investigated by IR,¹H NMR, CD spectra, and X-ray crystallographic analysis. All peptides 1a,b and 2a,b formed 3₁₀-helical structures in solution. X-ray crystallographic analysis revealed that right-handed (P) 3₁₀-helices were present in 1a and 1b and a mixture of right-handed(P) and left-handed (M) 3₁₀-helices was present in 2b in their crystalline states.

Peptide nucleic acid (PNA) monomers with a methyl group at the β-position have been synthesized. The modified monomers were incorporated into PNA oligomers using Fmoc chemistry for solid-phase synthesis. Thermal denaturation and circular dichroism (CD) studies have shown that PNA containing the S-form monomers was well suited to form a hybrid duplex with DNA, whose stability was comparable to that of unmodified PNA-DNA duplex, whereas PNA containing the R-form monomers was not.

We designed and synthesized nonsecosteroidal vitamin D receptor (VDR) ligands that formed H-bonds with six amino acid residues (Tyr143, Ser233, Arg270, Ser274, His301 and His393) of the VDR ligand-binding domain. The ligand YR335 exhibited potent transcriptional activity, which was comparable to those of 1α,25-dihydroxyvitamin D3 and YR301. The crystal structure of the complex formed between YR335 and the VDR ligand-binding domain was solved, which revealed that YR335 formed H-bonds with the six amino acid residues mentioned above.

Stapled helical l -leucine-based heptapeptides were synthesized and used as catalysts for the enantioselective epoxidation of α,β-unsaturated ketones. All N-terminal free stapled peptides were successfully used as chiral catalysts. Among them, the use of H-hS3,7hS-10 gave epoxide products with high enantioselectivities of up to 99% ee. Furthermore, the dominant conformations of the N-terminal protected stapled peptides R3,7R-10 and hS3,7hS-10 were investigated by 1H NMR, IR, CD spectra, and X-ray crystallographic analysis. The peptide R3,7R-10 formed a right-handed (P) α-helix in solution and in the crystalline state, while hS3,7hS-10 formed a right-handed (P) 310-helix in solution.

Four diastereomeric-Leu-Leu-Aib-Leu-Leu-Aib-peptides, Boc-D-Leu-L-Leu-Aib-L-Leu-L-Leu-Aib-OMe (1), Boc-L-Leu-D-Leu-Aib-L-Leu-L-Leu-Aib-OMe (2), Boc-L-Leu-L-Leu-Aib-D-Leu-L-Leu-Aib-OMe (3), and Boc-L-Leu-L-Leu-Aib-L-Leu-D-Leu-Aib-OMe (4), were synthesized. The crystals of the four hexapeptides were characterized by X-ray crystallographic analysis. Two diastereomeric hexapeptides 1 and 2 having D-Leu(1) or D-Leu(2) were folded into right-handed (P) 310-helical structures, while peptide 3 having D-Leu(4) was folded into a turn structure nucleated by type III′ and I-turns, and peptide 4 having D-Leu(5) was folded into a left-handed (M) 310-helical structure. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.

Stabilized short helical heptapeptides containing a combination of an α-aminoisobutyric acid as a helical promoter and l / d -serine derivatives to produce cross-linked units were synthesized. The cyclic peptide R3,7R-2, which had d -serine derivatives at its 3rd and 7th positions, formed a stable right-handed (P) α-helix in solution and the crystalline state. Furthermore, its N-terminal free helical peptide catalyzed the enantioselective epoxidation of (E)-chalcone to afford the epoxide in a high yield and moderate enantioselectivity.

A single chiral cyclic α,α-disubstituted amino acid, (3S,4S)-1-amino-(3,4-dimethoxy)cyclopentanecarboxylic acid [(S,S)-Ac5cdOM], was placed at the N-terminal or C-terminal positions of achiral α-aminoisobutyric acid (Aib) peptide segments. The IR and 1H NMR spectra indicated that the dominant conformations of two peptides Cbz-[(S,S)-Ac5cdOM]-(Aib)4-OEt (1) and Cbz-(Aib)4-[(S,S)-Ac5cdOM]-OMe (2) in solution were helical structures. X-ray crystallographic analysis of 1 and 2 revealed that a left-handed (M) 310-helical structure was present in 1 and that a right-handed (P) 310-helical structure was present in 2 in their crystalline states. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.

Three diastereomeric -Leu-Leu-Aib-Leu-Leu-Aib- peptides composed of the same numbers of L-Leu, D-Leu, and Aib residues were synthesized: Boc-L-Leu-L-Leu-Aib-D-Leu-D-Leu-Aib-OMe (1), Boc-L-Leu-D-Leu-Aib-L-Leu-D-Leu-Aib-OMe (2), and Boc-L-Leu-D-Leu-Aib-D-Leu-L-Leu-Aib-OMe (3). The crystals of the three peptides were characterized by X-ray crystallographic analysis as follows: (1) orthorhombic, P2(1)2(1)2(1), a = 21.383 A, b = 11.070 A, c = 19.560 A, Z = 4, R(1) = 0.0527, and R(w) = 0.1562; (2) monoclinic, P2(1), a = 9.391 A, b = 21.278 A, c = 11.662 A, beta = 99.125, Z = 2, R(1) = 0.0507, and R(w) = 0.1447; and (3) triclinic, P1, a = 12.545 A, b = 14.913 A, c = 15.330 A, alpha = 77.622, beta = 66.601, gamma = 78.839, Z = 2, R(1) = 0.0775, and R(w) = 0.1971. The three diastereomeric peptides, 1, 2, and 3, showed unique conformations. That is to say, 1 was folded into a left-handed (M) 3(10)-helical structure, 2 was folded into a distorted beta-hairpin nucleated by a type II' beta-turn-like structure, and 3 was folded into an S-shape turn structure based on two type II/III beta-turns.

The crystal structures of two diastereomeric -Pro-Pro-(Aib)4- sequences, Cbz- l -Pro- l -Pro-(Aib)4-OMe (1) and Cbz- d -Pro- l -Pro-(Aib)4-OMe (2), have been determined by X-ray crystallographic analysis. The crystals of the two compounds were characterized by the following parameters: (1) monoclinic, P21, a=10.543 A, b=8.103 A, c=22.642 A, β=97.679, Z=2, R1=0.104, and Rw=0.327; (2) orthorhombic, P212121, a=10.470 A, b=10.953 A, c=32.405 A, Z=4, R1=0.040, and Rw=0.046. In the asymmetric unit of 1, the homochiral l -Pro1- l -Pro2 adopts a polyproline II structure, which induces a left-handed (M) 310-helical structure in the following -(Aib)4- sequence. The preferred conformation of diastereomeric 2, which contains heterochiral d -Pro1- l -Pro2 segments, was similar to that of 1 with differences at the N-terminal d -Pro residue.

One chiral L-valine (L-Val) was inserted into the C-terminal position of achiral peptide segments constructed from α-aminoisobutyric acid (Aib) and α,β-dehydrophenylalanine (ΔZPhe) residues. The IR, 1H NMR and CD spectra indicated that the dominant conformations of the pentapeptide Boc-Aib-ΔPhe-(Aib)2-L-Val-NH-Bn (3) and the hexapeptide Boc-Aib-ΔPhe-(Aib)3-L-Val-NH-Bn (4) in solution were both right-handed (P) 310-helical structures. X-ray crystallographic analyses of 3 and 4 revealed that only a right-handed (P) 310-helical structure was present in their crystalline states. The conformation of 4 was also studied by molecular-mechanics calculations. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.

Vitamin D3 analogues have been developed for a mutant vitamin D receptor (VDR), Arg274Leu. The mutant VDR has a mutation at Arg274, which forms an important hydrogen bond with 1α-OH of 1α,25-dihydroxyvitamin D3 to anchor the ligand tightly in the VDR ligand binding pocket. Stereoselective synthesis of the A-ring part of the novel vitamin D analogue, 2α-(3-hydroxypropyl)-1α-methyl-25-hydroxyvitamin D3 (4), from d -galactose was accomplished with the key steps of the introduction of the methyl and allyl groups to the chiral building blocks. The new analogue 4 is ca. 7.3-fold more active than the natural hormone 1α,25-dihydroxyvitamin D3 (1).

We designed and synthesized 1alpha- and 1beta-hydroxymethyl-2alpha-(3-hydroxypropyl)-25-hydroxyvitamin D(3) (2a,b) and related analogues 2alpha-(3-hydroxypropyl)-25-hydroxyvitamin D(3) (3), Posner's analogues of 1alpha- and 1beta-hydroxymethyl-25-hydroxyvitamin D(3) (4a,b), as well as 2alpha-(3-hydroxypropyl)-1alpha,25-dihydroxyvitamin D(3) (5), to confirm the effect of the 1alpha-hydroxy group and/or 2alpha-(3-hydroxypropyl) group of vitamin D(3) analogues with the modified A-ring moiety on the mutant vitamin D receptor, VDR(Arg274Leu). The 2alpha-(3-hydroxypropyl) group showed better effect on enhancement of the transcriptional activity through the mutant VDR than the 1alpha- and 1beta-hydroxymethyl groups.

Chiral cycloalkane-trans-1,2-diols (+/-)-3 and (+/-)-8 having a diester moiety have been prepared from dimethyl dialkenylmalonate using olefin metathesis by Grubbs catalyst, followed by epoxidation and acidic hydrolysis. Kinetic resolution of racemic cyclopentane-trans-1,2-diol (+/-)-3 by lipase-catalyzed transesterification afforded an optically active monoacetate (-)-5 of 95% ee in 46% yield and the recovered diol (-)-3 of 92% ee in 51% yield, and that of cycloheptane-trans-1,2-diol (+/-)-8 gave a monoacetate (+)-10 of 95% ee in 51% yield and the diol (-)-8 of99% ee in 43% yield, respectively. The enantiomer selectivity of racemic cyclic trans-1,2-diols bearing a diester moiety by lipases (Amano PS and Amano AK) was opposite to that of the reported simple racemic cycloalkane-trans-1,2-diols. To explain the lipase-catalyzed enantiomer selectivity, computer modeling of lipase-substrate complexes was performed. Furthermore, the optically active diester (-)-8 could be efficiently converted into an optically active seven-membered-ring alpha,alpha-disubstituted amino acid (4R,5R)-(-)-15.

Two types of cationic cyclic α,α-disubstituted α-amino acids: ApiC2NH2 (which possesses a lysine mimic side chain) and Api(C2Gu) (which possesses an arginine mimic side chain), were developed. These amino acids were incorporated into an arginine-based peptide sequence [(L-Arg-L-Arg-dAA)3: dAA=ApiC2NH2 or Api(C2Gu)], and the relationship between the secondary structures of the resulting peptides and their ability to pass through cell membranes was investigated. The peptide containing Api(C2Gu) formed a stable α-helical structure and was more effective at penetrating cells than the nonhelical Arg nonapeptide (R9). Furthermore, the peptide was able to deliver plasmid DNA into various types of cells in a highly efficient manner.

Six novel carbocyclic oxetanocin A analogs (2-chloro-C.OXT-A; COA-Cl) with various hydroxymethylated or spiro-conjugated cyclobutane rings at the N(9)-position of the 2-chloropurine moiety were synthesized and evaluated using human umbilical vein endothelial cells. All prepared compounds (2a-f) showed good to moderate activity with angiogenic potency. Among these compounds, 100 µM cis-trans-2',3'-bis(hydroxymethyl)cyclobutyl derivative (2b), trans-3'-hydroxymethylcyclobutyl analog (2d), and 3',3'-bis(hydroxymethyl)cyclobutyl derivative (2e) had greater angiogenic activity, with relative tube areas of 3.43±0.44, 3.32±0.53, and 3.59±0.83 (mean±standard deviation (S.D.)), respectively, which was comparable to COA-Cl (3.91±0.78). These data may be important for further development of this class of compounds as potential tube formation agents.

Vitamin D receptor (VDR) is a family of nuclear receptors (NR) that regulates physiological effects such as the immune system, calcium homeostasis, and cell proliferation. We synthesized non-secosteroidal VDR ligands bearing a long alkyl chain based on the diphenylpentane skeleton. The VDR-mediated transcriptional activities of the synthesized compounds were evaluated using a reporter gene assay and HL-60 cell differentiation-inducing assay. We herein described the structure-activity relationship and effects of alkyl-chain length on VDR-mediated transcriptional activity.

Background A new series of 1-aromatic methyl-substituted 3-(3,5-dimethylbenzyl)uracil and N-3,5-dimethylbenzyl-substituted urea derivatives were synthesized and evaluated as non-nucleoside HIV-1 reverse transcriptase inhibitors. Methods A series of new 6-azido and 6-amino derivatives of 1-substituted-3-(3,5-dimethylbenzyl)uracils were synthesized using our previously reported method, and three acyclic derivatives were synthesized from urea. The anti-HIV-1 activities of these compounds were determined based on the inhibition of virus-induced cytopathogenicity in MT-4 cells. The cytotoxicities of the compounds were evaluated using the viability of mock-infected cells. Results Some of these compounds showed good-to-moderate activities against HIV-1 with half maximal effective concentration (EC50) values in the submicromolar or subnanomolar range. Compared with emivirine, compound 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil showed significant anti-HIV-1 activity with an EC50 value of 10 nM and a high selectivity index of 1923. Preliminary structure–activity relationship studies and molecular modeling analyses were carried out to explore the major interactions between HIV-1 reverse transcriptase and the potent inhibitor 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil; these results may be important for further development of this class of compounds as anti-HIV-1 agents. Conclusion The excellent activity of 6-amino-3-(3,5-dimethylbenzyl)-1-(4-aminobenzyl)uracil (EC50: 0.010 ± 0.006 µM, SI: >1923) may serve as the basis for conducting further investigations on the behavior of this class of compounds against drug-resistant mutants.

A cyclic β-amino acid (APC(Gu)) bearing a side-chain guanidinium group has been developed. The APC(Gu) residue was incorporated into an α/β-peptide based on the Tat(47-57) fragment, leading to an oligomer with substantial helicity in methanol that enters HeLa cells much more readily than does the corresponding Tat α-peptide.

The title compound was prepared by inducing amide bond formation between methyl 2-[(2-aminophenyl)ethynyl]benzoate and 2-[(2-acetamidophenyl)ethynyl]benzoic acid in the presence of dichlorotriphenylphosphorane. The structure of the synthesized compound was determined on the basis of its 1H-nuclear magnetic resonance (NMR), 13C-NMR, and mass spectral data. Furthermore, the compound’s crystal structure is also reported.

The ready access to a new class of carbohydrate mimetics was demonstrated by the synthesis of tetrameric carbopeptoids, in which glycosidic bonds were replaced with amide linkages. We herein describe the detailed synthetis method of β(1→2)- and β(1→6)-linked carbopeptoids starting from each d -glucosamine and d -glucose derivative. The building blocks were polymerized using BOP reagent and DIEA to form a homooligomer. These produced carbopeptoids are resistant to glycosidases and have interesting biological activity. With conformational analysis by molecular modeling calculation, β(1→2)-linked decamer showed a typical 16-helix form as a mimic of β-peptide. Therefore, our polysaccharide analogues have potential as peptide foldamers.

In the present study, we describe the synthesis of new analogues of 1α,25-dihydroxyvitamin D 3 ( 1 ), which possess hydrophobic aromatic ring on the 2α position. Among these analogues, 2α-benzyl analogue showed the highest potency in the affinity for the wild type vitamin D receptor (VDR) and induction of HL-60 cell differentiation as well as transcriptional activity. Affinity for the mutant VDR related to hereditary vitamin D-resistant rickets (R274L) was also examined.

A concise and efficient synthetic approach to 2 alpha-(omega-hydroxyalkoxy)-1 alpha,25-dihydroxyvitamin D(3) (4a-c), including 2-epi-ED-71, was developed starting from D-glucose as a chiral template for the construction of the 2 alpha-modified A-ring precursors (11a-c). It was found that the best ligand for the bovine thymus vitamin D receptor (VDR) in this series is 4b, which has 1.8 times greater binding affinity for the bovine thymus VDR than that of the natural hormone 1. Interestingly, potency in the induction of HL-60 cell differentiation for 4a-c was almost the same or weaker than that of 1 despite the strong binding affinity for the VDR. Next, we were interested in the "double modification"of 1 based on 4a-c with C20-epimerization, affording 2 alpha-(omega-hydroxyalkoxy)-20-epi-1 alpha,25-dihydroxyvitamin D(3) (20-epi-4a-c). All three 2 alpha-substituted 20-epi analogues of 1 (20-epi-4a-c) exhibited stronger binding affinities for the VDR, and their conformations in the ligand binding domain of VDR were analyzed by molecular modeling. Double-modified analogues of 20-epi-4a-c showed marked HL-60 cell differentiation activity, and 20-epi-4a possesses an activity 58-fold higher than that of the natural hormone 1.