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Umami taste is imparted predominantly by monosodium glutamate (MSG) and 5′-ribonucleotides. Recently, several different classes of hydrophobic umami-imparting compounds, the structures of which are quite different from MSG, have been reported. To obtain a novel umami-imparting compound, N-cinnamoyl phenethylamine was chosen as the lead compound, and a rational structure-optimization study was conducted on the basis of the pharmacophore model of previously reported compounds. The extremely potent umami-imparting compound 2-[[[2-[(1E)-2-(1,3-benzodioxol-5-yl)ethenyl]-4-oxazolyle]methoxy]methyl]pyridine, which exhibits 27,000 times the umami taste of MSG, was found. Its terminal pyridine residue and linear structure are suggested to be responsible for its strong activity. The time taken to reach maximum taste intensity exhibited by it, as determined by the time-intensity method, is 22.0 s, whereas the maximum taste intensity of MSG occurs immediately. This distinct difference in the time-course taste profile may be due to the hydrophobicity and strong receptor affinity of the new compound.

Teneraic acid (piperidine-2,6-dicarboxylic acid) is a naturally occurring imino acid that comprises three stereoisomers due to its two asymmetric centers at C2 and C6. The configuration of natural teneraic acid is reported to correspond to trans-(2S,6S). However, a few studies are focused on the stereospecific synthesis of trans-(2S,6S)-teneraic acid. The present study investigates a convenient synthetic method that includes regiospecific anodic oxidation and stereospecific cobalt-catalyzed carbonylation to obtain trans-(2S,6S)-teneraic acid. Methyl (S)-N-benzoyl-α-methoxypipecolate, the key intermediate that displays a structure that corresponds to an intermediate (N-α-hydroxyalkyl amide) of intramolecular amidocarbonylation, was obtained via an anodic oxidation of methyl (S)-N-benzoylpipecolate. Subsequently, cobalt-catalyzed carbonylation converted the methyl (S)-N-benzoyl-α-methoxypipecolate to trans-(2S,6S)-N-benzoyl-teneraic acid dimethyl ester in good optical purity (>95% enantiomeric excess (ee)) and modest yield (63%). Finally, de-protection occurred via acidic hydrolysis to obtain trans-(2S,6S)-teneraic acid. The stereochemistry of synthesized teneraic acid was confirmed as corresponding to trans-(2S,6S) by comparing its physical properties with those of a cis-meso-isomer and those of a trans-(2S,6S)-isomer that were reported in previous studies.

Modulation of the calcium sensing receptor (CaSR) is one of the physiological activities of γ-glutamyl peptides such as glutathione (γ-glutamylcysteinylglycine). γ-Glutamyl peptides also possess a flavoring effect, i.e., sensory activity of kokumi substances, which modifies the five basic tastes when added to food. These activities have been shown to be positively correlated, suggesting that kokumi γ-glutamyl peptides are perceived through CaSRs in humans. Our research is based on the hypothesis that the discovery of highly active CaSR agonist peptides will lead to the creation of practical kokumi peptides. Through continuous study of the structure-CaSR-activity relation of a large number of γ-glutamyl peptides, we have determined that the structural requirements for intense CaSR activity of γ-glutamyl peptides are as follows: existence of an N-terminal γ-L-glutamyl residue; existence of a moderately sized, aliphatic, neutral substituent at the second residue in an L-configuration; and existence of a C-terminal carboxylic acid, preferably with the existence of glycine as the third constituent. By the sensory analysis of γ-glutamyl peptides selected by screening using the CaSR activity assay, γ-glutamylvalylglycine was found to be a potent kokumi peptide. Furthermore, norvaline-containing γ-glutamyl peptides, i.e., γ-glutamylnorvalylglycine and γ-glutamylnorvaline, possessed excellent sensory activity of kokumi substances. A novel, practical industrial synthesis of regiospecific γ-glutamyl peptides is also required for their commercialization, which was achieved through the ring opening reaction of N-α-carbobenzoxy-L-glutamic anhydride and amino acids or peptides in the presence of N-hydroxysuccinimide.

In the pathway of melanin biosynthesis, cysteine (Cys) is utilized for the synthesis of pheomelanin. Accordingly, Cys is considered to suppress the formation of brown-black eumelanin. Although attempts have been made to utilize Cys and its derivatives as skin-whitening agents, their instability and odor hinders their application as a cosmetic agent. Herein, N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid ethyl ester (AcCP2Et) was proposed as a candidate for a stable and prolonged-release derivative of Cys to inhibit dopachrome formation after its degradation in melanocytes. It was synthesized by acetylation of 2-methylthiazolidine-2,4-dicarboxylic acid 2-ethyl ester (CP2Et), the condensation derivative of Cys and ethyl pyruvate. AcCP2Et suppressed melanogenesis in melanocytes in vitro, was stable in phosphate buffer at 70°C for five days, and exhibited far less odor than CP2Et. Therefore, AcCP2Et was validated to be a useful deriative of Cys for application as a skin-whitening agent. AcCP2Et comprises four stereoisomers; thus characterization of each stereoisomer was required. The stereochemistry of AcCP2Et was confirmed via a single-crystal X-ray structure analysis of N-acetyl-2-methylthiazolidine-2,4-dicarboxylic acid (AcCP) derived from AcCP2Et. In the synthesis of AcCP2Et, the acetylation of CP2Et proceeded with epimerization at C4 to give trans-isomers when excess acetyl chloride and an organic amine was used, whereas it proceeded while retaining the original (R) configuration at C4 to give the cis- and trans-isomer when an equivalent of acetyl chloride with an inorganic base was used. These results indicate that the formation of an intermolecular mixed acid anhydride is responsible for the isomerization at the C4 asymmetric center.

Monatin, 4-hydroxy-4-(3-indolylmethyl)-glutamic acid, is a naturally occurring sweet amino acid. The (2R,4R)-monatin isomer has been found to be the sweetest among its four stereoisomers. A concise and efficient synthesis of (2R,4R)-monatin was accomplished by the alkylation of (4R)-N-tert-butoxycarbonyl (tBoc)-4-tert-butyldimethylsilyoxy-D-pyroglutamic acid methyl ester with tert-butyl 3-(bromomethyl)-1H-indole-1-carboxylate to give (4R)-N-tBoc-4-tert-butyldimethylsilyloxy-4-(N-tBoc-3-indolylmethyl)-D-pyroglutamic acid methyl ester, i.e., the lactam form of (2R,4R)-monatin with protecting groups. This was followed by the hydrolysis of the lactam ring and deprotection. The 4-hydroxyl D-pyroglutamic acid derivative was demonstrated to be a suitable precursor for the efficient preparation of (2R,4R)-monatin in high optical purity because the alkylation proceeded in regioselective and stereoselective manners at C4 to form appropriate asymmetric tetra-substituted carbon center; the resulting alkylated pyroglutamic acid derivative was then easily converted into the linear form of monatin.

The structures, flavor-modifying effects, and CaSR activities of γ-glutamyl peptides comprising sulfur-containing amino acids were investigated. The chemical structures, including the linkage mode of the N-terminal glutamic acid, of γ-L-glutamyl-S-(2-propenyl)-L-cysteine (γ-L-glutamyl-S-allyl-L-cysteine) and its sulfoxide isolated from garlic were established by comparing their NMR spectra with those of authentic peptides prepared using chemical methods. Mass spectrometric analysis also enabled determination of the linkage modes in the glutamyl dipeptides by their characteristic fragmentation. In sensory evaluation, these peptides exhibited flavor-modifying effects (continuity) in umami solutions less pronounced but similar to that of glutathione. Furthermore, the peptides exhibited intrinsic flavor due to the sulfur-containing structure, which may be partially responsible for their flavor-modifying effects. In CaSR assays, γ-L-glutamyl-S-methyl-L-cysteinylglycine was most active, which indicates that the presence of a medium-sized aliphatic substituent at the second amino acid residue in γ-glutamyl peptides enhances CaSR activity. Structural analyses and taste evaluations of g-L-glutamyl-S-(2-propenyl)-L-cysteine and its sulfoxide isolated from garlic and related peptides were performed using authentic chemically synthesized samples.

Teneraic acid (piperidine-2,6-dicarboxylic acid) is a naturally occurring imino acid that comprises three stereoisomers due to its two asymmetric centers at C2 and C6. The configuration of natural teneraic acid is reported to correspond to trans-(2S,6S). However, a few studies are focused on the stereospecific synthesis of trans-(2S,6S)-teneraic acid. The present study investigates a convenient synthetic method that includes regiospecific anodic oxidation and stereospecific cobalt-catalyzed carbonylation to obtain trans-(2S,6S)-teneraic acid. Methyl (S)-N-benzoyl-α-methoxypipecolate, the key intermediate that displays a structure that corresponds to an intermediate (N-α-hydroxyalkyl amide) of intramolecular amidocarbonylation, was obtained via an anodic oxidation of methyl (S)-N-benzoylpipecolate. Subsequently, cobalt-catalyzed carbonylation converted the methyl (S)-N-benzoyl-α-methoxypipecolate to trans-(2S,6S)-N-benzoyl-teneraic acid dimethyl ester in good optical purity (95% enantiomeric excess (ee)) and modest yield (63%). Finally, de-protection occurred via acidic hydrolysis to obtain trans-(2S,6S)-teneraic acid. The stereochemistry of synthesized teneraic acid was confirmed as corresponding to trans-(2S,6S) by comparing its physical properties with those of a cis-meso-isomer and those of a trans-(2S,6S)-isomer that were reported in previous studies.

Monatin is a naturally occurring, sweet amino acid comprising four stereoisomers due to its two asymmetric centers at C2 and C4. However, the characteristics of each stereoisomer have not yet been fully investigated. To obtain a sufficient amount of racemic monatin for optical resolution, a synthetic method was developed by modifying a possible biosynthetic pathway, i.e., a cross-aldol reaction and subsequent transamination. The key intermediate, 4-hydroxy-4-(3-indolylmethyl)-2-ketoglutaric acid, was obtained via the cross-aldol reaction of pyruvic acid and indole-3-pyruvic acid. Subsequently, the carbonyl group was converted to a hydroxyimino group through reaction with hydroxylamine and then to an amino group via hydrogenation to produce monatin. Next, the racemic monatin was divided into mixtures of two pairs of enantiomers through recrystallization. Finally, both enantiomers of the N-carbobenzoxy-γ-lactone derivatives of monatin were separated by preparative HPLC and deprotected. It was found that all optically pure stereoisomers exhibited a sweet taste. The isomer that displayed the most intense sweetness was the (2R,4R)-isomer, as determined by single crystal X-ray structure analysis of the monatin potassium salt, whereas the least sweet isomer was the (2S,4S)-isomer, which demonstrated a far lower sweetness than was previously reported.

By human sensory analyses, we found that various extracellular calcium-sensing receptor (CaSR) agonists enhance sweet, salty, and umami tastes, although they have no taste themselves. These characteristics are known as "kokumi taste" and often appear in traditional Japanese cuisine. Although GSH is a typical kokumi taste substance (taste enhancer), its mode of action is poorly understood. Here, we demonstrate how the kokumi taste is enhanced by the CaSR, a close relative of the class C G-protein-coupled receptors T1R1, T1R2, and T1R3 (sweet and umami receptors). We identified a large number of CaSR agonist gamma-glutamyl peptides, including GSH (gamma-Glu-Cys-Gly) and gamma-Glu-Val-Gly, and showed that these peptides elicit the kokumi taste. Further analyses revealed that some known CaSR agonists such as Ca(2+), protamine, polylysine, L-histidine, and cinacalcet (a calcium-mimetic drug) also elicit the kokumi taste and that the CaSR-specific antagonist, NPS-2143, significantly suppresses the kokumi taste. This is the first report indicating a distinct function of the CaSR in human taste perception.

L-Cystathionine is a key nonprotein amino acid related to metabolic conditions. The quantitative determination of L-cystathionine in physiological fluids by amino acid analysis is important for clinical diagnosis; however, certified reference material for L-cystathionine with satisfactory purity, content, and quantity has been unavailable until recently. Consequently, a practical and simple method for the preparation of L-cystathionine was examined, which involves thioalkylation of N-tert-butoxycarbonyl-L-cysteine tert-butyl ester, derived from L-cystine, with (2S)-2-(tert-butoxycarbonyl)amino-4-iodobutanoic acid tert-butyl ester, derived from L-aspartic acid, to obtain L-cystathionine with protecting groups, followed by single-step deprotection under mild conditions. This method produces L-cystathionine in high purity (99.4%) and having sufficient percentage content according to amino acid analysis, which could be used as a standard for the amino acid analysis of physiological fluids. Synthesis and amino acid analysis chromatogram of L-cystathionine.

Capsinoids represent a novel group of capsaicinoid-like substances found in a nonpungent cultivar, Capsicum annuum “CH-19 Sweet.” They have capsaicinoid-like physiological and biological properties while lacking the harmful stimuli of capsaicinoids. A large-scale synthesis of dihydrocapsiate (DCT) is established in this work. 8-Methynonanoic acid (MNA) was synthesized by copper-catalyzed cross-coupling of ethyl 6-bromohexanoate with isobutylmagnesium bromide and subsequent hydrolysis. Lipase-catalyzed chemoselective esterification of vanillyl alcohol and MNA was performed at 50 °C under reduced pressure to remove water without solvents or drying agents. A slightly larger stoichiometric amount of MNA was used and the purification in the final stage was simplified to leave a small amount of MNA in the product, because we found that the presence of a small amount of MNA is necessary to stabilize DCT. DCT was synthesized according to the production, and stabilization methods described here has been filed as a new dietary ingredient. Dihydrocapsiate was synthesized via lipase-catalyzed chemoselective esterification of vanillyl alcohol and 8-methylnonanoic acid under reduced pressure without solvents.

The effects of defatted safflower seed extract and its phenolic constituents, serotonin derivatives, on atherosclerosis were studied. Ethanol-ethyl acetate extract of safflower seeds (SSE) inhibited low-density lipoprotein (LDL) oxidation induced in vitro by an azo-containing free-radical initiator V70 or copper ions. Two serotonin derivatives [N-(p-coumaroyl)serotonin, CS; N-feruloylserotonin, FS] and their glucosides were identified as the major phenolic constituents of the extract. The study with chemically synthesized materials revealed that a majority of the antioxidative activity of SSE was attributable to the aglycones of these two serotonin derivatives. Orally administered CS and FS suppressed CuSO(4)-induced plasma oxidation ex vivo. Long-term (15 week) dietary supplementation of SSE (1.0 wt %/wt) and synthetic serotonin derivatives (0.2-0.4%) significantly reduced the atherosclerotic lesion area in the aortic sinus of apolipoprotein E-deficient mice (29.2-79.7% reduction). The plasma level of both lipid peroxides and anti-oxidized LDL autoantibody titers decreased concomitantly with the reduction of lesion formation. Serotonin derivatives were detected as both intact and conjugated metabolites in the plasma of C57BL/6J mice fed on 1.0% SSE diet. These findings demonstrate that serotonin derivatives of SSE are absorbed into circulation and attenuate atherosclerotic lesion development possibly because of the inhibition of oxidized LDL formation through their strong antioxidative activity.

We report here the synthesis and the conformation analysis by (1)H NMR spectroscopy and computer simulations of six potent sweet molecules, N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-aspartyl-S-tert-butyl-L-cysteine 1-methylester (1; 70000 times more potent than sucrose), N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-aspartyl-beta-cyclohexyl-L-alanine 1-methylester (2; 50000 times more potent than sucrose), N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-aspartyl-beta-cyan-L-phenyloalanine 1-methylester (3; 2000 times more potent than sucrose), N-[3,3-dimethylbutyl]-alpha-L-aspartyl-(1R,2S,4S)-7-methyl-2-hydroxy-4-phenylhexylamide (4; 5500 times more potent than sucrose), N-[3-(3-hydroxy-4-methoxyphenyl)propyl]-alpha-L-aspartyl-(1R,2S,4S)-1-methyl-2-hydroxy-4-phenylhexylamide (5; 15000 times more potent than sucrose), and N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-asaortyl-(1R,2S,4S)-1-methyl-2-hydroxy-4-phenylhexylamide (6; 15000 times more potent than sucrose). The "L-shaped" structure, which we believe to be responsible for sweet taste, is accessible to all six molecules in solution. This structure is characterized by a zwitterionic ring formed by the AH- and B-containing moieties located along the +y axis and by the hydrophobic group X pointing into the +x axis. Extended conformations with the AH- and B-containing moieties along the +y axis and the hydrophobic group X pointing into the -y axis were observed for all six sweeteners. For compound 5, the crystal-state conformation was also determined by an X-ray diffraction study. The result indicates that compound 5 adopts an L-shaped structure even in the crystalline state. The extraordinary potency of the N-arylalkylated or N-alkylated compounds 1-6, as compared with that of the unsubstituted aspartame-based sweet taste ligands, can be explained by the effect of a second hydrophobic binding domain in addition to interactions arising from the L-shaped structure. In our examination of the unexplored D zone of the Tinti-Nofre model, we discovered a sweet-potency-enhancing effect of arylalkyl substitution on dipeptide ligands, which reveals the importance of hydrophobic (aromatic)-hydrophobic (aromatic) interactions in maintaining high potency.

Photoirradiation at a wavelength of >300 nm of a deaerated suspension of cadmium(II) sulfide (CdS) particles in an aqueous solution of a mixture of stereoisomers of 2,6-diaminopimelic acid (DAP; (S,S)∶(R,S)∶(R,R) = 1∶2∶1) produced piperidine-2,6-dicarboxylic acid (PDC) via a redox-combined mechanism including oxidation and reduction by positive holes and photoexcited electrons, respectively. Both the yield and trans∶cis ratio of PDC markedly depended on the kinds of CdS photocatalysts, their pre-treatment, and the loading of fine platinum (or its oxide) particles. A CdS photocatalyst prepared by heat treatment of a commercial powder in hexagonal (wurtzite) structure at 1023 K in the presence of a small amount of air gave the highest yield and trans∶cis ratio. Analyses of the activated CdS powder by powder X-ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and BET surface area measurements revealed the formation of sulfur vacancies due to heat treatment, which promote the photoinduced cadmium metal (Cd0) deposition. The Cd0, deposited in situ on the CdS surface and detected by reduction of methylviologen, may act as a reduction site for photoexcited electrons toward a cyclic Schiff base intermediate produced by oxidation of DAP with positive holes followed by deamination and intramolecular condensation. Optically pure (R,R)- or (S,S)-PDCs were prepared successfully by photocatalytic reaction with the activated CdS particles using (R,R)- or (S,S)-DAPs, indicating that stereoselective conversion of organic compounds can be achieved via photocatalytic reaction under controlled conditions.

A dipeptide taste ligand L-aspartyl-D-2-aminobutyric acid-(S)-α-ethylbenzylamide was found to be about 2000 times more potent than sucrose. To investigate the molecular basis of its potent sweet taste, we carried out conformational analysis of this molecule and several related analogues by NMR spectroscopy, computer simulations and X-ray crystallographic studies. The results of the studies support our earlier model that an ‘L’-shape molecular array is essential for eliciting sweet taste. In addition, we have identified an aromatic group located between the stem and the base of the ‘L-shape’, which is responsible for enhancement of sweetness potency. In this study, we also assessed the optimal size of the essential hydrophobic group (X) and the effects of the chirality of the second residue toward taste. ©1997 European Peptide Society and John Wiley & Sons, Ltd.

Photoirradiation at wavelength > 300 nm onto a deaerated aqueous suspension of cadmium(II) sulfide (CdS) particles in an aqueous solution of a mixture of stereo isomers of 2,6-diamiopimelic acid (DAP) produced piperidine-2,6-dicarboxylic acid (PDC). Both yield and trans cis ratio of PDC markedly depended on the kind of CdS photocatalysts, its pre-treatment, and loading of fine platinum particles. A CdS photocatalyst prepared by heat-treatment at 1023 K in the presence of a small amount of air showed the highest yield and trans cis ratio.

This paper presents the living support system using IC card interface with disaster prevention system. There are many electronic and information devices in daily life, and these are improving for comfortable. However handicapped and elderly people are difficult to handle devices because there requires many buttons and keys for settings and controlling. On the other hand, engineers are discussing and developing to improve the interface, and also challenging keep safety for disasters. With these backgrounds, the authors propose an interface which controls devices only detections of IC cards, and then demonstrate performances of fundamental systems. In this paper, the IC card interface is applying to electrical devices in our daily life especially TV control, extended for keep safety with disaster prevention systems that are heat and seismic detectors.

This paper presents an IC card interface using embedded technology with universal remote controller for living support system. There are many electronic and information devices in daily life. However handicapped and elderly people can find that it is very difficult to handle devices because there is many buttons and keys on interfaces of them. Although devices are needed to simple interfaces, researchers and engineers are investigating on the interfaces. With this background, the authors propose an interface which controls devices with only IC cards in daily life, and it expects to become an easy interface for controlling of them. Previous research discussed an outline and fundamental of the system, so this paper shows that development and effectiveness of the system with universal remote controller for practical use.

N-Acyl derivatives of proline and 2-piperidinecarboxylic acid (pipecolic acid) were synthesized in moderate yield from N-acyl unsaturated cyclic amines through cobalt-catalyzed isomerization–carboxylation under hydroformylation conditions in the presence of H2O. A possible mechanism for the process is discussed which is related to that of the amidocarbonylation (cobalt-catalyzed formation of N-acyl α-amino acid from aldehyde, amide and carbon monoxide).

Humans have evolved to consume natural products in their environment and have acquired a sense of taste. Our ability to taste bitter and sour evolved to identify potentially dangerous food. On the contrary, the ability to recognize a sweet taste developed to identify an energy source, while a salty taste is a signal of minerals. As time progressed, humans began to use bitter, pungent, and even astringent tastes that were initially considered to be unpleasant. This may have been because we became aware that such substances were effective at improving health or even treating disease. Human food culture progressed further with the development of cooking methods that use spices and more dramatically through the enjoyment of fermentation products. There has been no recent comprehensive review on the chemistry of taste written from the perspective of natural products chemistry. In this chapter, several taste sensations found in natural products are described along with their structures. Although it is still very difficult to anticipate the taste quality and intensity from the structure of an organic compound, it is expected that recent progress in the study of receptors will contribute to a full understanding of the relationship between taste sensation and chemical structure.

α,ω-Diamino acid derivatives, such as lysine and ornithine, were synthesized via amidocarbonylation (cobalt-catalyzed formation of N-acyl α-amino acid from aldehyde, amide and carbon monoxide) of ω-(phthalimido)alkanals in good yield. The phthalimido group was proved to be intact under the conditions of amidocarbonylation. The hydroformylation-amidocarbonylation of N-phthaloyl-β,γ- and N-phthaloyl-γ,δ-unsaturated amines proceeds very nicely to give α,ω-diamino acid derivatives with good selectivity. Selective deprotection of α-N-acyl-ω-N-phthaloyl α,ω-diamino acids was achieved using hydrazine for the N-phthaloyl group and aminoacylase for the N-acetyl group to afford the optically active α,ω-diamino acid, respectively.

N-Acyl derivatives of proline and 2-piperidinecarboxylic acid (pipecolic acid) were synthesized in moderate yield from N-acyl unsaturated cyclic amines through cobalt-catalyzed isomerization–carboxylation under hydroformylation conditions in the presence of H2O. A possible mechanism for the process is discussed which is related to that of the amidocarbonylation (cobalt-catalyzed formation of N-acyl α-amino acid from aldehyde, amide and carbon monoxide).

Reductive elimination of vicinal acetylated halohydrins with Na 2 S 2 O 4 as the reducing agent and viologen as the reduction mediator in a two-phase water-organic system is described. 2',3'-Unsaturrated nucleosides such as 1-(5-O-acetyl-2,3-dideoxy-β-D-glycero-pent-2-enofuranosyl)adenine, -hypoxanthine and -uracil were obtained from 2'(3')-acetoxy-3'(2')-halogeno derivatives in good yields by meanes of this procedure

In this presentation, we describe an integrated approach for the molecular basis for sweet taste among dipeptide-based ligands. By comparing the results obtained from X-ray diffraction studies with the conformations from NMR analysis and molecular modeling, we have observed recurring topochemical motifs that agree with previous models for sweet taste. In our examination of the unexplored D zone of the Tinti­Nofre model, we have uncovered a sweet potency enhancing effect of a new set of aralkyl-substitutions on dipeptide ligands, which reveals the importance of aromatic­aromatic interactions in maintaining high potency.

1-(6-Carboxyhexyl)-5-[(E)-3-hydroxy-1-octenyl]midazole, an imidazole analogue of prostaglandin, was synthesized from 4(5)-hydroxymethylimidazole hydrochloride. The key step involves regioselective alkylation of 4(5)-tertbutyldimethylsilyloxymethylimidazole to give predominantly 1, 5-disubstituted imidazole.

The enolates of sec-thioamides 8 , which are generated by three different methods (scheme II and equation 1), are alkylated selectively at the α-carbon to the thiocarbonyl group. The unusual β′-lithiation to provide an intermediate 11 is observed for N-methyl-α, β-dimetylthioacrylamide and N-methyl-thiocyclohexenecarboxamide.

A crystal of inclusion compound of Aspartame (α-L-aspartyl-L-phenylalanine methyl ester, APM) with β-cyclodextrin (β-CD) was obtained from their aqueous solution. The Raman spectrum of this crystal indicates some differences from the spectral sum of APM and β-CD. An analysis of these spectral differences suggests that the phenyl moiety of APM is included in the cavity of β-CD in the inclusion compound. In addition, a Raman spectroscopic study of APM with 15N-substitution and N-deuteration indicates that the peptide backbone of APM undergoes some conformational change on APM going into the inclusion compound. Solid state 13C CP MAS- and gated-decoupling MAS–NMR spectra for the inclusion compound indicate that the phenyl ring rotates at a higher frequency than 270 MHz, that the Phe Cβ and phenyl ring Cl move at the frequency of about 270 MHz, and that the molecular motion of the other parts of APM occurs at lower frequency than 270 MHz.

1-(6-Carboxyhexyl)-5-[(E)-3-hydroxy-1-octenyl]midazole, an imidazole analogue of prostaglandin, was synthesized from 4(5)-hydroxymethylimidazole hydrochloride. The key step involves regioselective alkylation of 4(5)-tertbutyldimethylsilyloxymethylimidazole to give predominantly 1, 5-disubstituted imidazole.

The adjuvant effect of N-acyl-L-and D-phenylalanine derivatives on intestinal absorption of insulin was investigated in normal mice. The correlation between the chemical structural properties of the N-acyl moiety and the absorption-promoting activity was estimated from the glucose concentrations and the insulin levels in the blood of mice after oral combined administration of insulin and adjuvant. The chemical structural properties of N-acyl-phenylalanine derivatives necessary for adjuvant effect on intestinal absorption of insulin were as follows.1. An aromatic ring is present, separated by two atoms from the acyl carbonyl group.2. Either of X or Y is oxygen or X-Y is a double bond in Fig.2.3. The N-acyl moiety has small hydrophobic substituents, such as F, Cl, or Me at Rα, Rβ, Rη and has an appropriate hydrophilic-hydrophobic balance of the overall molecule.The use of these agents to enhance insulin absorption offers the possibility of a new approach to oral insulin therapy.