Search

The structure–activity relationships of a novel series of biaryl dihydroorotate dehydrogenase (DHODH) inhibitors related to teriflunomide are disclosed. These biaryl derivatives were the result of structure-based design and proved to be potent DHODH inhibitors which in addition showed good antiproliferative activities on peripheral blood mononuclear cells and good efficacies in vivo in the rat adjuvant-induced-arthritis model.

A series of N-pyrimidinyl-2-phenoxyacetamide adenosine A(2A) antagonists is described. SAR studies led to compound 14 with excellent potency (K(i) = 0.4 nM), selectivity (A(1)/A(2A) > 100), and efficacy (MED 10 mg/kg p.o.) in the rat haloperidol-induced catalepsy model for Parkinson's disease.

N-Thiodiglycoloyl (TDG) protection of O-acetylated glucosamine could be readily carried out with thiodiglycolic anhydride and then treatment with acetic anhydride in pyridine. Ensuing reaction with hydrazinium acetate and then base-catalyzed activation with trichlorocetonitrile afforded N-TDG protected glucosamine donor 3. Glycosylation of acceptors 8 and 5 in dichloromethane with TMSOTf as the catalyst gave β-glycosides 6 and 9 in high yields. For TDG cleavage MeONa/MeOH treatment followed by radical desulfurization with Bu3SnH/AIBN and reacetylation with Ac2O/pyridine was employed, thus giving N-acetyl glucosamine containing compounds 7 and 10 in a convenient, high-yielding procedure.

Glycoside bond formation generally requires activation of the sugar at the anomeric center. To this end, anomeric oxygen exchange reactions, resulting in the Koenigs-Knorr method and variations or, alternatively, activation through retention of the anomeric oxygen, resulting in the trichloroacetimidate method and in the phosphite method, have been proposed. The successful application of the trichloroacetimidate method to the total synthesis of GPI anchors is particularly worth mentioning. a(2-3)-Sialylation can be based on sialyl phosphites as glycosyl donors and on the nitrile effect for anomeric stereocontrol. This is exhibited for a preparative synthesis of ganglioside GM2 which is required for tumor vaccine studies. For the generation of a(2-8)-linkage between neuraminic acid residues anchimeric assistance by a 3-thiocarbonyloxy group is introduced. The required sialyl donor can be efficiently prepared and a-linkage to 8-O-unprotected neuraminic acid derivatives is almost quantitative. The limitations of chemical glycopeptide synthesis encourage to employ the protein biosynthesis machinery in combination with an expanded genetic code. This is exhibited for the synthesis of glycosylated hARF-1 protein.

Glucosamine was readily transformed into N-dimethylmaleoyl (DMM) protected derivative 1 which furnished trichloroacetimidate 4 as glycosyl donor. Reaction with various acceptors (5a–g) in the presence of TMSOTf as the catalyst afforded the corresponding β-glycosides 6a–g generally in high yields. Cleavage of the DMM group was readily accomplished by treatment with aqueous NaOH and then with HCl (pH 5). Starting from 1 also DMM group containing glycosyl acceptors 9 and 14a–c were synthesized. They furnished with trichloroacetimidates 12 and 4 as glycosyl donors β(1-4)- and β(1-3)-linked disaccharides 13 and 15a–c, respectively. From 18 as galactosyl donor and 14a as acceptor β(1-3)-linked disaccharide 19 was obtained in high yield, which is a versatile building block for the important Galβ(1-3)GlcNAc unit. 19 was transformed into trichloroacetimidate 21; glycosylation with 5e as acceptor gave trisaccharide 22 which furnished on partial deprotection Galβ(1-3)GlcNAcβ(1-4)Glc derivative 24. Thus, the wide applicability of DMM as amino protective group in oligosaccharide synthesis is exhibited.

Synthesis of Neu5Acα(2−3)Galβ(1−4)Glc and Neu5Acα(2−8)Neu5Ac derivatives 12α and 14α, from lactose derivative 6 and 2,3-dehydro-Neu5Ac derivative 7, respectively, with anchimerically assisted Neu5Ac donor 3e, 3f, or 3g has been studied. Reaction of halogenose 3e, having a 3-phenoxythiocarbonyloxy moiety as the assisting group, afforded with 6 and 7 in the presence of equimolar amounts of AgOTf as promoter α-sialosides 11α and 13α which were readily deoxygenated to afford 12α and 14α, respectively. Reaction of phosphite 3f, having a 3-bromo substituent as the potentially anchimeric assisting group, furnished in the presence of catalytic amounts of TMSOTf with 6 as acceptor α-sialoside 15α and with 7 as acceptor β-sialoside 17β, which gave on debromination 12α and 14β, respectively. Reaction of readily available phosphite 3g, having a 3-thiobenzoyloxy group as the anchimeric assisting group, afforded with 6 and 7 in the presence of catalytic amounts of TMSOTf in very high yields α-linked sialosides 21α and ...

2-O-Unprotected and 2-deoxy-2,3-dehydro-neuraminic acid derivatives 2, 4, and 10 exhibit enhanced acceptor properties at their 8-hydroxy group in sialylation reactions with phosphite 5 as donor; yet, mainly (10) or exclusively (2, 4) β-glycoside bond formation was observed. The 3-phenylthionocarbonate group as stereodirecting auxiliary group in the sialyl donor 11 led with 10 as acceptor to exclusive formation of α(2–8)-linked disaccharide.

The N-tetrachlorophthalimido-protected glucosamine donor 2 reacts with electron-rich phenol ethers 3a–c to afford aryl C-glycosides 4a–c. The N-tetrachlorophthaloyl group could be readily removed by sodium borohydride treatment and then phthalide formation or by treatment with ethylenediamine, respectively. The resulting product was subjected to reaction with acetic anhydride in pyridine to afford N,O-acetylated compounds 5a–c. After treatment with enthylenediamine also the N,O-unprotected compounds could be obtained as shown for 6c.

The trisaccharide α-L-Rha-(1-2)-α-L-Rha-(1-2)-α-L-Rha with a dioxolane-type spacer was obtained by using the trichloroacetimidate method in all of the glycosidation steps. After deprotection, the trisaccharide was coupled to BSA or KLH by reductive amination of the spacer aldehyde group.

Several ribofuranosyl derivatives bearing trichloroacetimidoyl or acetyl leaving groups in a Lewis acid promoted ribosylation reaction were prepared and used in an attempt to improve the yield and to avoid donor → acceptor transacetylation. Trichloroacetimidates were excellent donors affording disaccharides with very high yields under mild conditions. The corresponding 1-O-acetylated analogs could also be used with out transacetylation in the presence of boron trifluoride etherate.

Several ribofuranosyl derivatives bearing trichloroacetimidoyl or acetyl leaving groups in a Lewis acid promoted ribosylation reaction were prepared and used in an attempt to improve the yield and to avoid donor → acceptor transacetylation. Trichloroacetimidates were excellent donors affording disaccharides with very high yields under mild conditions. The corresponding 1-O-acetylated analogs could also be used with out transacetylation in the presence of boron trifluoride etherate.

Synthesis of Neu5Acα(2−3)Galβ(1−4)Glc and Neu5Acα(2−8)Neu5Ac derivatives 12α and 14α, from lactose derivative 6 and 2,3-dehydro-Neu5Ac derivative 7, respectively, with anchimerically assisted Neu5Ac donor 3e, 3f, or 3g has been studied. Reaction of halogenose 3e, having a 3-phenoxythiocarbonyloxy moiety as the assisting group, afforded with 6 and 7 in the presence of equimolar amounts of AgOTf as promoter α-sialosides 11α and 13α which were readily deoxygenated to afford 12α and 14α, respectively. Reaction of phosphite 3f, having a 3-bromo substituent as the potentially anchimeric assisting group, furnished in the presence of catalytic amounts of TMSOTf with 6 as acceptor α-sialoside 15α and with 7 as acceptor β-sialoside 17β, which gave on debromination 12α and 14β, respectively. Reaction of readily available phosphite 3g, having a 3-thiobenzoyloxy group as the anchimeric assisting group, afforded with 6 and 7 in the presence of catalytic amounts of TMSOTf in very high yields α-linked sialosides 21α and ...

Glucosamine was readily transformed into N-dimethylmaleoyl (DMM) protected derivative 1 which furnished trichloroacetimidate 4 as glycosyl donor. Reaction with various acceptors (5a–g) in the presence of TMSOTf as the catalyst afforded the corresponding β-glycosides 6a–g generally in high yields. Cleavage of the DMM group was readily accomplished by treatment with aqueous NaOH and then with HCl (pH 5). Starting from 1 also DMM group containing glycosyl acceptors 9 and 14a–c were synthesized. They furnished with trichloroacetimidates 12 and 4 as glycosyl donors β(1-4)- and β(1-3)-linked disaccharides 13 and 15a–c, respectively. From 18 as galactosyl donor and 14a as acceptor β(1-3)-linked disaccharide 19 was obtained in high yield, which is a versatile building block for the important Galβ(1-3)GlcNAc unit. 19 was transformed into trichloroacetimidate 21; glycosylation with 5e as acceptor gave trisaccharide 22 which furnished on partial deprotection Galβ(1-3)GlcNAcβ(1-4)Glc derivative 24. Thus, the wide applicability of DMM as amino protective group in oligosaccharide synthesis is exhibited.

Glycoside bond formation generally requires activation of the sugar at the anomeric center. To this end, anomeric oxygen exchange reactions, resulting in the Koenigs-Knorr method and variations or, alternatively, activation through retention of the anomeric oxygen, resulting in the trichloroacetimidate method and in the phosphite method, have been proposed. The successful application of the trichloroacetimidate method to the total synthesis of GPI anchors is particularly worth mentioning. a(2-3)-Sialylation can be based on sialyl phosphites as glycosyl donors and on the nitrile effect for anomeric stereocontrol. This is exhibited for a preparative synthesis of ganglioside GM2 which is required for tumor vaccine studies. For the generation of a(2-8)-linkage between neuraminic acid residues anchimeric assistance by a 3-thiocarbonyloxy group is introduced. The required sialyl donor can be efficiently prepared and a-linkage to 8-O-unprotected neuraminic acid derivatives is almost quantitative. The limitations of chemical glycopeptide synthesis encourage to employ the protein biosynthesis machinery in combination with an expanded genetic code. This is exhibited for the synthesis of glycosylated hARF-1 protein.

N-Thiodiglycoloyl (TDG) protection of O-acetylated glucosamine could be readily carried out with thiodiglycolic anhydride and then treatment with acetic anhydride in pyridine. Ensuing reaction with hydrazinium acetate and then base-catalyzed activation with trichlorocetonitrile afforded N-TDG protected glucosamine donor 3. Glycosylation of acceptors 8 and 5 in dichloromethane with TMSOTf as the catalyst gave β-glycosides 6 and 9 in high yields. For TDG cleavage MeONa/MeOH treatment followed by radical desulfurization with Bu3SnH/AIBN and reacetylation with Ac2O/pyridine was employed, thus giving N-acetyl glucosamine containing compounds 7 and 10 in a convenient, high-yielding procedure.

We have developed a highly convergent synthetic route for the synthesis of the branched structure of human milk octasaccharide β-D-galactopyranosyl-(13)-2-acetamido-2-de oxy-β-D-glucopyranosyl-(13)-β-D-galactopyranosyl)-(14)-2-acetamido-2-deoxy-β-D-glucopyranosyl-(16)-[β-D-galactopyranosyl-(13)-2-acetamido-2-deoxy-β-D-glucopyranosyl-(13)]-β-D-galactopyranosyl-(14)-α,β-Dglucopyranose (1). In the retrosynthetic analysis, target structure 1 was disconnected into building blocks 2−6. Starting from only four known building blocks − 4, 7, 8, and 12 − the required three disaccharide units were obtained, resulting after further protecting group manipulation and glycoside bond formation in the desired tetrasaccharides 13 and 16. Cleavage of the TBDMS group of 13 afforded tetrasaccharide 14, which was transformed into isolactosamine-β-(13)-lactosamine trichloroacetimidate 15. Removal of the 4b,6b-O-benzylidene group of tetrasaccharide 16 gave the lacto-N-tetraose acceptor 17, to afford the protected octasaccharide 18 on glycosylation with donor 15. Complete deprotection of the octasaccharide by way of 19 afforded target human milk oligosaccharide 1 in a short and efficient route.

Dehydroneuraminic acid derivative 5 was transformed in five efficient steps into sialyl donor 2, which has a phenylthio group on the b-side of the 3-position for anchimeric assistance and a diethyl phosphite residue as leav- ing group at the anomeric carbon. The known GM3 intermediate 10 was trans- formed into the 4b,4c,8c-O-unprotected acceptor 3, which was then allowed to react with 2 by using TMSOTf as catalyst and acetonitrile as solvent to afford the desired tetrasaccharide 12, which has an a(2 - 8)-linkage between two neuraminic acid residues. Removal of the phenylthio group gave intermedi- ate 13, which was transformed into O- tetraosyl trichloroacetimidate 16 as gly- cosyl donor. Application of the azido- sphingosine glycosylation procedure fur- nished GD3 (1) in high overall yield. Comparison of synthetic GD3 with bo- vine-brain-derived GD3 showed that there were similar effects in GD3-trig- gered uncoupling of mitochondrial res- piration and in induction of apoptosis in oligodendrocytes.

Previously we have described a series of novel A 2A receptor antagonists with excellent water solubility. As described in the accompanying paper, the antagonists were first optimized to remove an unsubstituted furyl moiety, with the aim of avoiding the potential metabolic liabilities that can arise from the presence of an unsubstituted furan. This effort identified a series of potent and selective methylfuryl derivatives. Herein, we describe the further optimization of this series to increase potency, maintain selectivity for the human A 2A vs the human A 1 receptor, and minimize activity against the hERG channel. In addition, the observed structure-activity relationships against both the human and the rat A 2A receptor are reported.

Previously we have described a novel series of potent and selective A2A receptor antagonists (e.g., 1) with excellent aqueous solubility.(1) While these compounds are efficacious A2A antagonists in vivo, the presence of an unsubstituted furyl moiety was a cause of some concern. In order to avoid the potential metabolic liabilities that could arise from an unsubstituted furyl moiety, an optimization effort was undertaken with the aim of replacing the unsubstituted furan with a more metabolically stable group while maintaining potency and selectivity. Herein, we describe the synthesis and SAR of a range of novel heterocyclic systems and the successful identification of a replacement for the unsubstituted furan moiety with a methylfuran or thiazole moiety while maintaining potency and selectivity.

Potent adenosine hA2A receptor antagonists are often accompanied by poor aqueous solubility, which presents issues for drug development. Herein we describe the early exploration of the structure-activity relationships of a lead pyrimidin-4-yl acetamide series to provide potent and selective 2-amino-N-pyrimidin-4-yl acetamides as hA2A receptor antagonists with excellent aqueous solubility. In addition, this series of compounds has demonstrated good bioavailability and in vivo efficacy in a rodent model of Parkinson's disease, despite having reduced potency for the rat A2A receptor versus the human A2A receptor.

The human genome encodes five nonpolymorphic major histocompatibility complex class I-like glycoproteins, CD1a to CD1e, that present lipid antigens for specific recognition by T lymphocytes. Using single alkyl chain detergents, we developed a protocol to generate recombinant human CD1b-lipid complexes. We present here the crystal structures of CD1b in complex with either phosphatidylinositol or ganglioside GM2 at 2.3 A and 2.8 A resolutions, respectively. The antigen-binding groove houses four interlinked hydrophobic channels that are occupied by the alkyl chains of the glycolipid plus two detergent molecules. A distinct exit beneath the alpha 2 helix further contributes to the plasticity of the binding groove. These structures reveal the mechanism by which two alkyl chain lipids bind to CD1b, and how CD1b can adapt to ligands of different alkyl chain length. They also suggest how very long alkyl chains, such as those of mycolic acid, could be fully contained within the binding groove. These results extend the spectrum of potential CD1b ligands by revealing that, in addition to two alkyl chain lipids, mono-alkyl and triple-alkyl chain lipids can be accommodated in the binding groove.

Dehydroneuraminic acid derivative 5 was transformed in five efficient steps into sialyl donor 2, which has a phenylthio group on the b-side of the 3-position for anchimeric assistance and a diethyl phosphite residue as leav- ing group at the anomeric carbon. The known GM3 intermediate 10 was trans- formed into the 4b,4c,8c-O-unprotected acceptor 3, which was then allowed to react with 2 by using TMSOTf as catalyst and acetonitrile as solvent to afford the desired tetrasaccharide 12, which has an a(2 - 8)-linkage between two neuraminic acid residues. Removal of the phenylthio group gave intermedi- ate 13, which was transformed into O- tetraosyl trichloroacetimidate 16 as gly- cosyl donor. Application of the azido- sphingosine glycosylation procedure fur- nished GD3 (1) in high overall yield. Comparison of synthetic GD3 with bo- vine-brain-derived GD3 showed that there were similar effects in GD3-trig- gered uncoupling of mitochondrial res- piration and in induction of apoptosis in oligodendrocytes.

D-Glucosamine can be readily transformed into 1,3,4,6-tetra-O-acetyl-2-deoxy-2-(2,2,2-trichloroethoxycarbonylamino+ ++) -D-glucopyranose (2). From this intermediate valuable glycosyl donors can be obtained; reaction with ethanethiol in the presence of boron trifluoride etherate afforded ethyl 3,4,6-tri-O-acetyl-2-deoxy-1-thio-2-(2,2, 2-trichloroethoxycarbonylamino)-beta-D-glucopyranoside (4) which gave, upon N-acetylation, the N-acetyl-N-trichloroethoxycarbonyl derivative (5). Selective removal of the 1-O-acetyl group in 2 followed by treatment with trichloroacetonitrile in the presence of base afforded 3,4,6-tri-O-acetyl-2-deoxy-2-(2,2,2-trichloroethoxycarbonylamino)- alpha -D-glucopyranosyl trichloroacetimidate (6). Reaction of 5 with five selectively protected glycosides as glycosyl acceptors in the presence of N-iodosuccinimide/trifluoromethanesulfonic acid as the promoter system furnished the corresponding beta-glycosides in good yields, thus exhibiting the valuable glycosyl donor properties of 5. Reductive removal of the trichloroethoxycarbonyl (Teoc) group afforded the corresponding N-acetyl-protected saccharides in high yields. The imidate 6 reacted with three of the above acceptors in the presence of catalytic amounts of trimethylsilyl trifluoromethanesulfonate to give the beta-linked disaccharides in even better yields. The direct replacement of the N-Teoc group by the N-acetyl group using zinc/acetic anhydride, via the free amines as transient intermediates, adds to the high efficiency and convenience of this methodology.

We have developed a highly convergent synthetic route for the synthesis of the branched structure of human milk octasaccharide β-D-galactopyranosyl-(13)-2-acetamido-2-de oxy-β-D-glucopyranosyl-(13)-β-D-galactopyranosyl)-(14)-2-acetamido-2-deoxy-β-D-glucopyranosyl-(16)-[β-D-galactopyranosyl-(13)-2-acetamido-2-deoxy-β-D-glucopyranosyl-(13)]-β-D-galactopyranosyl-(14)-α,β-Dglucopyranose (1). In the retrosynthetic analysis, target structure 1 was disconnected into building blocks 2−6. Starting from only four known building blocks − 4, 7, 8, and 12 − the required three disaccharide units were obtained, resulting after further protecting group manipulation and glycoside bond formation in the desired tetrasaccharides 13 and 16. Cleavage of the TBDMS group of 13 afforded tetrasaccharide 14, which was transformed into isolactosamine-β-(13)-lactosamine trichloroacetimidate 15. Removal of the 4b,6b-O-benzylidene group of tetrasaccharide 16 gave the lacto-N-tetraose acceptor 17, to afford the protected octasaccharide 18 on glycosylation with donor 15. Complete deprotection of the octasaccharide by way of 19 afforded target human milk oligosaccharide 1 in a short and efficient route.