Add time:09/08/2019         Source:sciencedirect.com

2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-glucopyra-nosyl chloride was condensed with the N-(benzyloxycarbonyl) derivatives of, respectively, L-seryl-glycine ethyl, L-seryl-L-alanine methyl, L-seryl-L-phenylalanine methyl, and L-seryl-L-aspartic dibenzyl esters to give (3-O-GlcpNAc-CbzN-L-Ser)-GlyOEt (8), (3-O-GlcpNAc-CbzN-L-Ser)-L-AlaOMe (9), (3-O-GlcpNAc-CbzN-L-Ser)-L-PheOMe (10), and (3-O-GlcpNAc-CbzN-L-Ser)-L-Asp(diOBzl) (11), respectively; O-(2-acetamido-3,4,6-tri-O-acetyl-β-D-glucopyranosy-l)-N-(benzyloxycarbonyl)-L-serine methyl ester was deblocked by treatment with hydrobromic acid in glacial acetic acid, followed by triethylamine, to give a glycoamino acid that was condensed with the N-(benzyloxycarbonyl) derivatives of the p-nitrophenyl ester of glycine, L-alanine, and L-proline, respectively, to give CbzNGly-(3-O)-Glcp NAc-L-SerOMe) (17), CbzN-L-Ala-(3-O-GlcpNAc-L-SerOMe), and CbzN-L-Pro-(3-O-GlcpNAc-L-SerOMe), respectively. Similarly, the glycopeptide resulting from 8 was condensed with the activated esters of glycine, L-alanine, L-phenylalanine, L-proline, and L-serine, respectively, to give CbzNGly-(3-OGlcpNAc-L-Ser)-GlyOEt, CbzN-L-Ala-(3-O-GlcpNAc-L-Ser)-GlyOEt, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-GlyOEt, and CbzN-L-Ser-(3-O-GlcpNAc-L-Ser)-GlyOEt, respectively; that from 9, with the p-nitrophenyl esters of glycine1,L-alanine, L-phenylalanine, L-proline, and L-leucine, respectively, to give CbzNGly-(3-O-GlcpNAc-L-Ser)-L-AlaOMe, CbzN-L-Ala(3-O-GlcpNAc-L-Ser)-L-AlaOMe, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L]-AlaOMe, CbzN-L-Pro-(3-O-GlcpNAc-L-Ser)-L-AlaOMe, and CbzN-L-Leu-(3-O-GlcpNAc- L-Ser)-L-AlaOMe, respectively; that from 10, with the derivatives of glycine, L-alanine, L-phenylalanine, and L-leucine, respectively, to give CbzNGly-(3-O-GlcpNAc-L-Ser)-L-PheOMe, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L-PheOMe, CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L-PheOMe, and CbzN-L-Leu-(3-O-GlcpNAc-L-Ser)-L-PheOMe, respectively; and that from 11, with the derivatives of glycine, L-alanine, L-phenylalanine, L-proline, and L-leucine, respectively, to give CbzNGly-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), CbzN-L-Ala-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), CbzN-L-Phe-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), CbzN-L-Pro-(3-O-GlcpNAc-L-Ser)-L-Asp(diOBzl), and CbzN-L-Leu-(3-O-GlcpNAc-L-Ser)-L-Asp-(diOBzl), respectively. O-(2-Acetamido-3,4,5-tri-O-acetyl-2-deoxy-β-D-gluco-pyranosyl)-N-(benzyloxycarbonyl)- L-asparaginylglycyl-L-serine methyl ester (20) was synthesized by treating the free amine of 17 with the p-nitrophenyl ester of N-(benzyloxycarbonyl)-L-asparagine. 2-Acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbo-nyl)-L-aspart-1-oyl-(glycyl-L-serine methyl ester)-4-oyl]-2-deoxy-β-D-glucopyranosylamine (41) was synthesized by the condensation of 2-acetamido-3,4,6-tri-O-acetyl-1-N-[N-(benzyloxycarbo-nyl)-L-aspart-4-oyl]-2-deoxy-β-D-glucopyranosylamine with glycyl-L-serine methyl ester. Attempts to transfer the 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-D-glucopyranosyl group from the hydroxyl group of L-serine in 20 to the amido group of L-asparagine, to give 41, were unsuccessful. The β-elimination of some of the glycodi- and glycotri-peptides was studied.

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