Synthesis and reactions of d-glucopyranosyl esters of phenylalanine and tyrosine: a study of the diazomethanecatalysed 1→2 acyl migration of the N-acylated α- d anomers

• Published in: Carbohydrate research 1980, Vol.80 (1), p.63-74
• Main Authors: Keglević, Dina, Pongračić, Mario, Horvat, Jaroslav
• Format: Article
• Language: English
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/S0008-6215(00)85315-X

The fully benzylated α- and β- d-glucopyranosyl esters of N-benzyloxycarbonyl-and N- tert-butoxycarbonyl- l-phenylalanine ( 1 and 5, respectively) have been converted into l- O-( l-phenylalanyl)-α- and -β- d-glucopyranose, which were isolated as trifluoroacetate salts ( 2α and 2β). On dissolution in water, l- O-[ N-( tert-butoxycarbonyl)- l-phenylalanyl]-α- d-glucopyranose ( 6α) gave the anomerised C-2 isomer 8 and hydrolysis products of 6α. Treatment of 6α with N, N-dimethylformamideethereal diazomethane gave the 2- O-acyl derivative 8α (>80%). l- O-( l-Tyrosyl)-α-( 12α) and β- d-glucopyranose ( 12β), isolated as the trifluoroacetate salts, were prepared from 2,3,4,6-tetra- O-benzyl-l- O-[ N-benzyloxycarbonyl- O-( tert-butyl)- l-tyrosyl]-α- and -β- d-glucopyranose ( 10) and characterised as the N-acetyl- ( 13) and tetra-acetate derivatives ( 14). Treatment of 13α with diazomethane caused extensive hydrolysis, but some rearrangement into the 2- O-acyl derivative 15α, which was characterised as crystalline 1,3,4,6-tetra- O-acetyl-2- O-( N-acetyl- O-acetyl- l-tyrosyl)-α- d-glucopyranose ( 16α). The foregoing l→2 acyl migrations and hydrolyses are competitive reactions, the relative rates of which are strongly affected by reaction temperature and the nature of the acyl group.