GLYCOSYL ESTERS OF AMINO-ACIDS .9. DIAZOMETHANE-CATALYZED REARRANGEMENT OF ALPHA-D-GLUCOPYRANOSYL ESTERS OF N-ACYLAMINO ACIDS INTO 2-O-ACYLAMINOACYL-ALPHA-D-GLUCOPYRANOSES

Both anomers of 1-O-[N-(tert-butoxycarbonyl)-L-α-glutamyl]-d-glucopyranose (2) were converted into the unprotected 1-esters, characterised as the trifluoroacetate salts 3α and 3β. On esterification with diazomethane and acetylation, the N-acetylated derivative of 3β and 2β gave the peracetylated 1-O-[5-methyl N-acetyl- and -tert-butoxycarbonyl-L-glutam-1-oyl]-β-d-glucopyranoses (4β and 6β), respectively. Similar treatment of 2α and 3β led to acyl migration, to yield 1,3,4,6-tetra-O-acetyl-2-O-[5-methyl N-(tert-butoxycarbonyl)-L-glutam-1-oyl]-α-d-glucopyranose (7α,64%) with traces of 7β, and a mixture (≈2:1:0.2) of the N-acetyl analogue of 7α (8α), 4α, and 8β, respectively. Treatment of 1-O-[5-methyl N-(tert-butoxycarbonyl)-L-glutam-1-oyl]-α-d-glucopyranose (10) and the corresponding glutam-5-oyl isomer 12 in N,N-dimethylformamide with diazomethane for 1 h resulted in 1 → 2 O-acyl transfer to give, upon acetylation, 7α and the fully acetylated 2-O-[1-methyl N-(tert-butoxy- carbonyl)-L-glutam-5-oyl]-α-d>-glucopyranose in yields of 70 and 90 %, respectively; in the absence of diazomethane, 10 and 12 remained unchanged. Similar experiments with α-d-glucopyranosyl esters of N-acetylglycine, N-acetylalanine, and N-(tert-butoxycarbonyl)phenylalanine yielded the 2-O-acyl derivatives in high yields and with high retention of anomeric configuration. The structures of the rearrangement products were proved both spectroscopically and chemically. The results imply that diazomethane functions as a base in the migration process. © 1979.