ESTERASE-CATALYZED REGIOSELECTIVE 6-DEACYLATION OF HEXOPYRANOSE PER-ACETATES, ACID-CATALYZED REARRANGEMENT TO THE 4-DEPROTECTED PRODUCTS AND CONVERSIONS OF THESE INTO HEXOSE 4-SULFATES AND 6-SULFATES

The esterase from Rhodosporidium toruloides has been used to catalyse the hydrolysis of a series of per-acetylated alpha-D-hexopyranoses and alpha-D-hexopyranosides. Per-acetylated glucose 4, mannose 6, N-acety lgalactosamine 8, galactose 10, methyl alpha-D-glucoside 12, methyl al pha-D-mannoside 14 and methyl alpha-D-galactoside 16 have been selecti vely cleaved at the C-6 position by the esterase to give the 6-OH deri vatives 5, 7, 9, 11, 13, 15 and 17. Acid-catalysed rearrangement of ac etates 5, 7, 13, 15, 11, 17 and 9 with 4-->6 acetyl migration gives th e corresponding 4-deprotected derivatives 22-28, respectively. Hydroly ses of beta-D-glucose pentaacetate 20 and alpha-D-lactose octaacetate 21 have been attempted, but no hydrolyses have been observed. 1,2,3,6- Tetraacylated alpha-D-hexopyranoses 3 and 22, derivatives of N-acetylg lucosamine and glucose respectively and 2,3,6-triacetylated alpha-D-he xopyranosides 24 and 25, derivatives of glucose and mannose, respectiv ely, have been hydrolysed by the esterase to the corresponding 4,6-dih ydroxy acetates 29, 18, 30 and 31. Acylation of methyl alpha-D-glucopy ranoside 32 catalysed by the esterase provides the C-6 monoacetate 33 and the C-3 monoacetate 34 in 4 and 5% yield, respectively. The sodium salts of N-acetylglucosamine, glucose, N-acetylgalactosamine, galacto se and mannose 6-sulfates 38-42, respectively, are prepared in two ste ps from the 6-deacetylated hexopyranoses 2, 5, 9, 11 and 7, respective ly. The sodium salts of N-acetylglucosamine, glucose and mannose 4-sul fates 43-45, respectively, are prepared in two steps from the 4-deacet ylated precursors 3, 22 and 26 which are obtained via acid catalysed 4 -->6 acyl migration of compounds 2, 5 and 7.