Glycosidase-catalysed synthesis of glycosides by an improved procedure for reverse hydrolysis: Application to the chemoenzymatic synthesis of galactopyranosyl-(1->4)-O-alpha-galactopyranoside derivatives.

beta-Galactosidase from Aspergillus oryzae, alpha-galactosidase from Aspergillus niger, beta-mannosidase from He[ir pomatia and beta-glucosidase from almond were used to synthesise different glycosides by reverse hydrolysis: Glc beta O(CH2)(6)OH 1 was obtained in 61% yield, beta-D-Glc-O(CH2)(3)CH=CH2 2 in 50% yield, beta-D-Glc-O(CH2)(2)Si(Me)(3) 3 in 11% yield, beta-D-Gal-O(CH2)(6)OH 4 in 48% yield, beta-D-Gal-O(CH2)(3)CH=CH2 5 in 22% yield, alpha-D-Gal-O(CH2)(6)OH 6 in 47% yield, alpha-D-Gal-O(CH2)(3)CH=CH2 7 in 37% yield and beta-D-ManO(CH2)(6)OH 8 in 12% yield. Using the appropriate glycosides methyl O-(2,3,4,6-tetra-O-benzyl-alpha-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzoyl-1-O-alpha-D-galactopyranoside 11 and 6'-benzoylhexyl-O-(2,3,4,6-tetra alpha-O-benzyl-(1-->4)-2,3,6-tri-O-benzoyl-1-O-beta-D-galactopyranoside 15 were synthesised. This chemoenzymatic approach avoided at least four chemical steps that would have been necessary in a conventional synthesis. Copyright (C) 1996 Elsevier Science Ltd