Enzymic glycosylation of (±)-(3,5/4,6)-3,6-diazido-4,5-dihydroxycyclohexene. A way to prepare stereochemically pure and enzyme resistant, basic pseudo-disaccharides as competitive enzyme inhibitors

By β-d-galactosylation of (±)-(3,5/4,6)-3,6-diazido-4,5-dihydroxycyclohexene, pure (+)-(3,5/4,6)-3,6-diazido-4-O-(β-d-galactopyranosyl)-5-hydroxycyclohexene (3) was obtained. The diamine (+)-(1,3/2,6)-3,6-diamino-1-O-(β-d-galactopyranosyl)-2-hydroxycyclohexane, derived from compound 3 by catalytic hydrogenation, is stable against enzymic cleavage and competitively inhibits β-d-galactosidase from Escherichia coli with a Ki-value of 5.5 mM. Sigmatropic rearrangement of 3 in methanolic solution partially led to an unseparable mixture of the regioisomers (3,5/4,6)-3,4-diazido-5-O-(β-d-galactopyranosyl)-6-hydroxycyclohexene and (3,5/4,6)-3,4-diazido-6-O-(β-d-galactopyranosyl)-5-hydroxycyclohexene. Catalytic hydrogenation thereof yielded an equally unseparable mixture of the diamines (1,3/2,4)-1,2-diamino-3-O-(β-d-galactopyranosyl)-4-hydroxycyclohexane and (1,3/2,4)-1,2-diamino-4-O-(β-d-galactopyranosyl)-3-hydroxycyclohexane, inhibiting β-d-galactosidase competitively with Ki 0.9 mM.