Synthesis of β‐D‐Glucopyranosides of some Hydroxylated Vitamin‐D Compounds
Cholesta‐5, 7‐diene‐1α, 3β‐diol (1a) was glycosylated with ‘α‐acetobromoglucose’ (2) as well as with ‘α‐acetobromocellobiose’ (4) to yield the 3‐(glycosides) 1b and 1c, respectively. Irradiation of these products with UV light followed by thermal isomerization led to the corresponding vitamin‐D derivatives 3a and 3c. Direct glucosylation of vitamin D~3~ (3f) and vitamin D~2~ (5a) with 2 gave the derivatives 3g and 5b, respectively. With 25‐hydroxycholecalciferol ( = calcidiol; 6a) as substrate, besides the 3‐(glucoside) 6b small amounts of the C(25)‐analog 6c were formed. The reaction of 1α, 25‐dihydroxycholecalciferol ( = calcitriol; 6e) with 2 furnished the 3‐ and the 1‐(glucoside) (6f and 6g, respectively) as the major components and the C(25)‐analog 6h in minor quantity. From the acetylated 3‐(glucosides) 3a, 3g, 5b, 6b, and 6f, the free glucopyranosides 3b, 3h, 5c, 6d, and 6i, respectively, were prepared as well as the free glucopy‐ranosyl‐glucopyranoside 3d from the acetylated disaccharide 3c.