Abstract
Glycosylation of the dammar-24-ene-3,12β,20( S)-triols with 2,3,4,6-tetra- O-acetyl-α- d-glucopyranosyl bromide ( A) in the presence of silver oxide in dichloro-methane gives a mixture of the acetylated 3-, 12-, 20-, 3,12-di-, and 3,20-di- O-β- d-glucopyranosyl derivatives in a total yield of 83–84.5%. Under similar conditions, the 3- O-acetyl derivatives of dammar-24-ene-3,12β,20( S)-triols give a mixture of 12- and 20- O-β- d-glucopyranosyl derivatives. Condensation of betulafolienetriol [dammar-24-ene-3α,12β,20( S)-triol] both with the glycosyl bromide A in the presence of mercuric cyanide in nitromethane and with 3,4,6-tri- O-acetyl-β- d-glucopyranose 1,2-( tert-butyl orthoacetate) in the presence of 2,4,6-trimethyl-pyridinium perchlorate in chlorobenzene under azeotropic distillation results in dehydration and 20-dehydroxyglucosides are formed.
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