Studies on the Chinese Crude Drug "Shoma." IV. Structure of Acetyl Shengmanol Xyloside, a Probable Precursor of some Known Cimicifuga Glycosides

Abstract

Acetyl shengmanol xyloside (I) (monohydrate) isolated from the underground part of Cimicifuga japonica (Ranunculaceae) has mp 280-281°, [α] D-23.7°. The peracetate (II) of I afforded, on acid hydrolysis in aq. methanol, 25-O-methyl cimigenol (VI) along with cimigenol (IV) and isodahurinol (V). I yielded 25-O-methyl cimigenol xyloside (VI) and 25-O-acetyl cimigenol xyloside (VII) on a mild treatment with p-toluene sulfonic acid in methanol, while it afforded cimigol 3-xyloside (VIII) on alkali treatment. This transformation of I into VI, and its stereoisomer (VIII) at C-15 and -24 was rationalized in view of different modes of reaction to open the epoxide ring of I on the acidic and the alkaline conditions. Acetyl shengmanol xyloside (I) was degradated with periodate in a solution of cyclohexylamine to afford an aldehyde-carboxylic acid, methyl ester (XIII) of which has structure (XV). On enzymatic hydrolysis, I yielded its genuine aglycone acetyl shengmanol (XVI), [α] D-16.1°, as an amorphous powder. The sugar moiety of I was concluded to be attached to C-3 oxygen of the genin (XVI) as β-D-xylopyranose. On the basis of chemical and spectral data, the structure of acetyl shengmanol xyloside (I) was proposed to be 23R, 24S-3β, 15ξ-dihydroxy-23-acetoxy-24, 25-epoxy 9, 19-cyclolanostan-16-one-3β-D-xylopyranoside. This xyloside (I) is unstable even in the separation procedures from the plant materials, and seems to be a precursor of naturally occurring xylosides of cimigenol, cimigol and their derivatives in C. japonica.