Solanum Alkaloids, 126. Degradation of Solasodine to 16β,22-Epoxy-23,24-dinorchol-5-ene-3β,22β-diol and Partial Synthesis of (23s)-23-Hydroxysolasodine
✍ Scribed by thi Quyen, Le ;Ripperger, Helmut ;Adam, Günter ;Schreiber, Klaus
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 625 KB
- Volume
- 1993
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
(22__R__,23__S__,25__R__)‐N‐Chloro‐22,26‐epiminocholest‐5‐ene‐3β,16β,23‐triol (11) and its 3,16,23‐O‐triacetyl derivative 15 were prepared from solasodine (1). Treatment of 11 or 15 with sodium methanolate yielded the 22,23‐secoaldehyde 16 as major product (Grob fragmentation) and (23__S__)‐23‐hydroxysolasodine (2) as minor product (Ruschig reaction). Hydrolysis of 16 with methanolic hydrochloric acid afforded 16β,22‐epoxy‐23,24‐dinorchol‐5‐ene‐3β,22β‐diol (17) and its 22‐O‐methyl derivative 18, the 3‐O‐acetate 19 of which was oxidized to the known acetyldiosgenin lactone (20), thus confirming the structures of 16–19. Compound 2 was shown to be identical in every respect with a rare spirosolane alkaloid, recently isolated from some Solanum species. Photolysis of (22__R__,23__S__,25__R__)‐3β,16β‐diacetoxy‐N‐chloro‐22,26‐epiminocholest‐5‐en‐23‐ol (10) yielded also via 22,23‐carbon‐carbon cleavage (20__S__)‐3β,16β‐diacetoxypregn‐5‐ene‐20‐carbaldehyde (21) as major product, which was converted by treatment with methanolic hydrochloric acid into the compound 18.