51 Gorgosterolの立体選択的合成

概要

論文の詳細を見る
Gorgosterol (1), isolated from the gorgonian, Plexaura flexuosa and the zoanthid, Palythoa tuberculosa, is a typical sterol with an unprecedented side chain. A common structural feature of 1 and the related demethylgorgosterol (2) is the presence of cyclopropane ring in the side chain having 22R, 23R, 24R stereochemistry. Although the synthesis of 2 was completed by us and other group several years ago, synthesis of 1 has not been reported so far. Herein, the first synthesis of 1 will be described. The three chiral centers mentioned above were constructed by highly stereoselective orthoester Claisen rearrangement and cyclopropane ring formation by intramolecular alkylation. First, in order to establish a stereoselective method for the introduction of desired C-22 stereochemistry, orthoester Claisen rearrangement of (22E)- and (22Z)-allylic alcohols 5 and 6 was investigated. The rearrangement of 5 was found to afford the ester 7ab in a satisfactory selectivity (5:1), which was converted to the lactones 8 for which the stereochemical assignment was carried out. Second, cyclopropane ring formation of the mesylate 11, obtained from the lactone 8a in three steps, was tried in a variety of conditions, one of which was revealed suitable in this case affording the ester 12 stereoselectively (>20:1). Third, the elaboration of the remaining side chain was attempted in two different routes, that is via the alcohols 15 and 16. Fortunately, the latter route gave a titled compound in good stereoselectivity (8:1) in respect of C-24 center. Structure of 1 was fully confirmed by m. p., mixed m. p., ^1H-NMR, and capillary GLC (OV-101).
天然有機化合物討論会の論文
1983-09-15

51 Gorgosterolの立体選択的合成

スポンサーリンク

概要

著者

関連論文

スポンサーリンク