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The Efficient and Enantiospecific Total Synthesis of Cyclopenta[b]phenanthrenes Structurally-related to Neurosteroids.

ABSTRACT: We report an efficient synthesis of cyclopenta[b]phenanthrenes functionalized at C-3 and C-8 from an optically pure Hajos-Parrish ketone. The key step is a neutral alumina catalyzed Michael addition of a Hajos-Parrish ketone derivative (4) to 1,7-octadien-3-one (2) in 98% yield. This Michael addition product went through Krapcho decarbomethoxylation, aldol condensation, lithium liquid ammonia reduction, Wacker oxidation and acid catalyzed cyclization to form cyclopenta[b]phenanthrene (1a) in 37% overall yield for the 7 steps.

SUBMITTER: Qian M

PROVIDER: S-EPMC3183745 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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The Efficient and Enantiospecific Total Synthesis of Cyclopenta[b]phenanthrenes Structurally-related to Neurosteroids.

Qian Mingxing M Covey Douglas F DF

Advanced synthesis & catalysis 20101001 11-12

We report an efficient synthesis of cyclopenta[b]phenanthrenes functionalized at C-3 and C-8 from an optically pure Hajos-Parrish ketone. The key step is a neutral alumina catalyzed Michael addition of a Hajos-Parrish ketone derivative (4) to 1,7-octadien-3-one (2) in 98% yield. This Michael addition product went through Krapcho decarbomethoxylation, aldol condensation, lithium liquid ammonia reduction, Wacker oxidation and acid catalyzed cyclization to form cyclopenta[b]phenanthrene (1a) in 37% ...[more]

PMID: 22022301

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