Transformed steroids—part 95

Kamernitzky, A. V.; Левина, И. С.; Mortikova, E. I.; Shitkin, V. M.; Él'yanov, B. S.

doi:10.1016/0040-4020(77)80328-1

Cited by 22 publications

(1 citation statement)

References 12 publications

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“…The need for high pressure to induce the cycloaddition of 8 to 7 is not without precedent. High pressures have proven effective in 1,3-dipolar cycloaddition reactions of azides, nitrones, nitronates, and diazomethane . Therefore, it seemed reasonable that the (3 + 2) cycloaddition might be achieved under conditions of higher pressure and temperature.…”

Section: Resultsmentioning

confidence: 99%

An Asymmetric Route to the Conanine BCDE Ring System. A Formal Total Synthesis of (+)-Conessine

1996

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The first enantioselective synthesis of the known (+)-conessine precursor (+)-benzohydrindan 23 from the chiral nonracemic bicyclic lactam 1 is described. The key transformation was the highly diastereoselective (3 + 2) cycloaddition of azomethine ylide 11a to lactam 7 in order to construct the pyrrolidine E ring system at any early stage in the synthesis. The requisite pyrrolidine methyl group at C-21 was stereoselectively installed late in the synthesis by lithiation of N-Boc-pyrrolidine intermediate 20 with sec-BuLi/TMEDA followed by quenching at −90 °C with iodomethane, furnishing the tetracyclic pyrrolidine 21. Reduction of t-Boc 21 with lithium aluminum hydride affords (+)-N-methyl tetracycle 23 in a concise 13-step synthesis from 1.

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