Yuehchukene synthesis

Cheng and Cheung also employed a 2-indolylzinc chloride 72 to couple with indole 71 in a synthesis of "inverto-yuehchukene" 73 [104]. Other Pd catalysts were no better in this low-yielding process. 

Electrophilic substitution of indole. This reaction strictly exploits the Lewis acidity of the LiClOa-Et system. It can be applied to a synthesis of yuehchukene. 

Scheme 12 Using Katritzky method in total synthesis of yuehchukene...

The above reaction sequence (Scheme 11), sometimes called the Katritzky method, has been exploited by a number of research groups for the preparation of 2-substituted IV-unsubstituted indoles [83, 102, 130, 218, 240-245], Gribble and Bergman used this chemistry to prepare 2-bromoindole and 2-iodoindole [246-248]. Bergman and Janosik further explored this sequence to prepare indol-2-yl sulfides and selenides [57,249,250]. Hudkins has used this chemistry to prepare 2-hydroxyatkylindoles en route to indolocarbazole derivatives [251, 252], The first step in Bergman s short total synthesis of yuehchukene used the Katritzky method and aldehyde 59, which gave 2-(hydroxyalkyl)indole 60 (Scheme 12) [253, 254]. 

Abstract The occurrence, structure, physiological activities as well as the synthesis of alkaloids having a carbazole skeleton is briefly reviewed. Emphasis is made on the synthesis, in particular on approaches towards girinimbine and the carbazomycines. Some new synthetic approaches based on indoles and 2-vinylindoles, and the use of carbazoles in the synthesis of the cyclopent[b]indole alkaloid yuehchukene will also be discussed. 

In another project aimed at the synthesis of cyclopent [h>]-indole alkaloids such as yuehchukene (29)which exhibits anti implantatory effects, it was found that carbazole derivatives like 27 could be readily prepared (Scheme 13). After dehydrogenation to 28, a dienone rearrangement gave the desired carbazole 26b. 

Yuehchukene is a novel class of bisindole alkaloids, first isolated as a racemate from Murraya paniculata, with a basic structure of hexahydroindeno[2,l-h]indole. It has been suggested that this compound exhibits mixed estrogen and antiestrogen activities as well as potent anti-implantation. In 2000 Ishikura and his team reported a concise procedure for their preparation a carbonylation reaction was applied for intermediate synthesis (Scheme 10.19) [94]. 

Kong, Y. C. and Cheng, K. F. 1989. Yuehchukene analogs and derivatives and related indoles, useful as female fertility-regulatmg agents, their synthesis, and pharmaceutical preparations. Brit U. K. Pat Appl. GB 2207670 A 19890208. 

This allylic substitution with LPDE is highlighted in the total synthesis of Yuehchukene (Scheme 3.12). 

Scheme 3.12 Synthesis of Yuehchukene utilizing an allylic substitution with LPDE.

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