Preparation of benzene, furan, and thiophene analogs of duocarmycin SA employing a newly-devised phenol-forming reaction |
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Authors: | Muratake H Hayakawa A Natsume M |
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Institution: | Research Foundation Itsuu Laboratory, Tokyo, Japan. |
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Abstract: | Five A-ring analogs of duocarmycin SA 9a-e were synthesized in racemic form modifying our second synthetic route toward duocarmycin SA. The problem encountered at the crucial phenol forming step to secure 17a, b from 16a, b under the conventionally used Kuwajima conditions was overcome by devising a more convenient method: simple heating of 16a-c in benzene in the presence of bis(triphenylphosphine)palladium(II) chloride (10 mol%), cesium carbonate (3 eq), and triphenylphosphine (0.3 eq) gave 17a-c in high yields of 86-91%. The intermediates 17a-e were readily led to the A-ring analogs (+/-)-9a-e almost according to the reported route. |
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