Reductive demercuration of organomercurials

Abstract

Organomercurials, which was generated by intra- and inter-molecular mercury-promoted electrophilic additions, have been reductively demercurated in situ efficiently using sodium borohydride in the presence of triethylborane at low temperature. The results of reductive demercuration under the conditions developed by us are described and compared with those under the best known method using sodium borohydride in the presence of phase transfer catalyst.12 Under our conditions, the frequently accompanying side reactions such as reductive elimination and oxidative demercuration have not been detected. For the synthesis of epoxy amino acid 13 as the key component of LB-7116, the key intermediate 49 has been synthesized from D-glucosamine hydrochloride. Conversion of 38 into cyanide 28 was unsuccessful. Alternatively, alcohol 45 was prepared from D-glucosamine over 11 steps. Alcohol 45 was sequentially converted into diacetonide, monoacetonide, tosylate and cyanide, of which the hydrolysis to carboxylic acid is in progress.