Synthesis of Eudistomins(I). Preparation of ($\pm$)-N(10)-Benzyloxycarbonyldebromoedudistomin L.

Four plausible precursors (21, 22, 24, and 25), just prior to formation of the oxathiazepine ring in eudistomin, were synthesized by the Pictet-Spengler condensation of N-hydroxytryptamine (15) or N-hydroxytryptophan ester (19) with cysteinal derivatives (5 and 10). In the case of the parent compound (21), one of these four precursors, treatment with dihalomethane in the presence of a phase transfer catalyst gave an eudistomin analogue (26) having the oxathiazepine ring in 35-50% yield.

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