THIOTROPOCIN BIOSYNTHESIS - SHIKIMATE ORIGIN OF A SULFUR-CONTAINING TROPOLONE DERIVATIVE

Feeding of [U-C-13(6)]glucose to Pseudomonas CB-104 gave labeled thiotropocin (1a and 1b). The C-13 NMR spectrum of the derived p-bromobenzyl thioether (2a and 2b) displayed a pattern of enhancements and couplings consistent with a shikimate origin for thiotropocin by way of a symmetrical phenylpyruvate (11) intermediate. The latter metabolite is proposed to undergo oxidative ring expansion followed by further oxidation and oxygen-sulfur exchange. These conclusions were further supported by specific and efficient incorporation of both [3-C-13]phenylalanine (13) and [1,2-C-13(2)]phenylacetic acid (12) into thiotropocin.