Cis-1,2-dihydrocatechol → Cyclohex-5-ene-1,2,3,4-tetrol

Beteiligte Stoffe

Reaktionsschritte

Compound 7 was readily obtained in large quantity and enantiomerically pure form by the biotransformation of iodobenzene using the genetically engineered micro-organism E. coli JM109 (pDTG601) which over expresses toluene dioxygenase (TDO), the enzyme responsible for this dihydroxylation reaction. In the first step of the reaction sequence, cis-1,2-dihydrocatechol 7 was converted into the corresponding acetonide, 8, under standard conditions. The acetonide was immediately reacted with ml-chloroperbenzoic acid (m-CPBA) so as to produce, in a completely regio- and diastereo-selective manner, the epoxide 10. This compound represented a potent electrophile which reacted with a range of nucleophiles at the allylic carbon of the epoxide ring so as to give conduritol and conduramine derivatives. In particular, reaction of compound 10 with 1,6-hexadiamine in dichloromethane at 18° C. for 4 days gave the dimeric species 11 in quantitative yield. The readily obtained bis-acetamido-derivative, 12, of the latter compound was subject to a Pd[0]-mediated carbomethoxylation reaction thereby producing the diester 13 wherein each six-membered ring incorporates an exocyclic carbon in an appropriate oxidation state as required for elaboration to pseudo-sugars.

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