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DOI: 10.1055/s-1997-1193
Total Synthesis of Racemic and Optically Active Sarkomycin
Publication History
Publication Date:
31 December 2000 (online)
trans-3-Carboxy-2-diethoxyphosphorylcyclopentanone (11), a key precursor of sarkomycin 1, has been synthesized in the rhodium(II) acetate promoted cyclization of diethyl 1-diazo-2-oxohept-6-enephosphonate (9), followed by transformation of the 3-vinyl moiety into the 3-carboxylic group. Racemic 11 has been resolved into enantiomers via diastereoisomeric enamine-type derivatives 13 resulting from its reaction with (-)-(S)-1-(1-naphthyl)ethylamine. The structure and absolute configuration of 13 have been determined by X-ray crystal structure analysis. The enantiomerically enriched (up to 77.6% ee) acid 11 has also been obtained in the enzyme-promoted hydrolysis of racemic 2-diethyoxyphosphoryl-3-methoxycarbonylcyclopentanone (12). The Horner-Wittig reaction of 11 with gaseous formaldehyde has been applied to introduce the exocyclic α-methylene moiety into the cyclopentanone system and thus to complete the synthesis of the racemate and, for the first time, each enantiomer of sarkomycin 1. A phenomenon of enantiomer self-discrimination has been observed in 31PNMR spectra of the nonracemic acid 11 and explained in terms of the formation of the hydrogen bonded homo- and hetero-dimers. The existence of dimeric structures has been confirmed by X-ray analysis of the structurally closely related trans-3-carboxy-2-diphenylphosphinoyl-cyclopentanone (16).
sarkomycin - resolution - enantiomer self-discrimination - enzymatic hydrolysis