Optically active monoester 2, developed during the synthetic study on deoxyaminoglycoside antibiotic fortimicin A, is now available on a kilo gram scale by pig liver esterase catalyzed hydrolysis from the corresponding meso diester 1. Introduction of various function into the cyclohexene ring is now feasible by utilizing the carboxyl group, methoxycarbonyl group and carbon-carbon double bond in 2. Our synthetic study to other biologically important compounds disclosed that the monoester 2 was successfully converted to the key intermediates, 7, 30 and 33, of the A-ring of vitamin D_3 metabolites, thienamycin and 1β-methyl carbapenem, respectively. The key features of the synthesis of the A-ring synthon 7 include the stereo- and regioselective introduction of two hydroxyl groups at C-1 and C-3, and construction of Z-dienol structure through the bicyclic intermediate 8. Efficient route to 7 will be useful for the exploitation of structure activity relationships of this biologically potent compounds. The synthesis of thienamycin and 1β-methyl thienamycin demonstrates that the stereocontrolled reactions in the bicyclic β-lactam 22 are beautifully achieved. The synthetic routes shown here well demonstrated that 2 is significantly useful as a chiral synthon.
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