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The labile tert-butyldimethylsilyl esters of the azetidinones 6-8b served as the crucial synthons in the preparation of the potentially useful ylide pyridyl thio esters 18-20. These intermediates were utilized to synthesize a host of title carbapenems 25-30d, 32, and 49-53. The antimicrobial properties and DHP-I susceptibility of these carbapenems were studied with reference to thienamycin.

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1) Total Synthesis of &Lactam Antibiotics. VI: R. A. Firestone, N. S. Macie-(2) R. W. Ratcliffe and B. G. Christensen, Tetrahedron Lett., 4645, 4649, (3) (a) We propose the name l-oxacephalothin for7&hienybcetamiloxadethiicephalosporanic acid. (b) A l-oxadethiicepham has been reported.

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2006 Benzopyran derivatives R 0350 6H-Benzo[c]chromen-6-one Derivatives as Selective ERβ Agonists. -Products (III) and (VII) exhibit the highest agonistic activity of all compounds tested (no yields given). -(SUN*, W.; CAMA, L. D.; BIRZIN, E. T.; WARRIER, S.; LOCCO, L.; MOSLEY, R.; HAMMOND, M. L.; ROHRER, S. P.; Bioorg.

Carbapenems are intravenous lifesaving hospital antibiotics. Once patients leave the hospital, they are sent home with antibiotics other than carbapenems since they cannot be administered orally due to lack of oral absorption primarily because of very highly polarity. A prodrug approach is a bona fide strategy to improve oral absorption of compounds. Design and synthesis, in vitro and in vivo evaluation of diversified prodrugs of ertapenem, one of the only once daily dosed carbapenems is described. Many of the prodrugs prepared for evaluation are rapidly hydrolyzed in rat plasma. Only bis-(5-methyl-2-oxo-1,3-dioxol-4-yl)methyl (medoxomil) ester prodrug was rapidly hydrolyzed in most of the plasmas including rat, human, dog, and monkey. Although the rate of conversion of ertapenem diethyl ester prodrug (6) was slow in in vitro plasma hydrolysis, it showed the best in vivo pharmacokinetic profile in dog by an intraduodenal dosing giving >31% total oral absorption.