DEVELOPMENT, SYNTHESIS, AND BIOLOGICAL EVALUATION OF (-)-TRANS-(2S,5S)-2-[3-[(2-OXOPROPYL)SULFONYL]-4-NORMAL-PROPOXY-5-(3-HYDROXYPROPOXY)-PHENYL]-5-(3,4,5-TRIMETHOXYPHENYL)TETRAHYDROFURAN, A POTENT ORALLY ACTIVE PLATELET-ACTIVATING-FACTOR (PAF) ANTAGONIST AND ITS WATER-SOLUBLE PRODRUG PHOSPHATE ESTER

(-)-trans-(2S,5S)-2-[3-[(2-Oxopropyl)sulfonyl]-4-n-propoxy-5-(3-hydroxypropoxy)phenyl]-5- (3,4,5-trimethoxy-phenyl)tetrahydrofuran (10) is one of the most potent platelet-activating factor (PAF) antagonists in vitro and in vivo developed to date. This diaryltetrahydrofuran derivative evolved from modifications of MK 0287 which has been evaluated in clinical studies for asthma. Two structural modifications of MK 0287 were made: (1) elaboration of the 3'-[(hydroxyethyl)sulfonyl] group to a beta-keto propylsulfonyl, and (2) replacement of the 5'-methyl ether by a 3-hydroxypropyl ether. Compound 10 potently and specifically inhibits the binding of [H-3]-C18-PAF to human platelet membranes (K(i) 1.85 nM) and PMN membranes (K(i) 2.89 nM). In vivo, 10 inhibits PAF-induced plasma extravasation and elevated N-acetyl-beta-D-glucosaminidase (NAGA) levels in male rats with ED50 values of 60-mu-g/kg, po and 4-mu-g/kg, iv respectively, and inhibits PAF-induced bronchoconstriction in guinea pigs with an ED50 value of 15-mu-g/kg after intraduodenal administration. Compound 15, a water-soluble phosphate ester prodrug derivative of 10 is at least equipotent to 10 in the in vivo models. Compound 19S, the primary and major metabolite of 10 and 15, is equipotent in in vitro and in vivo models.