Enantiomerically pure phosphonated carbocyclic 2'-oxa-3'-azanucleosides: synthesis and biological evaluation.

Starting from enantiomeric pure 1-[(3S,5R)- and 1-[(3R,5S)-3-(hydroxymethyl)-2-methylisoxazolidin-5-yl]-5-methylpyrimidine-2,4(1H,3H)-diones (-)7a and (+)7b, obtained by lipase-catalyzed resolution, pure diethyl{[(3S,5R)-2-methyl-5-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)isoxazolidin-3-yl]methyl}phosphonate (-)12a and diethyl{[(3R,5S)-2-methyl-5-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)isoxazolidin-3-yl]methyl}phosphonate (+)12b have been synthesized. The obtained compounds showed no cytotoxic activity versus the U937 cell line in comparison with AZT, and were poorly able to inhibit HIV infection in vitro.