(R)-2-[6-(1,2-Dihydroxy-ethyl)-2,2,4,6-tetramethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-yl]-isoxazolidine-3-carboxylic acid tert-butyl ester 87423-27-6 AIDS-050817 AIDS050817 NSC357584