Phosphonamidate compounds

Claim 1

A compound of the formula ##STR321## and a pharmaceutically acceptable salt thereof wherein: Y is oxygen or sulfur and the R 16 groups join to complete an unsubstituted 5- or 6-membered ring or said ring in which one or more of the carbons has a lower alkyl of 1 to 4 carbons or a di(lower alkyl of 1 to 4 carbons) substituent; R 1 is hydrogen, lower alkyl, or cycloalkyl; R 2 is hydrogen, lower alkyl, halo substituted lower alkyl, ##STR322## or R 1 and R 2 taken together are --(CH 2 ) n -- wherein n is an integer from 2 to 4; R 3 and R 6 are independently selected from the group consisting of hydrogen, lower alkyl, benzyl, benzhydryl, and ##STR323## wherein R 17 is hydrogen, lower alkyl, cycloalkyl, or phenyl, and R 18 is hydrogen, lower alkyl, lower alkoxy, phenyl or R 17 and R 18 taken together are ##STR324## R 13 is hydrogen, lower alkyl of 1 to 4 carbons, lower alkoxy of 1 to 4 carbons, chloro, bromo, fluoro, trifluoromethyl, hydroxy, phenyl, phenoxy, phenylthio, or phenylmethyl; r is an integer from 1 to 4; q is zero or an integer from 1 to 7; s is an integer from 1 to 8; and p is one, two or three provided that p is more than one only if R 13 is hydrogen, methyl, methoxy, chloro, or fluoro.