Dihydropyrones with improved antiviral activity

A compound or a pharmaceutically acceptable salt thereof of formula I

• wherein:
• R.sub.1 is H, 2- or 3- or 4- (CH.sub.2).sub.n' OR' or (CH.sub.2).sub.n' N(R').sub.2 where n' is 0 or 1 and wherein 2- or 3- or 4- refer to the point of substitution on the phenyl ring;
• R.sub.2 and R.sub.3 are independently H, OR, N(R).sub.2, a straight or branched alkyl of 1-4 carbons, a cycloalkyl of 3-6 carbons, F, Cl, Br, NRCOR, COR, CON(R).sub.2, OCOR, CO.sub.2 R, NRSO.sub.2 R, SO.sub.2 N(R).sub.2, NRSO.sub.3 R, NRSO.sub.2 N(R).sub.2, NRCON(R).sub.2, or R.sub.2 and R.sub.3 may be taken together to form a ring of 5-6 atoms optionally containing 1 or 2 heteroatoms;
• R.sub.4 is a straight or branched alkyl of 1-7 carbons, a cycloalkyl of 3-7 carbons, a heterocycle of 4-7 atoms containing 1-2 heteroatoms, or (CH.sub.2).sub.n Ph, all of which may be optionally substituted by F, Cl, Br, R, OR, SR, N(R).sub.2, CON(R).sub.2, NRCOR, SO.sub.2 R and COR;
• R.sub.5 is H, (CH.sub.2).sub.n OR, (CH.sub.2).sub.n N(R).sub.2, (CH.sub.2).sub.n NRCOR, (CH.sub.2).sub.n OSO.sub.2 N(R).sub.2, (CH.sub.2).sub.n OSO.sub.2 R, (CH.sub.2).sub.n NRSO.sub.2 N(R).sub.2, OCH.sub.2 CH.sub.2 OR, NRCH.sub.2 CH.sub.2 OR, (CH.sub.2).sub.n CN, (CH.sub.2).sub.n CON(R).sub.2, (CH.sub.2).sub.n NRCON(R).sub.2, C(CH.sub.3).sub.2 OR, (CH.sub.2).sub.n COR, (CH.sub.2).sub.n NRSO.sub.2 R, (CH.sub.2).sub.n CO.sub.2 R, O(CH.sub.2).sub.n" CO.sub.2 R, OCON(R).sub.2, NR(CH.sub.2).sub.n CO.sub.2 R, --(CH.sub.2).sub.n --NR--CS--N(R).sub.2, (CH.sub.2).sub.n -NRSO.sub.2 OR, wherein n is an integer of from 0 to 3;
• R.sub.6 is methyl, ethyl or isopropyl;
• R is independently H, a straight or branched alkyl of 1-5 carbons, a --(CH.sub.2).sub.n -cycloalkyl wherein the cycloalkyl is of 3-6 carbons and wherein n is an integer of from 0 to 3, --(CH.sub.2).sub.m --Ph, a (CH.sub.2).sub.m -heterocycle wherein the heterocycle is of 5-6 atoms with 1-3 heteroatoms and wherein m is an integer of from 0 to 3, and wherein the (R).sub.2 in N(R).sub.2 may be a heterocycle containing the nitrogen, all optionally substituted by F, Cl, Br, .dbd.O, --CN, --CF.sub.3, OR', COR', N(R').sub.2, CON(R').sub.2, or NR'COR';
• and
• R' is H, a straight or branched alkyl of 1-3 carbons, or Ph;
• and n" is an integer of from 1-2.