Patent ID: 7709510

Claim:
A compound having the formula: wherein R 6 is R 8 is isopropyl, isobutyl, methoxycarbonyl, methyl-pyridin-2-yl, 2-benzyloxyethyl or methyl-thienyl-CH 2 —; R 9 is hydrogen, ethyl, isopropyl, isobutyl, benzyl or 2-methylsulfonyl-ethyl; and R 13 is 2-chloroethyl, 2-methoxyethyl, 5-ethoxycarbonylpentyl, methyl-pyridin-3-yl, 2-benzyloxyethyl or 4-substituted phenyl where the substituent is trifluoromethyl, chloro, bromo, fluoro, cyano, methoxy, butoxy, cyanomethyl or methoxycarbonyl; or a pharmaceutically acceptable salt thereof.