AIDS-005481 AIDS005481 Penicillin deriv. [2R-[2.alpha.(R*),4.beta.(S)]]-5,5-Dimethyl-.alpha.-[(phenylacetyl)amino]-N-(phenylmethyl)-4-[[[1-(2-phenyl-1-(methyl)ethyl]amino]carbonyl]-2-thiazolidineacetamide