1,3-Thiazol-5-ylmethyl N-[(1S)-1-((4S,6S)-4-Benzyl-2-oxo-1,3-oxazinan-6-yl)-2-phenylethyl]carbamate is an intermediate in synthesizing Bis(thiazol-5-yl-methyl)[carbonylbis[imino[(2S,3S,5S)-3-hydroxy-1,6-diphenylhexane-5,2-diyl]]]dicarbamate (R535035). Ritonavir Impurity P is derived from 2S,3S,5S-5-Amino-2-[N-[[(5-thiozolyl)methoxy]carbonyl]amino]-1,6-diphenyl-3-hydroxyhexane (A630525), which is an intermediate in the synthesis of Ritonavir (R535000), a selective HIV protease inhibitor.w