Diastereoselective Synthesis of the HIV Protease Inhibitor Darunavir and Related Derivatives via a Titanium Tetrachloride-Mediated Asymmetric Glycolate Aldol Addition Reaction.

Darunavir is a potent HIV protease inhibitor that has been established as an effective tool in the fight against the progression of HIV/AIDS in the global community. The successful application of this drug has spurred the development of derivatives wherein strategic regions (e.g., P1, P1', P2, and P2') of the darunavir framework have been structurally modified. An alternate route for the synthesis of darunavir and three related P1 and P1' derivatives has been developed. This synthetic pathway involves the use of a Crimmins titanium tetrachloride-mediated oxazolidine-2-thione-guided asymmetric glycolate aldol addition reaction. The resultant aldol adduct introduces the P1 fragment of darunavir via an aldehyde. Transamidation with a selected amine (isobutylamine or 2-ethyl-1-butylamine) to cleave the auxiliary yields an amide wherein the P1' component is introduced. From this stage, the amide is reduced to the corresponding ß-amino alcohol and the substrate is then bis-nosylated to introduce the requisite p-nitrobenzenesulfonamide component and activate the secondary alcohol for nucleophilic substitution. Treatment with sodium azide yielded the desired azides, and the deprotection of the p-methoxyphenoxy group is achieved with the use of ceric ammonium nitrate. Finally, hydrogenation to reduce both the aniline and azide functionalities with concurrent acylation yields darunavir and its derivatives.

Diastereoselective and Enantioselective Synthesis of α-p-Methoxyphenoxy-ß-Lactones: Dependence on the Stereoelectronic Properties of the ß-Hydroxy-α-p-Methoxyphenoxycarboxylic Acid Precursors.

Treatment of ß-hydroxy-α-p-methoxyphenoxy carboxylic acids derived from the asymmetric glycolate aldol addition reaction with p-nitrobenzenesulfonyl chloride yielded divergent results depending on the nature of the ß-substituent of the carboxylic acid. Substrates bearing either alkyl substituents (R = -n-butyl, -n-octyl, -benzyl, isopropyl, -tert-butyl) or aryl systems bearing electron-withdrawing substituents (R = -p-C6H4Cl, -p-C6H4Br, -p-C6H4NO2) yielded ß-lactones. In contrast, α-p-methoxyphenoxy-ß-hydroxycarboxylic acids bearing electron-donating aryl groups or the sterically demanding 2-naphthyl group formed (Z)-alkenes.