Amides Sharpless asymmetric

Phenylalanine-derived oxazolidinone has heen used in O Scheme 52 as a chiral auxiliary for as)rmmetric cross-aldolization (Evans-aldol reactions [277,278,279,280,281,282,283,284, 285]). The 6-deoxy-L-glucose derivative 155 has heen prepared by Crimmins and Long [286] starting with the condensation of acetaldehyde with the chlorotitanium enolate of O-methyl glycolyloxazohdinethione 150. A 5 1 mixture is obtained from which pure 151 is isolated by a single crystallization. After alcohol silylation and subsequent reductive removal of the amide, alcohol 152 is obtained. Swem oxidation of 152 and subsequent Homer-Wadsworth-Emmons olefination provides ene-ester 153. Sharpless asymmetric dihydroxylation provides diol 154 which was then converted into 155 (O Scheme 60) (see also [287]). 

The O-benzylated aldehyde 517 was also coiu erted into the a,p-unsaturated ester 522 through Wadsworth-Emmons reactioiT-- with ethyl 2-(diethoxyphosphono)acetate5 ° in excellent yield (Scheme 88). The intermediate alkene 522 was subjected to Sharpless asymmetric dihydroxylalion " to afford the diol ester 523 in excellent yield and with a diastereoselectivity in excess of 95 5. Subsequent to alkali-catalyzed hydrolysis of 523, the carboxylic acid obtained was condensed with the p-lolucncsulfonalc salt of glycine benzyl ester or phenylalanine benzyl ester, by the action of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), to afford the benzyl-protected amide derivatives catalytic... 

Recently Lee and his collaborators reported a new route to the /3-lactam taxol side chain precursor through a /3-bromo amide (249). Thus, Sharpless asymmetric dihydroxylation of a cinnamide gave the diol 7.1.18 in 94-96% ee. After converting the diol to /3-bromo amide 7.1.19, treatment with TBAF or NaH gave the /3-lactam 7.1.20 in 93-94% yield without significant loss of optical purity. 

The most impressive methodology utilizing CT, which has been developed by the group of Sharpless, is the vicinal aminohydroxylation of olefins catalyzed by osmium tetroxide [15]. The method has been elegantly extended to a practical asymmetric synthesis [16]. The reaction system was employed to the achiral aminohydroxylation of a,P-unsaturated amides to afford two hydroxysulfonamide regio-isomers. The crude mixtures were cyclized to the aziridines in a one-pot procedure, without the need for purification of the intermediates [17] (Scheme 10). 

Demko, Z. P., Bartsch, M., Sharpless, K. B. Primary Amides. A General Nitrogen Source for Catalytic Asymmetric Aminohydroxylation of Olefins. Org. Lett. 2000, 2, 2221-2223. 

Applications of chirally modified titanium Lewis acids have been reported most cases use various acetal diols derived from tartrate as the chiral auxiliary26 33,31 90. Various methods of catalyst preparation are known, as well as the use of different types of dienes (open-chained, cyclopentadiene) and dienophiles (acroleins, acrylates, crotonates, fumarates and amides derived from oxazolidinone), including intramolecular cycloaddition30. Addition of 4 A molecular sieves can improve asymmetric induction31,34 (as observed with the Sharpless epoxidation, loc. cit 31 in ref 6) and shows remarkable solvent effects on enantioselectivity. This method has been applied to the asymmetric Diels-Alder cycloaddition of cyclopentadiene and open-chain dienes to acrylamides28, 35. 

Weber, R Bruckner, R. Asymmetric Dihydroxylation of Esters and Amides of Methacrylic, Tiglic, and Angelic Acid No Exception to the Sharpless Mnemonic Eur. ]. Org. Chem. 2015,2015, 2428-2449. 

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