Conjugate Addition of Heteroatom Nucleophiles and Subsequent Nef Reaction

2 Conjugate Addition of Heteroatom Nucleophiles and Subsequent Nef Reaction 

StereocontroUed total syntheses of pemciJldnic aacl S.S-cLoxicle and fi-armnopenidllanic add fromCSi-asparadc acidandC/f./fi-tartaric acid, respectively, have been repcrted fEq 4 37  

The stereoselective synthesis ofruin -fi-amino-ct-hydroxy acid derivadves using nucleophilic epoxidadon of Tarydthio-Tnitroalkenes has been reported fEq. 4.411.  

Stereocontrolled total syntheses of penicillanic acid S. S -dioxide and 6-aminopenicillanic add from (5)-asparatic add and (i ,i )-tartaric add, respectively, have been reported (Eq. 4.37).45 

Diastereoselective conjugate addition of oxygen and nitrogen- centered nucleophiles to nitroalke-nes derived from (+)-camphoisulfonic acid and ozonolysis give a-hydroxy and a-amino thiol acid derivatives (Eq. 4.39). In all cases, the (/ )-diasteromer is formed as the major component.49 

1 -(Phenylthio)nitroalkenes are also excellent intermediates for the synthesis of other heterocyclic ring systems. For example, tetrahydropyran carboxylic acid derivatives are formed by the intramolecular addition of oxygen nucleophile to l-(phenylthio)nitroalkene predominantly as the m-isomer (9.1 1) (see Eq. 4.40). The reaction may proceed via the chair-like transition state with two pseudo-equatorial substituents.50 

The stereoselective synthesis of awri-P-amino-a-hydroxy acid derivatives using nucleophilic epoxidation of 1-arytlthio-l-nitroalkenes has been reported (Eq. 4.41).54 

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