Menthol crotonates

Hydroperoxide-n-Butyllithium gives 50% de. Chiral 3-amino esters of 8-phenylmenthol have been prepared in 50-60% de by the addition of amines to the re face of 8-phenylmenthyl crotonate under 14-15 kbar pressures (eq 2). Much higher (75 to >99%) de is obtained using 8-0-naphthyl)menthol crotonate. The 3-amino esters obtained are of the proper configuration for conversion to biologically active 3-lactams. ... 

While sluggish under thermal conditions,274-275 the asymmetric conjugate addition of amines to alkyl crotonates is achieved at room temperature under high pressure (15 kbar).276 Thus, benzylamine can be added to the crotonate derived from 8-p-naphthyl menthol, with virtually complete diastereoselectivity. A related intramolecular 1,4-addition of an amine to a chiral enoate was used in a total synthesis of the alkaloid (-)-tylophorine.277 Additions of amines to chiral iron complexes of type (116) proceed with excellent selectivity and allow the preparation of homochiral p-lactams.l27128,l3() l32 In contrast, the addition of amine nucleophiles to chiral vinylic sulfoxides278-2811 and to chiral vinylsulfoximines281 proceeds with comparably low selectivities. 

Chiral crotonates derived from S-citroncllol, l-(—)-menthol, and S-solketol undergo 1,3-dipolar cycloaddition with cyclic and acyclic nitrones.66 Asymmetric 1,3-dipolar cycloaddition of optically active hifluoromethylated a, /l-unsaturated aiyl sulfones (43) with nitrones yield the corresponding isoxazolidmes (44) and (45) with high regio- and... 

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