Methods Involving 2-Dialkoxyphosphoryl 4- 5- Hydroxy or 4- 5- Aminoalkanoates as Key Intermediates

2 Methods Involving 2-Dialkoxyphosphoryl 4-(5-)Hydroxy or 4-(5-)Aminoalkanoates as Key Intermediates 

As mentioned earlier, a-diethoxyphosphoryl-y-oxoaUcanoates 131 can be readily obtained from the corresponding a-diethoxyphosphoryl-y-nitroaUcanoates by means of the Nef reaction. Both oxidative Nef reaction protocols [28e, 63] and spontaneous Nef reaction strategy [64a] were successfully developed resulting in a facile access 

In recent years, a few elegant approaches to a-diethoxyphosphoryl-S-lactones with diverse substitution pattern based on 2-diethoxyphosphoryl-5-oxoaIkanoates 

-70 to r.t. MClK=CaCl2 2H20, BaCl2 2H2O. CeCl3-7H20 

Such an approach for the synthesis of optically active a-methylene-8-lactones was further extended to include enamines derived from (J )- or (S)-dihydrocarvone and (R)- or (S)-l-phenylethylamine in the Michael addition step [71]. In such a manner, a synthesis of all four enantiomericaUy pure diastereoisomers of 7-isopropenyl-4a-methyl-3-methyleneoctahydrochromen-2-one was accomplished. Furthermore, the possibihty to control stereochemical outcome of the Michael addition step by employing chiral phosphinate auxihary in the starting dicyclohexylammonium acrylate was also demonstrated by KrawcTyk and coworkers [72]. 

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