Carnitine asymmetric synthesis

M. Kitamura, T. Ohkuma, H. Takaya, R. Noyori, A practical asymmetric synthesis of carnitine, Tetrahedron Lett. 1988, 29, 1555-1556. 

The silatropic ene pathway, that is, direct silyl transfer from an silyl enol ether to an aldehyde, may be involved as a possible mechanism in the Mukaiyama aldol-type reaction. Indeed, ab initio calculations show that the silatropic ene pathway involving the cyclic (boat and chair) transition states for the BH3-promoted aldol reaction of the trihydrosilyl enol ether derived from acetaldehyde with formaldehyde is favored [60], Recently, we have reported the possible intervention of a silatropic ene pathway in the catalytic asymmetric aldol-type reaction of silyl enol ethers of thioesters [61 ]. Chlorine- and amine-containing products thus obtained are useful intermediates for the synthesis of carnitine and GABOB (Scheme 8C.26) [62],... 

A simple method for the asymmetric hydroboration of a- and p-ketophospho-nates, their conversion to hydroxyphosphonates and the synthesis of phospho-carnitine, has been developed (Scheme 77). ... 

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