Chiral formyllithium

Chiral formyllithiums 475-478 have been prepared from the corresponding cyclic and acyclic. V./V-aceials. (V-Boc-Thiazolidines having an isopropyl group at the 4- or 5-position 479 or 480 were lithiated with w-BuLi at —78 °C and reacted with aldehydes to form only two of the four possible diastereomers with 40% or 70% diastereoselectivity for the major isomer 481 or 483, respectively (compare with compounds 482 and 484) (Scheme 125)678. 

Af-(Phenylsulfanylmethyl)oxazolidinones derived from camphor 494 can be lithiated with n-BuLi at —78°C to give the chiral formyllithium equivalent 478683 (Scheme 128). This intermediate added to aldehydes in good yields, but lower stereoselectivity than compound 477, to afford crystalline adducts, which allowed the isolation of the major diastereomer 495. Hydrolysis of these adducts gave a-hydroxy aldehydes, which can be oxidized with PCC to the corresponding a-hydroxy acids. 

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