4-Benzyloxybutylmagnesium bromide

Petrini and co-workers used the bis(methoxymethyl)-protected nitrone 150, also derived from L-tartrate, as an electrophile rather than as a 1,3-dipole (Scheme 21, top line) (89). In their key step, reaction with 4-benzyloxybutylmagnesium bromide gave the cyclic hydroxylamine 151 in 82% yield (de 90%). Transfer hydrogenation with ammonium formate and a palladium catalyst cleaved both the hydroxylamine and the benzyl ether, affording the aminoalcohol 152. Cyclization via the corresponding primary chloride created the protected indolizidine 153, acidic hydrolysis of vi4uch completed this short synthesis of ( + )-132 in 16%... 

Mono-addition of 4-benzyloxybutylmagnesium bromide to the acetal-protected L-tartaric acid bis(dimethylamide) 227 launched the synthesis of (4-)-lentiginosine (127) by Prasad and Pawar (Scheme 30). Reduction of the ketone (+)-228 formed in this way with sodium borohydride mediated by cerium trichloride gave the (R)-alcohol (—)-229 as an inseparable mixture of diastereomers (91 9). After mesylation and Sn2 reaction with... 

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