Meso-glutaric anhydrides

Scheme 10.10 Ring-opening reaction of meso-glutaric anhydrides with alcohols.

Song and coworkers further utilized squaramide 33 for methanolytic desym-metrization of meso-glutaric anhydrides (Scheme 10.35) [113, 114]. The authors attributed the high enantioselectivity to the fact that the cinchona-derived dimeric squaramide catalyst does not self-associate. The catalyst can be easily recovered from the reaction mixture after extractive acid/base work up. A thiourea-catalyzed version of this process had been reported by the same authors in 2008 [115]. 

Scheme 10.35 Desymmetrization of meso-glutaric anhydrides catalyzed by squaramide 33.

DMAP is an efficient desynmetrisation catalyst. [Wilhs J Chem Soc, Perkin 1 1765 7999.] Thus it allows the use of an achiral or meso molecule, e.g. 3-substituted gjutaric anhydride to react with chiral alcohols e.g. 7 -l-(l -naphthyl)ethanol to produce (l 7 ,37 )-l(r-naphthyl)ethyl methyl 3-substituted-pentanoate di-esters (after treatment with diazomethane), which are now chiral at C-3. The achiral carbon atom at C-3 in the glutaric anhydride becomes chiral in the pentanoate (mono-ester of glutarate). [Theisen Heathcock J Org Chem 53 2374 1988, Theisen Heathcock J Org Chem 58 142 7995.]... 

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