Lewis MeAl

I owe a lot to Federica Bertondn and Giovanni Boccaletti. During their stay as Erasmus students in Groningen they brought a little bit of Italy with them (I remember some very good meals). Also from a chemical point of view their stays were successful. The compounds prepared and purified by Federica are at the basis of the work described in this thesis. The work of Giovanni has paved the way to enantioselective Lewis-acid catalysis in water, which is perhaps the most significant result of this thesis. 

Malinow, M.R., McLaughlin, P., Naito, H.K., Lewis, L.A., and McNulty, W.P. 1978. Effect of alfalfa meal on shrinkage (regression) of atherosclerotic plaques during cholesterol feeding in monkeys. 

Reaction of sulfone pyrone 164c with enantiomerically pure vinyl ether (5)-355b in the presence of a Lewis add such as [4-Me-2,6-(r-Bu)2QH20]2-MeAl at -45°C in 1 1 toluene/methylene chloride gives the cycloadduct 356b in 93% yield as a 98 2 ratio of the endo diastereomers. This reaction is applied to the synthesis of la,25-dihydroxyvitamin D3 (354b) (90JOC3967). 

In general, a Lewis acid catalyzed 1,3 dipolar cycloaddition reaction of nitrones with vinyl ethers provides exo isomers predominantly. In fact, the MeAl BINOL catalyzed cycloaddition reaction of ethyl vinyl ether with diaryl nitrone furnished the corresponding product vhth high exo selectivity [121]. However, phosphoramide 6b as the chiral Bronsted acid catalyst exhibited high e-ndo selectivity in the same cycloaddition reaction (see Scheme 3.27). 

R. N. Meals and F. M. Lewis, Silicones, Reinhold Publishing Corp., New York, 1959. 

Finnigan, T. J. A. and Lewis, M. J. 1985. Nitrogen extraction from defatted rapeseed, with particular reference to United Kingdom commercial rapeseed meal. J. Sci. Food Agric. 36 520-530. 

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