gamma-siloxyallyltributylstannanes were selectively obtained as E or Z isomers from beta-tributylstannylacrolein upon reaction with lithium or magnesium alkylcyanocuprates. The ability of the reagents to give a high syn selectivity when added to iminium salts has been used for the efficient synthesis of (+/-)-1-deoxy-6,8a-di-epi-castanospermine from succinimide. The key step of the synthesis was the allylstannation of the N-allyliminium intermediate followed by ring closing metathesis.

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Organo-tin compounds S 4800Preparation of α-Substituted γ-Alkoxyallylstannanes from β-Tributylstannyl Acrolein Acetals: Scope of the Method and Primary Rationalization of the Obtained Results. -Synthesis of (Z)-α-substituted γ-alkoxyallylstannanes from β-tributylstannylacrolein acetals is achieved using lower order magnesium cyanocuprates. For less hindered systems the main reaction pathway seems to be an anti SN2' substitution on a cisoid conformation. Competitive pathways occur depending on the nature of the cuprate, on the size of the nucleophile and on the temperature. -(FLIEGEL, F.; BEAUDET*, I.; WATRELOT-BOURDEAU, S.; CORNET, N.; QUINTARD, J.-P.; J.