Diastereoselective alkylation of 2,3,4,6-Di-O-isopropylidene-2-keto-L-gulonic amides. Application to the asymmetric synthesis of 1-substituted-1,2,3,4-tetrahydroisoquinolines and 1-substituted-1,2,3,4,-tetrahydro-beta-carbolines.
The diastereoselective alkylation of amides 3a,b and 7a,b derived from gulonic acid is described. Substituted compounds are obtained in good yield and high diastereoselectivity. A mechanistic investigation establishes that the diastereoselectivity did not arise from an initial asymmetric deprotonation. The stereochemistry is then determined during the alkylation step.
Adam
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Laboratoire d'Hétérochimie Organique associé au CNRS, UMR 6014, IRCOF, INSA et Université de Rouen, Rue Tesnière, 76821 Mont Saint-Aignan Cedex, France.
Pannecoucke
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Combret
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Quirion
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