[reaction: see text] The intramolecular trans-cyclocarbolithiation of the alpha-lithiated 4-substituted 5-hexynyl carbamate (1S,4RS)-14 employing lithiodestannylation is presented. The 5-exo-dig cyclization products cis-/trans-16a were formed exclusively. The highly enantioenriched organotin precursor (S)-11 was synthesized via an asymmetric deprotonation of the corresponding alkyl carbamate 10 by the chiral complex sec-butyllithium/(-)-sparteine and subsequent substitution with tributyltin chloride.

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http://dx.doi.org/10.1021/ol0260674DOI Listing

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