A series of spiroketal C2-acetals was treated with an alkylsilane reagent in the presence of either TMSOTf or BF3.OEt2 to effect C2-substitution. Regioselective alkylation was successful, but in each case a monoanomeric spiroketal was the unexpected major product. The sequence provides a model for the synthesis of the CD subunit of altohyrtin A. (C) 1998 Elsevier Science Ltd. All rights reserved.
A series of spiroketal C2-acetals was treated with an alkylsilane reagent in the presence of either TMSOTf or BF3.OEt2 to effect C2-substitution. Regioselective alkylation was successful, but in each case a monoanomeric spiroketal was the unexpected major product. The sequence provides a model for the synthesis of the CD subunit of altohyrtin A. (C) 1998 Elsevier Science Ltd. All rights reserved.