Synthesis of azaspiro[4.5]decane systems by oxidative cyclization of olefinic precursors

Article abstract of DOI:10.1016/S0040-4020(98)00746-7

The synthesis of 6-benzyloxycarbonyl-1-oxa-6-azaspiro[4.5]decan-2-one (17) and 6-benzyloxycarbonyl-1,6-diazaspiro[4.5]decan-2-one (18) from the D,L-pipecolic acid derivative 10, is described. The synthesis of (±)-6- benzyl-3-methyl-1,6-diazaspiro[4.5]dec-3-ene-2,7-dione (29), the spiro structural unit of (±)-pandamarine (8) has been achieved by oxidative cyclization of the (Z) and (E) isomers of 5-(N-benzyl-4- carboxamidobutylidene)-3-methyl-3-pyrrolin-2-one (25) and (26). The stereoselectivity obtained in the intramolecular cyclization process has also been discussed.