SYNTHESIS OF AZASPIRO[4.5]DECANE SYSTEMS BY OXIDATIVE CYCLIZATION OF OLEFINIC PRECURSORS

The synthesis of benzyloxycarbonyl-1-oxa-6-azaspiro[4,5]decan-2-one (1 7) and 6-benzyloxycarbonyl-1,6-diazaspiro[4.5]decan-2-one (18) from th e D,L-pipecolic acid derivative 10, is described. The synthesis of yl- 3-methyl-1,6-diazaspiro[4.5]dec-3-ene-2,7-dione (29), the spiro struct ural unit of (+/-)-pandamarine (8) has been achieved by oxidative cyli zation of the (Z) and (E) isomers of 4-carboxamidobutylidene)-3-methyl -3-pyrrolin-2-one (25) and (26). The stereoselectivity obtained in the intramolecular cyclization process has also been discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.