The fused quinuclidine-valerolactone system Synthesis and conformation of 4-alkyl or 4-aryl-6-oxa-1-azatricyclo (4.2.2.027) dodecan-5-one

Michael addition of ethyl malonate, alkylmalonate and phenylacetate to 2-methylene-quinuclidin-3-one, followed by NaBH₄ reduction of the 3-oxo group in the resulting adduct, then acid hydrolysis and decarboxylation (in the case of malonates) gave 6-oxa-1-azatricyclo-(4.2.2.0^2,7)dodecan-5-one, its 4-alkyl and 4-aryl derivatives. A minor byproduct is 2-(trans-3-hydroxyquinuclidin-2-yl)-α-alkyl-propanoic acid which is unable to undergo cyclization to δ-lactone.