An approach to 1,3-disubstitued bicyclo[2.1.0]pentane (housane) derivatives was developed. The method relied on lithium bis(trimethylsilyl)amide-mediated intramolecular cyclization of trisubstitued cyclopentane carboxylates bearing a leaving group (at the C-4 position) and an additional substituent (at the C-3 atom), in turn synthesized from cyclopent-3-ene carboxylate. The synthetic sequence allowed for the preparation of both cis-and trans-1,3-disubstituted housane-1-carboxylic acids in diastereoselective manner on up to 80 g scale. In particular, bicyclic γ-amino acidsγ-aminobutyric acid analogueswere synthesized. It was shown that the bicyclo[2.1.0]pentane did not significantly affect pK a of the corresponding derivatives and slightly increased their hydrophilicity (by 0.07−0.25 Log P units) as compared to cyclopentane. X-ray diffraction studies showed that cis-and trans-1,3-disubstituted housanes can be considered as flattened analogues of the corresponding cyclopentane derivatives with fixed envelope conformation of the fivemembered ring.

A general approach to a new generation of spirocyclic molecules - oxa-spirocycles - was developed. The key synthetic step was iodocyclization. More than 150 oxa-spirocyclic compounds were prepared. Incorporation of...