Part I. Asymmetric synthesis of bicyclic analogues of risedronate as molecular probes of the mechanism of action of bisphosphonate antiosteoporotic drugs and potentially more efficacious antiosteoporotic agents. Part II. Facile preparation and functionalization of chiral stabilized ylides from common chiral auxiliaries using the Bestmann ylide and their use in Wittig reactions. Part III. Asymmetric organocatalysis: 1. An investigation of alpha-hydroxylation of aldehydes; 2. Synthesis of a novel camphor-based alpha-aminotetrazole organocatalyst.

摘要

Part I. A short and efficient asymmetric synthesis of a potentially potent antiosteoporotic agent, cis-2-azabicyclo[4.3.0]nonane-8,8-diphosphonic acid hydrochloride salt, in enantiomerically pure form from an easily-made, known compound was described. The synthesis was conducted in five steps in an overall yield of 41% on multi-gram scale. This method utilized a key coupling transformation between methylene-bisphosphonate and a sterically hindered chiral piperidine-bistosylate. Both cis-diphosphonic acid enantiomers have been prepared as molecular probes for nitrogen-containing bisphosphonate-mediated antiosteoporosis. This method was easily applied to the synthesis of the trans analogues, thereby providing access to potential drug candidates for osteoporosis.; Part II. Facile preparation and functionalization of chiral stabilized phosphorus ylides was described. These ylides were prepared from the direct addition to Bestmann ylide with chiral lactams developed in Boeckman laboratories followed by subsequent alkylation and acylation. The utility of these chiral reagents in the Wittig reactions for stereoselective construction of acyclic conjugated systems was briefly studied, and the effects of alpha-substitution were observed.; Part III. A novel camphor-based chiral alpha-aminotetrazole has been synthesized efficiently on multi-gram scale via a key imine intermediate arising from an in situ intramolecular condensation. An unprecedented direct asymmetric alpha-hydroxylation of aldehydes using phenylsulfonyloxaziridine with chiral camphor- and pyrrolidine-based alpha-amino tetrazoles as organocatalysts was described. Promising enantioselectivities (up to 62%) have been achieved in preliminary studies.