Substrate stereocontrol in bromine-induced intermolecular cyclization: asymmetric synthesis of pitavastatin calcium

Asymmetric Total Synthesis of Amphirionin-2

A convergent route for the asymmetric total synthesis of potent anticancer polyketide natural product amphirionin-2 has been developed. Our initial synthetic trials revealed that the proposed structures of amphirionin-2 need to be revised consistent with a recent report of Fuwa et al., where the actual structure of amphirionin-2 was established. The key features of our synthesis comprised Sharpless asymmetric dihydroxylation, followed by cycloetherification, Wittig olefination, Julia-Kocienski olefination, and Crimmins propionate aldol reaction.

Synthesis of a Hominal Bis(difluoromethyl) Fragment

This paper describes the synthesis of a discrete unit of hominal bis(gem-CF₂). The controlled introduction of fluorine atoms is a powerful synthetic tool to introduce dipole moments with minimal impact to sterics. Poly(vinylidene difluoride) is a striking example of the influence of fluorine atoms, which impart ferroelectric behavior from the alignment of the dipole moments of CF₂ units; however, it is prepared via direct polymerization of vinylidene difluoride. Thus, a different synthetic pathway is required to produce synthons containing discrete numbers of CF₂ groups in a hominal relation to each other. We found out that, in the case of short chains, the consecutive deoxofluorination of sequentially introduced keto groups is inefficient, as it requires harsh conditions and decreasing yields at each step. To solve this problem, we combined the selective desulfurative fluorination of dithiolanes with pyridinium fluoride and the deoxofluorination of keto groups with morpholinosulfur trifluoride. This strategy is highly reproducible and scalable, allowing the synthesis of the hominal bis(gem-CF₂) fragment as a shelf-stable tosylate, which can be used to install discrete chains of hominal bis(gem-CF₂) on a variety of synthons and monomers.

Stereocontrolled synthesis of rosuvastatin calcium via iodine chloride-induced intramolecular cyclization

A novel, stereoselective approach towards rosuvastatin calcium from the known (S)-homoallylic alcohol has been developed.