Biomedical subjects
Publications and source records attributed to Alessandra Puglisi.
[reaction: see text] A highly efficient (0.01 mol % of TfOH), operationally simple (room temperature, inexpensive, and commercially available catalyst), and diastereoselective (up to >98% de) method for Brønsted acid-catalyzed reaction of enol ethers to form cis-2,6-disubstituted tetrahydropyrans is disclosed.
The first examples of catalytic asymmetric ring-closing metathesis (ARCM) reactions of enol ethers are reported. To identify the most effective catalysts, various chiral Mo- and Ru-based catalysts were screened. Although chiral Ru catalysts (those that do not bear a phosphine ligand) promote ARCM in some cases, such transformations proceed in <10% ee. In contrast, Mo-based alkylidenes give rise to efficient ARCM and deliver the desired products in the optically enriched form. Thus, Mo-catalyzed enantioselective transformations allow access to various five- and six-membered cyclic enol ethers in up to 94% ee from readily available achiral starting materials. The first examples of catalytic ARCM that lead to the formation of all-carbon quaternary stereogenic centers are also disclosed. Mechanistic models that offer a plausible rationale for the identity of major enantiomers as well as the observed levels of enantioselectivity are provided. Representative examples demonstrate that the enol ether moiety and the unreacted alkene of the ARCM products can be discriminated with excellent site selectivity (>98%).
A new and efficient synthesis of a beta-lactam that is an advanced precursor of inhibitors of thrombin and tryptase is reported. The reaction sequence is based on the use of an inexpensive enantiomerically pure starting material and is designed to allow access to both enantiomers of the target molecules by epimerization of a side-product obtained along the synthesis. An improved procedure for the epimerization step that takes advantage of the use of a polymer-supported and recyclable phase-transfer catalyst is described.
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An efficient synthesis of a beta-lactam precursor of the serine protease, prostate-specific antigen inhibitor 1 has been accomplished. The synthesis relies on two completely stereoselective reactions that allow the introduction of the stereocenters at C-3 and C-4 of the azetidinone ring in a predictable manner.