Fmoc-L-aspartic acid a-allyl ester

Covering: 2000 to mid-2021The phosphate ester is a versatile, widespread functional group involved in a plethora of biological activities. Its presence in secondary metabolites, however, is relatively rare compared to other functionalities and thus is part of a rather unexplored chemical space. Herein, the chemistry of secondary metabolites containing the phosphate ester group is discussed. The text emphasizes their structural diversity, biological and pharmacological profiles, and synthetic approaches employed in the phosphorylation step during total synthesis campaigns, covering the literature from 2000 to mid-2021.

This review provides insight into the use of boric acid as a pharmaceutical, a buffer, and an adjuvant/excipient in pharmaceutical formulations. Boric acid is a Lewis acid with a pKa of 8.92-9.24 that is sensitive to temperature, ionic strength, and concentration. The pKa varies with concentration because of polymerization above 0.02 M. Boric acid reacts reversibly with alcohols, especially 1,2-diols including carbohydrates, with carboxylic acids, thiols, and amines. These esters/adducts, are also Lewis acids with lower pKa values. Boric acid can stabilize some materials while catalyzing the degradation of others. Boric acid is used in various dermal and women's hygiene products because of its mild antibacterial and antifungal activity. In ophthalmic products, it is used as a buffer and in combination with other preservatives to broaden the prservative spectrum. Boric acid has been used reluctantly in parenteral products but appears to be quite safe at low doses. However, at high exposure, toxicity, including death, has been reported in humans, especially in children. Animal toxicities have also been noted, including reductions in male sperm counts. Boric acid is well absorbed on oral dosing. Its biological half-life is about 21 h in humans and has an affinity for some tissues, especially bone.

The utility of an electron-deficient, air stable, and commercially available Lewis acid tris(pentafluorophenyl)borane has recently been comprehensively explored. While being as reactive as its distant cousin boron trichloride, it has been shown to be much more stable and capable of catalyzing a variety of powerful transformations, even in the presence of water. The focus of this review will be to highlight those catalytic reactions that utilize a silane as a stoichiometric reductant in conjunction with tris(pentafluorophenyl) borane in the reduction of alcohols, carbonyls, or carbonyl-like derivatives.