Electrophilic Hydroxylation and Electrophilic Amination of Electronrich Substrates: Reagents, Mechanism, and Synthetic Applications

摘要

From the literature data here discussed it appears clear that the use of electrophilic reagents for the direct introduction of hydroxyl or amino group is a powerful tool of organic synthesis in terms of yields, selectivities and mildness of reaction conditions. In some cases, e.g. the hydroxylation promoted by hydrogen peroxide. which is an environmentally friendly oxidant, they can be of industrial interest. However the real importance from the preparative point of view rests on the impressive stereoselectivity obtained in the hydroxylation and amination of enolates. These reactions are, in many cases, the key step in the preparation of enantiomericaily pure building blocks needed in the synthesis of natural products, pharmaceuticals, aminoacids and so on. Some examples are the preparation of the lateral tails of microginin 48, taxol 49 and the hydroxylatcd AB synthons for the preparation of rhodomycinones 50. All these compounds have been obtained by stereoselective hydroxylation of appropriate enolates with enantiomericaily pure oxaziridines 11.rnExamples of products in whose synthesis the key step is an electrophilic amination are diphthine 51 and diphthamide 52, both essential histidine-derived aminoacids constituents of the elongation factor 2. the lysine derivative 53, and the man-designed aminoacid analogs 54 and 55 with conformationally constrained side-chains.