A d-ribose-derived α-amino nitrile as a versatile intermediate for the collective synthesis of piperidine-type iminosugar C-glycosides

Rapid Generation of Tetrahydropyridines and Tetrahydroquinolines by Dearomative Cyanation/Grignard Addition

A rapid, practical and scalable method for the reductant and tansition-metal-free synthesis of a variety of novel 2,4-disubstituted tetrahydropyridines and tetrahydroquinolines is disclosed. The method is based upon dearomative functionalization of pyridines or quinolines to generate amino nitrile intermediates as masked iminium ions, which then reacted rapidly with various Grignard reagents in complete stereocontrol.

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin-Anh and Chelation-Control Models

This review describes the additions of allylmagnesium reagents to carbonyl compounds and to imines, focusing on the differences in reactivity between allylmagnesium halides and other Grignard reagents. In many cases, allylmagnesium reagents either react with low stereoselectivity when other Grignard reagents react with high selectivity, or allylmagnesium reagents react with the opposite stereoselectivity. This review collects hundreds of examples, discusses the origins of stereoselectivities or the lack of stereoselectivity, and evaluates why selectivity may not occur and when it will likely occur.

Lewis acid-catalysed nucleophilic opening of a bicyclic hemiaminal followed by ring contraction: Access to functionalized L-idonojirimycin derivatives

The Lewis acid-catalyzed nucleophilic opening of a D-gluco-configured bicyclic hemiaminal has been examined. Several Lewis acids and silylated nucleophiles have been screened allowing the introduction of acetophenone, phosphonate or nitrile at the pseudoanomeric position in satisfactory yields and high 1,2 trans stereoselectivities. Their skeletal rearrangement triggered by the N-benzyl anchimeric assistance provided the corresponding L-ido-configured piperidines displaying various functional groups at C-6 position in good yield.

[1,4]-sigmatropic rearrangement of chiral nitrones and their utilization in the synthesis of new iminosugars

A new mechanism of nitrone epimerization via [1,4]-sigmatropic rearrangement was proposed and a set of epimeric iminosugars was synthesized.