[reaction: see text] The first successful catalytic oxidation procedure for the chemoselective conversion of imines to nitrones is reported. The reaction is general, high yielding, and user and environmentally friendly, and furnishes a solution to the yet unanswered issue of regioselective access to nitrones by oxidation of nitrogen derivatives.

One-pot condensation/oxidation of primary amines and aldehydes using urea-hydrogen peroxide (UHP) as the stoichiometric oxidant in the presence of methyltrioxorhenium (MTO) as catalyst affords nitrones in a simple and regioselective manner. UHP is a practical and safe source of H2O2, and its use here instead of aqueous H2O2 solutions also simplifies greatly the workup procedure as extractions with organic solvents can be avoided. Typically, at the end of the reaction the solid urea is simply filtered off. From a sustainability point of view, this one-pot synthesis is simple to perform, takes place under mild conditions, has a high atom economy, and releases water as the only by-product.

We report the total synthesis of a series of pyrrolizidine analogues of casuarine (1) and their 6-O-α-glucoside derivatives. The synthetic strategy is based on a totally regio-and stereoselective 1,3-dipolar cycloaddition of suitably substituted alkenes and a carbohydrate-based nitrone. We also report the evaluation of the biological activity of casuarine and its derivatives towards a wide range of glycosidases and a mo-

N‐ Benzylidene‐benzylamine N‐oxide Methyltrioxorhenium Urea hydrogen peroxide Dibenzylamine

The first catalytic oxidation of aryl oximes to nitro compounds by means of methyltrioxorhenium and urea hydroperoxide is reported. The formation of carbamates, probably occurring through formation of nitrile oxide intermediates, has been observed from 2,6-disubstituted aryl oximes.