[reaction: see text] The first intermolecular radical addition onto ketoxime ethers is described. beta-Oxygenated quaternary alpha-amino acid derivatives IotaIota were obtained upon irradiation of alpha-alkoxycarbonyl ketoxime ethers Iota in the presence of suitable alpha-alkoxy carbon radical precursors and a sensitizer.

The 1,3-dipolar cycloaddition of sugar ketonitrones is a useful synthetic procedure to build up nitrogenated quaternary centers in terms of scope (substrate, dipolarophile, inter- and intramolecular versions), yield, and regio- and stereoselectivity. The hybrid ONIOM (B3LYP/6-31G(d):AM1) theoretical method followed by single-point energy calculations at the B3LYP/6-31G(d) level adequately perform to model this cycloaddition for the relatively large ketosugar precursors commonly used.

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Carbohydrates Carbohydrates U 0500Intra-and Intermolecular 1,3-Dipolar Cycloaddition of Sugar Ketonitrones with Mono-, Di-, and Trisubstituted Dipolarophiles. -The intra-or intermolecular cycloaddition of sugar-derived nitrones with various dipolarophiles provides a useful access to quaternary nitrogen-bearing centers in high regioselectivity. The influence of configuration and steric hindrance on the diastereoselectivity and the absolute configuration of the cycloadducts is studied in detail. In general, intramolecular cycloadditions of the in situ generated nitrones proceeds with excellent stereoselectivity. In contrast, stereoselectivity of intermolecular cycloadditions depends on the rigidity of the sugar-derived nitrone. Additionally, trisubstituted dipolarophiles are tolerated only in the intramolecular variant of this reaction. -(TORRENTE, S.; NOYA, B.; BRANCHADELL, V.; ALONSO*, R.; J.