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Enantioselective Preparation of 3,4,5-Trisubstituted 4,5-Dihydroisoxazoles and Their Stereoselective Elaboration of 5-Side Chain. -Mg 2+ ion-induced 1,3-dipolar cycloaddition of nitrile oxides [from (II)] to chiral α-silylallyl alcohols (I) provides an efficient access to dihydroisoxazole derivatives (III) in moderate yields and high stereoselectivities. Attempted desilylation with Bu 4 NF proceeds with ring expansion to furnish dihydrooxazines (IV) with retention of optical purity. Swern oxidation of the cycloadduct (IIIa) furnishes an acylsilane (V), an equivalent of a dihydroisoxazole-carbaldehyde. Lewis acid-promoted addition of allyltin reagent proceeds highly stereoselectively to give the dihydroisoxazole (VII)/(VIII) with enlarged side chain. -(KAMIMURA*, A.; KANEKO, Y.; OHTA, A.; MATSUURA, K.; FUJIMOTO, Y.; KAKEHI, A.; KANEMASA, S.; Tetrahedron 58 (2002) 47, 9613-9620; Dep. Appl.