TETRAHEDRON Tetrahedron 55 (1999) 10425-10436 Stereoselectivity of N-Benzyl-C-ethoxycarbonyl Nitrone Cycloaddition to (S)+Hydroxymethyl-2(5H)-furanone and Its Derivatives Vladimir Ondru&,a* Michal OrsQg,a Llubor Fi&eraa* and Nad’a Pr6nayovBb aDepartment of Organic Chemistry, Slovak University of Technology, SK-812 37 Bratislava, Slovak Republic bCentra/ Laboratory of Chemical Techniques, Slovak University of Technology, SK-812 37 Bratislava, Slovak Republic Received 24 February 1999; revised 7 June 1999; accepted 25 June 1999 Abstract: Stereoselectivity of the reaction of Kbenzyl-C-ethoxycarbonyl nitrone (3) with (S)-5-hydroxymethyl-2(5H)-furanone (2a) and its 5-alkoxy substituted derivatives Sb-f was investigated. The reaction proceeds in a highly face-selective manner, the products 4-6 resulting from approach anti to the hydroxymethyl or alkoxymethyl group of the dipolarophile. The exo-stereoselectivity increases as the size of protective group attached to lactone (2b-f) increases. Endo-exo diastereoselectivity is affected significantly by the solvent. Microwave irradiation strongly accelerates the reaction with little effect on the diastereoselectivity to give the syn adduct 8a in addition to anti cycloadducts 4a-6a. 0 1999Elsevier Science Ltd. All rights reserved. Keywords: IV&ones; cycloadditions; stereoselection; isoxazolidines; microwave heating This paper is dedicated to Professor Fumio Toda on the occassion of his 65” birthday INTRODUCTION The nitrone-olefin 1,3-dipolar cycloaddition is a powerful reaction in that it can create as many as three new contiguous stereogenic centers in a single step. Based on an evaluation of the nitrone cycloaddition,’ it was felt that the stereochemistry of these new centers could be controlled if the reaction system was properly designed. Asymmetric nitrone 1,3-dipolar cycloadditions involving the use of chiral dipolarophiles have been described.2a3 With the goal of developing a simple route to 0040-4020/99/$ - see front matter 0 1999 Elsevier Science Ltd. All rights reserved. PII: SOO40-4020(99)00568-2