Zinc(II) triflate-controlled 1,3-dipolar cycloadditions of C-(2-thiazolyl)nitrones: application to the synthesis of a novel isoxazolidinyl analogue of tiazofurin.

[reaction: see text] The cycloaddition reaction between C-(2-thiazolyl) nitrones and allylic alcohol takes place with complete exo selectivity when the reactions are carried out in the presence of 1 equiv of zinc triflate. The rate of the reaction is increased enormously under microwave irradiation. The use of a chiral dipolarophile allowed application of the methodology to the synthesis of a hitherto unknown enantiomerically pure isoxazolidinyl analogue of the C-nucleoside tiazofurin.