Based on these results, we have extended the scope of [3 + 2] cycloaddition of sultams 1-f with nitrones, nitrile oxides, and azomethine ylide generated from precursor 8. Thus, the reaction of sultams 1a-f with nitrones 6a-c provided corresponding bicyclic isoxazolidines 9a-p in moderate to good yields (42-93%) (Scheme 4). The reaction demonstrated high diastereoselectivity and provided single (3S*,3aS*,6aS*) diastereomers. No obvious reactivity patterns were established in this case, although the average product yield was lower for -sultams (66%) as compared to their five-membered ring counterparts (73%). Analogously, -sultams 1a and 1d reacted with chloroximes 7a-d to give isoxazolines 10a-h in 55-95% yield (Scheme 5). Two representatives 10c and 10d were not formed, likely due to lowered reactivity of the starting materials (nitrile oxide dimerization was observed instead, and starting sultam 1d was recovered). With sultams 1b, 1c, and 1e, the yields of products 10i-n were modest (20-35%), and some of them (i.e., 10l and 10m, R 3 = CO2Et, as well as all compounds derived from chloroxime 9b, R 3 = Ph) were not formed at all due to the reasons mentioned above. Finally, azomethine ylide generated from precursor 8 in the presence of LiF in MeCN at 60 C reacted with sultams 1d-f to give bicyclic pyrrolidine derivatives 11a-c in 48-82% yield (Scheme 6). Notably, this transformation was performed on up to 97.8 g scale without significant effect on the product yield. The synthetic utility of the obtained intermediates was illustrated by the preparation of biand trifunctional saturated bicyclic building blocks valuable for medicinal chemistry (Scheme 7). In particular, the two-step deprotection of both Nitrogen atoms in the molecules of 11a and 11b was performed via the mild catalytic hydrogenolysis followed by acidic cleavage of the carbamate group to give bicyclic amine hydrochlorides 15a and 15b in 85% and 81% yields, respectively. These products were exhaustively protected at both Nitrogen atoms with Boc2O -Et3N to give intermediates 16a and 16b (93% and 95% yield, respectively). In turn, compounds 16a and 16b were subjected to -carboxymethylation upon action of LiHMDS and then dimethyl carbonate; after an additional methanolysis step, amino acid derivatives 17a and 17b were obtained (84% and 88% yield, respectively). A possibility to synthesize of non-protected amino acid hydrochloride 19b and monoprotected derivative 20b via the standard functional group manipulations was also demonstrated. Finally, we have studied antiviral activity for several synthesized derivatives (i.e., 10g, 10k, 11d, and 11e) against herpes simplex virus 1, human papillomavirus, Varicella-Zoster virus, and human polyomavirus 1 (BK virus). It was found that compound 10g demonstrated submicromolar activity against BK virus, exceeding that of reference antiviral drug cidofovir (Table ).