Chelation-controlled 1,3-asymmetric induction in radical addition to gamma-hydroxy- and gamma-alkoxy-alpha-methylenecarboxylic esters

The radical-mediated reactions of gamma-hydroxy- and gamma-alkoxy-alpha-met hylenecarboxylic esters 3 (R-1 = Ph, I-Bu, and t-Bu, R-2 = H, Me, MOM, and MEM) with isopropyl iodide or cyclohexyl iodide performed in the presence o f Lewis acids gave the syn-adducts 4 predominantly, whereas the anti-adduct 5 was the major product in the reaction of 3 (R1 = Ph, R-2 = Me) with t-bu tyl iodide.