Chelation-controlled 1,3-asymmetric induction in the radical addition-allylation reactions of 4-hydroxy- and 4-alkoxy-2-methylenecarboxylic esters

The radical reaction of ethyl 4-methoxymethoxy-2-methylenealkanoates with e thyl iodide and allyltributyltin in the presence of MgBr2 gave exclusively ethyl (2R*,4R*)-2-allyl-4-methoxymethoxy-2-propylalkanoates in good yields, whereas the reaction of ethyl 4-hydroxy-2-methylenealkanoates performed in the presence of Et2AlCl gave exclusively (2S*,4R*)-4-alkyl-2-allyl-2-propy l-4-butanolides in good yields. The diastereoselectivities in the radical r eaction of 4-phenyl-substituted esters were moderate to good.