Synthesis of Benzomacrolactam by 11？endo Selective Aryl Radical Cyclization of 2？Iodobenzamide Derived from D？Galactose

encouraged by our previous studies of tri-n-butyltin-mediated radical cyclization reaction of o-iodobenzamides, we applied this methodology to the synthesis of benzomacrolactam 2 from methyl 4-o-allyl-2,3-di-o-benzyl-6-deoxy-6-(2-iodobenzoylamino)- α-d-galactopyranoside 1. apart from the macrolactam 2, resulting from regioselective 11-endo aryl radical cyclization, the hydrogenolysis produt 3 was obtained. the o-iodobenzamide 1 was prepared in eight conventional synthetic steps from methyl α-d-galactopyranoside. the unequivocal structures of 1, 2 and 3 were supported by 1h, 13c and dept nmr spectroscopy and by cosy and hmqc experiments.