Studies directed toward the total synthesis of tetronolide 1. An enantioselective synthesis of the octahydronaphthalene unit

An efficient enantioselective route to the octahydronaphthalene unit present in tetronolide ( 1 ), the stereochemically complex aglycone common to the tetrocarcins, a novel group of antitumor substances, is described. The sequence employs the intramolecular Diels-Alder reaction to control the relative stereochemistry present on the trans decalin ring system, and incorporates a masked acylating agent which should permit coupling of the two key fragments 2 and 3 as demonstrated by reaction of pentaene 4 with methanol and a model α-hydroxy ester.