An Efficient Synthesis of Carlosic Acid and Other 5-Carboxymethyltetronates from Malates

S-Carlosic acid was prepared in six steps and 32% yield from malic acid. Ring closure was effected by a domino addition-Wittig alkenation reaction with Ph 3 PCCO. A variant employing resin-bound malates furnished immobilized 5-carboxymethyltetronates. It should be amenable to parallelization and automation.