Sonochemistry and Biocatalysis: Two-Step Green Asymmetric Synthesis of Optically Active...

A green and practical synthetic route for obtaining chiral O,O-dialkyl-O-phenylphosphonate compounds is described here. The two-step synthetic strategy combines sonochemistry with an enzymatic asymmetric reduction. In the first step, aromatic hydroxyketones react with dialkyl H-phosphonates employing diphenyl ditelluride as an organocatalyst under ultrasound irradiation for 2 h at 25 °C. The ketophosphonate intermediates were obtained in satisfactory yields (70-97%). In the second step, bioreduction was performed employing Daucus carota bits in water at 25 °C for 72 h. The chiral O,O-dialkyl-O-phenylphosphonates were formed in good to excellent yields (50-98%) with satisfactory enantiomeric excesses (up to 99%). This eco-friendly and metal-free synthetic route can also be performed using a two-step sequential synthesis protocol (telescoping approach), reducing waste, cost, and time. The enantiomeric excess of the products was determined by a ³¹P NMR chiral discrimination protocol based on the racemic hydroxyphosphonates using a simple and rapid procedure.