Efficient construction of a chiral all-carbon quaternary center by asymmetric 1,4-addition and its application to total synthesis of (+)-bakuchiol

The conjugate addition of lithium divinylcuprate to (4S,2′E)-3-(6′-TBDPS-3′-methylhex-2′-enoyl)-4-phenyloxazolidin-2-one proceeded efficiently to create a chiral all-carbon quaternary center with a high diastereoselectivity (R:S = 95:5). The absolute configuration of the newly generated chiral center was confirmed by applying this methodology to the total synthesis of (+)-bakuchiol.