Mitsunobu reaction

"The availability of a stereodefined alcohol from reduction of a cyclic ketone raises the question of how one can obtain the corresponding stereoisomer. A solution to this problem is the Mitsunobu reaction, which provides a powerful tool for inverting the configuration of a given alcohol to its stereoisomer. The reaction involves conversion of the alcohol into a good leaving group capable of being displaced by a relatively weak nucleophile, generally a carboxylate ion (RCOO-). The product of stereochemical inversion is an ester, which on saponification leads to the alcohol of opposite configuration."