2-(Arylsulfinylmethyl)oxazinanes: chiral carbonyl equivalents. Application to the asymmetric synthesis of 1,2,3,4-tetrahydro-β-carbolines

2-(p-Tolylsulfinylmethyl)oxazinane, a chiral carbonyl equivalent, has been synthesised and used for the diastereoselective synthesis of tetrahydro-β-carbolines including intermediates of yohimbine and herman alkaloids. A fair degree of diastereoselectivity, comparable with other approaches, has been achieved.