1-(2'-Pyrrolidinethion-3'-yl)-1,2,3, 4-tetrahydro-.beta.-carboline-3-carboxylic acid 1-(2-Thioxo-3-pyrrolidinyl)-2,3,4,9-tetrahydro-1H-.beta.-carboline-3-carboxylic acid AIDS-137763 AIDS137763 NSC643007