7-Bromo-4-methyl-3,4-dihydro-2h-1,4-benzoxazine is useful reactant in the preparation of a purine-?based Hsp90 Inhibitor known as (2S)?-?1-?[4-?(2-?{6-?Amino-?8-?[(6-?bromo-?1,?3-?benzodioxol-?5-?yl)?sulfanyl]?-?9H-?purin-?9-?yl}?ethyl)?piperidin-?1-?yl]?-?2-?hydroxypropan-?1-?one (MPC-?3100).