... 3a,8,8-trimethyl-alpha-(2-methylpropyl)-4,6-methano-1,3,2-benzodioxaborole TEST ITEMSPECIFICATIONAppearanceWhite to off-white crystalline ... optical rotation+10°~+11°Loss on drying≤1.5%Assay (HPLC)≥98.0% Bortezomib Intermediate; (aR,3aS,4S,6S,7aR)-Hexahydro-3a ... ,8,8-trimethyl-alpha-(2-methylpropyl)-4,6-methano-1,3,2-benzodioxaborole