Synthesis of the unsymmetric hexakisphosphates 13a and 13b by phosphitylation with C2-symmetric P-amidite 9, followed by the gram-scale separation of the diastereomers 10a,b. The chiral auxiliary (Rχ) serves as an orthogonal protecting group throughout the synthesis. DCM = dichloromethane, PMB = para-methoxybenzyl, Fm = fluorenylmethyl, tBuOOH = tert-butylhydroperoxide, pTsOH = para-toluenesulfonic acid, mCPBA = meta-chloroperbenzoic acid, TFA = trifluoroacetic acid, FC = flash chromatography, XE = o-xylylene.