Synthesis and hydrogenolysis of dioxolane-type diphenylmethylene and fluoren-9-ylidene carbohydrate acetals containing a neighbouring substituted hydroxyl function

Series of dioxolane-type diphenylmethylene and fluoren-9-ylidene acetals of hexoses containing adjacent O-alkyl, deoxy or hydroxy functions were prepared and hydrogenolysed with the LiAlH4-AlCl3 reagent. The observed direction of ring-cleavage was discussed in terms of different influences, such as complex formation and orientation of the hydride reagent, the configurational arrangements of the free OH group to one of the oxygen atoms of the dioxolane ring, as well as the conformational relationship of the rings present in the 1,6-anhydro derivatives.