Abstract: The present application provides improved processes for the synthesis of eribulin intermediate, which generally comprise the steps of: a) De-protecting the eribulin-enone (compound 1) in tetrahydrofuran by using TBAF solution, buffered with imidazole HCl in the presence of molecular sieve and sodium sulphate to get an insitu mixture of eribulin-dione diastereomer at C12 carbon (compound 2). Then ketalization may be performed of eribulin-dione insitu intermediate containing mixture of diastereomer at C12 carbon (compound 2) with PPTS in dichloromethane to yield eribulin-diol (compound 3).