Abstract: This invention relates to an improved process for preparing substantially pure simvastatin (I), chemically known as (1S,3R,7S,8S,8aR)-8-[2-[(2R,4R)-4-hydroxy-6-oxotetrahydro-2-H-pyran-2-yl]ethyl]-3 ,7-dimeth-yl-1,2,3,7,8,8a-Hexahydronaphthalen-1-yl2,2-dimethyl butanoate, which comprises of: a) treating lovastatin (II) with an alkali metal hydroxide in a chosen suitable alcoholic solvent followed by relactonization to obtain the diol lactone intermediate (III) in a single vessel. b) selective silylation of 4-hydroxy group of diol lactone intermediate (III) with a chosen suitable silylating reagent to obtain mono silylated intermediate diol lactone (IV).

Abstract: This invention relates to an improved and scalable process for the preparation of substantially pure palonosetron and its acid addition salts, in particular hydrochloride (I) which comprises of, (a) converting intermediate (IIa) as such or as its freebase (II) to a crude mixture of diastereomeric palonosetrons (VIII) or (VIIIa) contaminated with varying amounts of unconverted intermediate (II) or (IIa) via hydrogenation under pressure with an appropriately chosen hydrogenation catalyst in an suitable organic solvent. (b) making the resulting crude mixture of diastereomeric palonosetrons (VIII) or (VIIIa) contaminated with varying amounts of unconverted intermediate (II) or (IIa) substantially free from (II) or (IIa) via halogenation reaction.