COMPOUNDS DERIVED diastereoisomers of tetrahydrofolic acid, process for the preparation and use in the synthesis of diastereomers 6s and 6r of reduced folates.

This invention relates to a novel diastereomeric process for preparing tetrahydrofolic acid derived. By reacting (i) acid (6RS) -folinique or a salt thereof, or (ii) 5,10-methenyl-5,6,7,8-tetrahydrofolic acid, with HCOOH pH 2.0-2.6 a precipitate is obtained consisting of a mixture of two diastereoisomers and orthoamide structural formulas: (CF DRAWING iN BOPI) wherein R is the radical p -benzoyl- (L) -glutamic acid, in a molar ratio IV / III of about 7/3, the compound III being called natural configuration and the compound IV of non-natural configuration known. Isolating the pure compound IV of said precipitate, and pure compound III of the corresponding filtrate. From Compound III and IV respectively diastereomers are prepared reduced folates and their natural configuration salts, and non-naturally respectively.