differences by methods known to those skilled in the art for example by chromatography or fractional crystallization enantiomers can be separated by converting the enantiomeric mixtures into a diastereomric mixture by reaction with an appropriate optically active compound e g alcohol separating the diastereomers and converting e g hydrolyzing the individual diastereomers to the corresponding pure enantiomers all such isomers including diastereomer mixtures and pure enantiomers are considered as part of the invention the compounds of formula 1 that are basic in nature are capable of forming a wide variety of different salts with various inorganic and organic acids although such salts must be pharmaceutically acceptable for administration to animals it is often desirable in practice to initially isolate the compound of formula 1 from the reaction mixture as a pharmaceutically unacceptable salt and then simply convert the later back to the free base compound by treatment with an alkaline reagent and subsequently convert the latter free base to a pharmaceutically acceptable acid addition salt the acid addition salt of the base compounds of this invention are readily prepared by treating the base compound with a substantially equivalent amount of the chosen mineral or organic acid in an aqueous solvent medium or in a suitable organic solvent such as methanol or ethanol.