etc in the presence of a base such as dimethylaminopyridine etc in a solvent such as acetone acetonitrile tetrahydrofuran thf dioxane etc this step is that where a lower alkylsulfonyloxy group or an optionally substituted arylsulfonyl group at the 4 position in an r configuration in a pyrrolidine ring of 2s 4r 2 r hydroxy 3r cyclic amine 3 yl methyl pyrrolidine compound when r 1 is an alkylsilyl group the alkylsilyl group is selectively eliminated and converted to a lower alkylsulfonyl group or an optionally substituted arylsulfonyl group is converted to an acylthio group in an s configuration the reaction is carried out either with a thiocarboxylate such as potassium thioacetate or sodium thioacetate in a polar a solvent such as acetonitrile acetone 1 2 dimethyl 2 imidazolidinone dmi dimethylacetamide dma dimethylformamide dmf dimethyl sulfoxide dmso etc or with a thiocarboxylic acid such as thioacetic acid thiobenzoic acid etc in the presence of a base such as potassium carbonate cesium carbonate etc this step is that where an acyl group in an acylthio group of a 2s 4s 2 r hydroxy 3r cyclic amine 3 yl methyl 4 acylthiopyrrolidine compound and a protecting group for an amino group on a pyrrolidine ring is and if an amino group on another cyclic amine ring has a protecting group this protecting group is also eliminated the reaction is carried out in an alcoholic solvent such as methanol ethanol etc or tetrahydrofuran thf or dioxane in the presence of a mineral acid such as hydrochloric acid sulfuric acid etc the reaction may also be carried out by treating with an aqueous solution of sodium hydroxide potassium hydroxide or lithium.