the levorotatory enantiomers of 3 - loweralkoxy - cyproheptadines are potent antiserotonin agents with a lower order of antihistaminic activity and substantially free of any anticholinergic activity . they are prepared by treatment of the levorotatory enantiomer of 3 - iodocyproheptadine with an alkali metal lower alkoxide in the presence of copper powder .