cycliacylation substrate the azatetralone 11 is then converted to the hydantoin aldose reductase inhibitor compound 12 by known methods european patent application no 86307712 1 these methods include condensing azatetralone 11 with an alkali metal cyanide e g sodium cyanide or potassium cyanide and ammonium carbonate to form the spiro imidazolidinedione product having the formula 12 the reaction is typically carried out in the presence of a inert polar organic solvent including cyclic ethers such as dioxane and tetrahydrofuran lower alkylene glycols like ethylene glycol water miscible lower alkanols such as methanol as well as n n di lower alkyl lower alkanoamides such as n n dimethylacetamide or formamide preferably the latter in general this reaction is conducted at temperatures from about 25 u00b0 c to about 150 u00b0 c upon completion of the reaction the desired product is isolated in a conventional manner by dilution with ice water and acidification further purification can be carried out by silica gel column chromatography the pharmaceutically acceptable acid addition salts of the final aldose reductase inhibitor compounds are prepared by treating the aforementioned organic bases with various mineral and organic acids which form non toxic acid addition salts having pharmacologically acceptable anions such as the hydrochloride hydrobromide hydroiodide sulfate or bisulfate phosphate or acid phosphate acetate lactate maleate fumarate citrate or acid citrate tartrate or bitartrate succinate gluconate saccharate methanesulfonate ethanesulfonate benzenesulfonate and p toluenesulfonate salts these compounds are all readily adapted to therapeutic use as aldose reductase inhibitors for the control of chronic diabetic complications in view of their ability to reduce lens.