further purification the named compound was prepared by cyclizing the aldehyde prepared in accordance with step d supra using sodium cyanide in dimethyl sulfoxide according to the following reaction str18 to a slurry of 50g nacn in 700 ml dmso was added 222g crude aldehyde in 80 ml dmso the temperature rose spontaneously to 65 u00b0 at which it was held by controlling the rate of addition of vi the temperature was then held at 65 u00b0 for an additional 4 hours the reaction mixture was diluted with 1 5l h 2 o and extracted with 6 u00d7 500 ml benzene the combined extracts were washed with 500 ml saturated nahso 3 2 u00d7 500 ml 5 nahco 3 3 u00d7 500 ml saturated nacl and then dried over caso 4 the benzene was removed on a rotary evaporator having 145g crude product about 50 55 pure after several vacuum distillations 65g of 98 pure product was obtained b p 119 121 mm hg the 39 h nmr was consistent with the structure the named compound was prepared by hydrolysis of the 6 cyano 2 2 tetrahydropyrandicarboxylate prepared in accordance with step e above by the following reaction str19 to a solution of 81g of 50 naoh and 80 ml.