h 2 o calc c 72 62 h 7 07 n 6 77 found c 72 40 h 6 94 n 6 83 a solution of n 1 2 3 4 dihydro 2h 1 benzopyran 4 yl ethyl 4 piperidinyl acetamide 3 3 g 10 9 mmol in 1 2n hydrochloric acid 35 ml was heated on a steam bath for 16 h the reaction mixture was cooled and neutralized with 50 sodium hydroxide solution ph 12 the basic aqueous solution was extracted with ethyl acetate the organic extracts were washed with distilled water dried na 2 so 4 filtered and evaporated in vacuo to afford the title compound 2 85 g 100 as an oily gum the title compound was used in the subsequent experiments without purification but could be further purified by the following means to a solution of the title compound 100 mg in methanol 0 2 ml 6n dioxane hcl 0 5 ml is added the resulting solution is evaporated in vacuo to afford a solid residue which is crystallized from methanol diethyl ether to afford the title compound as its dihydrochloride salt 60 mg anal c 16 h 24 n 2 o 2hcl 0 25 h 2 o calc c 56 89 h 7 91 n 8 29 found c 56 67 h 7 87 n 8 19 to a stirred solution of 1 2 3 4 tetrahydronaphthalene 2 carboxylic acid 176 mg 1 mmol and triethylamine 0 25 ml in methylene chloride 5 ml isobutylchloroformate 136 mg 1 mmol was added after 5.