A compound of the formula (I): ##STR1## wherein X.sup.1 and X.sup.2 do not exist or represent oxygen atom; A represents OH or acyloxy group having 1 to 4 carbon atoms; B represents hydrogen atom; A and B together represent a bond; R.sup.1 and R.sup.2 represent hydrogen atom or alkyl group having 1 to 4 carbon atoms, or R.sup.1 and R.sup.2 together represent 1,2-ethylene, 1,3-propylene, 1,4-butylene or 1,5-pentylene, and these alkylene groups may be substituted by alkyl group having 1 to 4 carbon atoms; R.sup.3 represents amido group of the formula: ##STR2## wherein n, R.sup.4, R.sup.5, R.sup.6, R.sup.7. R.sup.8. R.sup.9, R.sup.10 and R.sup.11 represent specific groups, and the pharmacological acceptable salts of the compounds which can form salts have strong activity for lowering blood pressure, and process therefor and pharmaceutical use of the compounds.