This invention relates to compounds of the formula ##STR1## or an optical isomer thereof wherein R.sup.1 and R.sup.2 are the same or different and are an alkyl or alkenyl group of 6 to 24 carbon atoms; R.sup.3, R.sup.4 and R.sup.5 are the same or different and are alkyl of 1 to 8 carbon atoms, aryl, aralkyl of 7 to 11 carbon atoms, or when two or three of R.sup.3, R.sup.4, and R.sup.5 are taken together to form quinuclidino, piperidino, pyrrolidino, or morpholino; n is 1 to 8; and X is a pharmaceutically acceptable anion.