Compounds of formula I ##STR1## in which R.sup.1 denotes hydrogen or methyl R.sup.2 denotes lower straight-chained or branched alkyl with 1 to 10 carbon atoms R.sup.3 denotes hydrogen or lower alkyl n denotes 0-12 R.sup.4 denotes alkyl, alkenyl or alkinyl with 6 to 24 carbon atoms, processes for the production thereof as well as pharmaceutical agents containing these compounds for the treatment of osteoporosis.