3-(alk-2-ynyloxy)carbonyl-5-oxazolidine carboxylic acid and its analogs having a formula ##STR1## and wherein R.sub.1 is hydrogen, aryl, heteroaryl, alkyl, alkenyl, alkynyl, R.sub.2 and R.sub.3 are independently selected from hydrogen, alkyl, alkenyl, alkynyl, aryl, heteroaryl, R.sub.4 is hydrogen, alkyl, alkenyl, alkynyl, aryl, substituted aryl, heteroaryl, R.sub.5 and R.sub.6 independently selected from hydrogen, alkyl, alkenyl,alkynyl, arly, heteroaryl, alkoxy, alkeyloxy, alkynyloxy, aryloxy, heteroaryloxy.