A series of 2-aryl and 2-alkyl derivatives of 5-alkyl-4-oxazoleacetic acids was synthesized and tested for hypolipidemic activity.Among them,5-isopropyl-2-(4-fluorophenyl)-4-oxazoleacetates exhibited potent activities,being more active than clofibrate [ethyl 2-(4-chlorophenoxy)isobutvratel. Keywords-hypolipidemic agent; 5-alkyl-4-oxazoleacetic acid; hypocholesterolemic activity; hypotriglyceridemic activity; platelet aggregation inhibition; aspartic acid azlactone; Dakin-West reactionIn the course of our studies on the development of hypolipidemic agents,a series of 2,5-disubstituted 4-oxazoleacetic acid derivatives was previously prepared and screened for hypolipidemic activity.Among them,some derivatives carrying thienyl 2)and furyl 3)groups at C-5 on the oxazole ring showed moderate to high activities.Above all,ethyl 2-(4-chlorophenyl)-5-(2-furyl)-4-oxazoleacetate has been found to be the most promising candidate for development with reduction of serum cholesterol and triglyceride in normal rats and especially in THLR/1 rats,a model of hereditary hyperlipidemia developed in our laboratory.4) Meanwhile,several research groups have also prepared 4-oxazoleacetic acid derivatives with various pharmaceutical activities.Brown reported that 2,5-diaryl and 2-cycloalkyl-4-oxazoleacetic acids were effective antiinflammatory agents.5) Yamanaka et al.showed ethyl 2-(4-chlorophenyl)-5-ethoxy-4-oxazoleacetate to be hypolipidemic.6)Recently,Meguro et al. reported 5-alkyl-2-cycloalkyl-4-oxazoleacetic acid derivatives as hypoglycemic agents.7)Thus, the substituents on the oxazole ring of 4-oxazoleacetic acid derivatives were considered to play an important role in the various physiological activities.Consequently,the relationships between structure and physiological properties are of much interest.The present study was undertaken to obtain a further insight into the hypolipidemic activity-structure relationships of 4-oxazoleacetic acid derivatives carrying 5-alkyl substituents.
ChemistryEthyl 4-oxazoleacetates(17-25)and the acids(26-31)were synthesized(as outlined in Chart 1)according to our previously reported method.2,3)The key intermediates,ethyl 3-(Nacylamino)-4-oxobutyrates(8-16),were prepared in two ways: by introduction of an acetic