The glucose transporter 4 (GLUT4) is a high-affinity glucose transporter that is predominantly expressed in the skeletal muscle, myocardium, and adipose tissue, and is the rate-limiting transporter of insulin-stimulated glucose uptake. Compounds that enhance the process of GLUT4 translocation in skeletal muscle would provide a novel treatment for type 2 diabetes mellitus. After a high-throughput screening (HTS) campaign and medicinal chemistry efforts, we identified the xanthene compound DS-1150b (16·tBuNH2) as a novel potent GLUT4 translocation enhancer. DS-1150b was found to promote GLUT4 translocation in L6-myotubes in rats and showed a glucose-lowering effect in an oral glucose tolerance test (oGTT) in a Zucker fatty rat model. Identification of naphthalene analog DS20060511 is also briefly described.