Considerable interests have been attracted by isosteviol and its derivatives because of their large variety of bioactivities. In this project, a series of novel 15-and 16-substituted isosteviol derivatives were stereoselectively prepared by means of functional interconversions in ring D of the tetracyclic diterpene isosteviol. All compounds synthesized were characterized by analysis of NMR, IR, HR-MS data, and the configurations of 33 and 37 were confirmed by X-ray crystallographic analysis. The antibacterial activities in vitro of these isosteviol derivatives were investigated; the synthetic compounds were more active against Gram-positive than Gram-negative bacteria, and were especially active against Bacillus subtilis. Among them, compound 27 (MIC ¼ 1.56 mg/ml) exhibited the highest antibacterial activity and thus may be exploitable as a lead compound for the development of potent antibacterial agents.

Degradation of GaN-based quantum well light-emitting diodesQuantum-confined Stark effects in the m -plane In 0.15 Ga 0.85 N ∕ Ga N multiple quantum well blue lightemitting diode fabricated on low defect density freestanding GaN substrate

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