积雪草酸衍生物的合成及抗肿瘤活性研究

以天然产物积雪草酸为起始原料,对其C-2、C-3、C-23位羟基、C-11位氢、C-28位羧基进行结构改造,合成了13个新的积雪草酸衍生物,其结构经MS及1H NMR等确证。采用MTT法,选用高表达人癌细胞(He La、Hep G2和BGC-823)对它们进行初步的体外抗肿瘤活性研究,结果表明,所测化合物对He La、Hep G2和BGC-823肿瘤细胞的抑制活性均明显强于积雪草酸,其中化合物I4和II4对He La、Hep G2和BGC-823细胞表现出很强的抑制活性,明显高于已上市药物吉非替尼,值得进一步研究。     

Ohmic Contact at Al/TiO_2/n-Ge Interface with TiO_2 Deposited at Extremely Low Temperature

TiO_2 deposited at extremely low temperature of 120°C by atomic layer deposition is inserted between metal and n-Ge to relieve the Fermi level pinning. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy indicate that the lower deposition temperature tends to effectively eliminate the formation of GeO_x to reduce the tunneling resistance. Compared with TiO_2 deposited at higher temperature of 250°C,there are more oxygen vacancies in lower-temperature-deposited TiO_2, which will dope TiO_2 contributing to the lower tunneling resistance. Al/TiO_2/n-Ge metal-insulator-semiconductor diodes with 2 nm 120°C deposited TiO_2 achieves 2496 times of current density at-0.1 V compared with the device without the TiO_2 interface layer case, and is 8.85 times larger than that with 250°C deposited TiO_2. Thus inserting extremely low temperature deposited TiO_2 to depin the Fermi level for n-Ge may be a better choice.