Combined with an effective copper-catalyzed triazole-forming reaction, a series of novel camptothecin derivatives were synthesized. Incorporating oligo（ethylene glycol） chains into the derivatives enhanced their wat...Combined with an effective copper-catalyzed triazole-forming reaction, a series of novel camptothecin derivatives were synthesized. Incorporating oligo（ethylene glycol） chains into the derivatives enhanced their water-solubility when compared to the parent compound （up to 55-fold）.展开更多
In this study the spectroscopic characteristics of a water-soluble derivative of hypocrellin A (HA), 14-dehydroxy-15-deacetyl-hypocrellin A-13-sulfonate(13-SO3Na-DDHA),and its one- and two-electron reduction products ...In this study the spectroscopic characteristics of a water-soluble derivative of hypocrellin A (HA), 14-dehydroxy-15-deacetyl-hypocrellin A-13-sulfonate(13-SO3Na-DDHA),and its one- and two-electron reduction products have been investigated. From the changes in absorbance with pH it was observed that the two phenolic hydroxy groups at C-3 and C-10 positions of 13-SO3Na-DDHA or HA dissociated stepwise with increase of pH values. The pKa values for 13-SO3Na-DDHA and HA were determined using an effective method established in this study. Attempts were also made to use absorption and ESR spectroscopies to study the photoreduction of 13-SO3Na-DDHA. It was found that 13-SO3Na-DDHA was directly reduced to its two-electron reduction product in buffered aqueous solution (pH 7. 7). However, in DMF-buffer (1 :1/ v : v,pH 7. 7), it proceeded with one-electron reduction to generate its semiquinone radical anions. The semiquinone radical anions decayed according to second-order kinetics. indicating that the termination went through protonation and disproportionation of the radical anions. Despite of four pheholic hydroxy groups in the molecule of the two-electron reduction product only two hydroxy groups seem to dissociate with increase of pH. This reflects that strong intramolecular hydrogen bonds are probably formed in the mono- and dian-ionic forms of the two-electron reduction product.展开更多
Phthalimide derivatives as nitrogen nucleophiles with α,β-unsaturated aldehydes for asymmetric aza-Michael additions have been reported. The reactions proceed smoothly to afford corresponding Michael adducts in goo...Phthalimide derivatives as nitrogen nucleophiles with α,β-unsaturated aldehydes for asymmetric aza-Michael additions have been reported. The reactions proceed smoothly to afford corresponding Michael adducts in good yields （up to 98%） and enantioselectivities （up to 95% ee）.展开更多
文摘Combined with an effective copper-catalyzed triazole-forming reaction, a series of novel camptothecin derivatives were synthesized. Incorporating oligo（ethylene glycol） chains into the derivatives enhanced their water-solubility when compared to the parent compound （up to 55-fold）.
基金Project supported by the National Natural Science Foundation of China.
文摘In this study the spectroscopic characteristics of a water-soluble derivative of hypocrellin A (HA), 14-dehydroxy-15-deacetyl-hypocrellin A-13-sulfonate(13-SO3Na-DDHA),and its one- and two-electron reduction products have been investigated. From the changes in absorbance with pH it was observed that the two phenolic hydroxy groups at C-3 and C-10 positions of 13-SO3Na-DDHA or HA dissociated stepwise with increase of pH values. The pKa values for 13-SO3Na-DDHA and HA were determined using an effective method established in this study. Attempts were also made to use absorption and ESR spectroscopies to study the photoreduction of 13-SO3Na-DDHA. It was found that 13-SO3Na-DDHA was directly reduced to its two-electron reduction product in buffered aqueous solution (pH 7. 7). However, in DMF-buffer (1 :1/ v : v,pH 7. 7), it proceeded with one-electron reduction to generate its semiquinone radical anions. The semiquinone radical anions decayed according to second-order kinetics. indicating that the termination went through protonation and disproportionation of the radical anions. Despite of four pheholic hydroxy groups in the molecule of the two-electron reduction product only two hydroxy groups seem to dissociate with increase of pH. This reflects that strong intramolecular hydrogen bonds are probably formed in the mono- and dian-ionic forms of the two-electron reduction product.
文摘Phthalimide derivatives as nitrogen nucleophiles with α,β-unsaturated aldehydes for asymmetric aza-Michael additions have been reported. The reactions proceed smoothly to afford corresponding Michael adducts in good yields （up to 98%） and enantioselectivities （up to 95% ee）.
