DFT and FT-IR analyses of hydrogen bonding in 3-substistuted-3-oxo-arylhydrazonopropanenitriles

Ab initio calculations, FT-IR and X-ray crystal analysis, indicated that the most stable configuration of 3-oxo-2-(phenylhydrazono)-3-(thien-2-yl)-propionitrile is the anti phenylhydrazone structure 1. Stability of such a conformation, over the possible E-form, 2, that would be stabilized by intramolecular hydrogen bonding, is due to interaction between electron-pair domains of the N, S and O atoms. However, the simulated and experimental IR frequency data indicated intermolecular hydrogen bonding between NH and CN, the latter being lowered to 2214 cm(-1). Studies on 3-oxo-3-phenyl-2-(phenylhydrazono)-propionitrile showed the same result, as well as, another intramolecular hydrogen association of the type N-H...O. This was clearly indicated by the absorbance of the carbonyl stretch at 1605 cm(-1). These data indicated the existence of a bifurcated hydrogen bond in 1a and a single intermolecular association in 1b.     

人参二醇类皂苷的生物转化动态及人参稀有皂苷C-K或F2的制备

为了低成本有效制备人参稀有皂苷C-K或F₂, 将A. niger g.848菌酶用于转化含有人参皂苷(质量分数)分别为49.6% Rb₁, 25.9% Rd, 19.3% Rc和5.23% Rb₂的西洋参二醇混合皂苷. 霉菌发酵时, 采用人参二醇皂苷诱导物比人参提取液诱导物的产酶总活力提高10%~15%. 所产的2种诱导酶均能水解人参二醇皂苷的3-O-和20-O-多种糖基, 均为人参皂苷酶Ⅰ型; 但是人参二醇皂苷诱导物所产酶几乎全部转化人参二醇皂苷为C-K, 而人参提取液诱导物所产酶则残留中间产物. 使用黑曲霉人参二醇皂苷诱导所产酶, 在转化西洋参二醇皂苷的动态研究中发现, 酶反应1.5~2.5 h, 主要为产物F₂; 酶反应12 h后, 主要产物为C-K皂苷. 基于此, 40 g人参二醇类皂苷在45 ℃粗酶反应24 h, 经处理得到含C-K质量分数为87%的23 g酶反应产物, C-K转化率达85%(摩尔分数). 用40 g西洋参二醇皂苷在45 ℃粗酶反应2.5 h, 经处理得到含有质量分数为58%的F₂和27%的C-K的26 g酶反应产物, F₂转化率为50.4%, C-K转化率为29.5%. 通过人参二醇皂苷诱导的黑曲霉粗酶转化人参二醇类皂苷动态研究, 建立了C-K转化率为85%, F₂转化率为50%的制备方法, 为大批量制备提供了基础依据.