نتایج جستجو برای: 20 one
تعداد نتایج: 2468724 فیلتر نتایج به سال:
Conformationally restrained substituted pregnane-20-one derivatives were obtained by an intramolecular nitrene addition onto a C-5/C-6 double bond involving a tethered C-19 sulfamoyl moiety. The resulting aziridine underwent regioselective nucleophilic ring opening at C-5 at room temperature with cyanide, fluoride, and acetate. In the isolated case of acetate, a reversal of regioselectivity was...
The title compound, C(21)H(34)O(4), is a steriod of the pregnane family prepared by the sequential oxidation and reduction of 3β,12β-diacet-oxy-20-ethyl-enedioxy-pregnan-14-ene. The con-formations of the six-membered rings are close to chair forms, while the five-membered ring adopts an envelope conformation. All the rings are trans-fused and an intra-molecular O-H⋯O hydrogen bond occurs. In th...
the purpose of this study was to examine the english language needs of medical students at tehran university of medical sciences . analysis of the needs took place for three groups: 320 undergraduate students, 30 postgraduate students and 20 university instructors. a triangulation approach to collect data was used in which a combination of the quantitative (using the questionnaires) and qualita...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید