نتایج جستجو برای: pentacyclic graphs
تعداد نتایج: 98241 فیلتر نتایج به سال:
A flexible and practical protocol for the asymmetric synthesis of renieramycin-type antitumor alkaloids is described, in which the stereoselective Pictet-Spengler cyclization of amino ester 16 and aldehyde 15 by regulating temperature and the automatic lactamization after N-deprotection of the cyclization product are exploited to rapidly construct the common pentacyclic framework. (-)-Renieramy...
Pentacyclic triterpenes are ubiquitously distributed throughout the plant kingdom, in a free form as aglycones or in combined forms, and have long been known to have a number of biological effects. The compounds-amyrin and -amyrin are commonly found in medicinal plants and oleo-resin obtained by bark incision of several species of Bursera or Protium of the Burseraceae family. Both in vitro a...
The phytochemical investigation on 1 g of materials from Gypsoplacamacrophylla (Zahlbr.) Timdal resulted in the discovery of gypmacrophin A, a rare pentacyclic sesterterpenoid; brialmontin III, a new polysubstituted depside and two known ones, brialmontins I and II. The structure and absolute configurations of gypmacrophin A were elucidated by spectroscopic analyses and computational methods. G...
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