Semisynthesis of Taxol®: an improved procedure for the isolation of 10-deacetylbaccatin III

From the needles of domestic yew, (Taxus baccata), 10-deacetylbaccatin III (10-DAB) can be isolated in quantities of up to 297 mg per kg of fresh needles. Additional quantities of 10-DAB can be obtained from the extract by NaBH4 mediated reductive hydrolysis of baccatin esters. A four-step procedure converts 10-DAB into taxol in 58% overall yield

Synthesis of new stereoisomeric nitrate esters derived from isosorbide-mononitrates

A synthesis of diastereomeric (7R) 7-endo-nitrooxy-3-oxo-2,5,9-trioxabicyclo[4.3.0]nonane (4b) and (7S) 7-exo-nitrooxy-3-oxo-2,5,9-trioxabicyclo[4.3.0] (7b) is described using D-glucitol as a starting compound. Bicyclic delta -lactones 4 and 7 are obtained in the reaction of 1,4-3,6-dianhydro-2-keto-D-glucitol-5-acylates 3 and 1,4-3, 6-dianhydro-5-keto-D-glucitol-2-acylates 6 with m-chloroperbenzoic acid. Hydrolysis of lactones 4b and 7b and subsequent esterification afforded the corresponding stereoisomeric (3R,4R) methyl (2-acetoxy-4-nitrooxytetrahydrofuran-3-yloxy)-acetate 10 and (3R,4S) isomer 12, respectively

Socratenon and its application to the learning of Italian language

Socratenon is a Web engine tuned to advanced Web education using the state-of-the-art Internet development technologies and tools. It enables interactive and creative learning/teaching management in four different domains (provider, administrator, teacher, and student). It also includes an interface to an artificial intelligence based tool for off-line improvement or learning curricula (ABITS or Aristotelon). One of the first applications of Socratenon was to help the learning of Italian language for Serbian students (the product was developed through a cooperation between universities in Salerno and Belgrade). This paper presents the basic elements of the Socratenon application and implementation philosophy, and discusses its possibilities in the general language- learning environment. It describes three different experiments and explains the lessons learned. The stress is on the statistical analysis of success of those who used our Web-based product and those who relied on the classical approaches

Mechanistic Investigation of Enediyne-Connected Amino Ester Rearrangement. Theoretical Rationale for the Exclusive Preference for 1,6- or 1,5-Hydrogen Atom Transfer Depending on the Substrate. A Potential Route to Chiral Naphthoazepines

International audienceMemory of chirality (MOC) and deuterium-labeling studies were used to demonstrate that the cascade rearrangement of enediyne-connected amino esters 1a and 1b evolved through exclusive 1,5- or 1,6-hydrogen atom transfer, subsequent to 1,3-proton shift and Saito–Myers cyclization, depending on the structure of the starting material. These results were independently confirmed by DFT theoretical calculations performed on model monoradicals. These calculations clearly demonstrate that in the alanine series, 1,5-hydrogen shift is kinetically favored over 1,6-hydrogen shift because of its greater exergonicity. In the valine series, the bulk of the substituent at the nitrogen atom has a major influence on the fate of the reaction. N-Tosylation increases the barrier to 1,5-hydrogen shift to the benefit of 1,6-hydrogen shift. The ready availability of 1,6-hydrogen atom transfer was explored as a potential route for the enantioselective synthesis of naphthoazepines