Preregularization and the path integral approach to the chiral anomaly

We explore the connection between perturbative and non-perturbative (path-integral) approaches to the axial anomaly. In particular, we show how the Jacobian associated with the fermionic measure corresponding to local axial transformations may be calculated directly from shift-of-integration-variable surface terms in four Euclidean dimensions. No regularization (explicit parametrization of UV infinities) is required in this approach, but invariance of the Jacobian under vector gauge transformations (i.e. preregularization) is required to remove a variable-of-integration ambiguity within the expression for the Jacobian of the fermionic measure.     

4. Biologisches Material

Ohne Zusammenfassung     

A new general access to either type of Securinega alkaloids: synthesis of securinine and (-)-allonorsecurinine

The syntheses of securinine and (-)-allonorsecurinine have been achieved starting from easily available alpha-amino acid derivatives and using as key steps a RCM and a Heck reaction for the formation of rings D and C, respectively. [reaction: see text]     

Introduction to the Proceedings of the Twelfth Symposium on Biotechnology for Fuels and Chemicals

Applied Biochemistry and Biotechnology -     

Probing the stereoselectivity of the Heck arylation of endocyclic enecarbamates with diazonium salts. Concise syntheses of (2S,5R)-phenylproline methyl ester and Schramm's C-azanucleoside

[reaction: see text] The diastereoselectivity of the Heck arylation of several chiral, nonracemic, five-membered endocyclic enecarbamates with aryldiazonium tetrafluoroborates was evaluated. The cis selectivity observed for some enecarbamates bearing coordinating groups was explored in the concise synthesis of the (2S,5R)-(+)-phenylproline methyl ester, a scaffold for the nonpeptide cholecystokinin antagonist (+)-RP 66803, and in the synthesis of Schramm's potent antiprotozoan C-azanucleoside.     

A new efficient route for multigram asymmetric synthesis of alkannin and shikonin

A short and convergent approach for the synthesis of alkannin, shikonin and shikalkin is presented. A Hauser-type annulation of cyanophthalide 26 with enone 7 affords the complete aromatic system in just one step with concomitant attachment of the entire side chain. Subsequent Corey's oxazaborolidine mediated asymmetric reduction of the above advanced intermediate, leads to the required isomer in high enantiomeric excess. Finally, a selective and high yielding deprotection protocol furnishes the title compounds as pure crystalline precipitates. Thus, a multigram synthesis of shikonin, alkannin and shikalkin is achieved in high yield and enantioselectivity.     

Reactions with the Arylhydrazones of α-Cyanoketones: The Structure of 2-Arylhydrazono-3-ketimino-nitriles

Analysis of the IR., UV., and polarographic data of a variety of 2-arylhydrazono-3-ketimino-nitriles indicated that these derivatives exist mainly in the intramolecularly chelated hydrazone structure 1 . Compounds 1 reacted with hydrazine hydrate to yield the corresponding 5-amino-4-arylazopyrazoles ( 3 ). Compounds 3a reacted with acetylacetone, ethyl acetoacetate, and diethyl malonate to yield the pyrazolo[1, 5-a]pyrimidine derivatives 4, 5 , and 7 respectively. Compound 3a also reacted with benzoylisothiocyanate to yield the pyrazolyl thiourea derivative 8 .