Total synthesis of new indolo[2,3-a]quinolizine alkaloids sempervirine type, potential pharmaceuticals

Total synthesis of the two series of new pentacycilc cycloalk[g]indolo[2,3-a]quinolizine alkaloids (modified sempervirine possessing the wide range of activity), has been elaborated in five steps from 5-acetyl-3-methylthio-1,2,4-triazine (obtained from the simple acyclic materials). In the two key steps: inverse electron demand Diels-Alder reaction of precursor with cyclic enamines and the following Fischer indolization of 3-acetyl-1-methylthiocycloalka[c]pyridines, the AB-DE synthons, has been obtained. The final stages: desulfuration, and formation of the C-ring via the Gribble method have led to the expected zwitterionic alkaloids. Model syntheses of the indolopyridocoline and its methoxy analogue from 2-acetylpyridine have been performed for investigation of the microwave-induced Fischer synthesis of sensitive indoles and for obtaining compounds for comparative study of spectroscopic data.     

On the magnetization fluctuations in the completely disordered paramagnetic medium

The space extension of a single magnetization fluctuation in the disordered paramagnetic medium defined within the coherent potential approximation is discussed. The thermodynamical potential functional for the subspace of nearly completely disordered configurations is derived.     

Free Cyclic Submodules in the Context of the Projective Line

We discuss the free cyclic submodules over an associative ring R with unity. Special attention is paid to those which are generated by outliers. This paper describes all orbits of such submodules in the ring of lower triangular 3 × 3 matrices over a field F under the action of the general linear group. Besides rings with outliers generating free cyclic submodules, there are also rings with outliers generating only torsion cyclic submodules and without any outliers. We give examples of all cases.     

Computational studies of the tropone natural products, thiotropocin, tropodithietic acid, and troposulfenin. Significance of thiocarbonyl-enol tautomerism

Computations provide insight to the stability and isomeric possibilities of thiotropocin, tropodithietic acid, and troposulfenin. Thiotropocin and tropodithietic acid contain a flat 7-membered ring and delocalized pi-bonds similar to those of tropylium ion (C(7)H(7)(+)). Troposulfenin is far less stable; it contains a puckered tropone ring and localized bonds similar to 1,3,5-cycloheptatriene. A facile 1,5-hydrogen shift suggests that thiotropocin and tropodithietic acid exist as a pair of interconverting tautomers. Loss of an acidic proton from these three tautomers produces the same conjugate base structure.     

Highly resolved electronic spectra and electronic structure of benzo[f]quinoxaline

Vibrational analysis of highly resolved phosphorescence (P), flourescence (F) and absorption spectra of benzo[f]quinoxaline (BQ) in Shpolskii matrices, at 77 K, was carried out. The spectra were dominated by phenanthrene-type fundamental vibrations. The appearance of several out-of-plane (op) modes in the P spectrum as well as the P lifetime, much shortened relative to that of the parent hydrocarbon, point to the proximity of the lowest n, π¹ and π, π¹ states of the BQ molecule. High activity of op modes in the F spectrum and complex structure of the absorption spectrum onset have been explained in terms of the pseudo-Jahn-Teller interaction between close-lying S₁ (π, π¹)and S₂(n, π¹) states.According to calculations of the BQ electronic structure, performed using a modified INDO CI method, the T₁(π, π¹)-T₂(n, π¹) and S₁(π, π¹-S₂(n, π¹) energy gaps are about 1200 and 700 cm^-1, respectively.     

Anomalous transport properties in disordered organic layers

The results of time-of-flight experiments for two different organic compounds, copper phthalocyanine and tetracene layers, are presented. These materials were investigated in the form of vacuum evaporated layers in which, as is known, transport phenomena are more complicated in comparison with those in monocrystals. The current-time profile observed for both materials was highly dispersive as judged by the phenomenological theory of stochastic hopping or multiple-trapping processes. The differences between theoretical prediction and experimental data are demonstrated, first of all, in the field dependence of the disorder parameters α₁ and α₂ for the initial and final parts of the log i versus log t plots, respectively. The results are compared with the experimental data for other materials, as well as with the results of numerical computations given by other authors.     

A Concise Route to a Key Intermediate in the Total Synthesis of Sempervirine1

Enantiopure γ-amino and γ-hydroxy-β-ketosulfones have been synthesized in high yields from α-diazoketones derived from the α-amino and α-hydroxy acid chiral pools.     

Two separate gene clusters encode the biosynthetic pathway for the meroterpenoids austinol and dehydroaustinol in Aspergillus nidulans

Meroterpenoids are a class of fungal natural products that are produced from polyketide and terpenoid precursors. An understanding of meroterpenoid biosynthesis at the genetic level should facilitate engineering of second-generation molecules and increasing production of first-generation compounds. The filamentous fungus Aspergillus nidulans has previously been found to produce two meroterpenoids, austinol and dehydroaustinol. Using targeted deletions that we created, we have determined that, surprisingly, two separate gene clusters are required for meroterpenoid biosynthesis. One is a cluster of four genes including a polyketide synthase gene, ausA. The second is a cluster of 10 additional genes including a prenyltransferase gene, ausN, located on a separate chromosome. Chemical analysis of mutant extracts enabled us to isolate 3,5-dimethylorsellinic acid and 10 additional meroterpenoids that are either intermediates or shunt products from the biosynthetic pathway. Six of them were identified as novel meroterpenoids in this study. Our data, in aggregate, allow us to propose a complete biosynthetic pathway for the A. nidulans meroterpenoids.