A novel enantioselective total synthesis of 20S proteasome inhibitor Salinosporamide A (NPI-0052; 1) is presented. Key features include intramolecular aldol cyclization of 6 to simultaneously generate the three chiral centers of advanced intermediate 5, cyclohexene ring addition using B-2-cyclohexen-1-yl-9-BBN, and inversion of the C-5 stereocenter by oxidation followed by enantioselective enzy...

The tricyclic skeleton of the gephyrotoxin amphibian alkaloids was synthesized via an enantioselective serial sequence involving nine discrete steps that furnished Kishi’s intermediate 5 in 22% overall yield. This efficient and expeditious synthetic approach exploits the inherent stereochemistry of a (1R)-2-tropinone derivative for the construction of the core cis-2,5disubstituted pyrrolidine r...

We prove that the vector bundles at the core of the KnizhnikZamolodchikov and quantum constructions of braid groups representations are topologically trivial bundles. We provide partial generalizations of this result to generalized braid groups. A crucial intermediate result is that the representation ring of the symmetric group on n letters is generated by the alternating powers of its natural...

spinal cord compression due to extramedullary hematopoiesis is a well-described and rare syndrome encountered in several hematological disorders including β-thalassemia. hereby, a 37-year old pregnant woman with intermediate β -thalassemia with paraparesis and lower limb hypoesthesia was presented. mri showed soft tissue masses in both sides of thoracic paraspinal area. histologically, a mixtur...

background: &beta-thalassemia; is the most common monogenic disorder in human. the (ct) polymorphism at -158 upstream region of the &gammag-globin; gene and pharmacological factors such as hydroxyurea have been reported to influence &gamma-globin; gene expression and the severity of clinical symptoms of &beta-thalassemia.; methods: in the present study, 51 &beta-thalassemia; intermediate patie...

Described here are mechanistic details of the chemical reactivities of two modified/saturated pyrimidine residues that represent naturally occurring forms of DNA damage: 5-thyminyl-5,6-dihydrothymine, commonly referred to as the "spore photoproduct" (SP), and 5,6-dihydro-2'-deoxyuridine (dHdU), formed via ionizing radiation damage to cytosine under anoxic conditions and also serving as a genera...

This study examined the ligninase-catalysed degradation of lignin model compounds representing the arylglycerol ,-aryl ether substructure, which is the dominant one in the lignin polymer. Three dimeric model compounds were used, all methoxylated in the 3and 4-positions of the arylglycerol ring (ring A) and having various substituents in the ,-ether-linked aromatic ring (ring B), so that competi...

T cells form intriguing patterns during adhesion to antigen-presenting cells. The patterns at the cell-cell contact zone are composed of two types of domains, which either contain short TCR/MHCp receptor-ligand complexes or the longer LFA-1/ICAM-1 complexes. The final pattern consists of a central TCR/MHCp domain surrounded by a ring-shaped LFA-1/ICAM-1 domain, while the characteristic pattern ...

The bioactive isoflavonoids of the Leguminosae often are methylated on the 4'-position of their B-rings. Paradoxically, reverse genetic evidence implicates alfalfa isoflavone O-methyltransferase (IOMT) in the biosynthesis of 4'-O-methylated isoflavonoids such as the phytoalexin medicarpin in vivo, whereas biochemical studies indicate that IOMT has strict specificity for methylation of the A-rin...

The 1,3-dipolar cycloaddition of methyl azide to C60 and the subsequent nitrogen elimination from the formed triazoline intermediate to yield the aziridine adduct have been studied using semiempirical and density functional methods. The results obtained show that the addition of methyl azide to C60 takes place in the ring junction between two six-membered rings leading to a closed [6,6]-trizoli...