Derivatization of an especially electron-rich diborane.

Starting with electron-rich ditriflato-diborane B(hpp)(OTf) (hpp = 1,3,4,6,7,8-hexahydro-2-pyrimido[1,2-]pyrimidinate), novel symmetric and unsymmetric diboranes B(hpp)X and B(hpp)XY with X,Y = Br, NCS, N or OTf are synthesized by substitution reactions with S1 mechanisms. The stability of the unsymmetric diboranes with respect to dismutation equilibria is evaluated.

"Golden" Cascade Cyclization to Benzo[c]-Phenanthridines.

Herein, we describe a gold-catalyzed cascade cyclization of Boc-protected benzylamines bearing two tethered alkyne moieties in a domino reaction initiated by a 6-endo-dig cyclization. The reaction was screened intensively, and the scope was explored, resulting in nine new Boc-protected dihydrobenzo[c]phenanthridines with yields of up to 98 %; even a π-extension and two bidirectional approaches were successful. Furthermore, thermal cleavage of the Boc group and subsequent oxidation gave substituted benzo[c]phenanthridines in up to quantitative yields.

Structural basis for allosteric regulation of Human Topoisomerase IIα.

The human type IIA topoisomerases (Top2) are essential enzymes that regulate DNA topology and chromosome organization. The Topo IIα isoform is a prime target for antineoplastic compounds used in cancer therapy that form ternary cleavage complexes with the DNA. Despite extensive studies, structural information on this large dimeric assembly is limited to the catalytic domains, hindering the exploration of allosteric mechanism governing the enzyme activities and the contribution of its non-conserved C-terminal domain (CTD).