Diastereo- and Enantioselective Synthesis of Tetracyclic Cycloheptanols through (4+3) Annulation via C-C/C-H Activation Cascade.

Transition metal-catalyzed annulations of four-membered rings via C-C activation are powerful tools to construct complex fused and bridged ring systems. Despite significant progress in (4+1), (4+2) and (4+4) annulations, the (4+3) annulation remains unexplored. Herein, we develop an asymmetric Rh-catalyzed intramolecular (4+3) annulation of α-arylalkene-tethered benzocyclobutenols for the synthesis of dihydrofuran-annulated dibenzocycloheptanols with two discontinuous chiral carbon centers via a C-C and C-H activation cascade. The reaction features excellent diastereo- and enantioselectivities and 100 % atom economy, and is applicable to late-stage modification of complex molecules.

miR-448-3p alleviates diabetic vascular dysfunction by inhibiting endothelial-mesenchymal transition through DPP-4 dysregulation.

Diabetes mellitus (DM) often causes vascular endothelial damage and alters vascular microRNA (miR) expression. miR-448-3p has been reported to be involved in the development of DM, but whether miR-448-3p regulates diabetic vascular endothelial dysfunction remains unclear. To investigate the molecular mechanism of diabetic vascular endothelial dysfunction and the role of miR-448-3p therein, Sprague-Dawley rats were injected with streptozotocin (STZ) to establish diabetic animal model and the rat aortic endothelial cells were treated with high glucose to establish diabetic cell model. For the treatment group, after the induction of diabetes, the miR-448-3p levels in vivo and in vitro were upregulated by adeno-associated virus serotype 2 (AAV2)-miR-448-3p injection and miR-448-3p mimic transfection, respectively. Our results showed that AAV2-miR-448-3p injection alleviated the body weight loss and blood glucose level elevation induced by STZ injection. The miR-448-3p level was significantly decreased and the dipeptidyl peptidase-4 (DPP-4) messenger RNA level was increased in diabetic animal and cell models, which was reversed by miR-448-3p treatment. Moreover, the diabetic rats exhibited endothelial damage and endothelial-mesenchymal transition (EndMT), while AAV2-miR-448-3p injection relieved those situations. In vitro experiments demonstrated that miR-448-3p overexpression in endothelial cells alleviated endothelial damage by inhibiting EndMT through blocking the transforming growth factor-ß/Smad pathway. We further proved that miR-448-3p negatively regulated DPP-4 by binding to its 3'-untranslated region, and DPP-4 overexpression reversed the effect of miR-448-3p overexpression on EndMT. Overall, we conclude that miR-448-3p overexpression inhibits EndMT via targeting DPP-4 and further ameliorates diabetic vascular endothelial dysfunction, indicating that miR-448-3p may serve as a promising therapeutic target for diabetic endothelial dysfunction.

Skeleton Reorganization of Substituted Benzocyclobutenols through Rh-Catalyzed C-C Bond Cleavage Manipulated by Hydrogen Transfer.

Although transition-metal-catalyzed C-C bond activation has been investigated extensively, C-C bond cleavage manipulated by hydrogen transfer has been unexplored. In this work, we disclose a skeleton reorganization of alkene-tethered benzocyclobutenols through Rh-catalyzed C-C bond cleavage coupled with intra- and intermolecular hydrogen transfer. The reaction pathway was well-tuned by the catalytic systems. As a result, divergent benzofurans bearing 4-ß-hydroxy or 4-ß-keto moieties were synthesized under pH- and redox-neutral conditions.