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871.
Kathleen Fuchs Dr. Samara Medina Rivero Anna Weidlich Dr. Frank Rominger Noel Israel Dr. Alexey A. Popov Prof. Dr. Andreas Dreuw Dr. Jan Freudenberg Prof. Juan Casado Prof. Dr. Uwe H. F. Bunz 《Angewandte Chemie (International ed. in English)》2023,62(32):e202305712
Two series of regioisomeric dicyanomethylene substituted dithienodiazatetracenes with formal para- or ortho-quinodimethane subunits were synthesized and characterized. Whereas the para-isomers (p-n, diradical index y0=0.01) are stable and isolable, the ortho-isomer (y0=0.98) dimerizes into a covalent azaacene cage. Four elongated σ-CC bonds are formed and the former triisopropylsilyl(TIPS) -ethynylene groups transformed into cumulene units. The azaacene cage dimer (o-1)2 was characterized by X-ray single crystal structure analysis and temperature-dependent infrared (IR), electron paramagnetic resonance (EPR, solid-state), nuclear magnetic resonance (NMR) and ultraviolet-visible (UV/Vis) spectroscopies (solution) indicating reformation of o-1. 相似文献
872.
Jiawei Sun Yuan Chen Sherif Shaban Ragab Wei Gu Ziqiang Tang Yuexun Tang Wenjun Tang 《Angewandte Chemie (International ed. in English)》2023,62(24):e202303639
Highly oxygenated cardiotonic steroids, such as ouabain, possess a wide spectrum of biological functions and remain significant synthetic challenges. Herein, we have applied an unsaturation-functionalization strategy and developed a synthetic method in addressing the C19-hydroxylation issue for efficient synthesis of polyhydroxylated steroids. An effective asymmetric dearomative cyclization allowed the construction of the C19-hydroxy unsaturated steroidal skeleton in only four steps from the Hajos-Parrish ketone ketal 7 . The synthetic sequence featured C3−OH-directed hydrogenation/epoxidation, m-CPBA-triggered epoxidation/SN2′ nucleophilic substitution, Birch reduction of an enone, and regioselective LiAlH4 reduction to furnish the polyhydroxy functionalities on the steroid skeleton with high stereochemical control and efficiency. This approach ultimately enabled the total synthesis of 19-hydroxysarmentogenin and ouabagenin in 18 and 19 steps, respectively, overall. The synthesis of these polyhydroxylated steroids offers synthetic versatility and practicality in the search for new therapeutic agents. 相似文献
873.
Wei Huang Jiahui Bai Prof. Dr. Yinlong Guo Prof. Dr. Qinglei Chong Prof. Dr. Fanke Meng 《Angewandte Chemie (International ed. in English)》2023,62(19):e202219257
Catalytic enantioselective coupling of 1,1-disubstituted allenes and aldehydes through regiodivergent oxidative cyclization followed by stereoselective protonation or reductive elimination promoted by chiral phosphine-Co complexes is presented. Such processes represent unprecedented and unique reaction pathways for Co catalysis that enable catalytic enantioselective generation of metallacycles with divergent regioselectivity accurately controlled by chiral ligands, affording a wide range of allylic alcohols and homoallylic alcohols that are otherwise difficult to access without the need of pre-formation of stoichiometric amounts of alkenyl- and allyl-metal reagents in up to 92 % yield, >98 : 2 regioselectivity, >98 : 2 dr and >99.5 : 0.5 er. 相似文献
874.
Dr. Mengting Liu Dr. Masao Ohashi Qingyang Zhou Dr. Jacob N. Sanders Prof. Erin P. McCauley Prof. Phillip Crews Prof. K. N. Houk Prof. Yi Tang 《Angewandte Chemie (International ed. in English)》2023,62(40):e202311266
We uncovered and reconstituted a concise biosynthetic pathway of the strained dipeptide (+)-azonazine A from marine-derived Aspergillus insulicola. Formation of the hexacyclic benzofuranoindoline ring system from cyclo-(l -Trp-N-methyl-l -Tyr) is catalyzed by a P450 enzyme through an oxidative cyclization. Supplementing the producing strain with various indole-substituted tryptophan derivatives resulted in the generation of a series of azonazine A analogs. 相似文献
875.
Ivana Némethová Dario Schmid Konrad Tiefenbacher 《Angewandte Chemie (International ed. in English)》2023,62(14):e202218625
Terpenes represent the largest and the most diverse class of natural compounds. This is remarkable as the whole variety is accessed from just a handful of highly conserved linear precursors. Modification of the cyclization precursors would enable a dramatic expansion of the accessible chemical space. However, natural enzymes do not enable us to tap into this potential, as they do not tolerate larger deviations from the prototypical substrate structure. Herein we report that supramolecular capsule catalysis enables facile access to diverse and novel terpenoid skeletons that formally can be traced back to C3-phenyl, benzyl, and homoprenyl derivatives of farnesol. Novel skeletons related to the presilphiperfolane core structure, as well as novel neoclovene derivatives were accessed efficiently in only four synthetic steps. Importantly, the products obtained carry functional groups that may be readily derivatized further. 相似文献