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19 Aug 05:20

[ASAP] Sequential Norrish–Yang Cyclization and C–C Cleavage/Cross-Coupling of a [4.1.0] Fused Saturated Azacycle

by Charis Amber Roberts, Bohyun Park, Li-Ping Xu, Jose B. Roque, Charles S. Yeung, Djamaladdin G. Musaev, Richmond Sarpong, and Rebecca Lyn LaLonde

TOC Graphic

The Journal of Organic Chemistry
DOI: 10.1021/acs.joc.1c01466
10 Jun 00:26

[ASAP] Concise Chemoenzymatic Synthesis of Fasamycin A

by Jian Li and Hans Renata

TOC Graphic

The Journal of Organic Chemistry
DOI: 10.1021/acs.joc.1c00526
25 Feb 01:48

[ASAP] Leptosperols A and B, Two Cinnamoylphloroglucinol–Sesquiterpenoid Hybrids from Leptospermum scoparium: Structural Elucidation and Biomimetic Synthesis

by Ji-Hong Gu†?, Wen-Jing Wang†?, Jun-Zi Chen†, Jun-Shan Liu§, Ni-Ping Li†, Min-Jing Cheng†‡, Li-Jun Hu†, Chuang-Chuang Li*‡, Wen-Cai Ye*†, and Lei Wang*†

TOC Graphic

Organic Letters
DOI: 10.1021/acs.orglett.0c00109
28 Mar 14:42

[ASAP] Nucleophile-Dependent Z/E- and Regioselectivity in the Palladium-Catalyzed Asymmetric Allylic C–H Alkylation of 1,4-Dienes

by Hua-Chen Lin, Pei-Pei Xie, Zhen-Yao Dai, Shuo-Qing Zhang, Pu-Sheng Wang, Yu-Gen Chen, Tian-Ci Wang, Xin Hong, Liu-Zhu Gong

TOC Graphic

Journal of the American Chemical Society
DOI: 10.1021/jacs.8b13582
03 Feb 01:55

Branched‐Selective Direct α‐Alkylation of Cyclic Ketones with Simple Alkenes

by Dong Xing, Xiaotian Qi, Daniel Marchant, Peng Liu, Guangbin Dong
Angewandte Chemie International Edition Branched‐Selective Direct α‐Alkylation of Cyclic Ketones with Simple Alkenes

An intermolecular direct branched‐selective α‐alkylation of cyclic ketones has been achieved using simple alkenes as the alkylation agents. 7‐Azaindoline is employed as a bifunctional ligand to facilitate enamine formation and guide subsequent C−H activation with an iridium catalyst. This method offers a straightforward and byproduct‐free means to access ketones with β‐stereocenters.


Abstract

Herein, we describe an intermolecular direct branched‐selective α‐alkylation of cyclic ketones with simple alkenes as the alkylation agents. Through an enamine‐transition metal cooperative catalysis mode, the α‐alkylation is realized in an atom‐ and step‐economic manner with excellent branched selectivity for preparing β‐branched ketones. Employment of a pair of bulky Brønsted acid and base as additives is responsible for enhanced efficiency. Promising enantioselectivity (74 % ee) has been obtained. Experimental and computational mechanistic studies suggest that a pathway through alkene migratory insertion into the Ir−C bond followed by C−H reductive elimination is involved for the high branched selectivity.

19 Jan 00:37

Total Synthesis and Conformational Study of Callyaerin A: Anti-Tubercular Cyclic Peptide Bearing a Rare Rigidifying (Z)-2,3- Diaminoacrylamide Moiety

by Margaret Anne Brimble, Shengping Zhang, Luis De Leon Rodriguez, Ivanhoe Leung, Greg Cook, Paul Harris

Abstract

The first synthesis of the anti-TB cyclic peptide callyaerin A (1), containing a rare (Z)-2,3-diaminoacrylamide bridging motif, is reported. Fmoc-formylglycine-diethylacetal was used as a masked equivalent of formylglycine in the synthesis of the linear precursor to 1. Intramolecular cyclization between the formylglycine residue and the N-terminal amine in the linear peptide precursor afforded the macrocyclic natural product 1. Synthetic 1 possessed potent anti-TB activity (MIC100=32 μm) while its all-amide congener was inactive. Variable-temperature NMR studies of both the natural product and its all-amide analogue revealed the extraordinary rigidity imposed by this diaminoacrylamide unit on peptide conformation. The work reported herein pinpoints the intrinsic role that the (Z)-2,3-diaminoacrylamide moiety confers on peptide bioactivity.

Thumbnail image of graphical abstract

A rigid structure: Callyaerin A, an anti-tuberculosis macrocyclic peptide containing a rare (Z)-2,3-diaminoacrylamide moiety, was synthesized in high yield using an uncommon building block, Fmoc-formylglycine-diethylacetal. Variable-temperature NMR studies revealed the high conformational rigidity that the (Z)-2,3-diaminoacrylamide moiety confers on peptide structure, thus highlighting its potential as a novel structural element for conformation constraints.