Translocation of Viable Gut Microbiota to Mesenteric Adipose Drives Formation of Creeping Fat in Humans.

A mysterious feature of Crohn's disease (CD) is the extra-intestinal manifestation of "creeping fat" (CrF), defined as expansion of mesenteric adipose tissue around the inflamed and fibrotic intestine. In the current study, we explore whether microbial translocation in CD serves as a central cue for CrF development. We discovered a subset of mucosal-associated gut bacteria that consistently translocated and remained viable in CrF in CD ileal surgical resections, and identified Clostridium innocuum as a signature of this consortium with strain variation between mucosal and adipose isolates, suggesting preference for lipid-rich environments. Single-cell RNA sequencing characterized CrF as both pro-fibrotic and pro-adipogenic with a rich milieu of activated immune cells responding to microbial stimuli, which we confirm in gnotobiotic mice colonized with C. innocuum. Ex vivo validation of expression patterns suggests C. innocuum stimulates tissue remodeling via M2 macrophages, leading to an adipose tissue barrier that serves to prevent systemic dissemination of bacteria.

Palladium-Catalyzed Transformations of Alkyl C-H Bonds.

This Review summarizes the advancements in Pd-catalyzed C(sp3)-H activation via various redox manifolds, including Pd(0)/Pd(II), Pd(II)/Pd(IV), and Pd(II)/Pd(0). While few examples have been reported in the activation of alkane C-H bonds, many C(sp3)-H activation/C-C and C-heteroatom bond forming reactions have been developed by the use of directing group strategies to control regioselectivity and build structural patterns for synthetic chemistry. A number of mono- and bidentate ligands have also proven to be effective for accelerating C(sp3)-H activation directed by weakly coordinating auxiliaries, which provides great opportunities to control reactivity and selectivity (including enantioselectivity) in Pd-catalyzed C-H functionalization reactions.

Palladium(II)-catalyzed highly enantioselective C-H arylation of cyclopropylmethylamines.

C-H arylation via a Pd(II)/Pd(IV) catalytic cycle has been one of the most extensively studied C-H activation reactions since the 1990s. Despite the rapid development of this reaction in the past two decades, an enantioselective version has not been reported to date. Herein, we report a Pd(II)-catalyzed highly enantioselective (up to 99.5% ee) arylation of cyclopropyl C-H bonds with aryl iodides using mono-N-protected amino acid (MPAA) ligands, providing a new route for the preparation of chiral cis-aryl-cyclopropylmethylamines. The enantiocontrol is also shown to override the diastereoselectivity of chiral substrates.

Enantioselective ortho-C-H cross-coupling of diarylmethylamines with organoborons.

The commonly used para-nitrobenzenesulfonyl (nosyl) protecting group is employed to direct the CH activation of amines for the first time. An enantioselective ortho-CH cross-coupling between nosyl-protected diarylmethylamines and arylboronic acid pinacol esters has been achieved utilizing chiral mono-N-protected amino acid (MPAA) ligands as a promoter.

Palladium(0)-catalyzed alkynylation of C(sp3)-H bonds.

The alkynylation of ß-C(sp(3))-H bonds in aliphatic amides with alkynyl halides has been enabled using Pd(0)/N-heterocyclic carbene (NHC) and Pd(0)/phosphine (PR3) catalysts. This is the first example of utilizing [AlkynylPd(II)L(n)] complexes to activate C(sp(3))-H bonds.

Ligand-enabled methylene C(sp3)-H bond activation with a Pd(II) catalyst.

Pd(II) insertion into ß-methylene C(sp(3))-H bonds was enabled by a mutually repulsive and electron-rich quinoline ligand. Ligand tuning led to the development of a method that allows for installation of an aryl group on a range of acyclic and cyclic amides containing ß-methylene C(sp(3))-H bonds.

Pd-catalyzed intermolecular C-H amination with alkylamines.

C-H amination of N-aryl benzamides with O-benzoyl hydroxylamines has been achieved with either Pd(II) or Pd(0) catalysts. Furthermore, we demonstrate that secondary amines can be directly used with benzoyl peroxide in a one-pot procedure that proceeds via the in situ generation of the appropriate O-benzoyl hydroxylamines. This catalytic reaction provides a new disconnection for the convergent synthesis of tertiary and secondary arylalkyl amines starting from benzoic acids.

Pd(II)-Catalyzed Cross-Coupling of C(sp2 )-H Bonds and Alkyl-, Aryl- and Vinyl-Boron Reagents via Pd(II)/Pd(0) Catalysis.

Pd(II)-catalyzed cross-coupling of ortho-C-H bonds in benzoic acid and phenylacetic acid amides with alkyl-, aryl- and vinyl-boron reagents have been achieved via Pd(II)/Pd(0) catalysis, demonstrating the unprecedented versatility of C-H activation reactions.

Ligand-enabled cross-coupling of C(sp3)-H bonds with arylboron reagents via Pd(II)/Pd(0) catalysis.

There have been numerous developments in C-H activation reactions in the past decade. Attracted by the ability to functionalize molecules directly at ostensibly unreactive C-H bonds, chemists have discovered reaction conditions that enable reactions of C(sp(2))-H and C(sp(3))-H bonds with a variety of coupling partners. Despite these advances, the development of suitable ligands that enable catalytic C(sp(3))-H bond functionalization remains a significant challenge. Herein we report the discovery of a mono-N-protected amino acid ligand that enables Pd(II)-catalysed coupling of γ-C(sp(3))-H bonds in triflyl-protected amines with arylboron reagents. Remarkably, no background reaction was observed in the absence of ligand. A variety of amine substrates and arylboron reagents were cross-coupled using this method. Arylation of optically active substrates derived from amino acids also provides a potential route for preparing non-proteinogenic amino acids.