Iterative synthesis of 1,3-polyboronic esters with high stereocontrol and application to the synthesis of bahamaolide A

A vast repertoire of secondary metabolites potentially influences community dynamics and biogeochemical processes in cold seeps

In deep-sea cold seeps, microbial communities thrive on the geological seepage of hydrocarbons and inorganic compounds, differing from photosynthetically driven ecosystems. However, their biosynthetic capabilities remain largely unexplored. Here, we analyzed 81 metagenomes, 33 metatranscriptomes, and 7 metabolomes derived from nine different cold seep areas to investigate their secondary metabolites. Cold seep microbiomes encode diverse and abundant biosynthetic gene clusters (BGCs). Most BGCs are affiliated with understudied bacteria and archaea, including key mediators of methane and sulfur cycling. The BGCs encode diverse antimicrobial compounds that potentially shape community dynamics and various metabolites predicted to influence biogeochemical cycling. BGCs from key players are widely distributed and highly expressed, with their abundance and expression levels varying with sediment depth. Sediment metabolomics reveals unique natural products, highlighting uncharted chemical potential and confirming BGC activity in these sediments. Overall, these results demonstrate that cold seep sediments serve as a reservoir of hidden natural products and sheds light on microbial adaptation in chemosynthetically driven ecosystems.

Enantioselective Copper-Catalyzed Ring-Opening Diboration of Arylidenecyclopropanes to Access Chiral Skipped 1,4- and 1,3-Diboronates

Two enantioselective approaches to synthesize chiral skipped diboronate compounds have been developed, relying on copper-catalyzed one-pot asymmetric ring-opening diboration of arylidenecyclopropanes. A wide range of arylidenecyclopropanes react smoothly with HBpin in the presence of CuOAc and (R)-DTBM-Segphos, affording chiral 1,4-diboronates with high enantioselectivity (up to 99% ee). Meanwhile, a variety of arylidenecyclopropanes react selectively with HBpin and B2pin2 in the presence of CuOAc and (S,S)-Ph-BPE with the sequential addition of MeOH, providing chiral 1,3-diboronates with high enantioselectivity (up to 98% ee). These enantioenriched 1,3- and 1,4-diboronates can undergo various enantiospecific transformations with minimal loss of their enantiopurity. Mechanistic studies reveal that these two diboration processes start with CuH-catalyzed ring-opening hydroboration of arylidenecyclopropanes to form a mixture of Z/E-homoallyl boronate intermediates, which subsequently undergo enantioselective CuH-catalyzed second hydroboration or Cu-Bpin-catalyzed protoboration to produce chiral 1,4-diboronates or 1,3-diboronates, respectively.

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of NP structure class diversity in relation to biota source and biome is discussed.

Enzymatic Resolution and Decarboxylative Functionalization of α-Sulfinyl Esters

α-Sulfinyl esters can be readily prepared through thiol substitution of α-bromo esters followed by oxidation to the sulfoxide. Enzymatic resolution with lipoprotein lipase provides both the unreacted esters and corresponding α-sulfinyl carboxylic acids in high yields and enantiomeric ratios. Subsequent decarboxylative halogenation, dihalogenation, trihalogenation and cross-coupling gives rise to functionalized sulfoxides. The method has been applied to the asymmetric synthesis of a potent inhibitor of 15-prostaglandin dehydrogenase.

Ni-Catalyzed 1,2-Alkyl Borylation and Silylation of Allenes En Route to [1,3]-Bis-Organometallic Reagents

A nickel-catalyzed multicomponent reaction that rapidly and reliably accesses [1,3]-bis-organometallic reagents from allenes is reported. The protocol exhibits a predictable regioselectivity pattern that enables the incorporation of B,B(Si) fragments across the allene backbone under mild conditions, thus offering a complementary platform for accessing polyorganometallic reagents possessing both sp2 and sp3 hybridization from readily available precursors.

Carbonyl Olefin Metathesis and Dehydrogenative Cyclization of Aromatic Ketones and gem-Difluoroalkenes

The beauty of one-pot cascade reaction lies in the efficient disconnection and construction of several bonds in a single reaction flask, without the isolation of any intermediates. Herein, we report the first photoinduced thermally promoted cascade reactions of readily available aromatic ketones and aromatic gem-difluoroalkenes for the synthesis of phenanthrenes which possess potential utility in drug design and materials science. The reaction combines carbonyl-olefin metathesis (cascade photoinduced [2+2] cyclization and thermally controlled retro [2+2] cyclization) and dehydrogenative cyclization (cascade photoinduced conrotatory 6π electrocyclization and collidine-promoted dehydrogenative aromatization) together in one pot. The oxidant-free, acid-free and metal-free reaction shows broad substrate scope and wide functional group tolerance.

A Pyridine Dearomatization Approach for the Gram Scale Synthesis of (±)-Sparteine

Both enantiomers of sparteine have suffered from pricing and supply chain variability, which has inspired efforts toward efficient chemical synthesis. Here, we build upon our reported synthesis of the matrine-type lupin alkaloids in order to synthesize (±)-sparteine. Specifically, selective quenching of the cyclization between glutaryl chloride and pyridine with methanol provides a functionalized quinolizidine core that was elaborated to (±)-sparteine in six additional steps on gram scale. This synthesis provides a scalable route to sparteine from inexpensive commodity chemicals utilizing a dearomative cyclization. In addition, this route provides concise access to (±)-lupinine.

Three-Component Photochemical 1,2,5-Trifunctionalizations of Alkenes toward Densely Functionalized Lynchpins

Radical remote 1,n-difunctionalization reactions (n > 2) of alkenes are powerful tools to efficiently introduce functional groups with selected distances into target molecules. Among these reactions, 1,5-difunctionalizations are an important subclass, leading to sought-after scaffolds, but typically suffer from tailored starting materials and strict limitations for the formed functional group in 2-position. Seeking to address these issues and to make radical 1,5-difunctionalizations of alkenes more applicable, we report a novel three-component 1,2,5-trifunctionalization reaction between imine-based bifunctional reagents and two distinct alkenes, driven by visible light energy transfer-catalysis. Key to achieving this selective one-step installation of three different functional groups via the choreographed formation of four bonds was the utilization of a 1,2-boron shift and the rigorous capitalization of radical polarities and stabilities. Thorough mechanistic studies were carried out, and the synthetic utility of the obtained products was demonstrated by various downstream modifications. Notably, in addition to the functionalization of individual functional groups, their interplay gave rise to a unique array of cyclic products.

Diastereodivergent Catalysis

Alongside enantioselective catalysis, synthetic chemists are often confronted by the challenge of achieving catalyst control over the relative configuration to stereodivergently access desired diastereomers. Typically, these approaches iteratively or simultaneously control multiple stereogenic units for which dual catalytic methods comprising sequential, relay, and synergistic catalysis emerged as particularly efficient strategies. In this Perspective, the benefits and challenges of catalyst-controlled diastereodivergence in the construction of carbon stereocenters are discussed on the basis of illustrative examples. The concepts are then transferred to diastereodivergent catalysis for atropisomeric systems with twofold and higher-order stereogenicity as well as diastereodivergent catalyst control over E- and Z-configured alkenes.