Diverse Library of 5a-Substituted Carba-Glucosamines

Carba-sugars─carbohydrate mimics in which the ring oxygen is replaced by a methylene group─are carbohydrate analogues of natural or synthetic origin that can have important biological functions. Especially, carba-aminosugars and glycosides containing carba-aminosugars are potent antibiotics. Furthermore, they have been shown to induce the self-cleavage reaction of the glmS riboswitch and thereby inhibit the ability of bacteria to synthesize glucosamine-6-phosphate, which is required to build up the bacterial cell wall. We report the synthesis of a library of 20 carba-glucosamine derivatives with various substituents at the carba-position including amines, alkyl, alkoxy, and aryloxy derivatives, fluorine derivatives, glycosylated derivatives, and a cyclopropane derivative. The compounds were obtained in an efficient way starting from late-stage synthetic intermediates of an earlier-developed synthesis of carba-substituted carba-glucosamines. All carba-glucosamine mimics were tested for their antibacterial properties against Bacillus subtilis, and some of them displayed promising activities in a filter disk assay.

Alcohols as Substrates in Transition-Metal-Catalyzed Arylation, Alkylation, and Related Reactions

Alcohols are abundant and attractive feedstock molecules for organic synthesis. Many methods for their functionalization require them to first be converted into a more activated derivative, while recent years have seen a vast increase in the number of complexity-building transformations that directly harness unprotected alcohols. This Review discusses how transition metal catalysis can be used toward this goal. These transformations are broadly classified into three categories. Deoxygenative functionalizations, representing derivatization of the C-O bond, enable the alcohol to act as a leaving group toward the formation of new C-C bonds. Etherifications, characterized by derivatization of the O-H bond, represent classical reactivity that has been modernized to include mild reaction conditions, diverse reaction partners, and high selectivities. Lastly, chain functionalization reactions are described, wherein the alcohol group acts as a mediator in formal C-H functionalization reactions of the alkyl backbone. Each of these three classes of transformation will be discussed in context of intermolecular arylation, alkylation, and related reactions, illustrating how catalysis can enable alcohols to be directly harnessed for organic synthesis.

Construction of fully substituted carbon centers containing a heteroatom and a CF3 group via in situ generated p-quinone methides

1,6-Conjugate additions of in situ generated δ-CF3-δ-substituted p-quinone methides have been achieved with a variety of heteronucleophiles under mild conditions, which led to facile and practical construction of fully substituted carbon centers including a heteroatom and a CF3 group. In particular, it was revealed that some amines themselves worked for efficient cleavage of the TBS protective group, and addition of a catalytic amount of an appropriate Brønsted acid was found to sometimes improve the progress of the desired process.

Copper-Catalyzed Synthesis of Hindered Ethers from α-Bromo Carbonyl Compounds

A catalytic method for the synthesis of sterically hindered ethers and thioethers from α-bromo carbonyl compounds and the corresponding nucleophiles using an inexpensive Cu(I) catalytic system is reported. This facile transformation takes place at ambient temperature and does not require the exclusion of air or moisture; thus, it is well-suited for the functionalization and derivatization of complex organic molecules.

A concise total synthesis of cochlearoid B

A T-type calcium channel inhibiting natural product cochlearoid B was synthesized in 7 linear steps.

Metal-mediated C–O bond forming reactions in natural product synthesis

Metal catalyzed reactions for the formation of C(sp²)–O bonds have had a dramatic impact in natural product synthesis. They have enabled the emergence of new bond disconnections, which notably resulted in remarkably efficient and short synthetic pathways. The use of these reactions for the formation of C–O bonds in natural product synthesis is overviewed in this critical review.

Synthesis of Highly Functionalized Triarylbismuthines by Functional Group Manipulation and Use in Palladium- and Copper-Catalyzed Arylation Reactions

Organobismuthines are an attractive class of organometallic reagents that can be accessed from inexpensive and nontoxic bismuth salts. Triarylbismuthines are particularly interesting due to their air and moisture stability and high functional group tolerance. We report herein a detailed study on the preparation of highly functionalized triarylbismuth reagents by triple functional group manipulation and their use in palladium- and copper-catalyzed C-, N-, and O-arylation reactions.

Synthesis of highly functionalized diaryl ethers by copper-mediated O-arylation of phenols using trivalent arylbismuth reagents

Highly functionalized diaryl ethers were prepared by copper(II) acetate mediated O-arylation reaction of phenols using trivalent organobismuthanes. The reaction is performed under simple conditions and tolerates a wide diversity of functional groups on the phenol and on the organobismuth reagent. Substoichiometric amounts of catalyst can be used by performing the reaction under an oxygen atmosphere. The N-arylation of pyridones is also reported.