https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Multicomponent reactions (MCRs) are fundamentally different from two-component reactions in several aspects. Among the MCRs, those with isocyanides have developed into popular organic-chemical reactions in the pharmaceutical industry for the preparation of compound libraries of low-molecular druglike compounds. With a small set of starting materials, very large libraries can be built up within a short time, which can then be used for research on medicinal substances. Due to the intensive research of the last few years, many new backbone types have become accessible. MCRs are also increasingly being employed in the total synthesis of natural products. MCRs and especially MCRs with isocyanides offer many opportunities to attain new reactions and basic structures. However, this requires that the chemist learns the “language” of MCRs, something that this review wishes to stimulate.

Multicomponent Reactions with Isocyanides.

The direct functionalization of C-H bonds in organic compounds has recently emerged as a powerful and ideal method for the formation of carbon-carbon and carbon-heteroatom bonds. This Review provides an overview of C-H bond functionalization strategies for the rapid synthesis of biologically active compounds such as natural products and pharmaceutical targets.

C-H bond functionalization: emerging synthetic tools for natural products and pharmaceuticals

In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Palladium-catalyzed cross-coupling reactions in total synthesis.

III. Foldamer Research 3910 A. Overview 3910 B. Motivation 3910 C. Methods 3910 D. General Scope 3912 IV. Peptidomimetic Foldamers 3912 A. The R-Peptide Family 3913 1. Peptoids 3913 2. N,N-Linked Oligoureas 3914 3. Oligopyrrolinones 3915 4. Oxazolidin-2-ones 3916 5. Azatides and Azapeptides 3916 B. The â-Peptide Family 3917 1. â-Peptide Foldamers 3917 2. R-Aminoxy Acids 3937 3. Sulfur-Containing â-Peptide Analogues 3937 4. Hydrazino Peptides 3938 C. The γ-Peptide Family 3938 1. γ-Peptide Foldamers 3938 2. Other Members of the γ-Peptide Family 3941 D. The δ-Peptide Family 3941 1. Alkene-Based δ-Amino Acids 3941 2. Carbopeptoids 3941 V. Single-Stranded Abiotic Foldamers 3944 A. Overview 3944 B. Backbones Utilizing Bipyridine Segments 3944 1. Pyridine−Pyrimidines 3944 2. Pyridine−Pyrimidines with Hydrazal Linkers 3945

A field guide to foldamers.

Treatment of 2-ketotax-3-enes with t-BuOK/t-BuOH/THF/65°C results in isomerization of the double bond into the 4,5-position and a trans-B/C ring fusion. Subsequent exposure to t-BuOK/THF/O2/P(OEt)3 introduces the C-1-hydroxyl group.

Isomerization, Autoxidation, and Epimerization for the Introduction of C-1 to C-5 Functionality into the Taxane ABC Ring System.

Treatment of 14 with Ac2O/Et3N resulted in [5+2] cyclization to give 2, which was further elaborated into 20, thus establishing the required stereochemistry in the top-half of guanacastepene 1.

Stereoselective Synthesis of the Bicyclo[5.3.0]decane Portion of the Diterpene Antibiotic Guanacastepene Using a Pyrylium-Ylide [5 + 2] Cycloaddition Reaction.

Treatment of the dihydropyridine 5 with fluoride anion resulted in in situ formation of the allenyldiene 4 which cyclized to the azabicyclo[2.2.2]octene 9. Subsequent elaboration to the alcohol 24 and rearrangement gave norsecurinine 2. The intermediate diol 16 was converted into prenirurine 34 which upon conversion into an N-oxide rapidly rearranged to give traces of nirurine 1 and norphyllanthine 38.

Synthesis of the Securinega Alkaloids (.+‐.)‐Norsecurinine and (.+‐.)‐ Nirurine from 3‐Hydroxypyridine.

Treatment of TIPS enol ethers with PhIO/TMSN3 followed by desilylation/elimination with fluoride ion gives good yields of the a,s-unsaturated ketone. Treatment of triisopropylsilyl enol ethers with PhIO/TMSN3 followed by fluoride ion gives good yields of the a,s-unsaturated ketone.

New Trialkylsilyl Enol Ether Chemistry: New Regiospecific Methodology for the Synthesis of α,β‐Unsaturated Cyclic Ketones.

Diphenyltelluroxide reacts with azidotrimethylsilane to give a remarkable stable adduct (Ph2TeN3)2O which was characterised by X-ray crystallography.

Philip Magnus

Papers

Isomerization, Autoxidation, and Epimerization for the Introduction of C-1 to C-5 Functionality into the Taxane ABC Ring System.

Stereoselective Synthesis of the Bicyclo[5.3.0]decane Portion of the Diterpene Antibiotic Guanacastepene Using a Pyrylium-Ylide [5 + 2] Cycloaddition Reaction.

Synthesis of the Securinega Alkaloids (.+‐.)‐Norsecurinine and (.+‐.)‐ Nirurine from 3‐Hydroxypyridine.

New Trialkylsilyl Enol Ether Chemistry: New Regiospecific Methodology for the Synthesis of α,β‐Unsaturated Cyclic Ketones.

The Structure of a Stable New Organotellurium Azide: Bis- Azidodiphenyltellurium(IV) Oxide.