Total Synthesis and Stereochemical Assignment of Penicitide A

Ni-Electrocatalytic Enantioselective Doubly Decarboxylative C(sp3)-C(sp3) Cross Coupling

The first examples of enantioselective doubly decarboxylative cross coupling are disclosed. Malonate half amides are smoothly coupled to a variety of primary carboxylic acids after formation of the corresponding redox-active esters under Ni-electrocatalytic conditions using a new chiral ligand based on PyBox, resulting in amides with α-alkylated stereocenters. The scope of the reaction is broad, tolerating numerous functional groups, and uniformly proceeds with high ee. Finally, the potential utility of this enantioselective radical-radical reductive cross coupling to simplify synthesis is demonstrated with numerous case studies.

Total synthesis of the antibacterial polyketide natural product thailandamide lactone

Stereoselective total synthesis of the structurally intriguing polyketide natural product thailandamide lactone was accomplished, and done so using a convergent approach for the first time to the best of our knowledge. The key features of this synthesis included use of a Crimmins acetate aldol reaction, Evans methylation, Urpi acetal aldol reaction, Sharpless asymmetric epoxidation and subsequent γ-lactonization for the installation of six asymmetric centers and the use of the Negishi reaction, Julia-Kocienski olefination, cross metathesis, HWE olefination and intermolecular Heck coupling for construction of a variety of unsaturated linkages. Pd(i)-based Heck coupling was introduced, for the first time to the best of our knowledge, quite efficiently to couple the major eastern and sensitive western segments of the molecule. The antibacterial activity of thailandamide lactone was also evaluated.

Late-Stage Functionalization: Total Synthesis of Beauveamide A and Its Congeners and Their Anticancer Activities

Asymmetric total synthesis of cyclotetradepsipeptide beauveamide A has been achieved for the first time. A macrolactamization strategy involving two possible sites has been explored to find the most effective route for cyclization. A late-stage functionalization approach has been adopted for easy access of non-natural analogues of beauveamide A for further biological evaluation. Interestingly, the anticancer activity of one of the synthesized analogues was better than that of the parent natural product.

Marine natural products

Covering: 2020This review covers the literature published in 2020 for marine natural products (MNPs), with 757 citations (747 for the period January to December 2020) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1407 in 420 papers for 2020), 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. A meta analysis of bioactivity data relating to new MNPs reported over the last five years is also presented.

Asymmetric Total Synthesis of Amphirionin-2

A convergent route for the asymmetric total synthesis of potent anticancer polyketide natural product amphirionin-2 has been developed. Our initial synthetic trials revealed that the proposed structures of amphirionin-2 need to be revised consistent with a recent report of Fuwa et al., where the actual structure of amphirionin-2 was established. The key features of our synthesis comprised Sharpless asymmetric dihydroxylation, followed by cycloetherification, Wittig olefination, Julia-Kocienski olefination, and Crimmins propionate aldol reaction.

Applications of the Horner–Wadsworth–Emmons Olefination in Modern Natural Product Synthesis

The Horner–Wadsworth–Emmons (HWE) reaction is one of the most reliable olefination reaction and can be broadly applied in organic chemistry and natural product synthesis with excellent selectivity. Within the last few years HWE reaction conditions have been optimized and new reagents developed to overcome challenges in the total syntheses of natural products. This review highlights the application of HWE olefinations in total syntheses of structurally different natural products covering 2015 to 2020. Applied HWE reagents and reactions conditions are highlighted to support future synthetic approaches and serve as guideline to find the best HWE conditions for the most complicated natural products.

1 Introduction and Historical Background

2 Applications of HWE

2.1 Cyclization by HWE Reactions

2.2.1 Formation of Medium- to Larger-Sized Rings

2.2.2 Formation of Small- to Medium-Sized Rings

2.3 Synthesis of α,β-Unsaturated Carbonyl Groups

2.4 Synthesis of Substituted C=C Bonds

2.5 Late-Stage Modifications by HWE Reactions

2.6 HWE Reactions on Solid Supports

2.7 Synthesis of Poly-Conjugated C=C Bonds

2.8 HWE-Mediated Coupling of Larger Building Blocks

2.9 Miscellaneous

3 Summary and Outlook

Total synthesis: the structural confirmation of natural products

This feature article highlights total synthesis as one of the reliable tools for the structural confirmation of natural products.

Cyclodepsipeptide alveolaride C: total synthesis and structural assignment

First stereoselective total synthesis of naturally occurring bioactive cyclodepsipeptide alveolaride C has been achieved using a convergent approach. This synthetic study enabled us to establish unambiguously the stereochemistry of three unassigned chiral centres embedded in the nonpeptidic segment as well as revised the stereochemistry of the proposed β-phenylalanine counterpart of the molecule. The key strategic features of this synthesis include Sharpless asymmetric dihydroxylation for installing the vicinal diol moiety, Julia–Kocienski olefination for constructing the aliphatic side chain, the Shiina protocol for intermolecular esterification, amide coupling and macrolactamization for the ring formation.

First total synthesis of natural cyclodepsipeptide alveolaride C has been accomplished with an unambiguous solution to its structural riddle.

Total synthesis of nafuredin B

Total synthesis of marine secondary metabolite nafuredin B has been achieved for the first time using a convergent strategy. Sharpless epoxidation followed by acid catalyzed epoxide opening were adopted to install the tetrasubstituted hydroxy center, whereas the iterative Julia-Kocienski olefination, Wittig olefination and HWE olefination afforded the olefin bonds. Ring closing metathesis in the presence of a free tetrasubstituted hydroxy group provided the unsaturated δ-lactone moiety. This synthetic study provided unambiguous structural confirmation of the isolated nafuredin B.

Biselyngbyolides A & C: their total synthesis and anticancer activities

Convergent strategies have been developed for the total synthesis of biselyngbyolides A & C, and their anticancer activities were described.