The Asymmetric Total Synthesis and Configuration Confirmation of Aplysiaenal and Nhatrangin A, Truncated Derivatives of Aplysiatoxin and Oscillatoxin

Asymmetric total syntheses of aplysiaenal (1) and nhatrangin A (2), truncated derivatives of the aplysiatoxin/oscillatoxin family of marine natural products, from configurationally defined intermediates are described. NMR spectra of our synthesized nhatrangin A did not match with either those obtained from authentic samples of the natural product or material obtained via two other total syntheses, but were similar to that obtained from a sample obtained in a third total synthesis. By independently synthesizing the fragments used in its total syntheses, we were able to confirm the configuration of nhatrangin A and clarified that the discrepancy in the spectroscopic data is due to salt formation of the carboxylic acid moiety.

Synthesis of structurally diverse derivatives of aconitine-type diterpenoid alkaloids and their anti-proliferative effects on canine breast cancer cells

As one of the most common malignancies in female dogs, no drugs have been developed specifically for the treatment of canine mammary carcinoma. In our previous study, a series of diterpenoid alkaloids derivatives were synthesized and exhibited good anti-proliferative activity in vitro against both normal and adriamycin-resistant human breast cancer cells lines. In this study, a series of structurally diverse aconitine-type alkaloids derivatives were also synthesized basing on the minimal modification principle, by modifying on A-ring, C-ring, D-ring, N-atom or salt formation on aconitine skeleton. Their anti-proliferative effects and mechanism on canine mammary cancer cells were investigated, exhibiting the importance of the substitution at A ring, the long chain ester at the C8, the hydroxyl group at the C13, the phenyl ring at the C14 and the N-ethyl group, while the methoxy group at the C1 and C16 showed little effect on the activity. The results of the proliferation, apoptosis and ultrastructure tests of the treated canine mammary carcinoma cells referred that the representative compound, aconitine linoleate (25) could block the cell cycle of canine mammary carcinoma cells in the G0/G1 phase, and exhibit the anti-proliferative effect by inducing apoptosis.

Formal enantioselective synthesis of nhatrangin A

A new and straightforward synthesis of the C1-C7 core fragment of nhatrangin A was achieved in 14 steps from achiral 3-hydroxybenzaldehyde, without the need of chiral reagents or enzymatic resolution to introduce the chiral centers. The key asymmetric steps include in particular a highly enantioselective organocatalyzed Michael addition on an aryl vinyl ketone, a Sharpless asymmetric epoxidation and a subsequent regioselective ring opening of the resulting chiral epoxide. This work represents the first formal enantioselective synthesis of nhatrangin A.

Synthesis of meta-Terphenyl-2,2''-diols by Anodic C-C Cross-Coupling Reactions

The anodic C-C cross-coupling reaction is a versatile synthetic approach to symmetric and non-symmetric biphenols and arylated phenols. We herein present a metal-free electrosynthetic method that provides access to symmetric and non-symmetric meta-terphenyl-2,2''-diols in good yields and high selectivity. Symmetric derivatives can be obtained by direct electrolysis in an undivided cell. The synthesis of non-symmetric meta-terphenyl-2,2''-diols required two electrochemical steps. The reactions are easy to conduct and scalable. The method also features a broad substrate scope, and a large variety of functional groups are tolerated. The target molecules may serve as [OCO](3-) pincer ligands.

Selective Synthesis of Partially Protected Nonsymmetric Biphenols by Reagent- and Metal-Free Anodic Cross-Coupling Reaction

The oxidative cross-coupling of aromatic substrates without the necessity of leaving groups or catalysts is described. The selective formation of partially protected nonsymmetric 2,2'-biphenols via electroorganic synthesis was accomplished with a high yield of isolated product. Since electric current is employed as the terminal oxidant, the reaction is reagent-free; no reagent waste is generated as only electrons are involved. The reaction is conducted in an undivided cell, and is suitable for scale-up and inherently safe. The implementation of O-silyl-protected phenols in this transformation results in both significantly enhanced yields and higher selectivity for the desired nonsymmetric 2,2'-biphenols. The use of a bulky silyl group to block one hydroxyl moiety makes the final product less prone to oxidation. Furthermore, the partially silyl-protected 2,2'-biphenols are versatile building blocks that usually require tedious or low-yielding synthetic pathways. Additionally, this strategy facilitates a large variety of new substrate combinations for oxidative cross-coupling reactions.

Marine natural products

This review covers the literature published in 2013 for marine natural products (MNPs), with 982 citations (644 for the period January to December 2013) 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 (1163 for 2013), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.