Formal total synthesis of (±)-cortistatin A

A second-generation synthesis of the pentacyclic core of the cortistatins, a family of rearranged steroidal alkaloids that have recently attracted much attention, is reported. The improved sequence provides access to significant quantities of this key compound, which enabled a formal total synthesis of (±)-cortistatin A by conversion to the key Nicolaou/Hirama dienone. It is anticipated that this new, robust route to the pentacyclic core will facilitate the total synthesis of a range of natural products in the cortistatin family, as well as the construction of key structural analogs to probe the promising biological activity of these important compounds.     

Formal total synthesis of enigmazole A

A stereoselective formal total synthesis of enigmazole A, a marine macrolide isolated from Cinachyrella enigmatica, is described. Lewis acid mediated intramolecular allylation of an α-acetoxy ether, prepared from alcohol and carboxylic acid fragments was carried out to construct the methylene THP ring with high stereoselectivity. The late-stage macrolactonization of the corresponding seco-acid provided a known synthetic intermediate of enigmazole A.     

Formal total synthesis of shikonin via Dötz benzannulation

The Dötz benzannulation reaction provides mild conditions for the construction of highly functionalized aromatic compounds. We have utilized this method for the formal total synthesis of shikonin. The key step in our approach is the application of the Dötz benzannulation reaction between Fischer a chromium carbene complex and an optically active alkyne for the construction of the aromatic skeleton. This is followed by protecting group manipulation and formation of the epoxide moiety using the Sharpless procedure.     

Concise formal synthesis of (+)-pyripyropene A

A concise enantioselective synthesis of A/B bicyclic segment of naturally occurring α-pyrone meroterpenoid pyripyropene A is achieved in 9 steps (LLS) and 7.5% yield starting from R-(?)-carvone. The significant points of the synthesis include: (1) an intramolecular 1, 3-dipolar cycloaddition reaction to construct the A ring and assemble C4 quaternary carbon stereocenter as well; (2) reductive cleavage of the oxazole motif utilized Raney Ni/B(OCH₃)₃.     

Formal Syntheses of (±)‐Methylenomycins A and B

The syntheses of methyl ester of (±)‐desepoxy‐4,5‐didehydromethylenomycin A ( 4 ) and 2,3‐dimethyl‐5‐methoxycarbonyl‐2‐cyclopentenone ( 5 ) were accomplished from a common starting material, 2,3‐dimethyl‐4‐methoxyphenol (8), in only four and two steps in 35% and 53% overall yields, respectively. Photochemical rearrangements of masked p‐benzoquinones in methanol are the key steps.     

Total synthesis of Daphnodorin A

A total synthesis of Daphnodorin A, a member of the Daphnodorins, was accomplished. Key features of the synthetic strategy include construction of 2-substituted-3-functionalized benzofuran via intramolecular Heck reaction and a mild Barton–McCombie deoxygenation process mediated by triethylborane. The total synthesis provided Daphnodorin A in 19.7% or 5.6% overall yield over 7 or 15 steps.     

Formal synthesis of schulzeines B and C

A formal synthesis of schulzeines B and C, marine natural products with inhibitory effect against α-glucosidase, has been achieved. The key reactions of the synthesis are N-acyliminium ion cyclization, Sharpless asymmetric dihydroxylation, olefin cross metathesis, and asymmetric allylboration.     

A Formal Total Synthesis of (-)-Brevisamide

A formal total synthesis of (−)-brevisamide has been achieved. The synthetic approach highlights a chemoselective asymmetric dihydroxylation and a one-pot Fraser-Reid epoxidation/PMB protection reaction sequence.     

A scaleable formal total synthesis of dehydrogliotoxin

A formal total synthesis of the epidithiodiketopiperazine natural product, dehydrogliotoxin (2), utilizing an intramolecular ring closure to form key intermediate 5 is described.     

Racemic synthesis of an intermediate for the formal synthesis of madindoline A and B

On the basis of the application of the Darzens/ring-expansion process of cyclobutenedione developed previously by our group, a new strategy for the multisubstituted cyclopentene units of madindoline A and madindoline B has been reported in this paper. In light of the strategy, the synthesis of racemic Omura’s intermediate was finished in four steps and 34% overall yield, which furnished a new formal synthetic route to madindolines A and B.     

Reflections on the mechanism of the Barton-McCombie Deoxygenation and on its consequences2

The Barton-McCombie deoxygenation is a landmark reaction in organic chemistry. Its efficiency in generating carbon radicals from alcohols is unmatched, despite the passage of more than 40 years since its discovery. Its mechanism, far from being straightforward, is in fact quite subtle and conceptually part of a much larger family of very powerful thiocarbonyl controlled radical reactions. This general mechanistic manifold encompasses the degenerate transfer of xanthates and related thiocarbonylthio congeners, a process that also subtends the now popular RAFT/MADIX polymerization technology, the remarkably versatile Barton decarboxylation via thiohydroxamate esters, the generation of nitrogen-centered radicals from oxime xanthates and thiosemicarbazones and thiosemicarbazides, and certainly other transformations that will emerge in the coming years. The present overview retraces the history of the Barton-McCombie reaction, the evolution of the mechanistic aspects and the resulting consequences in terms of new transformations and synthetic applications.     

4-甲氧基-2,3,5-三甲基吡啶的合成新方法

以2，3，5-三甲基吡啶为原料，经氧化，硝化，甲氧基化，脱离四步反应合成 4-甲氧基-2，3，5-三甲基吡啶，总收率76%，其结构经IR，~1H NMR，~(13)C NMR 确证。     

Total synthesis of (+)-lentiginosine from d-glucose

A total synthesis of (+)-lentiginosine, a potent and selective amyloglucosidase inhibitor, is reported from a d-glucose-derived epoxide in 38% overall yield. In this synthesis, ambient conditions and readily available starting materials and reagents are used.     

First total synthesis of natural products cajanolactone A and cajanonic acid A

First total synthesis of cajanolactone A and cajanonic acid A has been achieved through steps of anion–anion condensations,cyclization,Williams etherification,selective demethylation,1 3-sigmatropic rearrangement and hydrolysis.This work provides an efficient method for future cajanonic acid A derivatives synthesis.     

Formal Synthesis of Vallesamidine

A novel route to the racemic selenide (1RS,12bRS)‐1‐ethyl‐2,3,6,7,12,12b‐hexahydro‐1‐[2‐(phenylseleno)ethyl]indolo[2,3‐a]quinolizin‐4(1H)‐one ( 13b ), a key intermediate in the total synthesis of vallesamidine ( 1 ), was elaborated. Compound 3a , obtained by Pictet–Spengler reaction of tryptamine and cyclohept‐4‐enyl‐1‐carbaldehyde ( 2c ), was oxidized with KMnO₄ to the diacid 4 , which was subsequently converted into the isomeric tetracyclic lactams 5a,b . After proper protection maneuvers, Barton decarboxylation of 10a,b , trapping with PhSe₂Ph, and Boc removal afforded 13b .     

First total synthesis of paecilodepsipeptide A

The first total synthesis of paecilodepsipeptide A is reported.A convergent,flexible strategy employing peptide chemistry and culminating in macrolactamisation is described.The previously reported structure of compound is confirmed.     

Total synthesis of pyripyropene A

The total synthesis of pyripyropene A, a potent ACAT2 inhibitor with high isozyme selectivity, was completed. Key features of the synthetic strategy include Ti(III)-mediated radical cyclization and Peterson olefination for the construction of the AB ring segment and stereoselective dihydro-γ-pyrone formation (C-ring). The total synthesis provided pyripyropene A in 5.3% overall yield over 17 steps.     

Entry into Major Groups Retaining Taxol via Sinenxan A

Compound 1 as a key intermediate of 1,7,9-trideoxytaxol was synthesized in ten steps from a biosynthetically available taxane,Sinenxan A. The key steps in the synthesis were deoxygenation at C-14,allylic oxidation at C-13 and construction of the oxetane ring.