Concise and Efficient Total Syntheses of Alkannin and Shikonin

Two enantiomic natural products with wound-healing properties , alkannin ( 1 ) and shikonin ( 2 ), are accessible by a short and efficient total synthesis. The success was achieved by a novel protecting system for masking of 5,8-dihydroxy-1,4-naphthoquinones (naphthazarins) and a highly stereoselective ketone reduction.     

New Asymmetric Synthesis of Alkannin and Shikonin

A new approach for asymmetric synthesis of alkannin and shikonin is presented. The chiral centers of the targets were introduced via an asymmetric C-arylation of-protected chiral glyceraldehyde in high de. The two enantiomers were prepared with the D-isopropylidenegly-ceraldehyde as the starting material.     

The Chemistry and Biology of Alkannin,Shikonin, and Related Naphthazarin Natural Products

Wound healing properties of plant extracts that contain the naphthoquinone natural products alkannin ( 1 ) and shikonin ( 2 ) have been known for many centuries. More recently, the biological properties of 1 , 2 , and related derivatives have been demonstrated experimentally, and their production both by cell cultures and chemical synthesis has been studied extensively.     

Chemoenzymatic Synthesis of Advanced Intermediates for Formal Total Syntheses of Tetrodotoxin

Advanced intermediates for the syntheses of tetrodotoxin reported by the groups of Fukuyama, Alonso, and Sato were prepared. Key steps include the toluene dioxygenase mediated dihydroxylation of either iodobenzene or benzyl acetate. The resulting diene diols were transformed into Fukuyama's intermediate in six steps, into Alonso's intermediate in nine steps, and into Sato's intermediate in ten steps.     

紫草素的全合成研究进展

综述了天然产物紫草素的全合成研究进展, 分析了紫草素的合成路线, 讨论了各合成方法的优缺点.     

Design,Synthesis and Anticancer Activity of Shikonin and Alkannin Derivatives with Different Substituents on the Naphthazarin Scaffold

Based on the asymmetric reduction of alkannin ketone derivative 4 by diisopinocampheylchloro-borane(DIP-Cl), a series of shikonin and alkannin derivatives was designed, synthesized and their anticancer activities against various kinds of cell lines were evaluated. The in vitro biological experiments demonstrated that compound S-10, a 5,8-O-dimethyl-1,4-dioxime alkannin derivative, not only displayed excellent antiproliferative activity against cancer cells, but also exhibited low toxicity towards normal cells. It could induce HCT-116 cell apoptosis, but had no impact on the cell cycle. The underlying anticancer mechanism of S-10 is most likely different from other shikonin and alkannin derivatives.     

埃博霉素的合成

埃博霉素(Epothilones)是一类新的具有抗癌活性的化合物, 其作用机理与紫杉醇相似。对天然埃博霉素及其衍生物的主要全合成进行了综述.     

Total Syntheses of Tubulysins

The total syntheses of tetrapeptides tubulysins D ( 1 b ), U ( 1 c ), and V ( 1 d ), which are potent tubulin polymerization inhibitors, are described. The synthesis of Tuv ( 2 ), an unusual amino acid constituent of tubulysins, includes an 1,3‐dipolar cycloaddition reaction of chiral nitrone D ‐ 6 derived from D ‐gulose with N‐acryloyl camphor sultam (?)‐ 9 employing the double asymmetric induction, whereas the synthesis of Tup ( 20 ), another unusual amino acid, involves a stereoselective Evans aldol reaction of (Z)‐boron enolate generated from (S)‐4‐isopropyl‐3‐propionyl‐2‐oxazolidinone with N‐protected phenylalaninal and a subsequent Barton deoxygenation protocol. We accomplished the total syntheses of tubulysins U ( 1 c ) and V ( 1 d ) by using these methodologies, in which the isoxazolidine ring was used as the effective protective group for γ‐amido alcohol functionality. Furthermore, to understand the structure‐activity relationship of tubulysins, we synthesized tubulysin D ( 1 b ) and cyclo‐tubulysin D ( 1 e ) from 2 ‐Me and 20 , and ent‐tubulysin D (ent‐ 1 d ) from ent‐ 2 ‐Me and ent‐ 20 , respectively. The preliminary results regarding their biological activities are also reported.     

Total Syntheses of Vancomycin

A total synthesis of the vancomycin aglycon 1 has eluded synthetic chemists for so many years that the preparation of this molecule has become a vendetta for some groups. Finally, and almost simultaneously, research teams led by Evans and by Nicolaou have succeeded. Similarities and differences in their synthetic approaches are highlighted herein.     

Formal Total Synthesis of Platencin

The right bicycle : A concise formal synthesis of platencin was based on an efficient oxygen‐mediated palladium‐catalyzed cycloalkenylation of 1 to form a bicyclo[3.2.1]octane, and a deoxygenative rearrangement of tosylhydrazone 2 to construct the bicyclo[2.2.2]octane 3 . The total yield of the core structure 4 of platencin was 17.5 % for 13 steps from a commercially available compound. Ts=p‐toluenesulfonyl, TBS=tert‐butyldimethylsilyl, Piv=pivaloyl.

     

Formal Total Synthesis of Aliskiren

The efficient and selective formal total synthesis of aliskiren is described. Aliskiren, a renin inhibitor drug, has received considerable attention, primarily because it is the first of the renin inhibitor drugs to be approved by the FDA. Herein, the formal synthesis of aliskiren by iridium‐catalyzed asymmetric hydrogenation of two allylic alcohol fragments is reported. Screening a number of N,P‐ligated iridium catalysts yielded two catalysts that gave the highest enantioselectivity in the hydrogenation, which gave the saturated alcohols in 97 and 93 % ee. In only four steps after hydrogenation, the fragments were combined by using the Julia–Kocienski reaction to produce late‐stage intermediate in an overall yield of 18 %.     

A Formal Total Synthesis of Aplysin

A formal, total synthesis of aplysin has been described employing intermolecular (2+2) cycloaddition reaction between ketene and an olefin as a key step.     

Total Syntheses of Vancomycin and Eremomycin Aglycons

Controlling the elements of planar and axial chirality are the principal challenges in the synthesis of the aglycon of vancomycin. Vancomycin is the prototypical member of the glycopeptide family of antibiotics which are effective for the treatment of infections by methicillin-resistant Staphylococcus aureus. The first total syntheses of the vancomycin and eremomycin aglycons provide insight into the influence of structure on kinetic and thermodynamic control of atropselective macrocyclizations.     

Total Syntheses and Biological Evaluation of Miuraenamides

The miuraenamides, relatively simple representatives of a class of cyclodepsipeptides with high antitumor activity, can be easily and flexibly obtained by the concept of peptide modification. A reaction sequence consisting of an aldol reaction, oxidation, and methylation of the glycine subunit of the cyclodepsipeptides allows the incorporation of the unusual α,β‐unsaturated dehydroamino acid in one of the last steps of the synthesis.