Concise Synthesis of Ximenynic Acid

Abstract

An improved synthesis of ximenynic acid (1) starting from castor oil has been developed with the direct chlorination of ricinstearolic acid as the key step. By this modification, the synthetic route was more concise and economic. The separation of geometric somers was achieved by repeated urea fractionation.

Supplemental materials are available for this article. Go the publisher's online edition of Synthetic Communications to view the free supplemental file.     

A Concise Total Synthesis of (+)‐(6S,9R,10R)‐Bovidic Acid

A straightforward strategy for the stereoselective synthesis of (+)‐bovidic acid has been developed in eleven steps with an overall yield of 8.85%. The synthesis started from commercially available nonanal, and the key reactions involved were Sharpless asymmetric dihydroxylation, Grignard reaction, and Corey? Bakshi? Shibata reduction.     

Preliminary Study on Lipase-catalyzed Synthesis of Polyesters Containing L-Malic Acid Units

Optically active L-malic acid has been known as an intermediate among the tricarboxylic acid cycle inside living organisms, and thus has been recognized as a kind of C-4 renewable natural resource. Poly(malic acid) and the polyesters containing L-malic ac…     

由(S)-和( R )-天冬氨酸合成( R )-和(S)-(2-苄氧乙基)环氧乙烷的改良方法

苄氧乙基环氧乙烷;不对称合成;由(S)-和( R )-天冬氨酸合成( R )-和(S)-(2-苄氧乙基)环氧乙烷的改良方法     

A Concise Synthesis of (E)- and (Z)-Neomanoalides

The first synthesis of (Z)-neomanoalide ( 4 ) and an improved synthesis of its (E)-isomer 3 was accomplished in a concise, regiocontrolled manner by exploiting 2-[(tert-butyl)dimethylsiloxy]-4{[(tert-butyl)dimethylsiloxy]-methyl}furan ( 6 ) as the key reagent. Lithiation of 6 and subsequent reaction with the (2Z)- or (2E)-isomer of (6E)-3-{[(tert-butyl)dimethylsiloxy]methyl}-7-methyl-9-(2′,6′,6′-trimethylcyclohex-1′-enyl)nona-2,6-dienyl bromide ( 5 ), followed by hydrolysis, afforded the corresponding neomanoalide.     

Concise Synthesis of Pentenyl Phenyl Acrylic Acid

Pentenyl phenyl acrylic acid is a structural unit of pepticinnamin E, a natural product and a bisubstrate inhibitor of FPTase. In this article, a new synthetic strategy was developed to prepare pentenyl phenyl acrylic acid with high stereoselectivity and high overall yield of 78.6%. The method used in producing these effects involved the application of a five‐step procedure. Pentenyl phenyl acrylic acid was synthesized starting from 2‐iodo‐benzyl alcohol through an E‐selective Wittig–Horner reaction, and then the Sonogashira reaction was used to produce 2‐(1‐pentynyl)‐E‐ethyl‐cinnamoylate, which was quantitatively hydrogenated, catalyzed by Lindlar catalyst.     

A Practical Synthesis of (2S, 3R)-3-Amino-2-methylpentanoic Acid from L-Aspartic Acid

L -Aspartic acid by successive N-tosylation, anhydride formation, and reduction was converted into (3S)-3-(tosylamino)butano-4-lactone ( 4 ). Electrophilic methylation of 4 , subsequent iodo-esterification and nucleophilic methylation, followed by saponification and deprotection, gave (2S, 3R)-3-amino-2-methylpentanoic acid ( 2 ) with an ee of > 99% in seven steps and in an overall yield of 34%.     

Concise Stereoselective Total Synthesis of (4R, 6R)-Lactone Moiety Analog of Mevinoline and Compactin

A simple and highly efficient synthetic route has been developed for analogue of HMGCo A reductase inhibitor (1). The strategy utilizes S-Corey–Bakshi–Shibata (CBS) reduction, FeCl₃-catalyzed C-H insertion of ethyl diazoacetate.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Novel Concise Synthesis of (-)-Clausenamide

A six‐step synthesis of (?)‐clausenamide is described. Optically pure (R,E)‐1,3‐diphenylallylic alcohol was acetylated and then subjected to an Ireland‐Claisen rearrangement, giving the γ,δ‐unsaturated acid, which underwent a substrate‐induced stereoselective bromolactonization to afford the expected all‐equatorial substituted bromo‐δ‐lactone. An unusual chemo‐selective aminolysis of the lactone resulted in the formation of a γ,δ‐epoxy‐amide in stereospecific manner. Base‐promoted cyclization of this intermediate and the subsequent Davis oxidation furnished the synthesis, delivering the final product in >99% ee and up to 34% overall yield.     

A Concise Approach to the Synthesis of Carnosic Acid Type Diterpenes

AIDS has seriously affected human being's health and about 13.9 million people have been killed by AIDS in the world. So far, A. Paris et al1 found that Carnosic acid and its analogs posses inhibitory effect on HIV-1 protease and HIV virus replication activity. In order to clarify the structure-active relationship of this kind of compounds, a concise approach was designed, which is a convergent synthesis. Best to our knowledge, it is the first successful convergent route in total synthes…     

(R)-2-甲基-7-炔-辛酸的合成

以1,5-戊二醇为起始原料,用Evans手性助剂诱导的烷基化反应构造了C-2手性中心,用Ohira-Bestmann试剂制备了末端炔基,通过13步反应,合成了(R)-2-甲基-7-炔-辛酸,总收率为17.1%,e.e.值大于99%.     

Concise asymmetric synthesis of (R)-(+)-tanikolide

A highly stereoselective total synthesis of (R)-(+)-tanikolide, a δ-lactonic marine natural product, was accomplished in seven steps from easily available starting materials with a 51% overall yield. An asymmetric synthesis of an α-hydroxy aldehyde having a stereogenic quaternary center, by the use of (S)-2-(anilinomethyl)pyrrolidine as a chiral auxiliary, was employed in a key step.     

A Concise Semi-Synthetic Approach to Betulinic Acid from Betulin

Betulin was convert to betulinic acid using two different synthetic routes. The first approach involved an oxidation of betulin using Jones' reagent to betulonic acid and subsequent NaBH₄ reduction to betulinic acid. The second approach involved steps utilizing different protecting groups on the alcohol functional groups of betulin and Jones' oxidation to circumvent the isomerization of the secondary alcohol of betulinic acid.     

A Concise Synthesis of Forskolin

A 24‐step synthesis of (±)‐forskolin is presented, which delivered hundred milligram quantities of this complex diterpene in one pass. Transformations key to our approach include: a) a strategic allylic transposition, b) stepwise assembly of a sterically encumbered isoxazole ring, and c) citric acid‐modified Upjohn dihydroxylation of a resilient tetrasubstituted olefin. The developed route has exciting potential for the preparation of new forskolin analogues inaccessible by semisynthesis.     

Expedient Synthesis of (R)-Patulolide A

An efficient derivation of the title compound has been formulated from easily accessible 10-undecenoic acid (1). Thus, dodec-11-en-2-ol (3), prepared from 1, was pyranylated and subjected to bromination with NBS followed by acetolysis to furnish (2E)-1-acetoxy-11-(tetrahydropyranyloxy)dodec-2-ene (5). Its hydrolysis, oxidation, and depyranylation afforded the (2E)-hydroxy ester (9). This, on Candida rugosa lipase-catalyzed acetylation, SeO(2) oxidation, hydrolysis, and Yamaguchi macrolactonization, led to (R)-patulolide A (I) with 67.1% ee. The enantiomeric excess was improved to 97% by first resolving the alcohol 3 via porcine pancreatic lipase catalyzed acetylation and converting the corresponding (R)-acetate (13) to I as done above.     

A Concise Synthesis of Fumagillol

A 13-step synthesis of (±)-fumagillol ( 1 ), the direct precursor of the potent angiogenesis inhibitors TNP-470 and fumagillin, from crotonaldehyde, diethylamine, and acrolein (see the scheme) has been achieved. The synthesis features a remarkable hetero-Claisen rearrangement. Small-molecule inhibitors of angiogenesis are promising chemotherapeutic agents for the treatment of cancer and inflammatory diseases.