An alternative total synthesis of Patulolide A

A new total synthesis of [R]‐Patulolide A from readily available (R)‐propylene epoxide obtained using the asymmetric synthetic approach is reported. The key reactions involved are ozonolysis and Yamaguchi macrolactonization, resulting in the ring system.     

Synthesis of Both Enantiomers of Flavanone and 2‐Methylchromanone

An efficient enantiospecific synthesis of the (R)‐ and (S)‐enantiomers of flavanone and 2‐methylchromanone is described. The key steps are a C,C‐bond formation by ring opening of a chiral epoxide with a dithiane anion, followed by a Mitsunobu cyclization. The products obtained have high enantiomeric purity.     

手性铝试剂促进的β-环氧醇动力学拆分研究

首次以手性联萘酚修饰的三乙基铝为催化剂对消旋的β-环氧醇的动力学拆分进行了研究, 初步研究结果表明其回收原料的ee值可达60%. 同时研究了不同条件下三乙基铝与手性配体形成的手性路易斯酸对β-环氧醇的动力学拆分的影响, 并探讨了在三乙基铝催化下的反应机理.     

Towards Stereoselective Synthesis of the C(31)–C(39) and C(20)–C(27) Fragments of Phorboxazole A

The stereoselective synthesis of the C(31)–C(39) and C(20)–C(27) fragments of phorboxazole A ( 1 ) was achieved from commercially available and inexpensive D ‐mannitol. Crimmins aldol reaction and a decarboxylative Claisen‐type reaction are the key steps for the C(31)–C(39) fragment, and L ‐proline‐catalyzed aldol reaction, Sharpless asymmetric epoxidation, and epoxide ring opening reaction with Gilman's reagent are the key steps for the C(20)–C(27) fragment of phorboxazole.     

First total synthesis of the anti-inflammatory and pro-resolving lipid mediator 16(R),17(S)-diHDHA

The first total synthesis of the anti-inflammatory and pro-resolving lipid mediator 16(R),17(S)-diHDHA, derived from docosahexaenoic acid (DHA), and its 16-epimer have been achieved. Two synthetic approaches are described for the synthesis of 16(R),17(S)-diHDHA. The first strategy started from DHA and used an enzymatic reaction, a vanadium catalyzed allylic epoxidation and a base-promoted epoxide isomerization. The second approach utilized a chiral pool strategy starting from 2-deoxy-d-ribose to establish the chiral centers; Wittig reactions, mild acetonide cleavage and ester hydrolysis were the key steps in the synthesis.     

An Iterative Acetylene–Epoxide Coupling Strategy for the Total Synthesis of Aspinolide A

The total synthesis of aspinolide A ( 1 ) was successfully achieved by an iterative acetylene? epoxide coupling strategy and a Yamaguchi lactonization as the key steps.     

A short and concise route to total synthesis of Dendrodolide L

A short and efficient method for the stereoselective synthesis of Dendrodolide L has been developed from inexpensive and commercially available starting material. This convergent synthesis utilizes Jacobsen kinetic resolution, regioselective ring-opening of epoxide and Yamaguchi macrolactonization as key steps.     

Stereospecific Syntheses of Chiral Epoxides Bearing 1,4‐Diyne or 1,4‐Enyne Unit Via Alkylative Epoxide Rearrangement

Abstract

Stereospecific syntheses of a series of chiral epoxides bearing the 1,4‐diyne or 1,4‐enyne unit were achieved through alkylative epoxide rearrangement, which proceeded in two steps: 1) coupling of epoxy tosylate with alkynyltrifluoroborate; and 2) ring‐closure of the resulting intermediate.     

Nucleophilic ring-opening of epoxide and aziridine acetates for the stereodivergent synthesis of β-hydroxy and β-amino γ-lactams

A highly regio- and stereoselective synthesis of novel β,γ-disubstituted γ-lactams with either an anti or syn relative configuration was developed from readily available epoxide and aziridine acetates. The key steps include the regio- and diastereocontrolled nucleophilic ring-opening of these three-membered heterocycles followed by mild reductive cyclization of the γ-azido ester intermediate. The method was also extended to an asymmetric synthesis of (4R,5S)-4-hydroxy-5-phenylpyrrolidin-2-one from a chiral epoxide acetate. The main features of this versatile synthesis of functionalized γ-lactams include the involvement of inexpensive reagents and mild conditions together with high chemical efficiency.     

Stereoselective synthesis of pachastrissamine (jaspine B)

A stereoselective synthesis in enantiopure form of the natural anhydrophytosphingosine pachastrissamine (jaspine B), a metabolite isolated from sponges, is described. The chiral epoxide (R)-glycidol was the starting material. Key steps of this synthesis are a Sharpless asymmetric epoxidation, an intramolecular stereospecific epoxide opening mediated by a trichloroacetimidate group, and the formation of a tetrahydrofuran ring via intramolecular nucleophilic displacement.     

First enantioselective total synthesis of (−)-heliannuol C

The first, efficient total synthesis of (−)-heliannuol C (1) was accomplished enantioselectively, using a chemoenzymatic desymmetrization of the σ-symmetrical diol, a ring closing metathesis, a diastereoselective epoxidation, and a regioselective reductive cleavage of epoxide as the key reaction steps.     

Total Synthesis and Biological Evaluation of Seiricuprolide and Pestalotioprolide B

The first total syntheses of seiricuprolide and pestalotioprolide B, rare 14-membered α,β-unsaturated macrolides embedding a chiral epoxide motif, were achieved in 17 steps with 1.9 % and 1.6 % overall yields, respectively. Our synthesis featured the key Shiina macrolactonization to construct the 14-membered macrocyclic skeleton, Wittig olefination to generate the (E)-α,β-unsaturated ester and selective reduction of advanced chiral propargylic alcohol intermediate to enable the exclusive formation of Z- or E-olefin at C8−C9. Synthetic seiricuprolide and pestalotioprolide B were evaluated for their cytotoxic activity against the HCT116 colon cancer cell line as well as their inhibitory effect on CFTR chloride channel activity in human intestinal epithelial (T84) cells. Preliminary structure–activity relationship suggested that the C5−C6 β-epoxide moiety suppressed both biological activities.     

Stereoregular polycarbonate synthesis: Alternating copolymerization of CO2 with aliphatic terminal epoxides catalyzed by multichiral cobalt(III) complexes

Completely stereoregular polycarbonate synthesis was achieved with the use of unsymmetric multichiral cobalt‐based complexes bearing a derived chiral BINOL and an appended 1,5,7‐triabicyclo[4.4.0] dec‐5‐ene as catalyst for the copolymerization of CO₂ and aliphatic terminal epoxides at mild conditions. The (S,S,S)‐Co(III) complex 1c with sterically hindered substituent group is more stereoregular catalyst for the copolymerization of CO₂ and racemic propylene oxide to afford a perfectly regioregular poly(propylene carbonate) (PPC), with >99% head‐to‐tail linkages, >99% carbonate linkages, and a K_rel of 24.4 for the enchainment of (R)‐epoxide over (S)‐epoxide. The isotactic PPC exhibits an enhanced glass transition temperature of 47 °C, which is 10–12 °C higher than that of the corresponding irregular polycarbonate. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Asymmetric Synthesis of the C（17）——C（28） Subunit of Didemnaketal B

The stereocontrolled synthesis of the C（17）--C（28） fragment 3 of didemnaketal B was accomplished in 21 steps from the natural （R）-（＋）-pulegone and （S）-（--）-citronellal. The key steps involved diastereoselective construction of two chiral carbon centers through the intramolecular chiral induction and uncommon Julia olefination of ketone forming the E-trisubstituted C（22）--C（23） double bound.     

Total synthesis of catenioblin B

Herein we report the first total synthesis of catenioblin B (1) via a titanium(IV) mediated regioselective epoxide ring-opening, Grignard reaction, Luche’s reduction and TEMPO/BAIB mediated intramolecular cyclization as the key steps.     

Expeditious Synthesis of Ramipril: An Angiotensin Converting Enzyme (ACE) Inhibitor

We document an efficient and cost‐effective synthesis of ramipril 1 utilizing (i) an environmentally benign process for the esterification of racemic 2‐aza‐bicyclo‐[3.3.0]‐octane‐3‐carboxylic acid hydrochloride 2 using boric acid as a catalyst and (ii) a robust resolution process for the synthesis of 3a by means of inexpensive and recyclable L‐(+)‐mandelic acid as key steps.     

Stereoselective total synthesis of (−)-brevisamide

The stereoselective total synthesis of (−)-brevisamide, a novel marine cyclic ether alkaloid isolated from dinoflagellate karenia brevis is described. The key steps involved in this synthesis are the Sharpless asymmetric epoxidation and regioselective ring opening of chiral epoxide by Gilman's reagent. The tetrahydropyran core has been constructed by an intramolecular S_N2 cyclisation.     

A common strategy for the stereoselective synthesis of anhydrophytosphingosine pachastrissamine (jaspine B) and N,O,O,O-tetra-acetyl d-lyxo-phytosphingosine

The highly stereoselective Grignard addition on chiralimine 8 and opening of chiral epoxide 9 with Grignard reagent have been used as key steps in the stereoselective synthesis of cytotoxic anhydrophytosphingosine pachastrissamine (jaspine B) and N,O,O,O-tetra-acetyl d-lyxo-phytosphingosine.     

New and Practical Synthesis of Montelukast Sodium,an Antiasthmatic Drug

Abstract

A new and practical synthesis of montelukast sodium, an antiasthmatic drug, is described. The key steps are the synthesis of nitrile derivative 4 by chiral reduction of keto ester 9 using (?)-DIP-Cl, synthesis of vinylquinoline framework 16 by Wittig reaction, and Heck coupling of nitrile 4 with vinylquinoline 16. The method is operationally simple and suitable for the industrial production of the drug substance.

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

First total synthesis of pro-resolving and tissue-regenerative resolvin sulfido-conjugates

The first total synthesis of the pro-resolving and tissue-regenerative resolvin sulfido-conjugates: 7S,8R,17S-RCTR1, 7S,8R,17S-RCTR2 and 7S,8R,17S-RCTR3, derived from docosahexaenoic acid, has been achieved. Two synthetic approaches are described. Chiral centers 7S and 8R were introduced in both approaches via a chiral pool strategy starting from 2-deoxy-d-ribose. The 17S chiral center was introduced either by a chiral pool strategy or by an enzymatic hydroxylation with lipoxidase. Wittig reactions, selective epoxide formation and epoxide opening with glutathione, l-cysteinylglycine and l-cysteine respectively, were the key steps in the synthesis.