Mechanistic Manifold and New Developments of the Julia–Kocienski Reaction

Aïssa, Christophe

doi:10.1002/ejoc.200801117

Cited by 254 publications

(112 citation statements)

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“…Notably, this last transformation was highly E stereoselective (> 93:7) and the mild conditions preserved the stereochemical integrity of the intermediate a-branched aldehyde. [24] Final removal of the three silyl groups was achieved with TBAF to afford iriomoteolide 3a (1) (Scheme 5), whose analytical and spectroscopic properties were in good accordance with the published data. [4] 7,8-O-isopropylidene derivative 2 was obtained by treatment of 1 with 2,2-dimethoxypropane in the presence of pyridinium para-toluenesulfonate.…”

supporting

confidence: 58%

Syntheses and Biological Evaluation of Iriomoteolide 3a and Analogues

2009

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Amphidinium species are an extremely prolific source of marine secondary metabolites.[1] Structurally unique polyketides such as amphidinolides, caribenolide I, and amphidinolactones have fostered the interest of chemists not only as challenging targets for total synthesis but also because of their potent anticancer activity.[2] Recently, the Amphidinium strain HYA024 was found to produce cytotoxic compounds such as iriomoteolides 1a-c, [3] and a rare 15-membered macrolide, iriomoteolide 3a (1).[4] With a novel carbon framework comprising eight stereogenic centers, four of them in allylic positions, compound 1 represents the first member of a unique and unprecedented 15-membered macrolide class. Compound 1 represents the first member of a unique and unprecedented 15-membered macrolide class. In addition, the preliminary physiological properties disclosed for 1 and its 7,8-O-isopropylidene derivative 2 are very promising, showing potent cytotoxicity against lymphoma cell lines in the low nanomolar range. [4] To confirm the assigned structure, further evaluate its biological activity, and determine whether its cellular targets are related to those of larger congeners such as amphidinolides, [5] substantial quantities of these compounds are required. Our retrosynthetic approach to 1 involved four major disconnections, which revealed key fragments 3-6 as summarized in Scheme 1. Fragment 6 was planned to be incorporated at the end of our synthetic sequence by a JuliaKocienski olefination because of its widely recognized performance in the elaboration of such sensitive settings and also to ensure a flexible late-stage diversification of the parent compound. An intermolecular esterification was envisioned to assemble fragments 3 and 4. Finally, we hypothesized that the C 2 -symmetry of the diol precursor of fragment 5 could be advantageously used to construct the 1,5-diene upon ring closure by a cross-metathesis (CM)/ringclosing metathesis (RCM) approach. We were relying on the excellent results achieved by the Grubbs-type carbene complexes in both CM and RCM processes with the expectation that the formation of a medium-sized ring would also be E,E stereoselective (Scheme 1).The required building block 3 (Scheme 2) was prepared by alkylation of the Evans oxazolidinone 7[6] with iodide 8.[7]Scheme 2. a) Na[N( , THF, 73 %; n) DDQ, CH 2 Cl 2 , pH 7 buffer, RT, 85 %. CSA = camphorsulfonic acid, DDQ = 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, DIBAL-H = diisobutylaluminium hydride, DIPT = diisopropyl tartrate, DMF = N,N-dimethylformamide, DMSO = dimethylsulfoxide, MS = molecular sieves, PMB = para-methoxybenzyl, PPTS = pyridinium para-toluenesulfonate, TBAF = tetra-n-butylammonium fluoride, TBDPS = tert-butyldiphenylsilyl, TBS = tert-butyldimethylsilyl.Scheme 1. Retrosynthetic analysis for iriomoteolide 3a (1).

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confidence: 58%

Syntheses and Biological Evaluation of Iriomoteolide 3a and Analogues

2009

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“…[15] In searching for a mild and convenient method for the deoxygenation of epoxides, [16] we considered the proposed mechanism of the modified Julia olefination, [17,18] in which a metallated benzothiazole sulfone 1 reacts with a carbonyl compound to give an intermediate alkoxide 2 that undergoes a Smiles-type rearrangement via 3, leading to fragmentation with loss of SO 2 from 4 to give alkene 6 and the benzothiazol-2-olate heterocycle 5 (Scheme 1). red faithfully to the alkene product, because of the S N 2 epoxide ring-opening reactions and the antiperiplanar SO 2 elimination reaction of the β-alkoxysulfinate intermediates.…”

Section: Introductionmentioning

confidence: 99%

New Methodology for the Conversion of Epoxides to Alkenes

Ross

McGeary

2010

Eur J Org Chem

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“…Recently improved syntheses of the fragments used in the Masamune synthesis of bryostatin 7 (2) were reported by Hale (Manaviazar et al 2006). A fourth synthesis of a naturally occurring bryostatin, in this case of bryostatin 16 (5), was reported by Trost (Trost and Dong 2008), and syntheses of a close analogue of bryostatin 1 (''almost bryostatin 1'') and other highly potent analogues have been described by Keck (Keck et al 2008, 2009). Both of these later total syntheses involved ca.…”

Section: Introductionmentioning

confidence: 95%

Approaches to the total synthesis of biologically active natural products: studies directed towards bryostatins

et al. 2010

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Progress on a total synthesis of the marine natural products, the bryostatins, is reviewed. Following studies aimed at the synthesis of the 1,16-and 17,27-fragments, procedures for the assembly of the macrocyclic ring of the bryostatins were investigated. Although ring-closing metathesis was not found to be useful for the synthesis of bryostatins with geminal dimethyl groups at C18, the modified Julia reaction was found to be useful for the stereoselective formation of the 16,17-double-bond and led to a synthesis of an advanced macrocyclic intermediate. Several novel synthetic procedures feature in this work.

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Mechanistic Manifold and New Developments of the Julia–Kocienski Reaction

Cited by 254 publications

References 109 publications

Syntheses and Biological Evaluation of Iriomoteolide 3a and Analogues

Syntheses and Biological Evaluation of Iriomoteolide 3a and Analogues

New Methodology for the Conversion of Epoxides to Alkenes

Approaches to the total synthesis of biologically active natural products: studies directed towards bryostatins

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