Stereoselective Formal Total Synthesis of (+)-Methynolide

Yadav, J. S.; Pratap, T. V.; Rajender, V.

doi:10.1021/jo0704762

Cited by 46 publications

(18 citation statements)

References 41 publications

(30 reference statements)

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“…Based on these NOE analyses, the relative configuration at C-2′ and C-3′ was assigned as 2′ R* 3′ R* Next, the absolute configuration of the epoxide in 2 was defined by conversion of the epoxide to the diol via the intermediate acetonide followed by application of the modified Mosher method 11. Treatment of 2 in acetone with BF 3 -Et 2 O resulted in a smooth conversion of the epoxide to the acetonide 10 12. In the 2D NOESY spectrum of 10 , the H-2′ proton (δ H 3.91) showed a strong correlation with H 3 -15′ (δ H 1.23) indicating that the configuration at C-3′ had been inverted to 3′ S* after formation of the acetonide.…”

Section: Resultsmentioning

confidence: 99%

Nitropyrrolins A−E, Cytotoxic Farnesyl-α-nitropyrroles from a Marine-Derived Bacterium within the Actinomycete Family Streptomycetaceae

et al. 2010

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Five new farnesyl-α-nitropyrroles, nitropyrrolins A-E (1-5), were isolated from the saline culture of the marine actinomycete strain CNQ-509. This strain belongs to the "MAR4" group of marine actinomycetes, which have been demonstrated to be a rich source of hybrid isoprenoid secondary metabolites. The structures of the nitropyrrolins are composed of α-nitropyrroles with functionalized farnesyl groups at the C-4 position. These compounds are the first examples of naturally-occurring terpenyl-α-nitropyrroles. Chemical modifications, including one-step acetonide formation from an epoxide, and application of the modified Mosher method, provided the full stereostructures and absolute configurations of these compounds. Several of the nitropyrrolins, nitropyrrolin D in particular, are cytotoxic toward HCT-116 human colon carcinoma cells, but show weak to little antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA).As part as our continuing interest in the chemistry and biomedical potential of sedimentderived marine actinomycetes, we have isolated a variety of new actinomycete taxa, which show the capacity to produce unique secondary metabolites.1 These taxa include the chemically prolific genera Salinispora2 and "Marinispora",3 members of which produce new structural classes of secondary metabolites including salinosporamide A,4 a potent proteasome inhibitor that recently completed phase I clinical trial for the treatment of cancer.5 Another group of marine-derived actinomycetes, designated as MAR 4, is proving to be of significant chemical interest.1 To date, at least 15 strains belonging to this group have been isolated from diverse marine sediments. Previous chemical studies of cultured MAR4 strains led to the discovery of a broad range of polyketide-terpenoid secondary metabolites including marinone,6 compounds in the napyradiomycin series7 and azamerone. 8 Further chemical analysis of the cultured MAR4 strain CNQ-509, isolated from a marine sediment sample collected off La Jolla, CA, has led to the discovery of a new set of hybrid * To whom Correspondence should be addressed. Tel: + 1 858 534 2133. Fax: +1 858 558 3702. wfenical@ucsd.edu. ‡ Scripps Institution of Oceanography. † Korea Institute of Science and Technology, Gangneung, Korea § Contributed equally to this work.Supporting Information Available: Spectroscopic data sets (1D and 2D NMR, ESI MS, UV/VIS, HRMS, etc) for 1-5, 1 H NMR spectra for 6 and (S)-Mosher ester of 11, 1 H NMR and 1 H-1 H COSY spectra for 9a, 9b, 12a, 12b, 13a, 13b, 14a and 14b, 1 H NMR and 2D NOESY spectra for 10 and 11, and 1 H and 13 C NMR spectra for 7 and 8. This material is available free of charge via the Internet at http://pubs.acs.org polyketide-terpenoid metabolites composed of sesquiterpenoid and α-nitropyrrole components. These compounds, nitropyrrolins A-E (1-5), are unusual examples illustrating rare pyrrole nitration in the α position with linear sesquiterpenoid substitution. The structures of these new compounds, including their absolu...

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Section: Resultsmentioning

confidence: 99%

Nitropyrrolins A−E, Cytotoxic Farnesyl-α-nitropyrroles from a Marine-Derived Bacterium within the Actinomycete Family Streptomycetaceae

et al. 2010

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“…The CH 2 Cl 2 was freshly distilled from CaH 2 under nitrogen and THF was freshly distilled from sodium/benzophenone under nitrogen. The substrates 1 , 9 , 10 , 11 , 13 , 14 , 15 , 18 were prepared according to the reported procedure. The N,P‐ligands L1 , L2 , L4 , L5 ,, L6 , L7 , L8 were prepared according to the reported procedure.…”

Section: Methodsmentioning

confidence: 99%

Thiazole, Imidazole and Oxazoline Based N,P‐Ligands for Palladium‐Catalyzed Cycloisomerization of 1,6‐Enynes

Liu

Rabten

et al. 2016

Eur J Org Chem

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A series of N,P‐ligands were prepared and evaluated in the asymmetric palladium‐catalyzed cycloisomerization of allyl propargyl ether substrates. The reactivity and enantioselectivity of the reaction was shown to be highly dependent on the chiral skeleton of the ligand structures with ee's ranging from 22–99 %. The proton source had a significant impact on the enantioselectivity. The generation of palladium hydride from formic acid led to the highest ee. A selectivity model based on a proposed transition state was used to predict and explain the enantiomeric outcome of the reaction.

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“…26 Swern oxidation 27 to give aldehyde 22 and Corey-Fuchs 28 alkynylation gave an intermediary alkyne in 59% yield from 21. Subsequent hydrostannation with tributylstannane and catalytic 2,2′-azobis(isobutyronitrile) delivered (E)-vinylstannane 23, 29 which was converted into the vinyl iodide (80% yield over two steps). Acetonide removal thereof with 1 M aqueous hydrogen chloride afforded fragment 12 (72% yield).…”

Section: Syn Lettmentioning

confidence: 99%