Total syntheses of subereamollines A and B

Shearman, James W.; Myers, R. M.; Brenton, James D.; Ley, Steven V.

doi:10.1039/c0ob00636j

Cited by 34 publications

(24 citation statements)

References 33 publications

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“…The zinc mediated chelate controlled intramolecular hydride delivery20 favored the trans isomer 19 over cis isomer 20 . The relative configurations of diastereomers 19 and 20 were assigned using 1 H and 13 C NMR which were consistent with literature data16a Accomplishing the synthesis of the known spiroisoxazoline ketone 9 and alcohol 19 also facilitated the formal syntheses of aerophobin‐1,16b aerothionin,16a homoaerothionin,16k aeroplysinin‐1,21 (±)‐purealin A,22 calafianin,23 subereamollines A and B16e through previously developed routes.…”

Section: Resultssupporting

confidence: 80%

“…Having in hand the coupling partners, we then executed our final set of reactions to furnish the desired natural product. In doing so, ester 19 was first hydrolyzed with LiOH‐MeOH to afford the corresponding carboxylic acid 27 which was further coupled with diamine 26 with ® T 3 P in CH 2 Cl 2 16e to afford (±)‐11‐deoxyfistularin‐3 ( 1 ) in 75 % yield as an inseparable diastereomeric mixture (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

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Doubling the Capacity of Lithium Manganese Oxide Spinel by a Flexible Skinny Graphitic Layer

et al. 2014

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By coating nanoparticular lithium manganese oxide (LMO) spinel with a few layers of graphitic basal planes, the capacity of the material reached up to 220 mA h g−1 at a cutoff voltage of 2.5 V. The graphitic layers 1) provided a facile electron‐transfer highway without hindering ion access and, more interestingly, 2) stabilized the structural distortion at the 3 V region reaction. The gain was won by a simple method in which microsized LMO was ball‐milled in the presence of graphite with high energy. Vibratory ball milling pulverized the LMO into the nanoscale, exfoliated graphite of less than 10 layers and combined them together with an extremely intimate contact. Ab initio calculations show that the intrinsically very low electrical conductivity of the tetragonal phase of the LMO is responsible for the poor electrochemical performance in the 3 V region and could be overcome by the graphitic skin strategy proposed.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Doubling the Capacity of Lithium Manganese Oxide Spinel by a Flexible Skinny Graphitic Layer

et al. 2014

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“…However, the oxidative methods for spiroisoxazoline synthesis remain restricted to aromatic systems with moderate isolated yields, and often required the use of toxic metallic based oxidants 16a–16d. However, the oxidative cyclization of oxime esters using diacetoxyiodosobenzene was proven to be the most suitable oxidation reagent for phenolic α‐oximino ester to date 16e,16g–16i. Very recently we also reported an efficient and alternative process to access spiroisoxazoline core structures as a model study toward this family of natural products 17…”

Section: Introductionmentioning

confidence: 99%

Divergent and Concise Syntheses of Spiroisoxazolines: First Total Synthesis of 11‐Deoxyfistularin‐3

Das

Hamme

2015

Eur J Org Chem

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A divergent and concise base-promoted Dieckmann-type keto-ester condensation strategy is demonstrated to generate two unique spiro [cyclohexadiene-isoxazoline] moieties. The consecutive di-bromination-elimination-bromination of the corresponding spiro moiety has been successfully utilized to furnish the desired core structure of many bromotyrosine derived spiroisoxazoline natural products. The spiroisoxazoline IntroductionThe natural occurrence and the discovery of new synthetic agents displaying antineoplastic activity are important topics of research in medicinal chemistry.[1] Since the first reports pertaining to the herbicidal and plant hormonal activity, [2] spiroisoxazoline containing natural products and their analogues have stimulated a great deal of interest in biomedicinal chemistry.[3] Among the broad spectrum of α-oximinotyrosine derived natural products isolated from marine sponges, in particular 11-deoxyfistularin-3 (1), [4a] purealidin P (6), [4b] and Q (7) [4d] are cytotoxic against the MCF-7 breast cancer cell line (LD 50 = 17 μg/L),[4a] murine lymphoma K1210 (IC 50 2.8 and 0.95 μg mL -1 , respectively), [4b] and human epidermal carcinoma KB (nasopharynx) (IC 50 7.6 and 1.2 μg mL -1 , respectively) [4d] cell lines (Figure 1). The other members from the same family are also widely known for their diverse pharmacological activities including antiviral, [5] antimicrobial, [6] anti-HIV, [7] antifungal, [8] antifouling, [9] Na + /K + ATPase inhibition, [10] HDAC inhibition, [11] histamine H 3 antagonism, [12] mycothiol S-conjugate amidase inhibition, [13] and isoprenylcysteine carboxymethyl transferase (Icmt) inhibition.[14] The distinguishable molecular diversity arises due to several prominent structural features including; (a) brominated spiroisoxazoline core that contains a cyclohexadiene, a bromo epoxy ketone, or a bromohydrin moiety, (b) the R or S absolute stereochemistry of the spiro stereogenic center of spiroisoxazoline amide core, (c) the presence of a [a]

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“…The likely reason for the initial discrepancy in the C‐2/C‐4 assignment was explained by Fattorusso and co‐authors as far back as 1994 and relates to the structure elucidation of the related metabolites, psammaplysins A and B . Nevertheless, the corresponding NMR data across the suite of related compounds continue to be incorrectly assigned, and this was highlighted as recently as 2011 by Ley and co‐authors who corrected the assignment for the subereamollines . Because of this inconsistency, a survey of the 13 C NMR data reported for molecules possessing cyclohexadienyl rings seemed warranted.…”

Section: Introductionmentioning

confidence: 99%

Unequivocal ¹³C NMR assignment of cyclohexadienyl rings in bromotyrosine‐derived metabolites from marine sponges

Kalaitzis

Davis

Quinn

2012

Magnetic Reson in Chemistry

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Bromotyrosine-derived compounds are commonly isolated from Verongida sponges and are a major class of marine natural products. Here we report on the unequivocal (13)C NMR assignment of the brominated carbons at positions C-2 and C-4 of the cyclohexadiene ring, two carbons whose resonances are often incorrectly assigned. Interpretation of HMBC data acquired for a series of known bromotyrosine analogues, which included ianthesine E(1), aerothionin (2), 11-hydroxyaerothionin (3), and 11,19-dideoxyfistularin-3 (4), allowed us to unequivocally assign the carbons in question, C-2 and C-4, through the observance of unique HMBC correlations from the C-1 hydroxyl proton. Here we present the complete 2D NMR data sets recorded in DMSO-d(6) for 2-4 that were used to confirm the assignment and establish the working model. Using this model, a survey of the literature revealed that many members of this structure class had been wrongly assigned. This paper serves to reassign those compounds whose (13)C NMR assignment at positions C-2 and C-4 of the cyclohexadiene ring should be reversed.

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Total syntheses of subereamollines A and B

Abstract: The first total syntheses of (+)- and (-)-subereamollines A and B are reported. The enantiomeric forms of the natural products were obtained by preparative chiral HPLC separation of the corresponding racemates.

Cited by 34 publications

References 33 publications

Doubling the Capacity of Lithium Manganese Oxide Spinel by a Flexible Skinny Graphitic Layer

Doubling the Capacity of Lithium Manganese Oxide Spinel by a Flexible Skinny Graphitic Layer

Divergent and Concise Syntheses of Spiroisoxazolines: First Total Synthesis of 11‐Deoxyfistularin‐3

Unequivocal ¹³C NMR assignment of cyclohexadienyl rings in bromotyrosine‐derived metabolites from marine sponges

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Total syntheses of subereamollines A and B

Abstract: The first total syntheses of (+)- and (-)-subereamollines A and B are reported. The enantiomeric forms of the natural products were obtained by preparative chiral HPLC separation of the corresponding racemates.

Cited by 34 publications

References 33 publications

Doubling the Capacity of Lithium Manganese Oxide Spinel by a Flexible Skinny Graphitic Layer

Doubling the Capacity of Lithium Manganese Oxide Spinel by a Flexible Skinny Graphitic Layer

Divergent and Concise Syntheses of Spiroisoxazolines: First Total Synthesis of 11‐Deoxyfistularin‐3

Unequivocal 13C NMR assignment of cyclohexadienyl rings in bromotyrosine‐derived metabolites from marine sponges

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Unequivocal ¹³C NMR assignment of cyclohexadienyl rings in bromotyrosine‐derived metabolites from marine sponges