Selective Cleavage of Benzyl Ethers

Congreve, Miles; Davison, Edwin C.; Fuhry, Mary Ann M.; Holmes, Andrew B.; Payne, Andrew N.; Robinson, R. Anthony; Ward, Simon E.

doi:10.1055/s-1993-22563

Cited by 67 publications

(43 citation statements)

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“…66 Warming the reaction mixture to room temperature caused significant erosion in chemical yield (entry 5). Other conditions screened for PMB deprotection/spiroketal formation include: TMSI, 67 I 2 in MeOH, 68 BCl 3 •Me 2 S complex 69 and MgBr 2 •Et 2 O. 70 …”

Section: Resultsmentioning

confidence: 99%

Synthesis of a 35-Member Stereoisomer Library of Bistramide A: Evaluation of Effects on actin State, Cell Cycle and Tumor Cell Growth

et al. 2009

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Synthesis and preliminary biological evaluation of a 35-member library of bistramide A stereoisomers are reported. All eight stereoisomers of the C1-C13 tetrahydropyran fragment of the molecule were prepared utilizing crotylsilane reagents 9 and 10 in our [4+2]-annulation methodology. In addition, the four isomers of the C14-C18 γ-amino acid unit were accessed via a Lewis acid mediated crotylation reaction using both enantiomers of organosilane 11. The spiroketal subunit of bistramide A was modified at the C39-alcohol to give another point of stereochemical diversification. The fragments were coupled using standard peptide coupling protocol to provide 35 stereoisomers of the natural product. These stereochemical analogs were screened for their effects on cellular actin and cytotoxicity against cancer cell lines (UO-31 renal and SF-295 CNS). The results of these assays identified one analog, 1.21, with enhanced potency relative to the natural product, bistramide A.

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Section: Resultsmentioning

confidence: 99%

Synthesis of a 35-Member Stereoisomer Library of Bistramide A: Evaluation of Effects on actin State, Cell Cycle and Tumor Cell Growth

et al. 2009

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“…Treatment of 13 with BBr 3 in CH 2 Cl 2 [50] resulted in complete decomposition of the fullerene compound, as indicated by a strong color change. The use of LiI/SiCl 4 /BF 3 ·OEt 2 , [51] BCl 3 , [52] BCl 3 /NBu 4 + Br À [53] , or HBr/H 3 CCOOH as ethercleaving reagents showed no conversion of the reactant even after several days and at higher temperatures. In contrast, after heating a solution of 13 and NaI in HBr/ H 3 CCOOH (1:1) and CHCl 3 to reflux, cleavage of one ether bond could be detected by mass-spectrometric analysis, but this deprotection was reversible.…”

Section: Selective Functionalization Of the Equatorial Addend Zonementioning

confidence: 98%

Synthesis and Orthogonal Functionalization of [60]Fullerene e,e,e‐Trisadducts with Two Spherically Defined Addend Zones

Beuerle

Hirsch

2009

Chemistry A European J

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e,e,e-Trisadducts 13 and 15 have been prepared by a highly regioselective threefold cyclopropanation of tripodal malonates 10 and 12 with C60. The yield and regioselectivity depend on the length and structure of the tethers that connect the malonate units to the focal benzene core of 13-15. As a consequence of the template-directed synthesis, all e,e,e-trisadducts were formed as in/out isomers exclusively and contain two spherically well-defined addend zones with equatorial and polar orientation, respectively. By variation of the outer malonate termini of the tethers, selective functionalization of the equatorial addend zone could be achieved, thus leading to fine-tuning of intermolecular interactions, such as solubility or aggregation phenomena. After removal of the focal benzene moiety in 14 and 15, selective functionalization of the polar addend zone could be achieved. Strong intramolecular hydrogen-bonding networks of the polar substituents in the polar addend zone could be observed by 1H NMR spectroscopic analysis. By orthogonal functionalization of both addend zones, fullerene derivatives 44-48 could be synthesized as one single in/out isomer, thus greatly enhancing the potential of e,e,e-trisadducts as building blocks in supramolecular architectures.

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“…The PMB (PMB = p-methoxybenzyl) ether in (À)-36 was readily removed with borontrichloride-dimethyl sulfide complex [44] to provide the secondary alcohol (+)-37 in readiness for chlorination (Scheme 9). However, we were disappointed to find that attempted chlorination of the secondary alcohol (+)-37 under a wide variety of conditions, [1-(chloro-2-methylpropenyl)dimethylamine, [36,37] carbon tetrachloride and trioctylphosphane, [45] triflate followed by benzyltriethylammonium chloride, [46] failed to yield any products containing a chlorine substituent.…”

Section: Catalystmentioning

confidence: 99%

“…Debenzylation of the lactone (À)-43 was smoothly accomplished by the use of boron trichloride-dimethyl sulfide complex, [44] yielding the secondary alcohol (À)-50 (Scheme 12). The debenzylation of secondary benzylethers with this Lewis acid is known to be sluggish and the above reaction took three days to reach completion.…”

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Synthesis of (+)‐Obtusenyne

Mak

Curtis

Payne

et al. 2008

Chemistry A European J

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An enantioselective synthesis of the halogenated medium-ring ether natural product (+)-obtusenyne is reported which uses the ring expansion of a seven-membered ketene acetal by means of a Claisen rearrangement to construct the core nine-membered oxygen heterocycle. The trans substituents across the ether linkage were established by using a transition-metal-catalyzed intramolecular hydrosilation reaction of an exo-cyclic enol ether. In addition, a formal synthesis of ent-obtusenyne from 2-deoxy-D-ribose is reported. A number of interesting points regarding the chemistry of medium-ring oxygen heterocycles are highlighted.

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Selective Cleavage of Benzyl Ethers

Cited by 67 publications

References 0 publications

Synthesis of a 35-Member Stereoisomer Library of Bistramide A: Evaluation of Effects on actin State, Cell Cycle and Tumor Cell Growth

Synthesis of a 35-Member Stereoisomer Library of Bistramide A: Evaluation of Effects on actin State, Cell Cycle and Tumor Cell Growth

Synthesis and Orthogonal Functionalization of [60]Fullerene e,e,e‐Trisadducts with Two Spherically Defined Addend Zones

Synthesis of (+)‐Obtusenyne

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