Photoisomerization of the B20H18-2 Ion

Hawthorne, M. Frederick; Pilling, Richard L.

doi:10.1021/ja00968a044

Cited by 50 publications

(16 citation statements)

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“…Another useful facet of the n-B20Hj-ion is its photochemical reactivity (19). This anion rearranges upon exposure to ultraviolet light to produce a photoisomer (i-B2gH2) as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Successful therapy requires the site-specific delivery of relatively large amounts (15)(16)(17)(18)(19)(20) jig of B per g of tissue) of boron to tumors (2). Strategies employed have included the use of boron compounds with some natural affinity for tumors, such as 4-(dihydroxyboryl)phenylalanine (BPA) (3) or the mercaptoundecahydro-closo-dodecaborate dianion (B12H,,SH2-; BSH) (4); the attachment ofboron-containing species to other molecules such as porphyrins (5); and the conjugation of boron-rich compounds with tumor-specific monoclonal antibodies and their fragments (6).…”

mentioning

confidence: 99%

“…The polyhedral borane anion derivatives used were prepared by published methods (17)(18)(19)(20)(21). Disodium mercaptoundecahydro-closo-dodecaborate (Na2B12Hi1SH) was a gift from the Callery Chemical (Pittsburgh).…”

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confidence: 99%

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Model studies directed toward the boron neutron-capture therapy of cancer: boron delivery to murine tumors with liposomes.

Shelly

Feakes

Hawthorne

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

153

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The successful treatment of cancer by boron neutron-capture therapy (BNCT) requires the selective concentration of boron-10 within malignant tumors. The potential of liposomes to deliver boron-rich compounds to tumors has been assessed by the examination of the biodistribution of boron delivered by liposomes in tumor-bearing mice. Small unilamellar vesicles with mean diameters of 70 nm or less, composed of a pure synthetic phospholipid (distearoyl phosphatidylcholine) and cholesterol, have been found to stably encapsulate high concentrations of water-soluble ionic boron compounds. The hydrolytically stable borane anions B,.H01, B,2H11SH2-, B20H170H4-B2]HT3, and the normal form and photoisomer of B2oH 2-were encapsulated in liposomes as their soluble sodium salts. The tissue concentration of boron in tumor-bearing mice was measured at several time points over 48 h after i.v. injection of emulsions of liposomes containing the borane anions. Although the boron compounds used do not exhibit an affinity for tumors and are normally rapidly cleared from the body, liposomes were observed to selectively deliver the borane anions to tumors. The highest tumor concentrations achieved reached the therapeutic range (>15 jtg of boron per g of tumor) while maintaining high tumor-boron/blood-boron ratios (>3). The most favorable results were obtained with the two isomers of B2OH _. These boron compounds have the capability to react with intracellular components after they have been deposited within tumor cells by the liposome, thereby preventing the borane ion from being released into blood.Boron neutron-capture therapy (BNCT), first proposed by Locher in 1936 (1), is based upon the propensity of the 10B nucleus to undergo the 10B + 1n -* 'Li + 'He reaction with thermal neutrons. This process releases 2.28 MeV of kinetic energy, which is distributed between the a-particle and the 7Li+ ion. The effective distance of travel of these two ions in tissue is limited to approximately one cell diameter. During their passage through the interior of a cell, the energetic fission products cause ionization-tracking and cellular damage with associated cytotoxicity. Since the neutron capture cross-section of the 10B nucleus is 103 to 104 greater than that of all elements of physiological importance, the selective concentration of 10B atoms within cancer cells, followed by irradiation with thermal neutrons, should result in the destruction of the tumor cells even in the presence of neighboring normal cells.The development of effective targeting strategies for the selective transport ofboron to cancer cells has been the single most urgent problem in the area of BNCT. Successful therapy requires the site-specific delivery of relatively large amounts (15-20 jig of B per g of tissue) of boron to tumors (2). Strategies employed have included the use of boron compounds with some natural affinity for tumors, such as 4-(dihydroxyboryl)phenylalanine (BPA) (3) or the mercaptoundecahydro-closo-dodecaborate dianion (B12H,,SH2-; BSH) (4); the attac...

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“…Another useful facet of the n-B20Hj-ion is its photochemical reactivity (19). This anion rearranges upon exposure to ultraviolet light to produce a photoisomer (i-B2gH2) as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Model studies directed toward the boron neutron-capture therapy of cancer: boron delivery to murine tumors with liposomes.

Shelly

Feakes

Hawthorne

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

153

View full text Add to dashboard Cite

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“…6 Further, the pentagonal pyramidal motif is also that of the binary borane nido-B 6 H 10 , isoelectronic with the [C 6 H 6 ] 2+ dication. Several allotropes of elemental boron exist, in which {B 12 } icosahedra are connected in different ways. 7 When combined with other elements from the Periodic Table, the chemistry of boron expands to yield a very rich library of architectural constructs in any dimension.…”

Section: Introductionmentioning

confidence: 99%

Borane Polyhedra as Building Blocks for Unknown but Potentially Isolatable New Molecules – Extensions based on Computations of the Known B18H22 Isomers

Oliva¹,

Rué²,

Kennedy³

et al. 2013

Croat. Chem. Acta

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Abstract. Known borane polyhedral cluster characteristics can be used for predicting new architectural constructs. We propose additional structures derived from B 18 H 22 : three positional isomers different from the well-known anti-B 18 H 22 and syn-B 18 H 22 boranes. We have also derived two new cyclic structures based on the condensation of borane pentagonal pyramids and bipyramids. The concatenation of polyhedral borane molecules is also considered from a mathematical point of view.

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“…32 ) and 7 (ref. 33 ) were the first syntheses of the closo-skeleton which involved borane insertion 34 or amine-induced dehydrogenation 35 reactions, respectively.…”

Section: Preparation Of the Parent Clustersmentioning

confidence: 99%

Four Decades of Organic Chemistry of closo-Boranes: A Synthetic Toolbox for Constructing Liquid Crystal Materials. A Review

Kaszyński

1999

Collect. Czech. Chem. Commun.

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Introduction and transformations of organic functional groups to ten- and twelve-vertex closo-boranes and heteroboranes is reviewed in the context of preparation of liquid crystalline compounds. The review, containing 198 references, is designed as a synthetic manual for materials chemists and focuses on methods for engineering molecules with elongated shapes and variable dipole moments. Several underdeveloped aspects of closo-borane chemistry are identified.

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Photoisomerization of the B₂₀H₁₈^-2 Ion

Cited by 50 publications

References 0 publications

Model studies directed toward the boron neutron-capture therapy of cancer: boron delivery to murine tumors with liposomes.

Model studies directed toward the boron neutron-capture therapy of cancer: boron delivery to murine tumors with liposomes.

Borane Polyhedra as Building Blocks for Unknown but Potentially Isolatable New Molecules – Extensions based on Computations of the Known B18H22 Isomers

Four Decades of Organic Chemistry of closo-Boranes: A Synthetic Toolbox for Constructing Liquid Crystal Materials. A Review

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