The structure-quenching relationship in 9-aminoalkylanthracenes is examined by the synthesis and fluorescence evaluation of five derivatives; it is observed that benzylic 2° and 3° amines lead to ≥95% quenching of anthracene fluorescence in water, while other amines afford substantially lower quenching efficiencies.
Benzo-fused boron-containing heterocycles (benzoborauracils), 1-hydroxy-1H-2,4,1-benzodiazaborin-3-one (3a), 1-hydroxy-2-methyl-1H-2,4,1-benzodiazaborin-3-one (3b), and 1-hydroxy-2-phenyl-1H-2,4,1-benzodiazaborin-3-one (3c) were synthesized, and their structures were established on the
basis of 1H, 13C, and 11B NMR spectroscopies, mass spectrometry, and microelemental analyses.
The structures of compounds 3b and 3c were unambiguously confirmed by X-ray crystallographic
analyses. 11B NMR spectral analyses of the methanolic solutions of benzoborauracils 3a−c confirmed
the formation of the corresponding bis-methanol adducts 13a−c. The structure of the N-Ph bis-methanol adduct 13c was confirmed by X-ray crystallography. The stabilities of these bis-methanol
adducts depend on the substituent at the N2 position of 3a−c. The bis-methanol adducts are readily
reconverted to the corresponding benzoborauracils upon removal of methanol. The first stable
benzoborauracil nucleoside, 4-[5-O-(tert-butyldimethylsilyl)-2,3-O-disopropylidene-α-d-ribofuranosyl]-1-hydroxy-2-methyl-1H-2,4,1-benzodiazaborin-3-one (25) was prepared in two steps by treatment
of 2-aminophenylboronic acid with 5-O-(tert-butyldimethylsilyl)-2,3-O-diisopropylidene-d-ribofuranose followed by its reaction with methylisocyanate.
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