Die Konstitution der Aristolochiasäure-IV

Different conformational families of pyrimidine·purine·pyrimidine triple helices depending on backbone composition

“…Phosphoramidites were purchased from Applied Biosystems (dA, dG, dC, and T) and from BioGenex Laboratories (San Ramon, CA) (rA, rG, rC, and U). Nucleoside 2 Nucleoside 1 was prepared as described (23,24). To a solution of 1 (2.7 g, 6.87 mmol) in CH30H (100 mL) was added 10% palladium on carbon (300 mg) and the mixture was shaken under H2 (50 psi) for 10 h. The reaction mixture was filtered through Celite and the filtrate was evaporated to dryness to give .…”

Reaction of arylboronic acids and their derivatives with lead tetra-acetate. The generation of aryl–lead triacetates, and meta- and para-phenylenebis(lead triacetate), in situ for electrophilic arylation

“…(14) was collected by means of a centrifuge as a fine powder (15 mg); GH(CDCI3) 0.88 (9 H, t, 3 x CH,), 1.08 (6 H, m, 3 x CH2), 1.34 (6 H, m, 3 x CH2), 1.50 (6 H, m, 3 x CH2), 2.10 (9 H, s, 3 x OAc), 7.56 and 7.65 (4 H, AA'BB', '07Pb satellites gave J2,Pb 396 Hz and J3,pc 202 Hz, 2-, 6-H and 3-, 5-H respectively).…”

α-(2H-1-Benzopyran-2-ylidene)-α-(methylthio)acetonitrile, a Chromylidene Acetonitrile

“…Coumarin and many of its derivatives have marked physiological effects and lasing properties (Kuo, 1994;Fabian, 1985). Only a few examples of their methylene derivatives (C==CXY instead of C==O) are known because the lactone ring has very low reactivity in direct condensations, such as Reformatsky (X = H, Y = CO2Et; Pailer & Vostrowsky, 1971) or Knoevenagel reactions (X = Y = CN; Tkach et al, 1992); other strategies have been developed from benzopyrylium salts (X = H, Y = Ph; Iwasaki & Akiba, 1987), 3-cyanocoumarins (X = H, Y = CN; Junek & Wilfinger, 1970) or salicylaldehydes (X = CHO, Y = CO2Et; Werner et al, 1994). Even when the compounds exist, the ZIE configuration has never been determined; in the last example of those cited above, the authors note an easy Z/E isomerization due to a low energy barrier (18 kcal).…”