Conformation of ribooligonucleotide duplexes containing an alternating C-G sequence which show an unusual circular dichroism spectrum.

Total synthesis of (+)-jatropholones A and B. Exploitation of the high-pressure technique

“…The above enamine was dissolved in water (75 mL), acetic acid (75 mL), and THF (150 mL) and the resultant dark-brown solution stirred at room temperature for 48 h. The reaction mixture was then added to water (200 mL) and chloroform (200 mL), the phases were separated, and the aqueous phase was extracted with chloroform. The combined organic extracts were dried (MgSQ4), and the solvent was removed in vacuo to give a residue which was purified by flash column chromatography (20-25% ethyl acetate/hexane) to give 15.1 g (68%) of diketoacetate 14 as a pale-yellow oil: IR (neat) 3450 (m), 2950 (s), 1730 (s), 1640 (s), 1235 (s); NMR (250 MHz, CDC13) 8.80 (br s, 0.17 H, enol OH), 5.27, 5.20 (2q, 7 = 7 Hz, 1 H), 3.75, 3.46 (2t, 7 = 7.5 Hz, 0.83 H, keto form), 2.90-1.8 (m, 9 ), 1.45 (3d, 7=7 Hz, 3 H); electron impact mass spectrum, m/e 198.0907 (M+, caled for C10H14O4 198.0892).…”

“…After 5 min, the mixture was poured into water (25 mL) and extracted with ether, the combined organic extracts dried (K2C03), and the solvent removed in vacuo. The acid-sensitive enone 28 thus obtained (65.5 mg, 92%) was used without further purification: IR (neat) 3600-3200 (m), 1710 (s), 1680 (s) cm"1; NMR (250 MHz, CDC13) b 7.34-7.29 (m, 5 ), 4.71 (t, J = 5 Hz, 1 H), 4.44 (center of AB, J = 11.7 Hz, 2 ), 4.02 (d, J = 8 Hz, 1 H), 3.57 (br s, 1 ), 2.8-0.8 (m, 11 ), 1.26 (s, 3 ), 1.11 (s, 3 ), 1.04 (s, 3 H). Enone 28 (200 mg, 0.5 mmol) was dissolved in a mixture of 16 mL of dry pyridine and 125 mL of dry CH2C12 under nitrogen. The mixture was cooled to 0 °C and thionyl chloride (1.5 mL, 20.5 mmol) added dropwise.…”

Electrochemical reduction of aqueous bicarbonate to formate with high current efficiency near the thermodynamic potential at chemically derivatized electrodes

“…ramers (1 A2t0 unit/mL) were measured in 0.1 M NaCl, 0.01 M phosphate buffer (pH 7.5). The deoxyhexamer (1 A260 unit/mL) was measured in 4 M NaCl, 0.01 M phosphate buffer (pH 7.5).…”