The solvent effect on the enthalpy of hydrolysis of cyclic adenosine 3′,5′‐monophosphate. A quantumchemical study

Abstract

These spectra were recorded by and discussed with Mr. H . Hienisrru and Mr. W . A . Mellink. Mass spectra were obtained on a AEI MS-902 by Mr. A . Kiewiet. Optical rotations were measured on a Perkin Elmer 241 Polarimeter. The O R D and C D spectra were recorded on a Cary 60 recording spectropolarimeter equipped with a Cary 6002 C D accessory. 4-(9-Fluoreylidene) -I ,2,3.4-tetrahydrophenunthrene ( 5 )a. The coupling of 9-fluorenone (4) and 2,3-dihydro-4(1H)phenanthrone (3) was performed following the general procedure described for the coupling of 3'. A mixture of 3 (2.05 g, 10.5 mmol) and 4 (1.89 g, 10.5 mmol) in 25 ml of T H F was added to the slurry of the Ti(ll) species. After a work-up as described previously 3.5 g of a yellow oil was obtained. Chromatography over alumina (petroleum ether 40/60 as eluent) yielded an apolar product mixture, which could be separated via preparative TLC (AI,O,, not-activated, n-hexane) in 9,9'-bifluorenyl (6) (0.20 g. 0.66 mmol, 13",,. m.p. 248-249°C. lit.:" m.p. 247°C) cross coupled olefin 5 (0.12 g, 0.34 mmol, 3.2 %) and 1 + 2 (0.38 g, 1.04 mmol, 19 7,).b. The coupling was performed as described above, using a mixture of 3 (0.78 g, 4.0 mmol) and 4 (3.06 g. 17.0 mmol) in 25 ml of THF. After work-up as described previously. 3.4 g of a red semisolid was obtained. Column chromatography (Al,O,, petroleum ether 40/60) followed by preparative TLC (of the apolar fraction of the first separation) yielded bifluorenylidene, 7 ( I . I4 g, 2.0 mmol, 35%, and 5 (0.34 g, 0.9 mmol, 25 %). Crystallization of 5 from n-hexane, yellow needles, m.p. 236-238°C. UV (n-hexane): A , , , 355 nm (1.54 x lo4), 262 (4.15 x 10,) 218 (15.0 x lo4, sh).

Empirical Correlations Between Conformational Parameters in β‐D‐Furanoside Fragments Derived from a Statistical Survey of Crystal Structures of Nucleic Acid Constituents Full Description of Nucleoside Molecular Geometries in Terms of Four Parameters

“…Modifications at the C8 (purines) or C6 (pyrimidines) position promote the occupation of syn or high-anti regions by steric and/or electronic interference. A special case is constituted by the N-type formycines, oxoformy- cin B (87) and methyIformycin (33). The C-glycosidic bond apparently is responsible for X-values (-164°and -155°) outside the syn-range normally encountered for N-type ribofuranosides (X --90°).…”