Nucleoside cyclic 3',5'-phosphates: chair-twist equilibria of the phosphate rings of methyl phosphate and phenylphosphonate derivatives of cTMP.
The cis and trans forms of thymidine methyl cyclic 3',5'-phosphate (9) and of the corresponding phenylphosphonate derivatives (10) were prepared in two steps from the corresponding cyclic amide. 1H NMR spectroscopy showed the phosphorus-containing six-membered rings of cis-9 (MeO and thymin-1-yl cis) to be in the chair conformation, but trans-9 to be approximately 40% in the twist conformation in pyridine-d6 and 33% in acetone-d6. For trans-9, there was resistance of conversion of the chair form into the twist form with the MeO group pseudo-axial with a delta G degrees(C-->T) value of 3.0 kcal/mol. Similarly, for cis-10 (23-39% twist population in CD3CN, acetone-d6, and CDCl3), a delta G degrees(C-->T) value of 0.5-0.6 kcal/mol for placement of the phosphoryl oxygen pseudo-axial was obtained. Both values are taken to be approximations for delta G degrees(C-->T) for cTMP. For trans-10, the twist conformation was populated to the extent of 6-13% with a delta G degrees(C-->T) value of 1.3 kcal/mol.
Nelson
K A
KA
Department of Chemistry, University of Utah, Salt Lake City 84112.
Bentrude
W G
WG
D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008968:Molecular Conformation; D015394:Molecular Structure; D009712:Nucleotides, Cyclic / Q000737:chemistry*; D063065:Organophosphonates / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D011522:Protons; D012997:Solvents; D013237:Stereoisomerism; D013938:Thymidine Monophosphate / Q000737:chemistry*
D009712:Nucleotides, Cyclic; D063065:Organophosphonates; D010710:Phosphates; D011522:Protons; D012997:Solvents; D013938:Thymidine Monophosphate; C045337:cyclic 3',5'-thymidine monophosphate