James J. Einck

Selective Methylation of Nucleosides1

Abstract Phenylalanine tRNA from Ehrlich ascites cells and Novikoff hepatoma has been found to contain 1-methyl-guanosine (5a) 2. The tRNA methyl transferases of e.g., normal liver tissue do not produce this N-methylated nucleoside. Indeed the urine of various human cancer patients has recently been found to contain unusually large amounts of certain partially methylated nucleosides and in amounts sufficient to serve as markers for evaluating disease progression.3 In general, a variety of methylated nucleosides4 have been discovered in animal RNA especially in tRNA and mRNA, and syntheses of these modified nuclesodies has been attempted using such reagents as methyl iodide,5 diazomethane,6 dimethyl sulfate,7 and trimethyl phosphate.8

Structural Biochemistry 14. Permethylation of Nucleosides

Abstract Prominent molecular ions are generally observed in the field ionization (FI) mass spectra of unprotected nucleosides.2 In the one exception so far observed, that of guanosine, we found the simple methyl derivative, N2,N2-dimethylguanosine, to afford an easily detectible molecular ion. The electron impact (EI) mass spectrum of N2,N2-dimethylguanosine also displayed a molecular ion and suggested that nucleoside methyl derivatives might be more easily studied by EI methods. For this purpose and the more important objective of developing methods for sequencing small nucleic acid units by computer assisted3 FI-EI mass spectrometry, a program was initiated (1967) to explore permethylation of nucleosides. We believe protection by permethylation to be superior to pertrimethylsilylation and acetylation principally for reasons involving molecular weight and stability. Concurrently it was anticipated that such nucleoside methylation studies would afford routes to partially mathylated nucleosides of value in...

The structure of 3β-acetoxy-15α-(o-nitrobenzoyl)oxy-5β,14β-bufa-8,20,22-trienolide

The title bufadienolide, C33H37NO8, M r = 575.66, is orthorhombic, space group P212~2 ~, with a = 31.53 (2), b = 11.533 (6), c = 8.221 (4)A, Z = 4, D m = 1.27, D c = 1.28 Mg m -3, ~(Mo Ka) = 0.054 mm -1, F(000) = 1224. The structure was solved by direct methods in which the required additional phase information was only obtained by the examination of a centrosymmetric projection. Refinement by least squares yielded a final R = 0.095 for 1383 observed reflections. There is cis fusion of the A/B and C/D rings, while the B/C rings are fused by a double bond.