A comparative study of the IR spectra of alkaloids containing piperidine and quinolizidine rings in the 2500–2830 cm−1 region
Summary1. A comparative method of studying the conformational states of alkaloids of the piperidine and quinolizidine series by comparing the intensities of the IR bands in the 2500–2830 cm−1 region in the solid and liquid states has been proposed.2. It has been shown that the process of inversion and other labile conformational transformations affect the number, frequency, and intensity of the vibrational transitions in the “Bohlmann region.”
Conformation of the C15 lupine alkaloids
Methods have been developed for preparing 17α-deuterio-, 17β-deuterio-, and l7-dideuteriolupanines. The nuclear magnetic resonance and infrared spectra of these provided strong evidence that ring C in the alkaloid is in a boat conformation in solution. Reduction of these compounds to the deuterated sparteines confirmed the same geometry for sparteine. In contrast, moilodeuteration of aphylline at C-17 showed that i t had an all-chair conformation in solution. 13β-Hydroxylupanine was shown to have the same conformation as lupanine in solution, but to adopt an all-chair conformation in the solid state. Interpretation of the nuclear magnetic resonance spectra enabled the conformation of ring C of 15-oxosparteine to be assigned. The oxidation and reductions involving C-17 of lupanine have been shown to be highly stereospecific, and an interpretation is given of the difference betmeen the dehydrogenation of lupanine by mercuric acetate and those by Nbromosuccinimide or by the mercuric acetate - ethylenediatnin...
Synthesis of 2,4-dideoxy-.beta.-D-erythro-hexopyranosyl nucleosides
The synthesis of 1-(2,4-dideoxy-β-D-erythro-hexopyranosyl)thymine (12) 1 was accomplished using two different synthetic routes. It was obtained starting either from 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose or from tri-O-acetyl-D-glucal. The other modified nucleosides, with either a cytosine, guanine, or adenine moiety, were synthesized using the second reaction scheme. Deoxygenation reactions were accomplished with the (2,4-dichlorophenoxy)thiocarbonyl derivatives generated in situ