Studies on the Biogenesis of the Ring Systems of Nicotine

An Isotopic Study of Nicotine Biosynthesis in Relation to the Krebs Tricarboxylic Acid Cycle*

“…We have suggested (Dawson and Christman, 1961) that the carbon atoms of positions 1 through 4 of the pyridine ring may arise from an intermediate related to citric acid in a manner such that the carbon of position 3 of citrate becomes the carbon of pyridine ring position 3 of nicotinic acid and subsequently of nicotine. This view is supported by the findings of Griffith et al (1960) and of Byerrum and Griffith (1961) that about 50% of the pyridine ring activity acquired from acetic-2-C14 acid and from /5-alanine-2-C14 is located in ring position 3, and by our observation that about 25% of the pyridine ring activity acquired from /3-alanine-2-C14 is located in ring position 2. If citric acid were converted symmetrically into nicotinic acid (a proximal precursor of the nicotine pyridine ring) by a pathway which avoids the Ogston effect, the remaining 25% of label should occur in ring position 4.…”

Molecular Rotations of Methylcyclohexanols in Relation to Their Structures

“…13 The methylcyclohexanols and their observed molecular rotations are listed in Table I. (10) Reference *13 in the previous paper.5 (11) (.12) Owing to its symmetry, the central group (the cyclohexane ring) does not appear in the calculations. Moreover, because of the small polarizabilities of the H atom and the C-H bond, the (µ1 20 08 value caused by the dynamic coupling effect of the H atom can be neglected.…”