1 - piperidine conformations

Fig. 5. Structure and activity profiles of the epi C-I6, C-14, C-20 diastereomer of 20 -deoxy VBL (a) and of the vinblastine unnatural piperidine conformational isomer (b). The parameters of activity, determined as described in Table 1, were as follows ...

The application of calorimetric methods to the determination of the position of conformational equilibria in reduced heterocyclic systems may be illustrated by reference to work157 on the piperidine equilibrium. If A and A represent the energy differences between the yV-Hai and N-Heq piperidine conformers and between the chair and twist-boat conformations, respectively, then the partition coefficient Q for the complete conformational equilibria may be expressed as... 

The two pyrrolopiperidine stereoisomers 42a and 42c were isolated in the individual form(m.p., 139-140and 155-157°C, respectively). Analysis of the spin-spin coupling constants in H-NMR spectra indicates that the piperidine conformation is a half-chair with a transdiequatorial arrangement of methyl groups at C4 and C7. 

Conformation of piperidine Conformational equilibria or preferred conformer State Reference... 

Fig. 1. Conformational representation of the piperidine ring of morphine (1) and analogues meperidine (7, R = H, R = COOC2H ) and alphaprodine (7, R = R = 0CC2H ). The chiral center of interest in stmcture (7) is starred (see text).

C chemical shifts, 2, 15 Piperidine, 2-aIkyI-JV-nitro-conformation, 2, 160 Piperidine, 4-amino-synthesis... 

Piperidin-4-one, 1-hydroxy-2,2,6,6-tetramethyl-conformation, 2, 117 Piperidin-4-one, 2,2,6,6-tetramethyl-hydrochloride conformation, 2, 114... 

Draw or build a molecular model of what you would expect to the most stable conformation of the piperidine derivative In which the hydro- gen bonded to nitrogen has been replaced by methyl. ... 

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