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Lupin alkaloids 6. Stereochemistry of bis-quinolizidine alkaloids with γ-oxo-α,β-enamine system
1 H nmr, 1 H, 1 H and 1 H, 13 C COSY, and 2D J-resolved spectra of multiflorine ( 1 ) and 13α-hydroxymultiflorine ( 2 ) in CDCl 3 were taken. Some erroneously determined chemical shifts in 1 were corrected and for the first time signals in 2 were assigned. Most of the coupling constants in 1 and 2 w...
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| Published in: | Canadian journal of chemistry 1994-01, Vol.72 (1), p.193-199 |
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| Main Authors: | , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that cite this one |
| Online Access: | Get full text |
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| Summary: | 1
H nmr,
1
H,
1
H and
1
H,
13
C COSY, and 2D J-resolved spectra of multiflorine (
1
) and 13α-hydroxymultiflorine (
2
) in CDCl
3
were taken. Some erroneously determined chemical shifts in
1
were corrected and for the first time signals in
2
were assigned. Most of the coupling constants in
1
and
2
were established. A coupling constant of H7-H17β and chemical shifts for H17β, C14, and C8 were used to define the conformational equilibrium of boat or chair forms in the C rings, in
1
and
2
in solution. The results obtained confirm the previous findings based on chemical shifts of C12: ca. 75 and 70% of the "boat" conformer in
1
and
2
, respectively, at room temperature. Of all the criteria used, the H7-H17β coupling constant seems to be least sensitive to the influence of substituents at rings A and D. From the Haasnoot equation, torsion angles of HCCH in regions of molecular geometry featuring low sensitivity to conformational changes were calculated. The hydroxyl group at position 13α has a slight influence on the geometry of ring D. |
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| ISSN: | 0008-4042 1480-3291 |
| DOI: | 10.1139/v94-030 |