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β-AMYRIN
ß-AMYRIN
Nature generates several important carbon frameworks byfolding squalene epoxide in different conformations.
The Protola-
nosterol precursor to Cholesterol arises from a 'chair-boatchair1 arrangement whilst ß -Amyrin is created by a 'chair1-^ chair-chair' alignment! J
/L^
Squalene
H
epoxide
H 6
— [ e y e l i sat ion 1-
0-AMYRIN
1.
L. Ruzieka, Experientia, _9, 357 (1953); A. Eschenmoser, L. Ruzieka, 0. Jeger and D. Arigoni, Helv. Chim. Acta, 3§, I890 (1955).
2.
Experiments with labelled precursors have confirmed Ruzicka's hypothesis (H. H. Rees. G. Britton and T. W. Goodwin, Biochem. J., 103, 52 (I967); H. H. Rees, G. Britton and T. W. Goodwin, Biochem. J., 1θ6, 659 (1968); D. H. R. Barton, G. Mellows, D. A. Widdowson and J. J. Wright, J. Chem. Soc., (C), 1142 (I97I)).
3.
^C-Labelling studies with mevalonic acid have verified this hypothesis experimentally (S. Seo, Y. Tomita and K. Tori, Chem. Comm., 270 (1975)).
7
ß-AMYRIN
4.
Recently, (S)-squalene 2,3 oxide was found to be the exclusive precursor of J3 -amyrin in plant systems (D. H. R. Barton, T. R. Jarman, K. G. Watson and D. A. Widdowson, Chem. Comm., 86l (1974)).
8
Nature generates several important carbon frameworks byfolding squalene epoxide in different conformations.
The Protola-
nosterol precursor to Cholesterol arises from a 'chair-boatchair1 arrangement whilst ß -Amyrin is created by a 'chair1-^ chair-chair' alignment! J
/L^
Squalene
H
epoxide
H 6
— [ e y e l i sat ion 1-
0-AMYRIN
1.
L. Ruzieka, Experientia, _9, 357 (1953); A. Eschenmoser, L. Ruzieka, 0. Jeger and D. Arigoni, Helv. Chim. Acta, 3§, I890 (1955).
2.
Experiments with labelled precursors have confirmed Ruzicka's hypothesis (H. H. Rees. G. Britton and T. W. Goodwin, Biochem. J., 103, 52 (I967); H. H. Rees, G. Britton and T. W. Goodwin, Biochem. J., 1θ6, 659 (1968); D. H. R. Barton, G. Mellows, D. A. Widdowson and J. J. Wright, J. Chem. Soc., (C), 1142 (I97I)).
3.
^C-Labelling studies with mevalonic acid have verified this hypothesis experimentally (S. Seo, Y. Tomita and K. Tori, Chem. Comm., 270 (1975)).
7
ß-AMYRIN
4.
Recently, (S)-squalene 2,3 oxide was found to be the exclusive precursor of J3 -amyrin in plant systems (D. H. R. Barton, T. R. Jarman, K. G. Watson and D. A. Widdowson, Chem. Comm., 86l (1974)).
8