XII
Contents
2.3.4 Retro-halolactonisation . . . . . . . . . . . . . . . . . 35
2.4 Final Synthetic Route to Hederagonic Acid . . . . . . . . . . 36
2.4.1 Economic Considerations . . . . . . . . . . . . . . . . 38
2.5 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . . 39
3 Experimental Section
41
3.1 General Information . . . . . . . . . . . . . . . . . . . . . . . 41
3.2 Experimental Procedures . . . . . . . . . . . . . . . . . . . . 42
3.2.1 12α-Chloro-3β-hydroxyolean-28,13β-olide (26a) . . . . 42
3.2.2 12α-Bromo-3β-hydroxyolean-28,13β-olide (26b) . . . . 43
3.2.3 12α-Chloro-3-oxo-olean-28,13β-olide (27a) . . . . . . . 45
3.2.4 12α-Bromo-3-oxo-olean-28,13β-olide (27b) . . . . . . . 46
3.2.5 12α-Chloro-3-(hydroxyimino)-olean-28,13β-olide (6a) . 47
3.2.6 12α-Bromo-3-(hydroxyimino)-olean-28,13β-olide (6b) . 48
3.2.7 12α-Chloro-3-(methoxyimino)-olean-28,13β-olide (29a) 50
3.2.8 23-Acetoxy-3-(acetoxyimino)-12α-chloro-olean-28,13βolide (7a) . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.2.9 23-Acetoxy-3-(acetoxyimino)-12α-bromo-olean-28,13βolide (7b) . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2.10 12α-Bromo-23-hydroxy-3-oxo-olean-28,13β-olide (8b) . 53
3.2.11 Hederagonic acid (23-Hydroxy-3-oxo-olean-12-en-28oic acid) (1) . . . . . . . . . . . . . . . . . . . . . . . . 54
References and Notes
57