Both enantiomers of the pyrrolizidine alkaloid trihydroxyheliotridane 1 have been prepared in an efficient and stereocontrolled fashion in 10 steps. Key steps involve the microbial oxidation of chlorobenzene with Pseudomonas putida to afford chiral cyclohexadienediol4 with high enantiomeric excess and its conversion to lactone 7, from which either enantiomer of azide 18 can be prepared. The azides are converted to the title compounds via a [4+ 11 ...
