Microbial Oxidation of Chloroaromatics in the Enantiodivergent Synthesis of Pyrrolizidine Alkaloids: Trihydroxyheliotridanes

Article abstract of DOI:10.1021/jo00302a037

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 cyclohexadienediol 4 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+1> pyrroline annulation based on an intramolecuular azide-diene cycloaddition/thermal rearrangement.