6- Oxonorleucine

The significance of chiral unnatural amino acids to drug and natural product synthesis is shown in the example of the antihypertensive dmg omapatrilat (Vanlev ), which is composed of no less than three amino acid derived intermediates [144-147]. Diverse biocatalytical approaches to L-6-oxonorleucine were made (Fig. 21). Two different enzymes were applied in reductive amination reactions to produce derivatives of the desired intermediate. 

Fig. 21 Enzymatic synthesis of unnatural amino acids as building blocks for omapatrilat. (a-c) Enzymatic approaches to 6-oxonorleucine analogs...

The base-free Ag" catalyzed Wolff rearrangement of 5-diazo-4-oxonorleucine 35 afforded the carboxylic acid 36 at room temperature on sonication using an ultrasound cleaning bath. ... 

---