Engineered biosynthesis of antiprotealide and other unnatural salinosporamide proteasome inhibitors.

A new shunt in the phenylalanine biosynthetic pathway to the nonproteinogenic amino acid L-3-cyclohex-2'-enylalanine was exploited in the marine bacterium Salinispora tropica by mutagenesis to allow for the genetic engineering of unnatural derivatives of the potent proteasome inhibitor salinosporamide A (2) such as antiprotealide (1).