The biosynthesis of tropic acid. Part 6. Enantioselective, intact incorporation of (R)-(+)-3-phenyllactic acid into the tropic acid ester alkaloids of Datura

Application of Metabolic Engineering to the Production of Scopolamine

“…This enzyme removes putrescine from the polyamine pool and drives the methylated compound exclusively toward alkaloid production ( Figure 3 ). Feeding experiments [ 13 , 14 , 15 ] have demonstrated that this is a flux limiting step. The oxidative transamination of N -methylputrescine yields an aminoaldehyde that is primed for cyclisation to an N -methylpyrrolinium intermediate [ 16 ].…”

The role and source of 5′‐deoxyadenosyl radical in a carbon skeleton rearrangement catalyzed by a plant enzyme

“…1 (for a review see [1]). Due to its similarity to the rearrangement of methylmalonyl CoA to succinyl‐CoA it was originally speculated that coenzyme B 12 is involved in the reaction [2–4]. Since, in spite of some claims [5–7], no trace of vitamin B 12 has ever been found in plants this idea was abandoned [8, 9].…”

The biosynthesis of shikimate metabolites

“…This establishes that the R enantiomer of phenyllactic acid in littorine 112 is the one processed, and rules out phenylpyruvate as a precursor, since this would result in loss of 2 H. A similar conclusion was reached based on feeding of the separate enantiomers of phenyllactic acid to the roots of Datura stramonium plants, though in the aerial parts, substantial incorporations of the S enantiomer were recorded. 248 In further experiments, 249 (RS)--3-phenyl[2-3 H]lactic acid was used as precursor, giving hyoscyamine with 3 H located at C-3 of tropic acid. The chirality at the 3-hydroxymethyl was then established as S by reductive conversion to a chiral methyl and subsequent oxidation to acetate, indicating that any back migration of hydrogen from the benzylic position must involve inversion.…”