Synthesis of analogues of 5-aminolaevulinic acid and inhibition of 5-aminolaevulinic acid dehydratase
Syntheses are described of several analogues of 5-aminolaevulinic acid (ALA), which are potential inhibitors of ALA dehydratase (porphobilinogen synthase), an early enzyme of tetrapyrrole biosynthesis.Most of the analogues are relatively weak competitive inhibitors of the enzyme from Bacillus subtilis or irreversible inhibitors due to multiple alkylation of the enzyme but the 3-oxa and 3-thia analogues are potent mechanism-based inhibitors which inactive, by acylation of a nucleophilic residue, probably the active-site lysine residue.The kinetics of the inactivation by 3-thiaALA have implications for the mechanism of the enzymic reaction.
Appleton, Diana,Duguid, A. Bruce,Lee, Sung-Koo,Ha, Young-Jin,Ha, Hyun-Joon,Leeper, Finian J.
p. 89 - 102
(2007/10/03)
Ester Enolate Claisen Rearrangements of Allyl α-Fluoroacetates and α-Fluoropropanoates
The ester enolate Claisen rearrangement of allyl α-fluoroacetates 1 forms 2-fluoroalkenoic acids 2 in good to excellent yield with good internal asymmetric induction.This selectivity was unexpected as stereoselective deprotonation of fluoroacetates is not normally possible.The selective formation of the required α-fluoro silyl ketene acetal 3 was found to result from the stereoselective rearrangement of the allyl α-fluoro-α-silylacetate isomer.Although silyl ketene acetals derived from α-fluoropropanoates 7 also rearranged, control of internal asymmetric induction was not possible.