Intermediacy of Eudesmane Cation during Catalysis by Aristolochene Synthase

Faraldos, Juan A., Kariuki, Benson ORCID: https://orcid.org/0000-0002-8658-3897 and Allemann, Rudolf Konrad ORCID: https://orcid.org/0000-0002-1323-8830 2010. Intermediacy of Eudesmane Cation during Catalysis by Aristolochene Synthase. Journal of Organic Chemistry 75 (4) , pp. 1119-1125. 10.1021/jo902397v

Full text not available from this repository.

Abstract

Aristolochene synthase from Penicillium roqueforti (PR-AS) catalyzes the formation of the bicyclic sesquiterpene (+)-aristolochene (5) from farnesyl diphosphate (1, FDP) in two mechanistically distinct cyclization reactions. The first reaction transforms farnesyl diphosphate to the uncharged intermediate (S)-(−)-germacrene A (3) through a macrocyclization process that links C1 and C10 upon magnesium ion-assisted diphosphate ester activation. In the second reaction mediated by PR-AS, a protonation induced cyclization has been suggested to generate the highly reactive trans-fused eudesmane cation 4 as a consequence of the precise folding of the enzyme-bound germacrene A intermediate. This contribution describes the use of the transition state analogue inhibitor 4-aza-eudesm-11-ene to explore the intermediacy of cation 4 as an on-path intermediate in the biosynthesis of aristolochene. 4-Aza-eudesm-11-ene as the hydrochloride salt 6 was stereospecifically synthesized in seven steps and 37% overall yield starting from chiral enamine 9. The synthetic sequence featured a highly regio- and stereoselective deracemization reaction of 9 that gave rise to the corresponding Michael adduct in >95% diastereomeric excess as evidenced by optical rotation and NMR measurements. 6 acts as a potent competitive inhibitor of PR-AS (Ki = 0.35 ± 0.12 μM) independent of the presence of diphosphate (Ki = 0.24 ± 0.09 μM). The failure of exogenous PPi to enhance the binding affinity of 6 for PR-AS could be interpreted against an eudesmyl cation/diphosphate anion pair mechanism as the enzymatic strategy to stabilize the highly reactive eudesmane cation 4. In addition, these observations seem to rule out simple favorable electrostatic and/or hydrogen bonding interactions between the active site anchored diphosphate ion and the ammonium ion 6 as the binding mode. Ammonium ion 6 seems to act as a genuine mimic of eudesmane cation (4) that most likely binds the active site of PR-AS in a productive conformation resembling that adapted by 4 during the PR-AS-catalyzed synthesis of 5.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry Cardiff Catalysis Institute (CCI)
Subjects:	Q Science > QD Chemistry
Publisher:	ACS
ISSN:	0022-3263
Funders:	BBSRC
Last Modified:	18 Oct 2022 14:26
URI:	https://orca.cardiff.ac.uk/id/eprint/17466

Citation Data

Cited 20 times in Scopus. View in Scopus. Powered By Scopus® Data

Actions (repository staff only)

Edit Item