An Efficient Chemoenzymatic Synthesis of Dihydroartemisinic Aldehyde

Abstract

Artemisinin from the plant Artemisia annua is the most potent pharmaceutical for the treatment of malaria. In the plant, the sesquiterpene cyclase amorphadiene synthase, a cytochrome‐dependent CYP450, and an aldehyde reductase convert farnesyl diphosphate (FDP) into dihydroartemisinic aldehyde (DHAAl), which is a key intermediate in the biosynthesis of artemisinin and a semisynthetic precursor for its chemical synthesis. Here, we report a chemoenzymatic process that is able to deliver DHAAl using only the sesquiterpene synthase from a carefully designed hydroxylated FDP derivative. This process, which reverses the natural order of cyclization of FDP and oxidation of the sesquiterpene hydrocarbon, provides a significant improvement in the synthesis of DHAAl and demonstrates the potential of substrate engineering in the terpene synthase mediated synthesis of high‐value natural products.

Exploiting the Synthetic Potential of Sesquiterpene Cyclases for Generating Unnatural Terpenoids

“…For example,1 2-hydroxy-FPP was transformed by the amorphadiene synthase from Artemisia annua to yield the artemisinin precursor dihydroartemisinic aldehyde in 34 %y ield. [4] With the natural substrate 17,the yield could recently be raised to over 90 %u nder continuous flow conditions. [5] These few examples demonstrate that chemo-enzymatic use of TCs is an emerging field of research with prospects to access new terpene derivatives and even new terpenoid backbones.…”

“…Them ost remarkable product is the tricyclic cyclobuta- [3,4]cyclohepta[1,2-c]tetrahydrofuran derivative 25 obtained from ether 18.D espite the structural differences between presilphiperfolan-8-b-ol (9)a nd the derivative 25,asensible proposal for its formation is depicted in Scheme 3. The biosynthesis of 9 from FPP (17) [14] is initiated by formation of the humulyl cation 37.N ext, ac ationic cascade leads to cyclopentaindanyl cation 40 via cyclobutane 38 and bicyclic bridged cation 39,followed by athird cyclization.…”

Silent catalytic promiscuity in the high-fidelity terpene cyclase δ-cadinene synthase

“…Recombinant AS and ADS were prepared and purified according to previously published procedures17,18 and both ( R )- 11 and ( S )- 11 were tested as inhibitors using a standard radiolabelled assay involving conversion of tritium labelled FDP by each enzyme and scintillation counting of the pentane extractable products 5 b . Terpene synthases are known to efficiently bind cation-PP i pairs and inhibition was assessed both in the presence and absence of 250 μM diphosphate (Table 1).…”

Concise synthesis of artemisinin from a farnesyl diphosphate analogue

“… 14 As an example, it has been shown that ADS catalyses the cyclisation of 12-hydroxy FDP ( 6 ) to produce dihydroartemisinic aldehyde ( 7 ) ( Scheme 4 ) with a 34% yield. 12 The seemingly moderate yield is common for sesquiterpene cyclases as the reaction is limited by the release of the hydrocarbon products from the aqueous incubation media. 15 Aldehyde 7 is a well-established intermediate in the biosynthesis of artemisinin ( 1 ).…”

“…Amorphadiene synthase (ADS) is able to convert 6 in a single step to dihydroartemisinic aldehyde (DHAAl, 7 ), an advanced intermediate of artemisinin. 12 This route does not proceed via amorphadiene ( 3 ) and therefore avoids several redox steps. Increasing the oxidation state at the linear precursor stage produces a two-step synthesis of 4 , which significantly shortens the synthesis of artemisinin ( 1 ).…”