The Synthesis of Certain Phomentrioloxin A Analogues and Their Evaluation as Herbicidal Agents

Abstract

A series of 28 analogues of the phytotoxic geranylcyclohexentriol (-)-phomentrioloxin A (1) has been synthesized through cross-couplings of various enantiomerically pure haloconduritols or certain deoxygenated derivatives with either terminal alkynes or borylated alkenes. Some of these analogues display modest herbicidal activities, and physiological profiling studies suggest that analogue 4 inhibits photosystem II in isolated thylakoids in vitro.

The Exploitation of Enzymatically‐Derived cis‐1,2‐Dihydrocatechols and Related Compounds in the Synthesis of Biologically Active Natural Products

“…Using closely related chemistries we have also been able to prepare the naturally occurring and phytotoxic geranylcyclohexentriol (−)‐phomentrioloxin ( 85 ) as well as a series of analogues including the deoxy‐compound 86 that has been shown, through various tests conducted by colleagues at BASF in Germany, to display modest herbicidal activities . Physiological profiling studies suggest that this analogue inhibits photosystem II in isolated thylakoids in vitro .…”

Replacement of Less-Preferred Dipolar Aprotic and Ethereal Solvents in Synthetic Organic Chemistry with More Sustainable Alternatives

“… 302 A publication by Hutzler and co-workers in 2017, outlining routes to the synthesis of herbicides, included a rhodium-catalyzed hydroboration of alkynes with HBpin, with a solvent choice of cyclohexanone. 301 The reaction, carried out below room temperature (18 °C), yielded the desired Z -alkene in 52% yield after 2 h ( Scheme 33 ).…”

The Application of Dioxygenase‐Based Chemoenzymatic Processes to the Total Synthesis of Natural Products

“…Regio-and stereo-selective cis-dihydroxylation of the latter compound under the Upjohnc onditions and using N-methylmorpholine N-oxide (NMO) as the stoichiometric oxidant afforded the corresponding diol 10 [62 %f rom 2 (X = I)],t he allylic hydroxyl group of which was readily and selectively protected, using triiso-propylsilyl triflate (TIPSOTf), as the corresponding TIPSether 11.T his allowedt he remaining free hydroxyl group to be O-methylated by standardmeans anda fter removal of the TIPS ether with tetra-n-butylammonium fluoride( TBAF) then compound 12 was obtained.S onogashira cross-coupling of the last compound with the dienyne 13 afforded the anticipated product 14 that on exposure to aqueous acetic acid at elevated temperatures gave the naturale nantiomeric form, 15,o fp homentrioloxin. By relatedm eansa na rray of analogues was generated and on evaluation in glasshouse trialsconducted by colleagues at BASF in Germany it was established [26] that a number of thesea re active as herbicides. However,t heir seeming lack of as pecific mode of action has precluded development of them in commercial settings.…”

“…Sonogashira cross‐coupling of the last compound with the dienyne 13 afforded the anticipated product 14 that on exposure to aqueous acetic acid at elevated temperatures gave the natural enantiomeric form, 15 , of phomentrioloxin. By related means an array of analogues was generated and on evaluation in glasshouse trials conducted by colleagues at BASF in Germany it was established that a number of these are active as herbicides. However, their seeming lack of a specific mode of action has precluded development of them in commercial settings.…”