Total synthesis of (+)-epiepoformin, (+)-epiepoxydon and (+)-bromoxone employing a useful chiral building block, ethyl (1R,2S)-5,5-ethylenedioxy-2-hydroxycyclohexanecarboxylate

Relationships between the stereochemistry and biological activity of fungal phytotoxins

“…[72][73][74][75][76][77][78][79][80] The OR power of some natural cyclohexenone oxides has been calculated by means of an appropriate calculation program both in the gas phase and in solution by means of the polarizable continuum model. This method was applied to the following cyclohexenone oxides: (1)-chaloxone, first isolated from the fungus Chalara microspora; (1)-epiepoformine, purified by Nagasawa et al, 53 from the culture filtrate of an unidentified fungus isolated from a diseased leaf, with marked inhibition activity against the germination of lettuce seeds, which has been the subject of several synthetic attempts; 74,81 (1)-epoformine, a natural product isolated from the culture broth of Penicillium claviforme, which possesses antibiotic and cytotoxic properties; 78 (1)-epitheobroxide, which is not a natural product, but an epimer of natural (2) activity. For (1)-chaloxone and (1)-epiepoformine, which possess high (about 300 units) optical rotations, gas-phase calculations are able to reproduce the experimental values both in sign and order of magnitude, and the inclusion of the solvent effects only leads to a better agreement between experiment and prediction: this allows safe assignment of the absolute configuration.…”

Enantioselective Synthesis of Natural Polyoxygenated Cyclohexanes and Cyclohexenes from [(p‐Tolylsulfinyl)methyl]‐p‐quinols

“…The natural enantiomer has been synthesized by several authors using different strategies: Ogasawara et al [19] based their approach on a retro-Diels-Alder reaction to recover the cyclohexenone fragment from a stereoselectively functionalized quinone Diels-Alder adduct, previously asymmetrized by isomerization with an enantiopure BINAP-Rh I catalyst, [20] while the formation of a bicyclic adduct in a cinchonine-catalysed reaction between 3-hydroxy-2-pyrone and an acrylamide derived from a chiral oxazolidinone was the key step in the approach of Okamura et al [21] (À)-Quinic acid was the starting material in the synthesis reported in 2000 by Maycock et al, [22] , whereas a chiral building block obtained by enzymatic reduction was used by Kitahara et al [23] to synthesize (+)-7 in 2003.…”

Asymmetric synthesis of chiral cycloalkenone derivatives via palladium catalysis

“…10). Pleasingly, upon exposure to H 2 O 2 and catalytic benzyltrimethylammonium hydroxide (Triton B), [18] 17 cleanly underwent epoxidation to give 38 as a single diastereomer ( 1 H NMR) and in 99% ee (chiral HPLC). Thus, the oxygenation and the absolute and relative stereochemistry of the trans epoxyquinoids were set, with excellent enantio- and diastereoselectivity, in three steps from commercial 1,3-cyclohexadiene.…”

“…The analytical data for 44 , including optical rotation, was in line with data reported for material prepared through an enzymatic approach. [18] …”