Jatrophane Diterpenes: Preparation of the Western Fragment of Pl‐3

Abstract

Jatrophane diterpenes are structurally intriguing natural products with promising biological properties. Herein, the synthesis of the western fragment of the Euphorbiaceae constituent Pl‐3 starting from (1R,5S)‐bicyclo[3.2.0]hept‐2‐en‐6‐one is described. Key steps in the sequence include a Baeyer–Villiger oxidation, an iodolactonization reaction, and the installation of the northern side chain through the addition of a lithiated vinyl bromide. The overall efficiency of the route is increased by taking advantage of latent symmetry.

Aerobic Baeyer–Villiger Oxidation Catalyzed by a Flavin‐Containing Enzyme Mimic in Water

“…[b] Yield of product isolated by using reaction conditions from Ref. with specific yields calculated from NMR analysis (see the Supporting Information). [c] Data from Ref.…”

“…For the sake of comparison, the chemical BV reaction was also performed using over‐stoichiometric amounts of hydrogen peroxide in acetic acid, and afforded a mixture of 1 and 2 in 91 % yield and 85 % selectivity. The biomimetic reaction using dioxygen appears, therefore, to be competitive with the use of hydrogen peroxide.…”

Enzymatic Kinetic Resolution by Addition of Oxygen

“…[57] This important research highlights the ability of biotransformations to provide valuable enantioenriched intermediates on an industrially relevant scale.T hese compounds are key chiral intermediates in ap lethora of reported natural product syntheses (Scheme 11 b). Thus,t he enantiomerically enriched lactone 28 has been used to prepare the Corey lactone diol (leading to the synthesis of av ast selection of prostaglandins, [58] including the shown prostaglandin F2a [59] and latanoprost [60] ), jatrophane diterpenes such as PI-3, [61] the tigliane ring system, [62] callipeltoside A, [63] strigol, [64] methyl epijasmonate, [65] pseudomonic acid C, [66] carbonucleoside 29, [67] and various antivirals;the ketone 27 finds application in the synthesis of mupirocin H, [68] brefeldin A, [69] magellanine and magellaninone, [70] pseudomonic acid C, [71] 17-deoxyprovidencin, [72] and hybridalactone. [73] Scheme 8. a) CHMO Acineto -catalysed BV KR of five-and six-membered cyclic ketones (selected product examples shown);b )extension of the methodology to SmI 2 -mediated reductive cyclisation;c)complex natural products containing cycloheptanol and cyclooctanolc ore structures.…”

Progress in the Preparation of Jatrophane Diterpenes

“…[77] Racemic bicyclic ketone 246 was used as a readily available starting material, which, after reduction of the carbonyl group, was later employed in a kinetic resolution. The efficiency of the synthesis was increased by taking advantage of the latent symmetry of an advanced intermediate that allowed the utilization of both enantiomeric antipodes.…”