A concise synthesis of yaequinolones J1 and J2 is reported. The route is based on the aryne insertion into the sigma-C-N bond of an unsymmetric imide followed by a diastereoselective aldol cyclization of the resulting N-acylated aminobenzophenone. The chromene motif is generated in the first step by an organocatalytic tandem Knoevenagel electrocyclization of citral and 2-bromoresorcinol. The approach adheres to the ideality principle, using almost exclusively strategic bond-forming reactions.
A highly stereocontrolled totalsynthesis of (−)-yaequinolone J1 and (+)-yaequinolone J2 was accomplished using an Evans auxiliary to establish a syn-diol unit in an acyclic appendage to a preformed benzopyran core bearing a homoprenyl group. The first totalsynthesis of a complex member of this family of 3,4-dioxygenated 3,4-dihydro 4-aryl quinolin-2-(1H)-ones also allowed the assignment of absolute
eight enantiopure isomers of yaequinolone J1 (1), yaequinolone J2 (2), 4′-desmethoxyyaequinolone J1 (3), and 4′-desmethoxyyaequinolone J2 (4). The key synthetic steps were extended and 34 racemic analogues modified at the 4-aryl, the N-position, and the pyran ring were designed and synthesized. All the synthesized compounds were evaluated for their anti-inflammatory activities in RAW 264.7 cells of