A synthesis of polycyclic aromatic compounds by the calcium acetate-induced aromatization of polyoxoalkanedioates generated from diesters and acetoacetate dianion

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

“…Based on their earlier investigations ofbiomimetic-type condensations of dianions to aromatic systems [98], they prepared the naphthalenediol 126 by successive condensation of glutaric ester 125 with acetoacetate and acetate anions. The aldehyde 127 was then prepared by a sequence of palladium-catalyzed dealkox-ydecarbonylation, basecatalyzed ring closure, protection as MOM ether, and DIBAL reduction.…”

Polyketide Assembly Mimics and Biomimetic Access to Aromatic Rings

“…Because the use of previous Harris conditions or analogous conditions at pH 9 were unsuccessful [60], aromatization was performed using base-catalyzed aldol condensation and subsequent addition of a strong acid. Ring-closing metathesis was thus applied to cyclize ester 73 into the natural (S)-(−)-zearalenone (74). This approach was further slightly modified to give access to (+)-montagnetol and (+)-erythrin [61].…”

“…After the partial synthesis of important naphthoquinones [74], one of the most prominent landmark accomplishments of this methodology led to the biomimetic synthesis of (−)-urdamycinone B (123), a potent antibiotic produced by Streptomyces fradie (Scheme 13.39) [75]. Access to the naphthol derivative 124 was performed following the same cyclization by Ca(II) salts.…”

General Approach to Anthrapyran Antibiotics Exemplified by the Synthesis of rac‐γ‐Indomycinone

“…In this communication, we disclose a general approach to the anthrapyran antibiotics, which is exemplified by the synthesis of rac-γ-indomycinone (24b). The first steps follow the linear route of Yamaguchi et al; [11,12] however, the synthesis is shortened, and the overall yield is improved from 40 % to 87 % by starting from hydroxyglutarate 1 via enones 2 to the phenol 3, skipping an intermediate conversion of the hydroxy group into the acetate, and instead employing the acid-catalyzed elimination of water (Scheme 1). Another shortcut was the direct one-step conversion of the di-tert-butyl ester 4, obtained by silver oxide mediated methylation of phenol 3 in 96 % to the monomethyl ester 5 by treatment of 4 with acidic methanol (93 %).…”