Synthetic Studies of Indoles and Related Compounds. XXVII. A New Synthesis of Crenatine from Ethyl Indole-2-carboxylate.

Molecular Construction Using Formamide as a C1 Feedstock

“…In 1958, Chuen and Fenton [42c] described the synthesis of a bisformyl derivative (69 % yield) of 9,12‐diphensuccinadione by refluxing a mixture of dione, 90 % formic acid and formamide for 24 h. In 1991, Murakami et al [42d] . used ketone, formic acid, formamide and (NH 4 ) 2 SO 4 in an autoclave (190 °C for 7 h) to obtain 3 examples of N ‐substituted formamides.…”

Simple indole alkaloids and those with a nonrearranged monoterpenoid unit (1999)

“…91 Further, two new β-carboline alkaloids, hedyocapitelline 117a and hedyocapitine 117b, have been 96 Total syntheses of 4,8-dioxygenated β-carboline alkaloids 123a, 123b, 123c, and 123d, isolated from Simarubaceae plants, 97 have been established. 98 The key steps are an improved Fischer indolization 99 for the synthesis of 7- Manzamine A 127, which exhibits potent antitumor activity in a number of assays, 100 was the first member of this group of alkaloids to be isolated. Enantioselective total syntheses of a biogenetic precursor 101 of manzamine alkaloids ircinal A 126, isolated from the Okinawan marine sponge of Ircinia sp.…”

Synthesis of 1,4‐Disubstituted and 1‐Substituted β‐Carbolines via 3‐Substituted 2‐Acylindoles

“…A prominent 1,3,4trisubstituted β-carboline alkaloid is lavendamycin (5), a cytotoxic metabolite from Streptomyces lavendulae, which was not developed further due to solubility and toxicity issues. [6] Published approaches to 1,4-disubstituted β-carbolines require either multiple steps, [3] often going through 1-oxo- [4,7] and 4-oxo intermediates, [3,8] or are limited to 4-aryl derivatives. [9] In continuation of our efforts to develop novel synthetic methods in this field, namely for 1-substituted, [10] 1,3disubstituted [11] and 1,3,4-trisubstituted β-carbolines, [12] we now focused on the synthesis of the poorly investigated chemotype of 1,4-disubstituted β-carbolines.…”

“…Published approaches to 1,4‐disubstituted β‐carbolines require either multiple steps, [3] often going through 1‐oxo‐ [4,7] and 4‐oxo intermediates, [3,8] or are limited to 4‐aryl derivatives [9]…”