Acyl indoles. II. Indolo[2,1‐b]quinazolones from 1‐(2‐Aminobenzoyl)indoles

Synthesis of Psychrophilin E

“…The reaction mixtures were combined after stirring at rt for 4 d and then quenched with H 2 O (100 mL), and the mixture was extracted with EtOAc (4 × 80 mL). The combined organic layers were washed with brine (100 mL), dried over MgSO 6.21 (d, J = 8.0, 1 H, NH-Ac), 5.10 (ddd, J = 11.5, 8.1, 5.5, 1 H, H-2), 4.56 (dd, J = 8.3, 2.9, 1 H, H-20), 3.37 (dd, J = 12.8, 5.4, 1 H, H-3a), 3.25 (ddd, J A = 7.2, J B = J C = 9.4, 1 H, H-23a), 2.87 (t, J = 12.1, 1 H, H-3b), 2.17 Method B. TFA (0.7 mL, 9.4 mmol) was added to a stirred solution of Boc-amide 24a (24 mg, 43 μmol) in CH 2 Cl 2 (4.8 mL) at 0 °C, and the mixture was stirred at rt for 1 h. The reaction mixture was concentrated in vacuo and then put under high vacuum for 30 min to remove the excess TFA. The crude TFA salt (24 mg) was used directly in the next step without further purification.…”

“…Interestingly, psychrophilins A–D ( 1 – 4 ) contain an unprecedented nitro-tryptophan moiety and are the only naturally occurring cyclic peptides known to possess a nitro group. Furthermore, to the extent of our knowledge, the synthesis of an amide bond between the indole-nitrogen of tryptophan and an anthranilic acid has not been previously reported, but there is literature precedent on the synthesis of such a bond between an indole-nitrogen and anthranilic acid. , As part of our ongoing synthetic program to examine the pharmacological properties of macrocyclic peptides, − our attention focused on the synthesis of this structurally unique family of cyclic peptides.…”

N-Alkylation-Initiated Redox-Neutral [5 + 2] Annulation of 3-Alkylindoles with o-Aminobenzaldehydes: Access to Indole-1,2-Fused 1,4-Benzodiazepines

“…For instance, compound I has been identified as a type of antihypertensive . Despite their bioactive significance, only sporadic synthetic routes have been disclosed to access these scaffolds over the past decades . Unfortunately, these limited examples are largely dependent on burdensome multistep operations and harsh reaction conditions, resulting in low efficiency and unsatisfactory step economy and atom economy, which sets a barrier for their practicability in synthetic chemistry and drug discovery (see Scheme b).…”