Redetermined structure of oxaline: absolute configuration using Cu Kα radiation

Abstract

Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.002 Å; R factor = 0.035; wR factor = 0.089; data-to-parameter ratio = 10.0.In the title compound, C 24 H 25 N 5 O 4 , the stereogenic C atom bonded to three N atoms and one C atom has an S configuration and its directly bonded neighbour has an R configuration. An intramolecular N-HÁ Á ÁO hydrogen bond supports the near coplanarity of the two C 3 N 2 -five-membered rings [dihedral angle = 5.64 (10) ]. In the crystal, molecules are linked by N-HÁ Á ÁN hydrogen bonds, forming a C(8) chain propagating in [001]. The chains are connected by C-HÁ Á ÁO interactions, generating a three-dimensional network. The previous study [Nagel et al. (1974). Chem. Commun. pp. 1021-1022] did not establish the absolute structure and no atomic coordinates were published or deposited. Related literatureFor the previous structure, see : Nagel et al. (1974). For background to oxaline and its properties, see: Steyn (1970); Koizumi et al. (2004). For puckering parameters, see : Cremer & Pople (1975). ExperimentalCrystal data

Asymmetric Total Synthesis of Indole Alkaloids Containing an Indoline Spiroaminal Framework

“…9a Although reproducible NMR spectra data could be obtained by using [D 5 ]pyridine as solvent, no naturally occurring sample could be obtained to help confirm the synthetic compound as being oxaline ( 3 ). Eventually, we confirmed the structure of our final product by X‐ray analysis,40 as depicted in Scheme , which was identical to the reported ORTEP plot of naturally occurring 3 10. Moreover, the optical rotation of synthetic 3 was identical to the reported value of naturally occurring oxaline {synthetic 3 : [ α ]${{{25\hfill \atop {\rm D}\hfill}}}$ =−49.5 ( c =0.5, MeOH),41 naturally occurring 3 : [ α ]${{{25\hfill \atop {\rm D}\hfill}}}$ =−45.0 ( c =0.3, MeOH)} 4…”

“…Although the bioactivity5–7 and biosynthesis8 of this family of compounds have been studied in detail, because of their unique chemical structure, their absolute stereochemistries have only been speculated, except for oxaline ( 3 ) and meleagrin A ( 6 ), for which absolute configuration have been elucidated by X‐ray analysis 9. 10 Therefore, we set 1 as the initial synthetic target and reported the first generation total synthesis of 1 and clarified its absolute stereochemistry in 2013 11. Despite the unique structure of the neoxaline family, only our group has achieved the total synthesis of a compound in this family.…”

OxaD: A Versatile Indolic Nitrone Synthase from the Marine-Derived Fungus Penicillium oxalicum F30

“…3–5 Oxaline ( 2 ) and meleagrin ( 3 ) have been less frequently isolated from fungal cultures. 6,7 Roquefortine C ( 1 ) is found in low levels in industrially produced blue cheese, 8 grain, 9–12 and animal feedstocks, 13 and while cytotoxic effects of varying degrees have been observed in mice 14,15 and cockerels, 16 roquefortine C has shown little to no cytotoxicity in a number of human cell lines. 12,17,18 Roquefortine C is known to bind to iron, inactivating hepatic cytochrome P450s 19 and inhibiting growth of gram-positive bacteria containing heme proteins.…”

Triazaspirocycles: Occurrence, Synthesis, and Applications

“…A recent crystal structure of the indole alkaloid oxaline shows an envelope conformation for the indole five membered ring as well as an intramolecular N-H---O hydrogen bond which results in a low dihedral angle for the two C 3 N 2 rings, Fig. ( 7 ) [21]. In the crystal structure of dibromoagelaspongin, an envelope conformation is observed for both the tetrahydroimidazolone and the imidazole rings, while the pipe-ridine ring C exhibits a distorted twist-conformation [22].…”