Assignment of the ¹³C and ¹⁵N NMR spectra of the antitumour antibiotic streptonigrin

Abstract

The assignments of the two pyridyl nitrogens and two amino nitrogens in the antitumour antibiotic streptonigrin, and all carbon resonances, were determined by 15 N (HSQC, HMBC) and 13 C (HSQC, HMBC) NMR techniques. These data provide useful probes for determination of the site(s) of metal complexation in the drug, which are important in the mechanism of antitumour activity.

The total synthesis of streptonigrin and related antitumor antibiotic natural products

“…25 Using modern HMBC, HMQC, NOESY, and NOE techniques, Harding and co-workers succeeded in assigning all carbon, hydrogen, and nitrogen resonances to substantiate the structure of streptonigrin as 1. 33,34 This group also conducted variable temperature studies to assign the four nitrogen resonances, and similar experiments proved to be most useful in analyzing metal complexes of streptonigrin. 35 Their efforts paved the way for the attribution of the signals in streptonigrone (2) and lavendamycin (3).…”

1H, 13C and 15N NMR assignments of phenazopyridine derivatives

“…1 The structures of these compounds can differ considerably; some are stable as the azo tautomer, whereas others prefer the hydrazo form or appear as mixtures of both tautomers. 2 -4 Detailed 1 H, 13 C and 15 N interpretations have been used as an important tool for the study of azo-hydrazo tautomerism processes. 1,5,6 Some dyes have been used in medicine, a typical example being phenazopyridine hydrochloride (1), which has been in use for many decades as a drug to reduce pain, burning and discomfort associated with urinary tract infections or irritation.…”

“…(Table 1) to NH 2 -6, since it shows a clear correlation with the C-5 signal at υ 100.0. The failure to detect the NH 2 -2 signal can be attributed to the weak and significantly exchange-broadened signal 15 of the amino protons. The 13 C NMR spectrum of 2 shows the expected nine signals (Table 2), from which the protonated carbons at υ 138.1, 129.0, 127.7, 121.0 and 100.0 were unambiguously assigned, using the gHSQC experiment, to C-4, C-m, C-p, C-o and C-5, respectively.…”

“…MHz, respectively. Spectra were referenced to TMS for 1 H and13 C and to neat MeNO 2 , υ D 0, for15 N. The 1 H,13 C correlation experiments were performed using standard manufacturer-supplied gHSQC 17 and gHMBC 18 pulse programs. Typically the proton spectral widths in the gHSQC experiment were 12 820.5 Hz for F 1 and 3601.0 Hz for F 2 , the experiment being optimized for a 1 J(C,H) coupling of 140 Hz, whereas in the gHMBC experiment the spectral widths for F 1 and F 2 were 18 115.9 and 3601.0 Hz, respectively, and the n J(C,H) value set to 8 Hz.…”

“…Typically the proton spectral widths in the gHSQC experiment were 12 820.5 Hz for F 1 and 3601.0 Hz for F 2 , the experiment being optimized for a 1 J(C,H) coupling of 140 Hz, whereas in the gHMBC experiment the spectral widths for F 1 and F 2 were 18 115.9 and 3601.0 Hz, respectively, and the n J(C,H) value set to 8 Hz. The 1 H,15 N correlation experiments were performed using standard gHMQC and gHMBC pulse sequences. 18b,c,19 The HMQC experiment was acquired with 1024 data points and spectral widths of 2362.4 Hz for F 2 and 54 945.1 Hz for F 1 , and was optimized for a 1 J(N,H) coupling of 90 Hz.…”