The isolation and structure elucidation of rebeccamycin l_, a new antitumor agent from Nocardia aerocoligenes, is described. The NMR spectra of 1 and its peracetate 2 are discussed. Recently we have isolated a novel antitumor antibiotic rebeccamycin 1 from fermentations of Nocardia aerocoligenes, strain c38383-RK-2 (ATCC 39243).1 Rebeccamycin was isolated by extraction of the mycelial mat of the fermentation with THF. Evaporation of the extracts followed by trituration of the crude solids with ether yielded crude rebeccamycin which was recrystallized from THF-MeOH to yield pure rebeccamycin as a yellow solid, mp326-330Β°C (decomposition), ai1 (THF) = + 131'. The IR spectrum of 1 had bands characteristic of hydtoxyl groups and a cyclic imide (IR bands at 3418, 3355, 1752 med., 1704 strong, cm -1 ). The UV spectrum of 1 in methanol showed two maxima at 238 (a=75.75) and 314 -(a=90.51) with shoulders at 256, 293, 362 and 390 nm. Addition of dilute base gave bands at 314, 285, and 237 nm. No shifts were observed on addition of dilute acid. The elemental formula C27H21C12N307 was determined by elemental analysis and mass spectroscopy. 2 The CI mass spectrum of 1 exhibited an ion at M/e 570(M+l) and a parent ion at M/e 394(M-C7H14 05). Minor ions at M/e 422 and M/e 436 were also observed. The 'H NMR spectrum of 1 in DMSO-d6 exhibited resonances at 611.37(S, lH, N6-H), 10.30(s, 1H. N13-H), 9.27(d, lo, C8-H), 9.09(d, lH, C4-H), 7.74(d, lH, ClO-H), 7.69(d, lH, CZ-H), 7.45(t, ZH, C3-H+C9-H), 6.97(d, 1H. Cl'-H). 5.45(d. lH, C3'-OH), 5.36(t. lH, C6'-OH), 5.03(d. 1H. C2'-OH). 3.90(bt, 2H. C6'-CH2), 3.66(quin, 1H. C5'-H), 3.56(dt. lH, C2'-H) 3.53(t, 1H. C4'-H) 3.48(s, 3H, C4'-OCH3) 3.45(obscured, lH, C3'- H). The 13C NMR spectrum of 1. is listed in Table 1.
Treatment of 1 with acetic anhydride/pyridina gave the tetracetate 2 in good yield as a yellow solid, mp145-147'C. The 'H NMR spectrum of 2 was very similar to that of L in the