J. Org. Chem. 1988,53, 6115-6118 Table I. IH and 13C NMR Assignments of Prionitin ( 1 ) O carbon 'H 13c 26.64 1-Ha 3.16 (ddd, 16.8, 4.2, 2.6) 1-HP 2.80 (ddd, 17.0, 12.3, 4.4) 23.71 2-Ha 2.16 (dddd, 17.4, 12.1, 4.4, 2.5) 2-HB 1.66 (ddd, 17.4, 12.3, 4.5) 62.87 3.34 (dd, 12.2, 4.6) 3 4 93.58 127.33 5 152.12 6 153.22 7 8 118.07 130.81 9 10 129.46 11 7.08 (d, 8.8) 126.07 7.68 (d, 8.8) 119.98 12 124.87 13 14 120.81 28.07 15 2.37 (s) 25.68 16 3.52 (sept, 6.7) 1.31* (d, 6.7) 21.33' 17 21.53t 1.38* (d, 6.7) 18 21.95 1.71 (ns) 19 18.89 20 1.17 (9) 47.74 OCH3 3.88 (s) OSpectra were recorded in CDC13. Proton chemical shifts are reported as 6 values (ppm) from internal TMS at 300 MHz. Carbon chemical shifts are reported as 6 values (ppm) at 90.8 MHz. (*,t) Interchangeable. able, the use of one-bond or long-range HECTOR spectroscopic techniques were precluded. Magnetization transfer via irradiation of 3-H resulted in enhancements of 6 26.64, 129.46, and 152.12, which could be assigned as C-1, C-10, and (2-6, respectively. Irradiation of 1-Ha enhanced the aliphatic methine carbon a t 6 62.87, which should be C-3, and the aromatic quaternary carbons a t 6 127.33 and 130.81. T h e latter two signals, C-5 and C-9, were distinguished through the irradiation of 2-Ha, which resulted in enhancements a t 6 93.58 (C-4), 127.33 (C-5), and 129.46 (C-10). Selective I N E P T irradiation of 12-H enhanced the signals at 6 130.81 (C-9) and 120.81, assigned as C-14, indicating that this latter carbon was substituted by the aromatic methyl group. CSCM 1D irradiation of the 13C satellite of 12-H enhanced the signal a t 6 119.98, permitting the assignment of (2-12, and consequently the other aromatic methine carbon, C-11 (6 126.07). Finally, selective I N E P T irradiation of 11-H confirmed the assignment of C-10 (6 129.46) and permitted the assignment of C-13 a t 6 124.87. T h e complete assignment of the 13C NMR spectra of prionitin (1) is shown in Table I. The relative location of the isopropyl, methyl, and methoxy groups was firmly established by a NOE experiment. Irradiation of the methyl singlet a t 6 2.37 resulted in enhancement of the methoxyl (6 3.88) and the isopropyl methyl groups (6 1.31 and 1.38), thereby placing the aromatic methyl group a t C-14. Prionitin ( l ) , which represents a novel diterpenoid skeleton, was evaluated in the P-388 cytotoxicity assay where a n ED50 value a t 9.2 hg/mL was observed. Compounds displaying an ED,, 4 wg/mL are regarded as act i ~ e .Studies ~ of the remaining active compounds present in the plant are in progress.
Experimental Section Melting point was determined on a Kofler-type hot-stage apparatus and is uncorrected. Optical rotation was measured with a Perkin-Elmer 241 polarimeter. Ultraviolet spectra were recorded with a beckman DU-7 spectrophotometer, and infrared spectra
6115
were obtained with a Nicolet MX-1 interferometer. Mass spectrum was determined on a Varian MAT 112s double-focusing mass spectrometer at 80 eV. The 'H NMR spectra were obtained with a Nicolet NMC 360 instrument operating at 360 MHz. The 13CNMR measurements were performed with a Nicolet NMC 360 instrument operating at 90.8 MHz. Tetramethylsilane (TMS) was used as the internal standard, and chemical shifts are reported as 6 values (ppm). Homonuclear COSY spectra were recorded at 1K with a Varian XL-300 spectrometer. Standard Varian pulse sequences were used. The one-dimensional heteronuclear 'HJ3C shift correlation (CSCM 1D) and selective INEPT experiments were performed on a Nicolet NMC 360 spectrometer. Data sets of 16K covering a spectral width of loo00 Hz were acquired. Proton pulse widths were calibrated by using a sample of acetic acid in 10% C6Ds .('V = 6.7 Hz) in a 5-mm NMR tube. The radio frequency field strength for the soft proton pulse was on the order of 25 Hz in these experiments. For 1-Ha, 2 - H a , and 3-H protons, 4 Hz was used as the 35value and 6 Hz was used for the irradiation 11-H and 12-H. Twenty thousand acquisitions were accumulated in each irradiation. Plant Material. The plant material of S. prionitis Hance was collected in the Jiang-Xi Province of China in June 1986 and identified by Dr. X.-L. Huang. A voucher sample is deposited in the herbarium of the Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, People's Republic of China. Isolation of Prionitin (1). Dried and powdered roots of S. prionitis (11 kg) were extracted with EtOH (140 L), and the combined extracts were evaporated in vacuo. The residue was distributed between CHC13(10 L) and H20 (10 L), and the organic layer was washed with H 2 0 (2 X 2 L), dried, and evaporated to a residue (520 g), which was subjected to column chromatography on Si gel (3 kg), eluting with CHC13. The fractions were evaporated, examined by TLC, and purified further through preparative TLC to yield prionitin (5 mg, 0.001%) having the following physical and spectroscopic properties: mp 98-100 "C; IR (KBr) ,,v 2975, 2955, 1645,1575,1470,1370, 1300, and 1100 cm-'; UV (MeOH) ,A, (log t) 254 (4.41) and 296 (3.56) nm; 'H NMR , see Table I; 13C NMR, see Table I; mass spectrum, m/z (relative intensity) 310 (M', loo), 295 (7), 267 (12), 253 (8), 237 (lo), 195 (41, 165 (6).
Acknowledgment. T h e work was supported, in part, by a grant from the Division of Cancer Treatment, National Cancer Institute, Bethesda, MD. We thank the Research Resources Center of the University of Illinois at Chicago for providing NMR and mass spectroscopic facilities. Registry No. 1, 117469-56-4.
Synthesis of Acylpyrroles via a-(Dimet hy1amino)-a-pyrrolylacetonitriles'
Brian L. Bray2 and Joseph M. Muchowski* Syntex Research, Institute of Organic Chemistry, Palo Alto, California 94304 Received May 31, 1988 Acylpyrroles are intermediates of considerable importance and numerous methods have been devised to provide synthetic access thereto. The 2-acyl compounds are most efficaciously prepared by the direct acylation of a-unsubstituted pyrroles with acid chlorides (in the presence or absence of a Lewis acid ~ a t a l y s t ) Vilsmeier-Haack ,~ (1) Contribution No. 769 from the Syntex Institute of Organic Chem-
(9) Geran, R. I.; Greenberg, N. H.; McDonald, M. M.; &%"che= Abbott, B. J. Cancer Chemother. R e p . 1972, 3, 1.
0022-3263/88/ 1953-6115$01.50/0
istry. (2) Syntex Research Post-Doctoral Fellow, 1987-1988.
1988 American Chemical Society
6116 J. Org. Chem., Vol. 53, No. 26, I988
Notes
-m
Scheme I
+ I
Mezh=CHCI
CI-
2
I
R
Scheme I1 +
CH=NMe2
CI-
R
2 . 2 LDA THF/-78*
