Pergamon
PII: S0031-9422(96)00375-5
Phytochemistry, Vol. 43, No. 4, pp. 839-842, 1996 Copyright © 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0031-9422/96 $15.00 + 0.0O
TAXANES FROM TAXUS MAIREI
SHUNG-JIM YANG, JIM-MIN FANG and Yu-SHIA CHENG*Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China
(Received in revised form 29 April 1996) Key W o r d lndex--Taxus maire; Taxaceae; taxane; twigs; diterpenoids.
A b s t r a c t - - F o u r new taxane diterpenes, 9a-hydroxy-14fl-(2-methylbutyryl)oxy-2a,5a, lOfl-triacetoxytaxa-4(20),
11-diene, 2a,5t~,9ot, 1 Off, 14fl-pentaacetoxytaxa-4(20), 11-diene, 5a-(cinnamoyl)oxy-7fl-hydroxy-9a, 1 Off- 13 a-tri- acetoxytaxa-4(20),ll-diene and 5ct-hydroxy-9a, lOfl,13ct-triacetoxytaxa-4(20),ll-diene, along with 12 known taxa-4(20),ll-dienes, have been isolated from twigs of Taxus mairei and their structures determined by spectral methods. Copyright © 1996 Elsevier Science Ltd
INTRODUCTION
The chemical constituents of the plants of the Taxus
genus have been extensively investigated [1-3], partly due to the finding of an antitumour agent, taxoi [4].
Taxus mairei is the only species belonging to the genus
Taxus found in Taiwan. A few taxane derivatives have been isolated from the heartwood of this plant [5, 6]. We report herein 16 taxane diterpenes having C4(20)- exocyclic double bonds isolated from the twigs of T.
mairei.
RESULTS AND DISCUSSION
A concentrated acetone extract of the twigs of T.
mairei was diluted with water and extracted with ethyl acetate. The ethyl acetate soluble material was chro- matographed to give 16 taxanes (1-16), 12 of which were known: 2a,5a,10fl,14fl- tetraacetoxytaxa-4(20), 11-diene (1) [7], 14fl-(isobutyryl)oxy-2a,5a, lOfl-tri-
acetoxytaxa-4(20),ll-diene (2) [7], 14fl-(2-methyl- butyryl)oxo- 2a,5cr, 10fl- triacetoxytaxa- 4(20), 11 - diene (3) [7], yunnanxane (4) [8], taxuyunnanine B (7) [9], 5 a - (cinnamoyl)oxy - 9tr,10fl,13a - triacetoxytaxa - 4 ( 2 0 ) , l l - d i e n e (8) [10, 11], 2tr-deacetoxytaxinine J (10) [12], taxinine J (11) [6], taxacin (12) [13], taxusin (13) [14, 15], 5a,7fl,9c~,lOfl,13ct-pentaacetoxytaxa-
4(20),1 l-diene (15) [16] and 5or - hydroxy - 2c~,7fl,9a, 10/~, 13 tz - pentaacetoxytaxa - 4(20), 11 - diene (16) [17]. Compounds 1 - 3 have been found in cell cultures of T. chinensis var. mairei [7].
Compound 5 gave rise to a molecular ion [M] ÷ at
mlz 562.312 consistent with a molecular formula C 3 1 H 4 6 0 9 . The ' H NMR spectrum (Table 1) showed
*Author to whom correspondence should be addressed.
resonances of four methyl groups at 8 0.87 (s), 1.12 (s), 1.58 (s) and 2.12 (s), which are characteristic of taxane diterpenes. In addition to the resonances for three acetyl groups at 8 169.8 (s), 169.9 (s), 170.5 (s), 21.3 (q), 21.3 (q) and 21.9 (q), the ~3C NMR spectrum (Table 2) displayed a signal at 8 175.6 (s) attributable to an ester group. The a-methylbutyrate moiety was indicated by the proton resonances at 8 0.85 (t, J = 7.2 Hz,
CH3),
1.11 (d, J = 7.2Hz,
CH3),
1.46 (m, CH2) and 2.34 (m, CH). The proton resonances at 8 4.84 (br s) and 5.28(br s) as well as the carbon signals at 8 141.8 (s) and 117.5 (t) suggested the presence of a methylene group. The structure of 5 was assigned as 9a-hydroxy-14fl-(2- methylbutyryl)oxy - 2a,5ct, 10ft - triacetoxytaxa - 4(20), l l-diene. The methylbutyrate group was located at C-14 by IH-1H COSY, HMBC, and HMQC. The corresponding H-14 signal occurred at 8 4.93 (dd, J =
4.4 and 8.8 Hz). The absolute configuration of the side chain was tentatively assigned to have the (S)-configu- ration based on the literature [7, 8]. The 2fl-, 5fl- and 10o~-protons geminal to the acetoxy groups had chemi- cal shifts [8 5.23 (dd, J = 2.6 and 6.4 Hz), 5.29 (1H, br
s) and 5.80 (d, J = 10Hz)] close to those values in taxuyunnanine B. Compound 5 had a hydroxyl group at C-9 as its H-9fl signal occurred at 8 4.19 (d, J = l0 Hz) whereas the H-9fl signal in taxuyunnanine B occurred at 8 5.77. The ~H NMR spectrum also exhibited a characteristic signal of H-3a at 8 2.92 (lH, d, J = 6 Hz).
Compound 6 was assigned the molecular formula C3oH42Oto ([M] + = m / z 562.276). The 1H and 13C NMR spectra (Tables 1 and 2) were similar to those of compound 7 except that the signals of the methylbutyrate group in 7 were replaced with the signals of an acetyl group in 6. The structure of 6 was assigned as 2a,5a,9ot,10fl,14fl-pentaacetoxytaxa-4(20), ll-diene. From the ~H-1H COSY spectrum the reso- 839
840 SHUNG-JIM YANG et al.
Table 1. 1H NMR spectral data for taxanes 5, 6, 9 and 14 (CDCI3)
H 5 6 9t 14 1 1.82 (d, 2.4)* 190 (d, 2.4) 1.76 (m) 2 5.32 (dd, 5.38 (dd, 2.4, 6.4) 2.4, 6.3) 3 2.92 (d, 6.4) 2.93 (d, 6.3) 2.93 (d, 3.9) 3.26 (d, 4.5) 5 5.29 (br, s) 5.24 (br, s) 5.55 (br s) 4.26 (br s) 7 4.32 (dd, 4.8, 11.1) 9 4.19 (d, 10.0) 5.76 (d, 10.2) 6.05 (d, 11.1) 5.73 (d, 10.2) 10 5.80 (d, 10.0) 6.03 (d, 10.2) 6.25 d, 11.1 ) 6.07 (d, 10.2) 13 2.87 (dd, 2.83 (dd, 5.77 (br t, 5.67 (dd, 9.2, 19.2) 9.0, 19.2) 7.8) 3.3, 7.8) 2.32 (m) 2.40 (m) 14 4.93 (dd, 4.93 dd, 1.12 (dd, 4.4, 8.8) 4.8, 9.0) 4.5, 15.3) 2.78 (m) 16 1.58 (s) 1.68 (s) 1.73 (s) 1.55 (s) 17 1.12 (s) 1.09 (s) 1.01 (s) 0.97 (s) 18 2.12 (s) 2.15 (s) 2.22 (s) 2.08 (s) 19 0.87 (s) 0.82 (s) 0.81 (s) 0.68 (s) 20 4.84 (br s) 4.84 (br s) 4.97 (br s) 4.71 (br s) 5.28 (br s) 5.30 (br s) 5.35 (br s) 5.09 (br s) 2' 2.34 (m) 3' 1.46 (m) 4' 0.85 (t, 7.2) 5' 1.11 (d, 7.2)
*The values in parentheses are coupling constants (Hz).
fCinnamoyl data: 8 7.74 (d, 16.0), 6.52 (d, 16.0) and %37-7.48 (5H).
Table 2. ~3C NMR spectral data for taxanes 5, 6, 9 and 14 (CDC13, 6 in ppm) C 5 6 9* 14 1 59.0 58.4 40.0 2 70.0 70.2 69.9 3 44.1 44.2 37.3 4 141.8 141.3 146.2 5 78.6 78.3 78.2 6 28.5 28.3 34.5 7 25.8 27.2 70.5 8 44.8 44.8 46.2 9 76.2 76.7 76.5 10 76.0 72.4 71.6 11 133.2 132.7 134.9 12 137.0 t37.2 137.1 13 39.7 39.4 70.0 14 69.9 69.8 31.8 15 36.8 36.9 39.3 16 26.2 25.8 27.1 17 31.5 31.6 31.0 18 21.0 21.0 13.1 19 22.4 17.3 15.2 20 117.5 118.3 115.9 1' 175.6 2' 41.0 3' 26.7 4' 11.5 5' 13.9 *Cinnamoyl data: 6 166.0, 118.3, 145.6, 134.0, 128.0, 128.9 and 130.5.
nance at 8 4.93 (dd, J = 4.8 and 9.0 Hz) was assigned to H-14o~. No coupling was observed between H - l f l and H-14c~, because these two protons were nearly orthogonal.
39.5 Compound 9 (C35H4409) gave rise to a molecular 32.3 ion [M] + at m / z 608.293 (calc. 608.297). The IR 36.1 spectrum showed absorptions at 1730, 1715 and 153.3 1630 cm -~ attributable to normal and conjugated ester 77.4 groups. In the ~H N M R spectrum, three acetoxy groups 26.4
29.0 appeared at 6 1.82 (s), 2.00 (s) and 2.06 (s). The 43.4 resonances at 8 7.74, 6.52 (AB quartet, J = 16 Hz) and 74.3 7 . 3 7 - 7 . 4 8 (5H) indicated the presence of a cinnamoyl 72.8 group. By comparison of the ~H and ~3C N M R spectra 136.1 of 9 with those o f 8 and 2ot-deacetoxytaxinine J, the 137.2 structure of 9 was assigned as 5 1 - ( c i n n a m o y l ) o x y - 7 f l - 70.2 hydroxy - 9t~,10fl,13ce - triacetoxytaxa - 4(20),11 - diene. 26.0 The chemical shifts of the 5fl-, 9fl- and 10a-protons 38.7 [8 5.55 (br s), 6.05 (d, J = 11.1 Hz) and 6.25 (d, J = 27.4
I 1.1 Hz)] were close to the values in 8 and 10. Because 32.3
15.8 the dihedral angle between H - 1 0 a and H-9fl was 17.1 nearly 180 °, these protons exhibited a large coupling 111.1 constant ( l l . 1 H z ) . The H - 7 ~ in 9 was geminal to a hydroxyl group and resonated at 8 4.32 (dd, J = 4.8 and 11.1 Hz), whereas the H-7ot in 10 geminal to an acetoxy group appeared at a lower field (8 5.70).
Compound 14
(C26H3807),
[M] + at m / z 462.260, gave ~H an d~3C N M R spectra similar to those of 13 (C24H3608). Compound 14 had three acetoxy groups as shown by the signals at 6 H 2.02 (s), 2.05 (s) and 2.07Taxanes from Taxus mairei 841
(s), whereas compound 13 had four acetoxy groups. The structure of 14 was assigned as 5ot-hydroxy- 9a,10fl,13ot-tdacetoxytaxa-4(20),ll-diene. The proton resonances at 8 5.09 (1H, br s) and 4.71 (1H, br s)
were attributable to the methylene group at C-4. The 9fl- and 10ot-protons appeared as an AB system at 8 5.73 and 6.07 with a large coupling constant (10.2 Hz). From the ~H-tH COSY spectrum, H-5fl and S 4.26 geminal to a hydroxyl group was correlated with H-6ot (at (5 1.75), h-6fl (at t~ 1.65) and H-20 ~at (5 5.09). The signal at t~ 5.67 (H-13fl) showed correlations with H-14ot (t~ 1.12), H-14fl (t~ 2.78) and H-18 ((5 2.08).
In summary, the twigs of T. mairei contain various taxane diterpenes. Isolation of taxanes 1-7 is signifi- cant since taxanes having substituents at C-14 are rare.
EXPERIMENTAL
General. Mp: uncorr; 1H NMR: 300 MHz; ~3C NMR 75 MHz; HPLC: Hibar Lichrosorb Si 60 column (10/~m or 7 ~m, 2 5 c r u x 1 cm i.d.).
Plant material. Twigs ( 1.2 kg) of T. mairei, collected in the remote mountains at an elevation of ca 2100 m (Tong-Shi, Taichung county), were exhaustively ex- tracted with Me2CO (7 1 × 3). The Me2CO extract was concd to give 100 g of residue, which was diluted with H20 and extracted ( × 3 ) with EtOAc. The combined EtOAc extracts were coned to give an oil (75 g), which was absorbed with 110 g silica gel and then subjected to CC on a column packed with 650 g silica gel. Eiution was with gradients of hexane, EtOAc and Me2CO. The portion obtained from elution with EtOAc-bexane (30-
AcO
18t~OAc
20
R 1OAc
I' 2'
2
OCOCHI~e2
1' 2' 5' 3' 4' 3 OCOCHMcCH2Me 4 OCOCHMeCH(OH)MeAcO
OAc
A c O , , . ~ 2H "
-
EH R1 H// bCOCH=CHC6H5
9 H H 10 H OH 11 H OAc 12 OAc OAcAcO
R1
~ O A c
5 OH OCOCHMeCH2Me 6 OAc OAc 7 OAc OCOCHMeCH2Me=AcO OAc OCOCsHs
'",,
U - ~ C O .,,.ll ICOCH=CHC6Hs
12
A c O ' " ' " ' ~
R1 R 2 13 H H OAc 14 H H OH 15 H OAc OAc 16 OAc OAc OH842 SHUNG-JIM YANG et al.
60%) was further subjected to flash chromatography and HPLC with elution with EtOAc-CHzCI 2 (20- 40%) or Me:CO-hexane (30-50%) to give 2 (12 mg), 3 (80mg), 1 (75mg), 7 (28mg), 13 (21mg), 6 (55mg), 10 (90mg), 11 (10mg), 15 (79mg), 4 (22 rag), 5 (15 rag), 14 (11 mg), 8 (15 rag), 9 (30 mg), 12 (13mg) and 16 (12mg) in ascending order of polarity.
9et - Hydroxy- 14B - ( 2- methylbutyryl )oxy- 2tx,5ot, l O[3- t r i a c e t o x y t a x a - 4 ( 2 0 ) , l l - d i e n e (5). Amorphous solid, [a] 23 +65.8 ° (CHC13; c 0.55). FABMS (NBA) m / z
(rel. int.): 585 [M + Na] ÷ (15), 503 (4), 461 (10), 443
K B r
(6), 401 (6), 341 (16), 281 (30), 57 (100). IR ~'m,x
- - I
cm : 3456, 1725, 1620.
2ct,5ot,9ot,1013,1413 - Pentaacetoxytaxa - 4(20),11 -
diene (6). Needles, mp 132-133 °, [a] 25 +26 ° (CHCL3; c 2.4). FABMS (NBA) m / z (rel. int.): 562 [M] + (3), 503 (5), 443 (14), 383 (9), 323 (12), 263 (40), 135 (100). IR v,,a~Km cm-l. 2929, 1730, 1234, 1021.
5 ce - ( C innamoy l )oxy - 7f3 - hydroxy - 9ct,1013,13ct - tri- a c e t o x y t a x a - 4 ( 2 0 ) , l l - d i e n e (9). Yellow gum. [a]~) 5
+20 ° (CHC13; c 0.5). FABMS (NBA) m / z (rel. int.): 608 [M] + (20), 590 (13), 548 (100), 488 (30), 428 (16). IR v~,~' x' c m - ' : 3469, 1730, 1631, 1234, 1159, 1021.
5e~ - Hydroxy - 9e~, 10f~, 13~x - triacetoxytaxa - 4(20), 11 -
diene(14). Needles, mp 204-206 °, [a]~ 6 +266 ° (CHC13; c 0.9). FABMS (NBA) m / z (rel. int.): 462 [M] + (6), 444 (20), 403 (70), 343 (63), 283 (100), 265
- - 1
(58). IR /:maxKar cm : 3485, 1734, 1235, 1019, 898.
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