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CHEMISTRY & BIODIVERSITY – Vol. 10 (2013)
namic acid (32 mg, 0.2 mmol) furnished 8 (17 mg, 37%). White solid. M.p. 145–1508. IR (KBr): 3393,
2925, 2853, 1708, 1637, 1608, 1457, 1386, 1309, 1272, 1179. 1H-NMR (400 MHz): 1.01 (s, 3 H); 1.07 (s, 3 H);
2.37 (s, 3 H); 4.00 (d, J¼11.0, 1 H); 4.36 (d, J¼11.0, 1 H); 4.81 (br. s, 1 H); 4.98 (br. s, 1 H); 6.38 (d, J¼
16.0, 1 H); 7.18 (d, J¼8.2, 2 H); 7.42 (d, J¼8.2, 2 H); 7.63 (d, J¼16.0, 1 H). HR-ESI-MS (pos.): 471.2881
([MþNa]þ , C30H40NaOþ3 ; calc. 471.2875).
ent-Kaur-16-ene-13,19-diol 19-O-a-Methylcinnamate (¼(5b,8a,9b,10a,13a)-13-Hydroxykaur-16-en-
18-yl (2E)-2-Methyl-3-phenylprop-2-enoate; 9). Treatment of 4 (38 mg, 0.1 mmol) with a-methylcin-
namic acid (39 mg, 0.2 mmol) afforded 9 (39 mg, 70%). Amorphous solid. IR (KBr): 3339, 2925, 2849,
2627, 1706, 1682, 1634, 1575, 1449, 1261, 1203, 1122. 1H-NMR (400 MHz): 1.04 (s, 3 H); 1.08 (s, 3 H); 2.13
(br. s, 3 H); 4.00 (d, J¼11.0, 1 H); 4.37 (d, J¼11.0, 1 H); 4.82 (br. s, 1 H); 4.99 (br. s, 1 H); 7.31–7.35 (m,
3 H); 7.39–7.43 (m, 2 H); 7.67 (br. s, 1 H). HR-ESI-MS (pos.): 471.2853 ([MþNa]þ , C30H40NaO3þ ; calc.
471.2875).
ent-Kaur-16-ene-13,19-diol 19-O-2-Cyanocinnamate (¼(5b,8a,9b,10a,13a)-13-Hydroxykaur-16-en-
18-yl (2E)-2-Cyano-3- phenylprop-2-enoate; 10). Treatment of 4 (50 mg, 0.2 mmol) with 2-cyano-3-
phenylacrylic acid (50 mg, 0.3 mmol) yielded 10 (14 mg, 19%). Amorphous solid. IR (KBr): 3414, 2927,
2851, 2223, 1727, 1606, 1450, 1270, 1205, 1189, 1108, 1092. 1H-NMR (400 MHz): 1.07 (s, 3 H); 1.08 (s, 3 H);
4.12 (d, J¼11.0, 1 H); 4.47 (d, J¼11.0, 1 H); 4.82 (br. s, 1 H); 4.99 (br. s, 1 H); 7.49–7.53 (m, 2 H); 7.55–
7.57 (m, 1 H); 8.00 (br. d, J¼7.3, 2 H); 8.24 (s, 1 H). HR-APCI-MS (pos.): 460.2878 ([MþH]þ
,
C30H38NOþ3 ; calc. 460.2852).
ent-Kaur-16-ene-13,19-diol 19-O-3-(Pyridin-3-yl)acrylate (¼(5b,8a,9b,10a,13a)-13-Hydroxykaur-
16-en-18-yl (2E)-3-(Pyridin-3-yl)prop-2-enoate; 11). Treatment of 4 (20 mg, 0.07 mmol) with 3-
(pyridin-3-yl)acrylic acid (20 mg, 0.1 mmol) afforded 11 (17 mg, 59%)). White solid. M.p. 132–1388.
IR (KBr): 3352, 2924, 2853, 1710, 1646, 1613, 1587, 1457, 1419, 1288, 1193, 1090, 1025. 1H-NMR
(400 MHz): 1.02 (s, 3 H); 1.07 (s, 3 H); 4.03 (d, J¼11.0, 1 H); 4.39 (d, J¼11.0, 1 H); 4.82 (br. s, 1 H); 4.99
(br. s, 1 H); 6.51 (d, J¼16.1, 1 H); 7.35 (dd, J¼4.9, 7.7, 1 H); 7.65 (d, J¼16.1, 1 H); 7.86 (dt, J¼1.5, 7.7,
1 H); 8.61 (dd, J¼1.5, 4.9, 1 H); 8.76 (d, J¼1.5, 1 H). HR-APCI-MS (pos.): 436.2879 ([MþH]þ
,
C28H38NOþ3 ; calc. 436.2852).
ent-Kaur-16-ene-13,19-diol 19-O-3-Phenylpropionate (¼(5b,8a,9b,10a,13a)-13-Hydroxykaur-16-en-
18-yl 3-Phenylpropanoate; 12). Treatment of 4 (31 mg, 0.1 mmol) with 3-phenylpropanoic acid (34 mg,
0.2 mmol) afforded 12 (25 mg, 56%). Amorphous solid. IR (KBr): 3524, 2931, 2853, 1724, 1664, 1444,
1394, 1373, 1292, 1248, 1176, 1106. 1H-NMR (400 MHz): 0.90 (s, 3 H); 1.01 (s, 3 H); 2.63 (t, J¼7.8, 2 H);
2.95 (t, J¼7.8, 2 H); 3.86 (d, J¼11.0, 1 H); 4.22 (d, J¼11.0, 1 H); 4.81 (br. s, 1 H); 4.97 (br. s, 1 H); 7.18–
7.21 (m, 3 H); 7.26–7.28 (m, 2 H). HR-ESI-MS (pos.): 459.2854 ([MþNa]þ , C29H40NaO3þ ; calc.
459.2875).
ent-Kaur-16-ene-13,19-diol 19-O-Benzoate (¼(5b,8a,9b,10a,13a)-13-Hydroxykaur-16-en-18-yl Ben-
zoate; 13). To a soln. of 4 (50 mg, 0.2 mmol) in dried pyridine (5 ml), PhCOCl (54mg, 0.4 mmol) was
added. After 24 h, H2O (30 ml) was added, and the mixture was extracted with Et2O (2ꢂ30 ml). The
Et2O fraction was washed with H2O (2ꢂ ), dried (Na2SO4), and evaporated under reduced pressure to
give a mixture (139 mg), which was subjected to TLC (hexane/AcOEt 7:3) and HPLC (tR 10.4 min) to
furnish 13 (6 mg, 9%). White solid. M.p. 117–1228. IR (KBr): 3339, 2928, 2850, 1715, 1663, 1603, 1451,
1282, 1121. 1H-NMR (400 MHz): 1.08 (s, 3 H); 1.09 (s, 3 H); 4.12 (d, J¼11.0, 1 H); 4.49 (d, J¼11.0, 1 H);
4.82 (br. s, 1 H); 4.99 (br. s, 1 H); 7.45 (br. t, J¼7.8, 2 H); 7.56 (br. t, J¼7.4, 1 H); 8.04 (br. d, J¼7.1, 2 H ) .
HR-ESI-MS (pos.): 431.2554 ([MþNa]þ , C27H36NaO3þ ; calc. 431.2562).
ent-Kaur-16-ene-13,19-diol 19-O-4’,4’,4’-Trifluorocrotonate (¼(5b,8a,9b,10a,13a)-13-Hydroxykaur-
16-en-18-yl (2E)-4,4,4-Trifluorobut-2-enoate; 14). Treatment of 4 (31 mg, 0.1 mmol) with 4,4,4-
trifluorocrotonic acid (44 mg, 0.3 mmol) yielded 14 (16 mg, 37%). White solid. M.p. 95–998. IR
1
(KBr): 3401, 2929, 2854, 1731, 1458, 1330, 1268, 1136, 1120. H-NMR (400 MHz): 0.98 (s, 3 H); 1.04 (s,
3 H); 4.01 (d, J¼11.0, 1 H); 4.39 (d, J¼11.0, 1 H); 4.82 (br. s, 1 H); 4.98 (br. s, 1 H); 6.49 (dq, J¼1.8, 15.6,
1 H); 6.75 (dq, J¼6.4, 15.6, 1 H). HR-APCI-MS (pos.): 409.2346 ([MþHꢀH2O]þ , C24H32F3O2þ ; calc.
409.2354).
Methyl ent-Kaur-16-en-19-oate (¼ Methyl (5b,8a,9b,10a,13a)-Kaur-16-en-18-oate; 16). As described
for the preparation. of 3, treatment of 15 (119 mg, 0.4 mmol) with TMSꢀCHN2 (1.2 ml, 0.7 mmol) gave 16
(121 mg, 97%), which was identified by spectral comparison with literature data [26].