Molecules 2017, 22, 694
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103.63, 98.11, 89.61, 83.78, 69.87, 62.53, 55.03, 54.97, 52.96, 51.77, 50.71, 50.09, 41.86, 39.72, 35.63, 21.60,
20.39, 16.54, 13.88. HRMS for C32H40NO10 (M + NH4)+ 598.2647. Found: 598.2648.
Synthesis of 13-Acetoxy-ent-3
α,10
β-dihydroxy-20-norgibb-erella-1,16-diene-7,19-dioic acid-7-(2,4-dimethoxybenzyl)
ester-19,10-lactone ( ). To a solution of compound
4
3
(40 g, 68.9 mmol) dissolved in methanol (300 mL)
was slowly added a saturated potassium carbonate solution dropwise until the pH value of the mixture
reached 9–10. Then, the solution was stirred at r.t. for 40 min. The reaction mixture was acidified
until reaching a pH value of 7 with a hydrochloric acid solution (1 M). The reaction mixture was
washed with water (100 mL) and then with a solution of saturated brine (150 mL) after extraction
with dichoromethane (3
m.p. 125–126 C. H-NMR (300 MHz, CDCl3):
×
100 mL) to yield
4
without further purification. White solid, yield 83%,
7.27 (d, J = 8.2 Hz, 1 H), 6.50–6.47 (m, 2 H), 6.33
◦
1
δ
(d, J = 9.4 Hz, 1 H), 5.93 (dd, J = 9.3, 3.7 Hz, 1 H), 5.21 (s, 1 H), 5.19–5.10 (m, 2 H), 4.98 (s, 1 H), 3.84
(s, 3 H), 3.81 (s, 3 H), 3.23 (d, J = 10.9 Hz, 1 H), 2.82 (d, J = 10.9 Hz, 1 H), 2.47–2.09 (m, 6 H), 2.04 (s,
3 H), 1.98–1.74 (m, 3 H), 1.25 (s, 3 H). 13C-NMR (75 MHz, CDCl3):
δ 178.24, 171.80, 169.42, 161.23,
158.71, 153.50, 132.30, 131.48, 115.61, 107.69, 103.63, 98.12, 90.03, 83.92, 69.35, 62.61, 55.05, 54.98, 53.16,
52.35, 50.85, 50.77, 41.89, 39.80, 35.68, 21.63, 16.58, 14.00. HRMS for C30H38NO9 (M + NH4)+ 556.2541.
Found: 556.2546.
Synthesis of 3
(2,4-dimethoxybenzyl) ester-19,10-lactone (
α
-Methylsulfonyl-13-acetoxy-ent-10
β
-hydroxy-20-norgibberella-1,16-diene-7,19-dioic acid-7-
(30 g, 55.7 mmol) dissolved
5). To a solution of compound
4
in anhydrous pyridine (150 mL) was slowly added a solution of methylsulfonyl chloride (6.38 g,
61.27 mmol) dissolved in dichloromethane dropwise at 0 ◦C. After stirring the reaction mixture at r.t.
for 3 h, the mixture was washed with a solution of diluted hydrochloric acid (2 M, 500 mL) followed
by extractions with dichoromethane (3
×
150 mL) to yield
5 without further purification. White solid,
yield 95%, m.p. 80–82 ◦C. 1H-NMR (300 MHz, CDCl3):
δ
7.26 (d, J = 8.2 Hz, 1 H), 6.50 (s, 1 H), 6.47 (s,
2 H), 6.02 (dd, J = 9.3, 3.8 Hz, 1 H), 5.22 (d, J = 1.4 Hz, 1 H), 5.19–5.10 (m, 2 H), 5.07 (d, J = 3.8 Hz, 1 H),
4.98 (s, 1 H), 3.84 (s, 3 H), 3.81 (s, 3 H), 3.32 (d, J = 11.0 Hz, 1 H), 3.08 (s, 3 H), 2.80 (d, J = 11.0 Hz, 1 H),
2.47–2.09 (m, 5 H), 2.04 (s, 3 H), 2.01–1.72 (m, 4 H), 1.28 (s, 3 H). 13C-NMR (75 MHz, CDCl3)
δ 175.66,
171.01, 169.32, 161.29, 158.75, 153.25, 135.40, 131.55, 128.16, 115.52, 107.93, 103.65, 98.12, 89.47, 83.68,
62.62, 55.05, 55.00, 52.75, 52.28, 50.62, 50.54, 50.03, 41.76, 39.76, 38.37, 35.52, 21.60, 16.51, 14.44. HRMS
for C31H37O11S (M + H)+ 617.2051. Found: 617.2052.
Synthesis of
dimethoxybenzyl) ester-19,10-lactone (
3
α
-Azido-13-acetoxy-ent-10
β
-hydroxy-20-norgibberella-1,16-diene-7,19-dioic acid-7-(2,4-
(30 g, 48.6 mmol) and NaN3
6). A solution containing compound
5
(9.49 g, 145.94 mmol) dissolved in anhydrous dimethyl formamide (150 mL) was stirred at r.t. for
3 h. The reaction mixture was poured into iced water (150 g) and then extracted with ethyl acetate
(3
×
150 mL) to give a crude product 6. The combined organic layers were concentrated under reduced
pressure and followed by purification◦by silica gel chromatography to provide the intermediate
6.
1
White solid, yield 89%, m.p. 126–128 C. H-NMR (300 MHz, CDCl3):
δ
7.24 (d, J = 8.3 Hz, 1 H),
6.50–6.46 (m, 2 H), 6.41 (dd, J = 9.3, 2.0 Hz, 1 H), 5.92 (dd, J = 9.3, 2.6 Hz, 1 H), 5.20 (s, 1 H), 5.18–5.12
(m, 2 H), 4.97 (s, 1 H), 4.05 (t, J = 2.3 Hz, 1 H), 3.84 (s, 3 H), 3.80 (s, 3 H), 2.99 (d, J = 10.7 Hz, 1 H), 2.77
(d, J = 10.8 Hz, 1 H), 2.03 (s, 3 H), 1.29 (s, 3 H). 13C-NMR (75 MHz, CDCl3)
δ: 174.64, 171.22, 169.23,
161.30, 158.72, 153.20, 132.90, 131.56, 127.98, 115.42, 107.78, 103.67, 98.07, 88.17, 83.69, 63.84, 62.68, 57.27,
55.02, 54.97, 52.75, 50.62, 50.47, 50.43, 41.79, 39.80, 35.58, 21.58, 16.56, 14.51. HRMS for C30H37N4O8
(M + NH4)+ 581.2606. Found: 581.2605.
X-ray crystal structure of compound
6:
CCDC 1541695 contains the supplementary
crystallographic data for this paper. These data can be obtained free of charge via http://www.
Fax: +44 1223 336033; E-mail: deposit@ccdc.cam.ac.uk).