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Transcript of Stage Diels-Alder Reaction Synthesis of the Bioactive ... fileElectronic Supplementary Information...
Electronic Supplementary Information
Synthesis of the Bioactive Tetramic Acid JBIR-22 using a Late
Stage Diels-Alder Reaction
Alan R. Healy and Nicholas J. Westwood*
Electronic Supplementary Material (ESI) for Organic & Biomolecular Chemistry.This journal is © The Royal Society of Chemistry 2015
Table of Contents1. Late-stage DA cyclisations in the biosynthesis of tetramic acid derived natural products.........3
2. UPLC Analysis..............................................................................................................................5
3. Experimental procedures ...........................................................................................................6
4. NMR spectra of novel compounds .............................................................................................9
5. Bibliography..............................................................................................................................17
1. Late-stage DA cyclisations in the biosynthesis of tetramic acid derived natural products.
NH
O
HO
O
OH
OH
PyrE3
NH
O
HO
O
OH
OH
H
H
Pyrl4NH
OO
OH
H
H
HO
HO
NH
OO
O
H
H
CO2H
HO
HO
OOOOO
NH2O
O
NH
NH
R
OH
R = H: Pyrroindomycin AR = Cl: Pyrroindomycin B
HNO
OHO CO2H
OH
HN
O
O
H
H
HO HO CO2HcghA
HN
O O
HN
O O
HN
H
HN
O O
HNHN
O O
HN
H
O OH
O
HN
O O
H
HN
OO
H
O
O
OHO
O
chaetoglobosin A
cytochalasin E
Sch210972(3)
(A)
(B)
(C)
Scheme S1 (A) Dedicated cyclases “Diels-Alderases” PyrE3 and Pyrl4 have very recently been show to act in tandem to catalyse the formation of two cyclohexene rings in the biosynthesis of Pyrroindomycins A and B.1 These enzyme-catalysed [4+2] cycloadditions occur after the formation of the tetramic acid ring core. (B) Proposed Sch210972 (3) biosynthetic pathway involving a cghA catalysed late-stage Diels-Alder cycloaddition.2 (C) An enzymatic IMDA cycloaddition is proposed in the biosynthesis of chaetoglobosin A and cytochalasin E involving a partially reduced tetramic acid ring system.2–4a
O
PO
EtOEtO
N
O
OO
CO2Et
NHO CO2Et
O
O
HO
O
PO
EtOEtO
N
O
OO
CO2EtN
CO2EtO
OHO
PO
EtOEtO O
NCO2EtO
OHO
PO
EtOEtO HO
O
9
5
(a)
10
N
O
O
HO
HO CO2Et
Scheme S2. One-pot domino cyclisation-HWE olefination. Reagents and conditions: (a) (i) tBuOK, THF, 0 C, 1 hour. (ii) 10, THF, 0 C r.t., 16 h, 85%. For a very similar mechanism for a related transformation see reference 4b
2. UPLC Analysis
Figure S1. The UPLC traces were obtained on an ACQUITY UPLC BEH C18 column (0.6 ml/min; solvent: 55 % MeCN (0.1% TFA)). (A) UPLC trace of the BF3.OEt2 catalysed IMDA cycloaddition (Table 1, entry 3). (B) UPLC trace of the Mg(II)-bis(oxazoline) complex 12 catalysed IMD cycloaddition (Table 1, entry 4).
3a 3b (A)
(B)
3. Experimental procedures
Isopropyl (2S,4S)-4-(4-(diethoxyphosphoryl)-N-methyl-3-oxobutanamido)-2-isopropyl-5-
oxotetrahydrofuran-2-carboxylate (9)
4N 1'
2'3'
4'P5O
2 3
O
1''O
2'''
O
3''
4''
1''' 2'''
O O O
OO
7'
8'
7' 8'O2
3
4O
N
1''
OO
3'''
4'''
2''
SO
O2
3
4O
NH
1''
OO
3'''
4'''
2''
76 9To a solution of 6 (205 mg, 0.62 mmol, 1.0 eq.) in THF (1.5 mL) at 0 C was added HCl (0.62 mL, 4.0
eq., 4 N in dioxane). The reaction was stirred for 10 minutes at this temperature before the addition
of a solution of NaBH3CN (117 mg, 1.86 mmol, 3.0 eq.) in MeOH (3 mL). The reaction was stirred for a
further 1 hour at 0 C before being concentrated in vacuo. The residue was partitioned between a
saturated aqueous solution of NaHCO3 (5 mL) and EtOAc (5 mL). The aqueous layer was extracted with
EtOAc (3 5 mL) and the combined organic extracts were washed with brine (10 mL), dried over
Na2SO4, filtered and concentrated in vacuo to yield the crude free amine 7. 1H NMR (500 MHz,
Chloroform-d) δ 4.25 (qd, J = 7.1, 2.2 Hz, 2H, C3’’’-H2), 3.54 (dd, J = 11.5, 8.4 Hz, 1H, C4-H), 2.74 (dd, J
= 12.8, 8.4 Hz, 1H, C3-H2), 2.46 (s, 3H, NHCH3), 2.25 (hept, J = 6.9 Hz, 1H, C1’’-H), 2.05 (dd, J = 12.8,
11.5 Hz, 1H, C3-H2), 1.78 (br s, 1H, NHCH3), 1.30 (t, J = 7.1 Hz, 3H, C4’’’-H3), 1.02 (d, J = 6.9 Hz, 3H, C2’-
H3), 0.99 (d, J = 6.9 Hz, 1H, C2’-H3); 13C NMR (126 MHz, Chloroform-d) δ 175.9 (C5), 171.2 (C1’’’), 87.3
(C2), 62.2 (C3’’’), 58.1 (C4), 35.9 (C3), 34.4 (NCH3), 34.3 (C1’’), 17.0 (C2’), 16.4 (C2’), 14.3 (C4’’’). To a
solution of 7 in anhydrous MeCN (6 mL) was added a solution of 8 in anhydrous MeCN (3 mL), and the
reaction was heated at reflux for 2.5 hours. The reaction was concentrated in vacuo and purified via
the Biotage SP4 (silica-packed SNAP column 12 g; 0-8% MeOH/DCM) to give the title product 9 as an
orange oil (220 mg, 79%). In CDCl3 at room temperature the title compound 9 exists as a (7 : 3) enol :
keto mixture. The NMR signals are reported for the major keto tautomer. 1H and 13C spectra are
complicated by 31P splitting. IR (thin film) ν max: 2978, 2936, 1784 (C=O), 1734 (C=O), 1636 (C=O), 1236,
1184, 1022; 1H NMR (500 MHz, Chloroform-d) δ 4.83 – 4.71 (m, 1H, C4-H), 4.33 – 4.21 (m, 2H, C3’’-H2),
4.21 – 4.07 (m, 4H, (C7’-H2)2), 3.81 (s, 2H, C2’-H2), 3.25 (dd, J = 22.6, 4.4 Hz, 2H, C4’-H2), 3.01 (s, 3H,
NCH3), 2.68 (dd, J = 12.8, 9.1 Hz, 1H, C3-H2), 2.47 (dd, J = 12.8, 11.4 Hz, 1H, C3-H2), 2.38 – 2.29 (m, 1H,
C1’’’-H), 1.37 – 1.28 (m, 9H, C4’’-H3, (C8’-H3)2), 1.05 (d, J = 6.9 Hz, 3H, C2’’’-H3), 1.02 (d, J = 6.9 Hz, 3H,
C2’’’-H3); 13C NMR (126 MHz, Chloroform-d) δ 195.7 (C3’), 172.1 (C5), 171.0 (C1’’), 167.3 (C1’), 87.2
(C2), 63.0 (d, J = 6.5 Hz, C7’), 62.4 (C3’’), 56.7 (C4), 49.7 (C2’), 42.5 (d, J = 125.9 Hz, C4’), 35.3 (NCH3),
34.2 (C1’’’), 31.5 (C3), 17.0 (C2’’’), 16.5 (C2’’’), 16.4 (C8’), 14.3 (C4’’). 31P NMR (202 MHz, Chloroform-d)
δ 19.2. m/z (ES+) 472.17 ([M+Na]+, 100 %); HRMS (ES+) Calcd for C19H32O9NPNa [M+Na]+: 472.1707,
found 472.1696; = -9.2 (c 1.0, MeOH).[α]20D
Ethyl (S)-2-hydroxy-2-(((S,E)-4-((2E,8E,10E)-1-hydroxydodeca-2,8,10-trien-1-ylidene)-1-methyl-3,5-
dioxopyrrolidin-2-yl)methyl)-3-methylbutanoate (5)
4N 1'
2'3'
4'P5O
2 3
O
1''O
2'''
O
3''
4''
1''' 2'''
O O O
OO
7'
8'
7' 8'
5 N23
4
1'' 2''3''
4''
4''
HO1'''
O
O
3'''
4'''O
O
1'
2'3'
4'5'
6'7'
8'
HO
9'
10'11'
12'
9 5
To a solution of 9 (100 mg, 0.22 mmol, 1.0 eq.) in THF (2.5 mL) at 0 C was added tBuOK (0.24 mL, 1.1
eq., 1M in THF) and the reaction was stirred for 40 minutes. To the mixture was added a solution of
105 (102 mg, 0.67 mmol, 3.0 eq.; 85% E,E-diene geometry) in THF (1 mL) and the reaction was stirred
for a further 15 minutes before being warmed to room temperature and stirred for 16 hours. The
reaction was quenched by the addition of an aqueous solution of HCl (3 mL, 1N) and extracted with
DCM (3 10 mL). The organic extracts were combined, washed with brine (10 mL), dried over Na2SO4,
filtered, concentrated in vacuo and purified via the Biotage SP4 (Reverse-phase silica-packed SNAP
column 4 g; 20-100% H2O/(MeOH:MeCN)) to give the title product 5 as an yellow oil (83 mg, 85%). In
CDCl3 at room temperature the 1H and 13C NMR spectra of 5 are complicated by the presence of
keto/enol tautomers and a minor E,Z,E isomer. The NMR signals are reported for the major tautomer.
IR (thin film) ν max: 2964, 2931, 1717 (C=O), 1690 (C=O), 1645 (C=O), 1586, 1449, 1242, 989; 1H NMR
(500 MHz, Chloroform-d) δ 7.24 – 7.13 (m, 1H, C3’-H), 7.08 – 7.03 (m, 1H, C2’-H), 6.04 – 5.90 (m, 2H,
C9’-H, C10’-H), 5.62 – 5.45 (m, 2H, C8’-H, C11’-H), 4.24 (q, J = 7.1 Hz, 2H, C3’’’-H2), 3.67 (dd, J = 9.6, 2.2
Hz, 1H, C2-H), 2.97 (s, 3H, NCH3), 2.37 – 2.29 (m, 2H, C4’-H2), 2.30 – 2.28 (m, 1H, C1’’-H2), 2.10 – 2.00
(m, 3H, C3’’-H, C7’-H2), 1.90 (dd, J = 14.5, 9.6 Hz, 1H, C1’’-H2), 1.71 (d, J = 6.4 Hz, 3H, C12’-H3), 1.57 –
1.45 (m, 2H, C5’-H2), 1.46 – 1.37 (m, 2H, C6’-H2), 1.31 (t, J = 7.1 Hz, 3H, C4’’’-H3), 0.94 (d, J = 7.3 Hz, 3H,
C4’’-H3), 0.93 (d, 7.3 Hz, 3H, C4’’-H3); 13C NMR (126 MHz, Chloroform-d) δ 196.3 (C3), 175.5 (C1’’’),
175.1 (C1’), 173.4 (C5), 151.8 (C3’), 131.6 (C10’), 131.4 (C8’), 130.8 (C9’), 127.2 (C11’), 121.6 (C2’), 98.9
(C4), 78.8 (C2’’), 64.5 (C2), 61.6 (C3’’’), 36.8 (C3’’), 34.9 (C1’’), 33.3 (C4’), 32.4 (C7’), 29.1 (C6’), 27.7
(C5’), 26.8 (NCH3), 18.1 (C12’), 17.5 (C4’’), 16.4 (C4’’), 14.5 (C4’’’); m/z (ES-) 446.25 ([M-H]-, 100 %);
HRMS (ES-) Calcd for C25H36O6N [M-H]-: 446.2548, found 446.2549.
JBIR-22 (3a/b)
9
87
611
10
54
32
1HO 3' 2'
N5'4'
6' 7'
8'9'
12'
O
10'OH
OH 11'
12O
O
H
H
9
87
611
10
54
32
1HO 3' 2'
N5'4'
6' 7'
8'9'
12'
O
10'OH
OH 11'
12O
O
H
H
3a 3b
The 1:1 mixture of JBIR-22 (3a/b) was synthesised as reported in Ref[8]. 3a/b was obtained as an
amorphous white solid (73 mg). Spectroscopic data was obtained for JBIR-22 3a/b-Et2NH salt. = [α]23D
+22.0 (c 0.7, MeOH); 1H NMR (500 MHz, Acetone-d6) δ 5.57 – 5.48 (m, 2H, 2 C4-H), 5.33 – 5.27 (m,
2H, 2 C5-H), 3.93 (dd, J = 11.1, 5.5 Hz, 1H, C2-H (3b)), 3.90 (dd, J = 11.1, 5.5 Hz, 1H, C2-H (3a)), 3.37
(dd, J = 10.1, 1.3 Hz, 2H, 2 C5’-H), 2.72 (s, 6H, 2 C10’-H3), 2.67 – 2.56 (m, 2H, 2 C3-H), 2.31 (dt, J
= 13.9, 1.5 Hz, 2H, 2 C6’-H2), 2.04 – 1.94 (m, 4H, 2 C8’-H, 2 x 1 of C10-H2), 1.76 – 1.66 (m, 8H, 2 1
of C7-H2, 2 C6-H, 2 1 of C8-H2, 2 1 of C9-H2), 1.63 (dd, J = 13.8, 10.1 Hz, 2H, 2 1 of C6’-H2), 1.51
– 1.41 (m, 2H, 2 C11-H), 1.30 – 1.28 (m, 4H, 2 1 of C8-H2, 2 1 of C9-H2), 1.09 – 0.98 (m, 2H, 2 1
of C7-H2), 0.91 (d, J = 6.7 Hz, 6H, 2 C9’-H3), 0.77 (d, J = 7.2 Hz, 3H, C12-H3 (3a)), 0.75 (d, J = 7.2 Hz, 3H,
C12-H3 (3b)), 0.73 – 0.67 (m, 2H, 2 1 of C10-H2); 13C NMR (126 MHz, Acetone) δ 196.40 (C1), 196.36
(C1), 196.0 (C4’), 195.8 (C4’), 180.5 (C11’), 180.4 (C11’), 174.8 (C2’), 174.7 (C2’), 133.6 (C4), 133.5 (C4),
131.2 (C5), 131.1 (C5), 101.5 (2 C3’), 80.0 (C7’), 79.9 (C7’), 63.3 (C5’), 63.2 (C5’), 51.07 (C2), 50.98
(C2), 43.4 (C6), 43.3 (C6), 37.4 (C11), 37.3 (C11), 37.2 (C6’), 37.1 (C6’), 36.62 (C8’), 36.60 (C8’), 34.4
(C7), 34.3 (C7), 32.3 (C3), 32.2 (C3), 31.1 (C10), 31.0 (C10), 27.7 (C9/C8), 27.6 (C9/C8), 18.7 (C9’), 18.7
(C9’), 18.34 (C12), 18.33 (C12), 16.8 (2 C12’); m/z (ES-) 418.23 ([M-H]-, 100 %); HRMS (ES-) Calcd for
C23H32O6N [M-H]-: 418.2235, found 418.2225. Spectroscopic data are in agreement with that reported
previously by us for the single diastereomers JBIR-22 3a and 3b.5 See Section 6 for the NMR spectra of
the 1:1 mixture of 3a/b.
4. NMR spectra of novel compounds
0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.511.0f1 (ppm)
0
500
1000
1500
2000
2500
3000
3500
4000
6.11
12.5
0
1.29
1.38
1.11
2.03
2.01
5.33
2.94
1.00
NP
O
O
O
O
CH 3
C H 3CH 3
C H 3
O O O
O
O
C H 3
C H 3
9, CDCl3, 500 MHz
102030405060708090100110120130140150160170180190200210220f1 (ppm)
-100
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
14.2
816
.44
16.4
816
.96
31.5
034
.23
35.2
7
41.9
842
.98
49.7
2
56.6
762
.42
62.9
663
.01
87.1
9
167.
3017
0.95
172.
09
195.
66
NP
O
O
O
O
CH 3
C H 3CH 3
C H 3
O O O
O
O
C H 3
C H 3
9, CDCl3, 500 MHz
0.81.01.21.41.61.82.02.22.42.62.83.03.23.43.63.84.04.24.44.64.85.05.25.45.65.8f2 (ppm)
0
10
20
30
40
50
60
70
80
90
f1 (
ppm
)
9 (HSQC), CDCl3, 500 MHz
0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.511.011.5f1 (ppm)
-200
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
6.77
3.61
2.44
2.42
3.45
1.01
3.01
3.55
3.08
1.08
2.41
2.04
2.00
1.09
1.01
N C H 3
C H 3
OH
O
O
CH 3
C H 3O
OOH
CH 3
5, CDCl3, 500 MHz
102030405060708090100110120130140150160170180190200210220f1 (ppm)
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
12000
13000
14000
14.4
916
.37
17.4
718
.13
26.7
927
.70
29.0
932
.35
33.3
134
.87
36.7
5
61.5
664
.48
78.7
8
98.9
0
121.
56
127.
2013
0.81
131.
3713
1.63
151.
75
173.
4017
5.11
175.
47
196.
28
N C H 3
C H 3
OH
O
O
CH 3
C H 3O
OOH
CH 3
5, CDCl3, 500 MHz
0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.0f2 (ppm)
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
f1 (
ppm
)
5 (HSQC), CDCl3, 500 MHz
0.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.08.59.09.510.010.511.011.5f1 (ppm)
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
0.93
2.98
5.97
1.39
1.18
5.05
2.05
0.95
1.16
2.72
0.84
1.00
1.11
1.06
OHN
CH 3C H 3
O
C H 3
O HO H
C H 3
O
O
H
H
OHN
CH 3C H 3
O
C H 3
O HO H
C H 3
O
O
H
H
3a/b, Acetone-d6, 500 MHz
0102030405060708090100110120130140150160170180190200210220f1 (ppm)
-400
-200
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
400016.8
418
.33
18.3
418
.68
18.7
326
.78
27.6
731
.00
31.0
532
.30
34.3
434
.39
36.6
036
.62
37.2
737
.39
43.3
143
.40
50.9
851
.07
63.2
263
.27
79.9
379
.95
101.
49
131.
1013
1.20
133.
4513
3.60
174.
7117
4.76
180.
3718
0.52
195.
8419
6.00
196.
3619
6.40
OHN
CH 3C H 3
O
C H 3
O HO H
C H 3
O
O
H
H
OHN
CH 3C H 3
O
C H 3
O HO H
C H 3
O
O
H
H
3a/b, Acetone-d6, 500 MHz
5. Bibliography
1 Z. Tian, P. Sun, Y. Yan, Z. Wu, Q. Zheng, S. Zhou, H. Zhang, F. Yu, X. Jia, D. Chen, A. Mándi, T. Kurtán and W. Liu, Nat. Chem. Biol., 2015, 1–10.
2 K. Watanabe, Chem. Pharm. Bull., 2014, 62, 1153–1165.
3 W. L. Kelly, Org. Biomol. Chem., 2008, 6, 4483–93.
4 G. Li, S. Kusari and M. Spiteller, Nat. Prod. Rep., 2014, 31, 1175–1201.
5 A. R. Healy, M. Izumikawa, A. M. Z. Slawin, K. Shin-ya and N. J. Westwood, Angew. Chemie Int. Ed., 2015, 54, 4046–4050.