3192
C.F.C. Lam et al. / Tetrahedron 68 (2012) 3187e3194
2.8 Hz, H2-17), 3.64 (2H, m, H2-26), 3.61 (2H, br m, H2-8), 3.36
(2H, dt, J¼6.0, 6.0 Hz, H2-25), 2.80 (2H, t, J¼7.6 Hz, H2-16), 2.00
(2H, br s, H2-7) (COOH not observed); 13C NMR (DMSO-d6,
s, 2ꢁH3-41), 2.82 (2H, t, J¼7.8 Hz, H2-16), 2.00 (2H, br s, H2-7); 13C
NMR (DMSO-d6, 150 MHz)
d 171.3 (C-3), 168.0 (C-28), 165.8 (C-23),
165.5 (C-11), 160.7 (C-32), 155.3 (C-34), 152.7 (C-36), 152.6 (C-19),
151.4 (C-30), 151.1 (C-1/C-5), 151.0 (C-10), 132.3 (C-14), 126.0 (C-38),
123.5 (C-21), 122.7 (C-12), 122.6 (C-2/C-4), 118.8 (C-15), 109.3 (C-31),
108.9 (C-37), 108.1 (C-39), 97.4 (C-35), 91.9 (C-20), 50.9 (C-22), 44.6
(C-6), 40.0 (C-17), 39.7 (2ꢁC-41), 38.7 (C-8/C-29), 38.2 (C-25/C-26),
33.5 (C-7), 17.9 (C-16); (þ)-FABMS m/z 791 [MþH]þ; (þ)-HRFABMS
m/z [MþH]þ 791.0807 (calcd for C35H3379Br2N6O6, 791.0828),
793.0804 (calcd for C35H3379Br81BrN6O6, 793.0808), 795.0806 (calcd
for C35H3381Br2N6O6, 795.0787).
100 MHz)
d 171.3 (C-3), 166.1 (C-23), 165.5 (C-11), 152.6 (C-19),
151.4 (C-10), 151.0 (C-1/C-5), 147.0 (C-33), 141.0 (C-30 or C-32),
132.3 (C-14), 129.8 (C-35), 128.5 (C-32 or C-30), 124.0 (C-34),
123.5 (C-21), 122.6 (C-2/C-4/C-12), 118.8 (C-15), 116.8 (C-31), 91.9
(C-20), 50.9 (C-22), 44.6 (C-6), 43.5 (C-17), 43.3 (C-26), 38.2 (C-8),
37.9 (C-25), 33.5 (C-7), 17.8 (C-16); 13C NMR data only assigned up
to C-35 as presence of fluorescein isomers hindered full assign-
ment of fluorescein moiety; (þ)-ESIMS m/z 951 [MþH]þ;
(þ)-HRESIMS m/z [MþH]þ 951.0425 (calcd for C43H3379Br2N6O8S,
951.0442), 953.0402 (calcd for C43H3379Br81BrN6O8S, 953.0426),
955.0393 (calcd for C43H3381Br2N6O8S, 955.0417).
4.1.14. N-13-Propargylacetamido discorhabdin C (24). Discorhabdin
C trifluoroacetate salt (7) (6.0 mg, 10.4 mmol) was dissolved in dry
acetone (2 mL), followed by addition of dry K2CO3 (20.0 mg,
4.1.12. N-13 (Lissamine rhodamine 2-aminoethyl acetamido) dis-
0.145 mmol) and 2-bromo-N-propargylacetamide (26)22 (12.0 mg,
corhabdin C (22). N-13 (2-Aminoethyl acetamido) discorhabdin C
68 mmol), and the mixture was purged under N2. The mixture was
trifluoroacetate salt (19) (5.46 mg, 12.0
mmol) was dissolved in dry
heated with stirring at 70 ꢀC for 2 h., after which the crude product
was purified by reversed-phase C18 flash column chromatography
(0e50% MeOH (0.05% TFA)), and reversed-phase phenyl-bonded
column chromatography (0e50% MeOH (0.05% TFA)) to yield 24 as
a purple non-crystalline trifluoroacetate salt (3.0 mg, 45%). tR
DMF (0.5 mL). Excess dry K2CO3 (15.0 mg, 0.109 mmol) was added,
turning the mixture colour from dark purple to orange. Lissamine
rhodamine sulfonyl chloride (5.9 mg, 10.2 mmol) was added, the
mixture was heated to 60 ꢀC and stirred under N2 at room temper-
ature for 1.5 h. The product was purified by reversed-phase C18 flash
column chromatography (0e80% MeOH (0.05% TFA)), yielding 22 as
a pink/purple non-crystalline trifluoroacetate salt (2.2 mg, 27%). tR
7.49 min (System B); nmax (ATR) 3270, 1678, 1591, 1541, 1326, 1200,
5.94 min (System B); nmax (ATR) 3288, 1675, 1541, 1326, 1200 cmꢂ1
;
1H NMR (DMSO-d6, 400 MHz)
d 10.12 (1H, br s, NH-9), 8.79 (1H, t,
J¼5.6 Hz, NH-24), 8.23 (1H, br s, NH-18), 7.73 (2H, s, H-1/H-5), 7.38
(1H, s, H-14), 5.00 (2H, s, H2-22), 3.90 (2H, obscured by water, H2-
25), 3.69 (2H, td, J¼7.6, 2.6 Hz, H2-17), 3.63e3.58 (2H, br m, H2-8),
3.17 (1H, d, J¼1.6 Hz, H-27), 2.82 (2H, t, J¼7.6 Hz, H2-16), 2.01 (2H, t,
1182 cmꢂ1 1H NMR (DMSO-d6, 600 MHz)
; d 10.12 (1H, br s, NH-9),
8.43 (1H, d, J¼2.8 Hz, H-30), 8.41 (1H, t, J¼6.0 Hz, NH-24), 8.22 (1H,
brs, NH-18), 8.08(1H, t, J¼6.0 Hz, H-27), 7.95 (1H, dd, J¼8.4, 2.8 Hz, H-
34), 7.71 (2H, s, H-1/H-5), 7.51 (1H, d, J¼8.4 Hz, H-33), 7.39 (1H, s, H-
14), 7.02 (2H, dd, J¼9.2, 2.2 Hz, H-42/H-47), 6.98 (2H, d, J¼9.2 Hz, H-
41/H-48), 6.94 (2H, d, J¼2.2 Hz, H-44/H-45), 4.98 (2H, s, H2-22),
3.66e3.61 (2H, m, H2-17), 3.62 (8H, obscured by water, 4ꢁH2-50),
3.61 (2H, br s, H2-8), 3.22 (2H, dt, J¼6.0, 6.0 Hz, H2-25), 2.97 (2H, dt,
J¼6.0, 6.0 Hz, H2-26), 2.78 (2H, t, J¼7.8 Hz, H2-16), 2.00 (2H, br t,
J¼5.4 Hz, H2-7),1.21 (12H, t, J¼7.2 Hz, 4ꢁH3-51); 13C NMR (DMSO-d6,
J¼5.6 Hz, H2-7); 13C NMR (DMSO-d6, 100 MHz)
d 171.3 (C-3), 165.5
(C-11/C-23), 152.6 (C-19), 151.4 (C-10), 151.1 (C-1/C-5), 132.3 (C-14),
123.5 (C-21),122.6 (C-2/C-4/C-12), 118.8 (C-15), 91.9 (C-20), 80.5 (C-
26), 73.4 (C-27), 50.6 (C-22), 44.6 (C-6), 43.5 (C-17), 38.2 (C-8), 33.5
(C-7), 28.1 (C-25), 17.8 (C-16); (þ)-FABMS m/z 557 [MþH]þ;
(þ)-HRFABMS m/z [MþH]þ 556.9823 (calcd for C23H1979Br2N4O3,
556.9824), 558.9793 (calcd for C23H1979Br81BrN4O3, 558.9803),
560.9797 (calcd for C23H1981Br2N4O3, 560.9783).
150 MHz) d 171.3 (C-3), 166.0 (C-23), 165.4 (C-11), 157.3 (C-35), 157.0
(C-37/C-39), 154.9 (C-43/C-46), 152.6 (C-19), 151.5 (C-10), 151.1 (C-1/
C-5), 147.9 (C-29 or C-31), 141.3 (C-31 or C-29),133.1 (C-32), 132.6 (C-
41/C-48), 132.4 (C-14), 130.7 (C-33), 126.5 (C-34), 125.5 (C-30), 123.5
(C-21), 122.6 (C-2/C-4/C-12), 118.7 (C-15), 113.5 (C-42/C-47), 113.4 (C-
36/C-40), 95.3 (C-44/C-45), 91.8 (C-20), 50.8 (C-22), 45.2 (4ꢁC-50),
44.6 (C-6), 43.4 (C-17), 41.8 (C-26), 38.8 (C-25), 38.2 (C-8), 33.5 (C-7),
17.8 (C-16), 12.4 (4ꢁC-51); (þ)-FABMS m/z 1102 [MþH]þ;
(þ)-HRFABMS m/z [MþH]þ 1102.1461 (calcd for C49H5079Br2N7O9S2,
1102.1478), 1104.1466 (calcd for C49H5079Br81BrN7O9S2, 1104.1458),
1106.1440 (calcd for C49H5081Br2N7O9S2, 1106.1437).
4.1.15. N-13-(3-Azidopropyl)-acetamido discorhabdin C (25). Discor-
habdin C trifluoroacetate salt (7) (12 mg, 20.9 mmol) was dissolved in
dry acetone (2 mL), followed by addition of dry K2CO3 (20.0 mg,
0.145 mmol) and 2-bromo-N-(3-azidopropyl)-acetamide23,24 (27)
(25.0 mg, 0.110 mmol), and the mixture was purged under N2. The
mixture was heated with stirring at 70 ꢀC for 2 h., after which the
crude product was purified by reversed-phase C18 flash column
chromatography (0e50% MeOH (0.05% TFA)) to yield 25 as a purple
non-crystalline trifluoroacetate salt (3.5 mg, 23%). tR 5.25 min (Sys-
tem C); nmax (ATR) 3247, 1674, 1543, 1327, 1200 cmꢂ1
;
1H NMR
10.09 (1H, br s, NH-9), 8.36 (1H, t, J¼5.4 Hz,
(DMSO-d6, 300 MHz)
d
4.1.13. N-13 (Coumarin 2-aminoethyl acetamido) discorhabdin C
(23). N-13 (2-Aminoethyl acetamido)discorhabdin C trifluoroacetate
salt (19) (6.1 mg, 7.7 mmol) was dissolved in dry acetone (0.5 mL).
NH-24), 8.22 (1H, br s, NH-18), 7.73 (2H, s, H-1/H-5), 7.37 (1H, s, H-
14), 4.96 (2H, s, H2-22), 3.80 (2H, t, J¼6.9 Hz, H2-27), 3.67 (2H, ob-
scured by water, H2-17), 3.62 (2H, br s, H2-8), 3.15 (2H, td, J¼6.9,
5.4 Hz, H2-25), 2.82 (2H, t, J¼7.8 Hz, H2-16), 2.01 (2H, br s, H2-7),1.68
Excess dry K2CO3 (15.0 mg, 0.109 mmol) was added, turning the
mixture colour from dark purple to orange. NHS-activated 7-
(2H, p, J¼6.9 Hz, H2-26); 13C NMR (DMSO-d6, 100 MHz)
d 171.3 (C-3),
dimethylaminocoumarin-4-acetic acid18,19 (5.3 mg, 15.4
mmol) was
165.6 (C-11), 165.4 (C-23), 152.6 (C-19), 151.4 (C-10), 151.1 (C-1/C-5),
132.3 (C-14), 123.5 (C-21), 122.6 (C-2/C-4/C-12), 118.7 (C-15), 91.9 (C-
20), 50.8 (C-22), 48.1 (C-27), 44.6 (C-6), 43.5 (C-17), 38.2 (C-8), 36.0
(C-25), 33.5 (C-7), 28.2 (C-26), 17.8 (C-16); (þ)-FABMS m/z 602
[MþH]þ; (þ)-HRFABMS m/z [MþH]þ 602.0139 (calcd for
C23H2279Br2N7O3, 602.0151), 604.0126 (calcd for C23H2279Br81Br
N7O3, 604.0126), 606.0127 (calcd for C23H2281Br2N7O3, 606.0110).
added, and the reaction mixture stirred under N2 at room tempera-
ture for 1.5 h. The crude product was purified by reversed-phase C18
flash column chromatography (0e50% MeOH (0.05% TFA)), followed
by Sephadex LH-20 column chromatography (MeOH (0.05% TFA)) to
yield23asa purplenon-crystallinetrifluoroacetate salt (3.8 mg, 55%).
tR 6.82 min (System B); nmax (ATR) 3330, 1615, 1677, 1537, 1201,
1135 cmꢂ1 1H NMR (DMSO-d6, 600 MHz)
; d 10.08 (1H, br s, NH-9),
8.37 (1H, br s, NH-24), 8.25 (1H, br s, NH-27), 8.22 (1H, br s, NH-18),
7.72 (2H, s, H-1/H-5), 7.52 (1H, d, J¼9.0 Hz, H-38), 7.35 (1H, s, H-14),
6.71 (1H, brd, J¼9.0 Hz, H-37), 6.60(1H, d, J¼1.8 Hz, H-35), 6.00 (1H, s,
H-31), 4.95 (2H, s, H2-22), 3.67 (2H, dt, J¼7.8, 4.2 Hz, H2-17), 3.61 (4H,
obscured by water, H2-8/H2-29), 3.15 (4H, m, H2-25/H2-26), 3.02 (6H,
4.1.16. 2-Bromo-N-(3-azidopropyl)-acetamide (27). 3-Bromopropyla-
mine hydrobromide (250 mg, 1.14 mmol) was added to a solution
of NaN3 (222 mg, 3.41 mmol) in H2O (2 mL) and stirred at 75 ꢀC for
16 h. The reaction mixture was then left to cool to room temperature
before addition of NaOH (50.0 mg, 1.25 mmol) and extraction with