Mar. Drugs 2019, 17, 176
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25
D
Oxopropylisoherqueinone A (
4
): brown, amorphous solid; [
α
]
+92 (c 0.2, MeOH); UV (MeOH) λ
max
(log
ε
) 224 (4.36), 274 (4.30), 357 (3.57) nm; IR (ZnSe)
ν
3382 (br), 1678, 1639, 1297 cm−1; 1H and
max
13C NMR data, Tables 1 and 2; HRFABMS m/z 415.1396 [M + H]+ (calcd for C22H23O8, 415.1393).
25
Oxopropylisoherqueinone B (
(log
5
): brown, amorphous solid; [
α
]
+43 (c 0.2, MeOH); UV (MeOH)
λ
max
D
ε
) 224 (4.36), 274 (4.30), 357 (3.57) nm; IR (ZnSe)
ν
3415 (br), 1679, 1640, 1297 cm−1; 1H and
13C NMR data, Tables 1 and 2; HRFABMS m/z 415.1396 [M + H]+ (calcd for C22H23O8, 415.1393).
max
25
4-Hydroxysclerodin (
213 (3.94), 280 (4.21), 312 (3.68) nm; IR (ZnSe)
6
): yellow, amorphous solid; [
α
]
−
52 (c 0.2, MeOH); UV (MeOH)
λ
max (log
ε
)
D
1
ν
3424 (br), 3069, 1729, 1460, 1286 cm−1; H and
13C NMR data, Tables 1 and 2; HRFABMS m/z 345.0977 [M + H]+ (calcd for C18H17O7, 345.0974).
max
3.4. Reduction of Herqueinones (1–6)
To a solution of 44.3 mg (114 µM) of 1 in 0.5 mL of glacial acetic acid was added 100.0 mg
(1.53 mM) of zinc dust under nitrogen atmosphere. The mixture was stirred at room temperature for
30 min and filtered through cotton with 1.0 mL of distilled water. The filtrate was left to stand for
45 min and extracted with 1.5 mL of ethyl acetate. Purification by analytical HPLC (YMC-ODS-A
column, 4.6
×
250 mm; H2O-MeCN (50:50); 0.7 mL/min) afforded the 4-deoxy derivative (1a, 6.8 mg)
(tR = 15.8 min) as a pure compound. Compounds 2–6 were reduced in a similar manner.
25
4-Deoxy-ent-peniciherqueinone (1a): [
α
]
−
23 (c 0.5, CHCl3); 1H NMR (CDCl3, 400 MHz) δH 13.14
D
(1H, s), 13.10 (1H, s), 13.07 (1H, s), 4.57 (1H, q, J = 6.5 Hz), 3.99 (3H, s), 2.71 (3H, s), 1.50 (3H, s), 1.44
(3H, d, J = 6.5 Hz), 1.25 (3H, s); ESIMS m/z 373.1 [M + H]+ (calcd for C20H21O7, 373.1).
25
4-Deoxy-12-hydroxynorherqueinone (2a): [
α
]
−
20 (c 0.3, CHCl3); 1H NMR (DMSO-d6, 400 MHz) δH
D
14.32 (1H, s), 13.52 (1H, s), 9.28 (1H, s), 8.72 (1H, s), 4.64 (1H, q, J = 6.5 Hz), 2.66 (3H, s), 1.49 (3H, s),
1.38 (3H, d, J = 6.5 Hz), 1.26 (3H, s); ESIMS m/z 359.1 [M + H]+ (calcd for C19H19O7, 359.1).
25
4-Deoxy-ent-isoherqueinone (3a): [
α
]
+34 (c 0.5, CHCl3); 1H NMR (DMSO-d6, 400 MHz) δH 13.52
D
(1H, s), 8.13 (1H, s), 7.48 (1H, br s), 7.14 (1H, br s), 4.69 (1H, q, J = 6.5 Hz), 3.13 (3H, s), 2.66 (3H, s), 1.47
(3H, s), 1.42 (3H, d, J = 6.5 Hz), 1.22 (3H, s); ESIMS m/z 357.3 [M + H]+ (calcd for C20H21O6, 357.3).
25
D
1
4-Deoxy-oxopropylisoherqueinone A (4a): [
α
]
+8 (c 0.5, CHCl3), +10 (c 0.5, MeOH); H NMR
(DMSO-d6, 400 MHz) δH 13.27 (1H, s), 8.48 (1H, s), 6.18 (1H, s), 5.73 (1H, s), 4.13 (1H, q, J = 6.5 Hz),
3.16 (2H, s), 2.80 (3H, s), 2.05 (3H, s), 1.35 (3H, s), 1.25 (3H, d, J = 6.5 Hz), 1.05 (3H, s); ESIMS m/z 399.1
[M + H]+ (calcd for C22H23O7, 399.1).
25
D
1
4-Deoxy-oxopropylisoherqueinone B (5a): [
α
]
+3 (c 0.5, CHCl3), +5 (c 0.5, MeOH); H NMR
(DMSO-d6, 400 MHz) δH 13.27 (1H, s), 8.47 (1H, s), 6.18 (1H, s), 5.71 (1H, s) 4.10 (1H, q, J = 6.5 Hz), 3.16
(2H, s), 2.80 (3H, s), 2.05 (3H, s), 1.34 (3H, s), 1.26 (3H, d, J = 6.5 Hz), 1.05 (3H, s); ESIMS m/z 399.1
[M + H]+ (calcd for C22H23O7, 399.1).
25
Sclerodin (6a
=
10): [α
]
−
18 (c 0.5, CHCl3); 1H NMR (CDCl3, 400 MHz) δH 11.5 (1H, s), 6.75 (1H, s),
D
5.06 (1H, q, J = 6.5 Hz), 2.69 (3H, s), 1.48 (3H, d, J = 6.5 Hz), 1.41 (3H, s), 0.92 (3H, s); ESIMS m/z 329.1
[M + H]+ (calcd for C18H17O6, 329.1).
3.5. Acetylation of 4-Deoxy-ent-peniciherqueinone (1a)
To a solution of 3.0 mg (2.7 mM) of 1a in 3.0 mL of pyridine was added 0.4 mL of Ac2O. After
stirring the mixture for 4 h at room temperature, the pyridine and excess Ac2O were removed under
vacuum. Purification by analytical HPLC (YMC-ODS column, 4.6
(40:60)) yielded 4-deoxy-9,11,12-triacetyl-ent-peniciherqueinone (1b) (tR = 35.8 min): [
×
250 mm; 0.7 mL/min; H2O-MeCN
25
α
]
−
35 (c 0.5,
D