Journal of Natural Products
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and HATU (20.0 mg, 52.6 μmol). After stirring at rt for 10 h, the
reaction mixture was diluted with EtOAc (10 mL), washed with 10%
aqueous citric acid (10 mL), saturated aqueous NaHCO3 (10 mL),
and brine (10 mL), dried (Na2SO4), and concentrated. The residual
oil was purified by PLC (CHCl3−EtOAc−MeOH, 5:5:1) to give
peptide (R)-13 (19.3 mg, 98% in 2 steps) as a colorless amorphous
and brine (10 mL), dried (Na2SO4), and concentrated. The residual
oil was purified by HPLC (Cosmosil PBr (ϕ 20 × 250 mm), MeOH−
H2O, 95:5, flow rate 5 mL/min, detection UV 215 nm) to give (43R)-
hoshinoamide C (1) (11 mg, tR = 43.1 min 84% in 2 steps) as a
colorless oil. The ratio of major and minor rotamers is 8:1: [α]28
D
1
+4.6 (c 1.00, CHCl3); IR (neat) 3312, 2960, 2931, 1632 cm−1; H
solid. The ratio of major and minor rotamers is 6:1: [α]28 +270 (c
NMR (400 MHz, CDCl3) for the major rotamer δ 7.40 (brd, J = 7.3
Hz, 1H, NH), 7.26−7.10 (m, 5H), 7.07 (brd, J = 8.5 Hz, 1H, NH),
6.98 (d, J = 8.2 Hz, 2H), 6.76 (d, J = 8.2 Hz, 2H), 6.73 (brd, J = 7.7
Hz, 1H, NH), 6.59 (brs, 1H, NH), 5.82 (t, J = 5.9 Hz, 1H, NH), 5.72
(brs, 1H, NH), 5.62 (dd, J = 7.7, 7.7 Hz, 1H), 4.89 (m, 1H), 4.71 (d,
J = 10.4 Hz, 1H), 4.66 (dd, J = 8.6, 6.3 Hz, 1H), 4.39 (dd, J = 8.2, 5.9
Hz, 1H), 4.23 (dt, J = 6.8, 6.8 Hz, 1H), 3.70 (s, 3H), 3.43−3.29 (m,
2H), 3.26 (dd, J = 14.0, 6.8 Hz, 1H), 3.23−3.13 (m, 2H), 3.11 (s,
3H), 3.00 (s, 3H), 2.88 (dd, J = 14.0, 8.6 Hz, 1H), 2.57 (t, J = 7.3 Hz,
2H), 2.25−2.15 (m, 3H), 2.11 (t, J = 7.3 Hz, 2H), 2.11 (m, 1H),
2.06−1.70 (m, 9H), 1.69−1.58 (m, 2H), 1.57−1.44 (m, 2H), 1.43−
1.34 (m, 4H), 1.32−1.20 (m, 5H), 1.17−1.03 (m, 2H), 0.97 (d, J =
6.6 Hz, 3H), 0.93 (d, J = 6.8 Hz, 3H), 0.92 (t, J = 6.8 Hz, 3H), 0.83
(d, J = 5.9 Hz, 3H), 0.80 (d, J = 6.3 Hz, 3H), 0.72 (d, J = 6.8 Hz, 3H),
0.63 (d, J = 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) for the major
rotamer δ 175.3, 174.5, 174.0, 173.3, 172.8, 172.0, 171.4, 170.2, 168.7,
154.9, 136.9, 132.7, 129.7 (2C), 129.6 (2C), 128.6 (2C), 126.9, 115.5
(2C), 61.4, 59.4, 56.0, 54.3, 53.4, 52.4, 48.4, 47.2, 41.8, 39.4, 36.4,
35.5, 35.3, 34.1, 34.0, 32.5, 32.4, 32.1, 31.7, 31.4, 31.1, 30.6, 29.7,
29.0, 27.3, 27.2, 26.7, 25.3, 25.0, 24.2, 23.3, 22.2, 19.6, 19.5, 17.3,
15.0, 11.4; HRMS (ESI-TOF) m/z 1097.6596 [M + Na]+ (calcd for
C58H90N8O11Na 1097.6627).
D
0.37, CHCl3); IR (neat) 3318, 2960, 2929, 1633 cm−1; 1H NMR (400
MHz, CDCl3) for the major rotamer δ 7.40 (brm, 1H, NH), 7.26−
7.12 (m, 5H), 6.91 (brm, 1H, NH), 6.61 (brs, 1H, NH), 6.41 (brm,
1H, NH), 5.73 (brm, 1H, NH), 5.63 (dd, J = 7.7, 7.7 Hz, 1H), 4.95
(m, 1H), 4.72−4.62 (m, 2H), 4.39 (dd, J = 8.2, 6.3 Hz, 1H), 4.27 (m,
1H), 3.71 (s, 3H), 3.40−3.30 (m, 2H), 3.26 (dd, J = 14.0, 6.8 Hz,
1H), 3.13−3.03 (m, 2H), 3.10 (s, 3H), 2.99 (s, 3H), 2.88 (dd, J =
14.0, 8.6 Hz, 1H), 2.31−2.12 (m, 6H), 2.11−1.92 (m, 5H), 1.92−
1.58 (m, 6H), 1.53−1.35 (m, 4H), 1.44 (s, 9H), 1.33−1.20 (m, 3H),
1.17−1.02 (m, 2H), 0.99 (d, J = 6.3 Hz, 3H), 0.93 (d, J = 6.8 Hz,
3H), 0.92 (t, J = 7.7 Hz, 3H), 0.84 (d, J = 5.9 Hz, 3H), 0.80 (d, J = 6.8
Hz, 3H), 0.73 (d, J = 6.8 Hz, 3H), 0.61 (d, J = 6.8 Hz, 3H); 13C NMR
(100 MHz, CDCl3) for the major rotamer δ 175.0, 174.3, 173.5,
172.6, 171.8, 171.0, 170.1, 168.5, 156.1, 136.9, 129.5 (2C), 128.5
(2C), 126.8, 79.1, 61.3, 59.3, 55.9, 54.1, 53.2, 52.3, 48.2, 47.1, 42.1,
40.7, 36.4, 35.2, 34.2, 32.5, 32.5, 32.3, 31.6, 31.3, 31.0, 30.5, 29.8,
29.0, 28.5 (3C), 27.4, 26.7, 25.3, 24.9, 24.2, 23.3, 22.1, 19.6, 19.4,
17.1, 15.0, 11.3; HRMS (ESI-TOF) m/z 1035.6502 [M + Na]+ (calcd
for C53H88N8O11Na 1035.6470).
Methyl N,N-(((S)-8-((tert-Butoxycarbonyl)amino)-4-methylocta-
noyl)-L-leucyl)-N-methyl-D-alloisoleucyl-L-lutaminyl-L-valyl-N-
methyl-D-phenylalanyl-L-prolinate ((S)-13). To a stirred solution of
hexapeptide 12 (14.3 mg, 16.7 μmol) in CH2Cl2 (2 mL) was added
TFA (1 mL) at rt. After stirring for 30 min, the reaction mixture was
concentrated to give crude amine·TFA. To a stirred solution of crude
amine·TFA and carboxylic acid (S)-7 (14.4 mg, 52.7 μmol) in DMF
(0.03 mL) cooled at 0 °C were added DIPEA (8.7 μL, 50 μmol) and
HATU (20.2 mg, 53.1 μmol). After stirring at rt for 9 h, the reaction
mixture was diluted with EtOAc (10 mL), washed with 10% aqueous
citric acid (10 mL), saturated aqueous NaHCO3 (10 mL), and brine
(10 mL), dried (Na2SO4), and concentrated. The residual oil was
purified by PLC (CHCl3−EtOAc−MeOH, 5:5:1) to give peptide (S)-
13 (14.2 mg, 84% in 2 steps) as a colorless amorphous solid. The ratio
of major and minor rotamers is 6:1: [α]28D +12.5 (c 1.00, CHCl3); IR
(43S)-Hoshinoamide C (2). To a stirred solution of peptide (S)-13
(10.9 mg, 10.1 μmol) in CH2Cl2 (2 mL) was added TFA (1 mL) at rt.
After stirring for 30 min, the reaction mixture was concentrated to
give crude amine·TFA. To a stirred solution of crude amine·TFA and
4-(4-hydoroxyphenyl)butanoic acid (5.5 mg, 30.5 μmol) in DMF
(0.01 mL) cooled at 0 °C were added DIPEA (0.01 mL, 57 μmol)
and HATU (12.1 mg, 31.8 μmol). After stirring for 8 h at rt, the
reaction mixture was diluted with EtOAc (10 mL), washed with 10%
aqueous citric acid (10 mL), saturated aqueous NaHCO3 (10 mL),
and brine, dried (Na2SO4), and concentrated. The residual oil was
purified by HPLC (Cosmosil PBr (ϕ20 × 250 mm), MeOH−H2O,
95:5, flow rate 5 mL/min, detection UV 215 nm) to give (43S)-
hoshinoamide C (2) (6.8 mg, tR = 42.3 min, 62% in 2 steps) as a
1
(neat) 3320, 2961, 2931, 2872, 1632 cm−1; H NMR (400 MHz,
colorless oil. The ratio of major and minor rotamers is 5:1: [α]28
D
1
+21.0 (c 1.00, CHCl3); IR (neat) 3316, 2960, 2932, 1632 cm−1; H
CDCl3) for the major rotamer δ 7.39 (brd, J = 6.8 Hz, 1H, NH),
7.33−7.08 (m, 5H), 7.00 (brd, J = 8.3 Hz, 1H, NH), 6.65 (brd, J = 6.8
Hz, 1H, NH), 6.49 (brm, 1H, NH), 5.80 (brm, 1H, NH), 5.63 (dd, J
= 7.8, 7.8 Hz, 1H), 4.94 (dd, J = 13.4, 6.8 Hz, 1H), 4.70−4.61 (m,
2H), 4.39 (dd, J = 8.3, 6.3 Hz, 1H), 4.28 (dd, J = 13.4, 6.8 Hz, 1H),
3.71 (s, 3H), 3.40−3.30 (m, 2H), 3.26 (dd, J = 14.2, 7.3 Hz, 1H),
3.13−3.03 (m, 2H), 3.10 (s, 3H), 2.99 (s, 3H), 2.87 (dd, J = 14.2, 8.3
Hz, 1H), 2.31−2.10 (m, 6H), 2.10−1.69 (m, 11H), 1.68−1.55 (m,
2H), 1.53−1.40 (m, 2H), 1.43 (s, 9H), 1.33−1.20 (m, 3H), 1.17−
1.02 (m, 2H), 0.99 (d, J = 6.3 Hz, 3H), 0.93 (d, J = 6.8 Hz, 3H), 0.92
(t, J = 7.8, 3H), 0.84 (d, J = 6.8 Hz, 3H), 0.80 (d, J = 6.8 Hz, 3H),
0.72 (d, J = 6.8 Hz, 3H), 0.62 (d, J = 6.8 Hz, 3H); 13C NMR (100
MHz, CDCl3) for the major rotamer δ 175.1, 174.3, 173.6, 172.6,
171.9, 171.1, 170.1, 168.5, 156.3, 137.0, 129.6 (2C), 128.5 (2C),
126.8, 79.2, 61.4, 59.4, 56.0, 54.1, 53.3, 52.4, 48.2, 47.1, 42.1, 40.7,
36.5, 35.3, 34.3, 32.6, 32.5, 32.4, 31.6, 31.3, 31.0, 30.6, 30.4, 29.0, 28.6
(3C), 27.5, 26.7, 25.4, 25.0, 24.2, 23.4, 22.2, 19.6, 19.4, 17.3, 15.0,
11.4; HRMS (ESI-TOF) m/z 1013.6671 [M + H]+ (calcd for
C53H89N8O11 1013.6651).
(43R)-Hoshinoamide C (1). To a stirred solution of peptide (R)-13
(12.4 mg, 12.2 μmol) in CH2Cl2 (2 mL) was added TFA (1 mL) at rt.
After stirring for 30 min, the reaction mixture was concentrated to
give crude amine·TFA. To a stirred solution of crude amine·TFA and
4-(4-hydoroxyphenyl)butanoic acid (6.6 mg, 36.6 μmol) in DMF
(0.02 mL) cooled at 0 °C were added DIPEA (0.01 mL, 57 μmol)
and HATU (14.1 mg, 37.1 μmol). After stirring at rt for 12 h, the
reaction mixture was diluted with EtOAc (10 mL), washed with 10%
aqueous citric acid (10 mL), saturated aqueous NaHCO3 (10 mL),
NMR (400 MHz, CDCl3) for the major rotamer δ 7.26−7.10 (m,
5H), 6.97 (d, J = 8.2 Hz, 2H), 6.76 (d, J = 8.2 Hz, 2H), 6.71 (brd, J =
7.3 Hz, 1H, NH), 6.62 (brs, 1H, NH), 5.90 (t, J = 5.7 Hz, 1H, NH),
5.73 (brs, 1H, NH), 5.63 (dd, J = 7.7, 7.7 Hz, 1H), 4.90 (m, 1H), 4.73
(d, J = 10.4 Hz, 1H), 4.66 (d, J = 5.9 Hz, 1H), 4.38 (dd, J = 8.2, 6.3
Hz, 1H), 4.24 (dt, J = 6.8, 6.8 Hz, 1H), 3.69 (s, 3H), 3.40−3.30 (m,
2H), 3.26 (dd, J = 14.3, 6.8 Hz, 1H), 3.23−3.13 (m, 2H), 3.11 (s,
3H), 3.01 (s, 3H), 2.87 (dd, J = 14.3, 8.2 Hz, 1H), 2.56 (t, J = 7.0 Hz,
2H), 2.23−2.15 (m, 3H), 2.11 (t, J = 7.3 Hz, 2H), 2.11 (m, 1H),
2.06−1.71 (m, 9H), 1.68−1.58 (m, 2H), 1.56−1.45 (m, 2H), 1.44−
1.17 (m, 9H), 1.13−1.11 (m, 2H), 0.97 (d, J = 6.8 Hz, 3H), 0.93 (d, J
= 6.3 Hz, 3H), 0.92 (t, J = 7.3 Hz, 3H), 0.82 (d, J = 6.3 Hz, 3H), 0.80
(d, J = 6.3 Hz, 3H), 0.72 (d, J = 6.8 Hz, 3H), 0.63 (d, J = 6.8 Hz, 3H);
13C NMR (100 MHz, CDCl3) for the major rotamer δ 175.2, 174.5,
173.9, 173.3, 172.6, 172.0, 171.3, 170.2, 168.6, 155.0, 136.9, 132.7,
129.7 (2C), 129.6 (2C), 128.5 (2C), 126.9, 115.5 (2C), 61.4, 59.4,
56.1, 54.3, 53.4, 52.4, 48.4, 47.1, 41.7, 39.4, 36.5, 35.6, 35.3, 34.1,
34.1, 32.5 (2C), 32.2, 31.7, 31.5, 31.1, 30.6, 29.7, 29.0, 27.4, 27.2,
26.7, 25.3, 25.0, 24.2, 23.3, 22.2, 19.5 (2C), 17.3, 15.1, 11.4; HRMS
(ESI-TOF) m/z 1097.6589 [M + Na]+ (calcd for C58H90N8O11Na
1097.6627).
Cell Growth Analysis. HeLa cells were cultured at 37 °C with 5%
CO2 in DMEM (Nissui) supplemented with 10% heat-inactivated
fetal bovine serum (FBS), 100 units/mL penicillin, 100 μg/mL
streptomycin, 0.25 μg/mL amphotericin, 300 μg/mL L-glutamine, and
2.25 mg/mL NaHCO3. HL60 cells were cultured at 37 °C with 5%
CO2 in RPMI (Nissui) supplemented with 10% heat-inactivated FBS,
133
J. Nat. Prod. 2021, 84, 126−135