Intensely Potent Doxorubicin Analogues
J ournal of Medicinal Chemistry, 1998, Vol. 41, No. 6 971
2.25 (m, 4 H, H-2, H-3), 1.38 (s, 9 H, C(CH3)3). 13C NMR:
172.03 (C-1), 136.65 (C-4), 114.97 (C-5), 79.82 (C(CH3)3), 34.45
(C-3), 28.87 (C-2), 27.83 (C(CH3)3). Anal. (C9H16O2) C, H.
ter t-Bu tyl 4-Oxobu ta n oa te (24). The compound was
prepared by ozonolysis of 23 (2.0 g, 12.8 mmol) as described
for 10a . The crude product was purified by column chroma-
tography on silica gel to give 24 as an oil (1.48 g, 73%). 1H
NMR: δ 9.70 (t, 1 H, H-4), 2.45 (m, 2 H, H-3), 2.60 (t, 2 H,
H-2), 1.35 (s, 9 H, C(CH3)3). 13C NMR: 200.17 (C-4), 171.22
(C-1), 80.51 (C(CH3)3), 38.42 (C-3), 27.73 (C(CH3)3), 27.60 (C-
2). Anal. (C8H14O3) C, H.
δ 8.03 (dd, J ) 8.2, 0.9 Hz, 1 H, H-1), 7.84 (t, J ) 8.2 Hz, 1 H,
H-2), 7.37 (dd, J ) 8.2, 0.9 Hz, 1 H, H-3), 6.76 (t, J ) 5.46 Hz,
1 H, H-6′′), 5.52 (t, J ) 1 Hz, 1 H, H-1′), 5.4 (bs, 1 H, H-7),
4.75 (s, 2 H, H-14), 4.14 (s, 3 H, 4-OCH3), 3.97 (m, 1 H, H-5′),
3.63 (m, 1 H, H-4′), 3.25 (d, J ) 16 Hz, 1 H, H-10a), 2.96 (d, J
) 16 Hz, 1 H, H-10b), 2.85 (m, 1 H, H-3′), 2.66 (m, 2 H, H-1′′),
2.36 (m, 1 H, H-8a), 2.23 (m, 1 H, H-8b), 2.05 (s, 6 H, 2 ×
OCOCH3), 1.82 (m, 1 H, H-2′a), 1.78 (m, 2 H, H-5′′), 1.75 (m,
1 H, H-2′b), 1.65 (m, 2 H, H-2′′), 1.40 (m, 2 H, H-3′′), 1.39 (m,
2 H, H-4′′), 1.32 (d, J ) 6 Hz, 3 H, H-6′). MS (FAB): m/z 744
(M + H)+. HRMS calcd for (C37H46NO15) 744.2867, found
744.2867.
N-(4,4-Dia cetoxybu t-1-yl)d oxor u bicin Hyd r och lor id e
(1a ). A stirred solution of doxorubicin hydrochloride (20 mg,
0.035 mmol) and 4-oxobutane 1,1-diacetate (10a ) (13.2 mg, 2
equiv, 0.07 mmol) in CH3CN-H2O (2:1) (5 mL) was treated
with a solution of NaBH3CN (1 M in THF) (24 µL, 0.67 equiv,
0.024 mmol). The mixture was stirred under a nitrogen
atmosphere at room temperature in the dark for 1 h. When
reaction was complete (as evidenced by TLC of a 5-µL aliquot),
the solution was diluted with H2O (8 mL) and then extracted
repeatedly (10 × 10 mL) with CHCl3-MeOH (5:1). The
combined extracts were dried and evaporated to give a red film
(16 mg) which was purified by preparative TLC using CHCl3-
MeOH (10:1) as eluent. The product was suspended in H2O
(1 mL) and acidified to pH 5 by dropwise addition of 0.05 N
hydrochloride (approximately 0.5 mL). The solution was
lyophilized to afford the title compound (10.2 mg, 39%). It was
stored under nitrogen in a tightly stoppered vessel at -78 °C
in the dark. TLC: silica gel, CHCl3-MeOH, 10:1; Rf ) 0.59.
1H NMR (free base): δ 8.05 (dd, J ) 8.1, 0.85 Hz, 1 H, H-1),
7.90 (t, J ) 8.1 Hz, 1 H, H-2), 7.42 (dd, J ) 8.1, 0.85 Hz, 1 H,
H-3), 6.75 (t, J ) 5.45 Hz, 1 H, H-4′′), 5.52 (bs, 1 H, H-1′), 5.31
(bs, 1 H, H-7), 4.72 (s, 2 H, H-14), 4.05 (s, 3 H, 4-OCH3), 3.95
(m, 1 H, H-5′), 3.61 (m, 1 H, H-4′), 3.32 (d, J ) 16.2 Hz, 1 H,
H-10a), 3.03 (d, J ) 16.2 Hz, 1 H, H-10b), 2.81 (m, 1 H, H-3′),
2.60 (m, 2 H, H-1′′), 2.44 (m, 1 H, H-8a), 2.22 (m, 1 H, H-8b),
2.02 (s, 6 H, 2 × OCOCH3), 1.75 (m, 2 H, H-2′a), 1.75 (m, 1 H,
H-3′′), 1.71 (m, 1 H, H-2′b), 1.42 (m, 2 H, H-2′′), 1.35 (d, J ) 6
Hz, 3 H, H-6′). MS (FAB): m/z 716 (M + H)+. HRMS calcd
for (C35H42NO15) 716.2554, found 716.2554.
N-(8,8-Dia cetoxyoct-1-yl)d oxor u bicin Hyd r och lor id e
(1e). The compound was prepared from doxorubicin hydro-
chloride (20 mg, 0.035 mmol), 8-oxooctane-1,1-diacetate (10e)
(17.1 mg, 2 equiv, 0.07 mmol), and NaBH3CN (1 M in THF)
(24 µL, 0.67 equiv, 0.024 mmol) in CH3CN-H2O (2:1) (5 mL)
as described for (1a ). TLC: silica gel, CHCl3-MeOH, 10:1; Rf
) 0.60). The yield was 11.72 mg (41%). 1H NMR (free base):
δ 8.05 (dd, J ) 8.2, 0.9 Hz, 1 H, H-1), 7.85 (t, J ) 8.2 Hz, 1 H,
H-2), 7.40 (dd, J ) 8.2, 0.9 Hz, 1 H, H-3), 6.72 (t, J ) 5.46, 1
H, H-8′′), 5.55 (t, J ) 1 Hz, 1 H, H-1′), 5.35 (bs, 1 H, H-7), 4.71
(s, 2 H, H-14), 4.16 (s, 3 H, 4-OCH3), 3.97 (m, 1 H, H-5′), 3.65
(m, 1 H, H-4′), 3.28 (d, J ) 16 Hz, 1 H, H-10a), 2.98 (d, J ) 16
Hz, 1 H, H-10b), 2.85 (m, 1 H, H-3′), 2.68 (m, 2 H, H-1′′), 2.35
(m, 1 H, H-8a), 2.25 (m, 1 H, H-8b), 2.04 (s, 6 H, 2 × OCOCH3),
1.85 (m, 1 H, H-2′a), 1.75 (m, 2 H, H-7′′), 1.76 (m, 1 H, H-2′b),
1.68 (m, 2 H, H-2′′), 1.41 (m, 2 H, H-3′′), 1.40 (m, 6 H, H-4′′,
H-5′′), 1.39 (m, 2 H, H-6′′), 1.35 (d, J ) 6 Hz, 3 H, H-6′). MS
(FAB): m/z 772 (M + H)+. HRMS calcd for (C39H50NO15
)
772.3180, found 772.3180.
N-(4,4-Diacetoxy-3,3-dim eth ylbu t-1-yl)doxor u bicin Hy-
d r och lor id e (1f). The compound was prepared from doxo-
rubicin hydrochloride (20 mg, 0.035 mmol), 2,2-dimethyl-4-
oxobutane 1,1-diacetate (10b) (15 mg, 2 equiv, 0.07 mmol), and
NaBH3CN (1 M in THF) (24 µL, 0.67 equiv, 0.024 mmol) in
CH3CN-H2O (2:1) (5 mL) as described for 1a . TLC: silica
gel, CHCl3-MeOH, 10:1; Rf ) 0.54. The yield was 10.8 mg
(39%). 1H NMR (free base): δ 8.02 (dd, J ) 8.15, 0.83 Hz, 1
H, H-1), 7.91 (t, J ) 8.15 Hz, 1 H, H-2), 7.54 (dd, J ) 8.15,
0.83 Hz, 1 H, H-3), 6.65 (s, 1 H, H-4′′), 5.52 (bs, 1 H, H-1′),
5.35 (bs, 1 H, H-7), 4.72 (s, 2 H, H-14), 4.03 (s, 3 H, 4-OCH3),
3.97 (bs, 1 H, H-5′), 3.60 (m, 1 H, H-4′), 3.35 (d, J ) 16.4 Hz,
1 H, H-10a), 3.05 (d, J ) 16.4 Hz, 1 H, H-10b), 2.95 (m, 1 H,
H-3′), 2.61 (m, 2 H, H-1′′), 2.40 (m, 1 H, H-8a), 2.26 (m, 1 H,
H-8b), 2.01 (s, 6 H, 2 × OCOCH3), 1.78 (m, 1 H, H-2′a), 1.73
(m, 1 H, H-2′b), 1.55 (s, 6 H, 2 × OCOCH3), 1.52 (m, 2 H, H-2′′),
1.35 (d, J ) 6 Hz, 3 H, H-6′). MS (FAB): m/z 744 (M + H)+.
HRMS calcd for (C37H46NO15) 744.2867, found 744.2889.
N-(5,5-Dia cetoxyp en t-1-yl)d oxor u bicin Hyd r och lor id e
(1b). The compound was prepared from doxorubicin hydro-
chloride (20 mg, 0.035 mmol), 5-oxopentane 1,1-diacetate (10c)
(14 mg, 2 equiv, 0.07 mmol), and NaBH3CN (1 M in THF) (24
µL, 0.67 equiv, 0.024 mmol) in CH3CN-H2O (2:1) (5 mL) as
previously reported.2 The yield was 10.3 mg (38%). TLC: silica
gel, CHCl3-MeOH, 10:1; Rf ) 0.60.
N-Meth yl-N-(5,5-d ia cetoxyp en t-1-yl)d oxor u bicin Hy-
d r och lor id e (1c). Formalin (3.3 µL of a 37% aqueous
solution, 41 µmol) was added to a solution of N-(5,5-diacetoxy-
pentyl)doxorubicin hydrochloride (1b) (3.0 mg, 4.1 µmol) in
CH3CN-H2O (2:1) (2 mL). The mixture was stirred for 30 min
at room temperature. NaBH3CN (1 M) in THF (4.1 µL, 4.1
µmol, 0.67 equiv) was added and the mixture was stirred for
an additional 24 h. The crude product was isolated as
described for 1a and purified by preparative TLC on silica gel.
The yield was 1 mg (33%). TLC: silica gel, CHCl3-MeOH,
10:1; Rf ) 0.60. 1H NMR (free base): δ 7.99 (d, J ) 8 Hz, 1 H,
H-1), 7.82 (t, J ) 8 Hz, 1 H, H-2), 7.36 (dd, J ) 8, 1 Hz, 1 H,
H-3), 6.65 (t, J ) 5.5 Hz, 1 H, H-5′′), 5.55 (t, 1 H, H-1′), 5.26
(bs, 1 H, H-7), 4.72 (s, 2 H, H-14), 4.05 (s, 3 H, 4-OCH3), 3.96
(m, 1 H, H-5′), 3.63 (m, 1 H, H-4′), 3.21 (d, J ) 16 Hz, 1 H,
H-10a), 2.95 (d, J ) 16 Hz, 1 H, H-10b), 2.61 (m, 1 H, H-3′),
2.50 (m, 2 H, H-1′′), 2.30 (s, 3 H, N-CH3), 2.2 (m, 2 H, H-8a,
H-8b), 2.00 (s, 6 H, 2 × OCOCH3), 1.74 (m, 4 H, H-2′a, H-2′b,
H-4′′), 1.35 (m, 2 H, H-3′′), 1.30 (d, J ) 6 Hz, 3 H, H-6′). MS
N-[[(2,2-Dia cetoxyeth yl)oxy]eth yl]d oxor u bicin Hyd r o-
ch lor id e (1g). The compound was prepared from doxorubicin
hydrochloride (20 mg, 0.035 mmol), [(2,2-diacetoxyethyl)oxy]-
acetaldehyde (16) (14.3 mg, 0.07 mmol), and NaBH3CN (1 M
in THF) (24 µL, 0.67 equiv, 0.024 mmol) in CH3CN-H2O (2:1)
(5 mL), as described for 1a . TLC: silica gel, CHCl3-MeOH,
10:1; Rf ) 0.6. The yield was 9.4 mg (34%). 1H NMR (free
base): δ 8.11 (dd, J ) 8.2, 0.8 Hz, 1 H, H-1), 7.82 (t, J ) 8.2
Hz, 1 H, H-2), 7.35 (dd, J ) 8.2, 0.8 Hz, 1 H, H-3), 6.75 (t, 1 H,
J ) 5.5 Hz, H-2′′′), 5.50 (t, J ) 1 Hz, 1 H, H-1′), 5.35 (bs, 1 H,
H-7), 4.75 (s, 2 H, H-14), 4.11 (s, 3 H, 4-OCH3), 3.93 (m, 1 H,
H-5′), 3.77 (m, 1 H, H-4′), 3.65 (m, 2 H, H-2′′), 3.54 (m, 2 H,
H-1′′′), 3.25 (d, J ) 16 Hz, 1 H, H-10a), 3.21 (m, 1 H, H-3′),
3.14 (m, 2 H, H-1′′), 2.95 (d, J ) 16 Hz, 1 H, H-10b), 2.35 (m,
1 H, H-8a), 2.25 (m, 1 H, H-8b), 2.24 (m, 2 H, H-2′a), 2.12 (m,
1 H, H-2′b), 2.01 (s, 6 H, 2 × OCOCH3), 1.34 (d, J ) 6 Hz, 3 H,
H-6′). MS (FAB): m/z 732 (M + H)+. HRMS calcd for (C35H42
NO16) 732.2504, found 732.2485.
-
(FAB): m/z 744 (M + H)+. HRMS calcd for (C37H46NO15
744.2867, found 744.2889.
)
N-[[(3,3-Dia cetoxyp r op yl)oxy]eth yl]d oxor u bicin Hy-
d r och lor id e (1h ). The compound was prepared from doxo-
rubicin hydrochloride (20 mg, 0.035 mmol), [(3,3-diacetoxypro-
pyl)oxy]acetaldehyde (21a) (15.2 mg, 0.07 mmol), and NaBH3CN
(1 M in THF) (24 µL, 0.67 equiv, 0.024 mmol) in CH3CN-H2O
(2:1) (5 mL), as described for 1a . TLC: silica gel, CHCl3-
MeOH, 10:1; Rf ) 0.6. The yield was 9.4 mg (34%). 1H NMR
N-(6,6-Diacetoxyh exyl)doxor u bicin Hydr och lor ide (1d).
The compound was prepared from doxorubicin hydrochloride
(20 mg, 0.035 mmol), 6-oxohexane 1,1-diacetate (10d ) (15 mg,
2 equiv, 0.07 mmol), and NaBH3CN (1 M in THF) (24 µL, 0.67
equiv, 0.024 mmol) in CH3CN-H2O (2:1) (5 mL) as described
for 1a . The yield was 10.75 mg (39%). 1H NMR (free base):