References and Notes
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<A NAME="RG17008ST-6A">6a</A>
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Lorence A.
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Bailly C.
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Torck M.
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For recent syntheses of (20S)-camptothecin, see:
<A NAME="RG17008ST-7A">7a</A>
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Liu G.-S.
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cycloadditions, see:
<A NAME="RG17008ST-10A">10a</A>
McMills MC.
Wright D. In The Chemistry
of Heterocyclic Compounds: Synthetic Applications of 1,3-Dipolar
Cycloaddition Chemistry Toward Heterocycles and Natural Products
Padwa A.
Pearson WH.
John Wiley and Sons;
New
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2002.
p.253-314
<A NAME="RG17008ST-10B">10b</A>
Mehta G.
Muthusamy S.
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2002,
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9477
<A NAME="RG17008ST-10C">10c</A>
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Curr. Chem.
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Padwa A.
Weingarten MD.
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Osterhout MH.
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1994,
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<A NAME="RG17008ST-11A">11a</A>
Marino JP.
Osterhout MH.
Price AT.
Sheehan
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849
<A NAME="RG17008ST-11B">11b</A> For the use of this reagent
for similar cyclizations, see:
Padwa A.
Prein M.
J. Org. Chem.
1997,
62:
6842
<A NAME="RG17008ST-12">12</A>
Compound 5:
mp 215-216 ˚C (dec.). ¹H NMR
(300 MHz, CD2Cl2): δ = 1.29
(t, J = 7.1 Hz, 3 H), 4.31 (q, J = 7.1 Hz, 2 H), 5.08 (s, 2
H), 7.69 (pseudo t, J = 7.5
Hz, 1 H), 7.82 (pseudo t, J = 7.2
Hz, 1 H), 7.93 (d, J = 7.9 Hz,
1 H), 8.36 (d, J = 7.2 Hz, 2
H). ¹³C NMR (75 MHz, CD2Cl2): δ = 14.6, 46.8,
62.5, 71.0, 128.6, 129.6, 130.0, 130.9, 131.2, 131.4, 132.2, 149.4,
150.1, 161.0, 161.5, 165.0. IR: 2142, 1736, 1717, 1655 cm-¹.
MS: m/z = 325 [M + H+].
HRMS: m/z [M + H+] calcd
for C16H13N4O4: 325.0937;
found: 325.0952.
<A NAME="RG17008ST-13">13</A>
Guy RK.
DiPietro RA.
Synth. Commun.
1992,
22:
687
<A NAME="RG17008ST-14">14</A>
Compound 7:
mp 169-170 ˚C. ¹H NMR (300
MHz, CDCl3): δ = 1.14 (t, J = 7.1 Hz, 3 H), 4.17-4.29
(m, 3 H), 4.81-4.94 (m, 3 H), 5.01 (s, 2 H), 6.30 (d, J = 2.7 Hz, 1 H), 7.25-7.40 (m,
5 H), 7.58 (pseudo t, J = 8.0
Hz, 1 H), 7.75 (pseudo t,
J = 8.5
Hz, 1 H), 7.83 (d, J = 8.2 Hz,
1 H), 8.12-8.14 (m, 2 H). ¹³C
NMR (75 MHz, CDCl3): δ = 14.1, 48.4,
62.8, 73.1, 80.5, 81.1, 101.7, 127.5, 127.9, 128.0 (2 ×),
128.2, 128.5, 128.6, 129.7, 130.3, 130.8, 137.1, 137.9, 149.0, 152.4, 166.6,
168.6. IR: 3428, 1744, 1659 cm-¹. MS: m/z = 431 [M + H+].
Anal. Calcd for C25H22N2O5:
C, 69.76; H, 5.16; N, 6.51. Found: C, 69.48; H, 5.04; N, 6.41.
<A NAME="RG17008ST-15">15</A>
Compound 8a:
mp 201-203 ˚C. ¹H NMR (300
MHz, CDCl3): δ = 1.35 (t, J = 7.2 Hz, 3 H), 4.42 (q, J = 7.1 Hz, 2 H), 5.22 (s, 2
H), 5.35 (s, 2 H), 7.17 (s, 1 H), 7.30-7.50 (m, 5 H), 7.66
(pseudo t, J = 7.6 Hz, 1 H),
7.82 (pseudo t, J = 8.3 Hz,
1 H), 7.91 (d, J = 7.8 Hz, 1
H), 8.20 (d, J = 8.5 Hz, 1 H), 8.32
(s, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 14.2,
49.2, 61.4, 71.1, 89.6, 109.6, 127.1, 128.1, 128.2, 128.31, 128.34, 128.7,
129.2, 129.6, 130.6, 131.2, 135.3, 147.8, 148.7, 152.0, 159.0, 164.9,
166.2. IR: 1718, 1651, 1602 cm-¹. MS: m/z = 413 [M + H+].
Anal. Calcd for C25H20N2O4:
C, 72.81; H, 4.89; N, 6.80. Found: C, 72.70; H, 4.84; N, 6.59.
<A NAME="RG17008ST-16A">16a</A>
Compound 8b: mp 246-248 ˚C. ¹H
NMR (300 MHz, CDCl3): δ = 1.49 (t, J = 7.0 Hz, 3 H), 4.50 (q, J = 7.1 Hz, 2 H), 5.23 (s, 2
H), 7.03 (s, 1 H), 7.67 (pseudo t, J = 7.3
Hz, 1 H), 7.83 (pseudo t, J = 7.2
Hz, 1 H), 7.93 (d, J = 8.3 Hz,
1 H), 8.24 (d, J = 8.5 Hz, 1
H), 8.37 (s, 1 H). ¹³C NMR (75 MHz,
CDCl3-MeOH, 4:1): δ = 14.1,
50.0, 61.9, 94.6, 128.0, 128.3, 128.4, 129.2, 129.3, 130.6, 131.4,
148.5, 149.7, 151.3, 155.9, 159.3, 171.5, 175.6. IR: 3447, 1660,
1616
cm-¹. MS: m/z = 323 [M + H+].
Anal. Calcd for C18H14N2O4: C,
67.08; H, 4.38; N, 8.70. Found: C, 67.23; H, 4.37; N, 8.71.
<A NAME="RG17008ST-16B">16b</A> For an alternative synthesis,
see:
Liao TK.
Nyberg WH.
Cheng CC.
J.
Heterocycl. Chem.
1971,
8:
373
<A NAME="RG17008ST-17">17</A>
Compound 8c:
mp 205-207 ˚C (dec.). ¹H NMR
(300 MHz, CDCl3): δ = 1.42 (t, J = 7.2 Hz, 3 H), 4.46 (q, J = 7.2 Hz, 2 H), 5.28 (s, 2
H), 7.28 (s, 1 H), 7.70 (pseudo t, J = 8.1
Hz, 1 H), 7.85 (pseudo t, J = 8.4
Hz, 1 H), 7.95 (d, J = 7.7 Hz,
1 H), 8.23 (d, J = 8.4 Hz, 1
H), 8.41 (s, 1 H). ¹³C NMR (75 MHz,
CDCl3): δ = 13.7, 50.8, 62.5, 94.8,
115.7, 116.2, 120.5, 128.1, 128.5, 128.7, 129.5, 131.1, 131.6, 148.7, 149.0,
150.4, 156.9, 158.1, 161.6. IR: 1730, 1654, 1616
cm-¹.
MS: m/z = 455 [M + H+].
Anal. Calcd for C19H13F3N2O6S:
C, 50.23; H, 2.89; N, 6.17. Found: C, 50.11; H, 2.99; N, 6.10.
<A NAME="RG17008ST-18">18</A>
Compound 9:
mp 261-263 ˚C (dec.). ¹H NMR
(300 MHz, CDCl3): δ = 1.46 (t, J = 7.2 Hz, 3 H), 4.52 (q, J = 7.1 Hz, 2 H), 5.30 (s, 2
H), 7.20-7.70 (m, 9 H), 7.84 (pseudo t, J = 7.7 Hz,
1 H), 7.95 (d, J = 8.1 Hz, 1
H), 8.26 (d, J = 8.4 Hz, 1 H), 8.40
(s, 1 H). ¹³C NMR (75 MHz, CDCl3): δ = 14.4,
49.9, 61.8, 97.1, 122.5, 122.9, 127.4, 127.9, 128.1, 128.2, 128.8, 129.0,
129.3, 129.5, 130.5, 131.0, 135.8, 136.8, 145.7, 147.1, 148.7, 152.4,
158.7, 166.3. IR: 1723, 1640, 1603
cm-¹.
MS: m/z = 409 [M + H+].
Anal. Calcd for C26H20N2O3: C,
76.46; H, 4.94; N, 6.86. Found: C, 76.37; H, 4.99; N, 6.67.
<A NAME="RG17008ST-19">19</A>
Compound 10a:
mp 261-263 ˚C (dec.). ¹H NMR
(300 MHz, DMSO-d
6): δ = 4.74
(d, J = 5.1 Hz, 2 H), 4.99 (t, J = 5.1 Hz, 1 H), 5.25 (s, 2
H), 7.30-7.50 (m, 3 H), 7.60-7.90 (m, 7 H), 8.10-8.25
(m, 2 H), 8.67 (s, 1 H). ¹³C NMR (100
MHz, CDCl3-MeOH, 4:1): δ = 49.8,
55.9, 99.4, 122.5, 126.4, 127.1, 127.6, 127.9, 128.0, 128.1, 128.2,
128.4, 128.5, 128.6, 128.9, 130.5, 131.3, 135.8, 136.3, 143.5, 147.4, 148.2,
152.3, 161.9. IR: 3310, 1652, 1580, 1566 cm-¹.
MS: m/z = 367 [M + H+].
HRMS: m/z [M + H+] calcd
for C24H19N2O2: 367.1447;
found: 367.1455.
<A NAME="RG17008ST-20">20</A>
Compound 10b:
mp 247-248 ˚C (dec.). ¹H NMR
(300 MHz, CDCl3): δ = 0.16 (s, 6 H),
0.93 (s, 9 H), 5.02 (s, 2 H), 5.27 (s, 2 H), 7.27-7.47
(m, 5 H), 7.59-7.73 (m, 4 H), 7.82 (pseudo t, J = 7.7 Hz, 1 H), 7.92 (d, J = 7.4 Hz, 1 H), 8.24 (d, J = 8.5 Hz, 1 H), 8.35 (s, 1
H). ¹³C NMR (75 MHz, CDCl3): δ = -5.1,
18.3, 26.0, 49.9, 56.6, 88.4, 98.4, 124.5, 127.2, 127.4, 127.5,
128.0, 128.1, 128.7, 128.8, 129.0, 129.6, 130.3, 130.9, 134.9, 136.6,
143.6, 147.7, 148.6, 153.2, 161.0. IR: 1656, 1651, 1593 cm-¹.
MS: m/z = 481 [M + H+]. Anal.
Calcd for C30H32N2O2Si:
C, 74.87; H, 6.71; N, 5.83. Found: C, 74.87; H, 6.76; N, 5.89.
<A NAME="RG17008ST-21">21</A>
Compound 10c:
mp 262-265 ˚C (dec.). ¹H NMR
(300 MHz, CDCl3): δ = 0.14 (s, 6 H),
0.90 (s, 9 H), 5.15 (s, 2 H), 5.27 (s, 2 H), 7.63-7.66
(m, 2 H), 7.80 (pseudo t, J = 8.4
Hz, 1 H), 7.90 (d, J = 8.1 Hz,
1 H), 7.90 (d, J = 8.1 Hz, 1
H), 8.20 (d, J = 8.5 Hz, 1 H),
8.34 (s, 1 H). ¹³C NMR (75 MHz, CDCl3): δ = -5.4,
18.3, 25.7, 50.3, 57.2, 97.4, 127.8, 127.9, 128.5, 129.8, 130.4,
130.9, 134.6, 143.5, 145.1, 149.0, 152.6, 160.7, 192.2. IR: 1697,
1651, 1600 cm-¹. MS: m/z = 407 [M + H+].
Anal. Calcd for C23H26N2O3Si:
C, 67.95; H, 6.45; N, 6.90. Found: C, 68.12; H, 6.43; N, 6.89.
<A NAME="RG17008ST-22">22</A>
Compound 11:
mp 200-201 ˚C. ¹H NMR (300
MHz, CDCl3): δ = 0.12 (s, 6 H), 0.91
(s, 9 H), 1.22 (t, J = 7.2 Hz, 3
H), 2.91 (q, J = 7.2 Hz, 2 H),
4.91 (s, 2 H), 5.28 (s, 2 H), 7.16 (s, 1 H), 7.65 (pseudo t, J = 7.0 Hz, 1 H), 7.81 (pseudo t, J = 7.7 Hz, 1 H), 7.92 (d, J = 8.4 Hz, 1 H), 8.20 (d, J = 8.4 Hz, 1 H), 8.37 (s, 1
H). ¹³C NMR (75 MHz, CDCl3): δ = -5.6, 7.6,
18.6, 25.8, 36.2, 50.3, 58.5, 98.5, 127.7, 127.8, 127.9, 128.0,
128.6, 129.6, 130.4, 130.9, 144.5, 148.7, 150.3, 152.5, 159.9, 205.6.
IR: 1708, 1649, 1596 cm-¹. MS: m/z = 435 [M + H+].
Anal. Calcd for C25H30N2O3Si:
C, 69.10; H, 6.96; N, 6.45. Found: C, 69.19; H, 7.07; N, 6.55.
<A NAME="RG17008ST-23">23</A>
Warner CR.
Walsh EJ.
Smith RF.
J.
Chem. Soc.
1962,
1232
<A NAME="RG17008ST-24A">24a</A>
Yabu K.
Masumoto S.
Yamasaki S.
Hamashima Y.
Kanai M.
Du W.
Curran DP.
Shibasaki M.
J.
Am. Chem. Soc.
2001,
123:
9908
<A NAME="RG17008ST-24B">24b</A>
Yabu K.
Masumoto S.
Kanai M.
Shibasaki M.
Heterocycles
2003,
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369
<A NAME="RG17008ST-25">25</A>
Compound (-)-12:
mp 228-231 ˚C (dec.); [α]D
²² -18
(c 1.3, CHCl3). ¹H
NMR (300 MHz, CDCl3): δ = 0.19 (s,
3 H), 0.20 (s, 3 H), 0.28 (s, 9 H), 0.93 (s, 9 H), 1.09 (t, J = 7.3 Hz, 3 H), 2.37 (q, J = 7.3 Hz, 2 H), 5.05 (ABq, J = 10.8 Hz, 1 H), 5.21 (ABq, J = 10.8 Hz, 1 H), 5.26 (s,
2 H), 7.58-7.66 (m, 2 H), 7.80 (pseudo t, J = 7.7
Hz, 1 H), 7.89 (d, J = 8.1 Hz,
1 H), 8.23 (d, J = 8.4 Hz, 1
H), 8.34 (s, 1 H). ¹³C NMR (75 MHz, CDCl3): δ = -5.4, -5.3,
1.0, 8.5, 18.5, 25.9, 37.2, 50.2, 56.6, 76.0, 99.1, 120.0, 127.5,
127.7, 128.0, 128.7, 129.8, 130.3, 130.7, 144.4, 148.9, 151.2, 152.7,
161.2. IR: 1652, 1598 cm-¹. MS: m/z = 534 [M + H+].
HRMS: m/z [M + H+] calcd
for C29H40N3O3Si2:
534.2608; found: 534.2616.
<A NAME="RG17008ST-26">26</A>
Dichloromethane was used as the solvent
for this reaction instead of a more usual one (THF or EtCN) because
of solubility problems. The reaction was performed at -20 ˚C for
the same reason.
<A NAME="RG17008ST-27">27</A>
Analytical HPLC of 12 was
performed on a Chiralpak® IA column (250 × 4.6
mm) using hexane-i-PrOH (9:1)
as the eluent with a flow rate of 1.0 mL/min and UV monitoring
at λ = 254 nm [t
R (+)-12 = 10.2 min; t
R (-)-12 = 7.5 min]. The separation
was performed using the same chiral support (250 × 10
mm) and eluent with a flow rate of 5 mL/min.
<A NAME="RG17008ST-28">28</A>
(20S)-Camptothecin
was purchased from Sigma-Aldrich.
