7372
W. Wang et al. / Tetrahedron 58 (2002) 7365–7374
126.2, 125.7, 66.9, 55.0, 52.5, 36.2; HRMS (FAB) calcd for
C28H26NO4 (MþH) 440.1826; found 440.1859.
J1¼5.7 Hz, J2¼14.1 Hz), 2.95 (1£1H, dd, J1¼5.1 Hz,
J2¼14.1 Hz), 2.78 (1£1H, dd, J1¼8.4 Hz, J2¼14.1 Hz),
2.68 (3£1H, dd, J1¼8.4 Hz, J2¼14.1 Hz), 1.69 (1£3H, s),
1.67 (3£3H, s); 13C NMR (75 MHz, CDCl3) d 172.5 (2C),
169.9, 169.7, 137.2, 136.4, 136.1, 133.9, 133.6, 133.5,
133.4, 133.0, 132.9 (2C), 132.8, 132.6, 132.5, 128.8, 128.7,
128.6, 128.5, 128.4, 128.1, 128.0, 127.8, 127.7, 127.3 (2C),
127.0, 126.9, 126.8, 126.7, 126.6, 126.4, 126.3, 126.2, 126.0
(2C), 125.9, 125.8, 125.7, 125.5, 53.3, 53.2, 52.34, 52.30,
35.9, 35.8, 23.0, 22.8; HRMS (FAB) calcd for C26H24NO3
(MþH) 398.1756; found 398.1750.
4.3.4. (R )-N a-Benzyloxycarbonyl-1-(1-bromo)-2-
naphthylalanine methyl ester 14b. In a similar manner
to the preparation of 9b, using (R, R ) (COD)Et-DuPHOS
Rh(I) OTf as a catalyst gave 14b in 99% yield. Mp 125–
126.58C;[a ]2D4¼20.44 (c 1.40, CHCl3); 1H NMR
(300 MHz, CDCl3) d 8.30 (1H, d, J¼8.4 Hz), 7.80 (1H, d,
J¼7.2 Hz), 7.71 (1H, d, J¼8.4 Hz), 7.48–7.62 (2H, m),
7.24–7.28 (6H, m), 5.40 (1H, d, J¼8.4 Hz), 5.03 (2H, s),
4.81 (1H, dd, J1¼6.3 Hz, J2¼8.1 Hz), 3.71 (3H, s), 3.55
(1H, dd, J1¼6.3 Hz, J2¼13.8 Hz), 3.42 (1H, J1¼8.1 Hz,
J2¼13.8 Hz); 13C NMR (75 MHz, CDCl3) d 172.3, 155.8,
136.4, 134.1, 133.8, 132.7, 128.6, 128.3 (2C), 128.2 (2C),
128.0, 127.8 (2C), 126.7, 125.2, 67.1, 54.4, 52.8, 39.7;
HRMS (FAB) calcd for C22H21BrNO4 (MþH) 442.0654 (Br
79), 444.0637 (Br 81); found 442.0654 (Br 79), 444.0657
(Br 81).
4.3. Procedures for preparation of compounds 10b–d
and 11b through palladium-catalyzed Suzuki coupling
reactions
A reaction flask fitted with a Teflon valve was charged with
a bromoarylalanine derivative, boronic acid (1.5 equiv.),
Na2CO3 (2.0 equiv.), Pd(PPh3)4 (5 mol%), benzene
(8 mL/mmol), and degassed water (1 mL/mmol), and then
was heated to 808C for 36 h. The reaction mixture was
passed through a short column containing a bottom 1 in.
layer of silica gel (230–400 mesh) and a top 1 in. layer of
NaHCO3 using ethyl acetate as eluent. The solvent was
removed under reduced pressure with a rotary evaporator.
The crude product was purified by flash column chroma-
tography using an appropriate mixture of ethyl acetate and
hexanes as eluent.
4.3.1. (S )-N a-Benzyloxycarbonyl-1-(1-naphthyl)-2-
naphthylalanine methyl ester 10b. 95% yield, two isomers
1
(ca. 1:2 ratio), H NMR (300 MHz, CDCl3) d 7.86–7.96
(3£4H, m), 7.51–7.60 (3£2H, m), 7.35–7.46 (3£3H, m),
7.07–7.26 (3£9H, m), 4.87–5.02 (3£3H, m), 4.51–4.66
(3£1H, m), 3.55, (1£1H, s), 3.53 (2£1H, s), 3.06 (2£1H, dd,
J1¼5.1 Hz, J2¼14.1 Hz), 2.96 (1£1H, dd, J1¼5.1 Hz,
J2¼14.1 Hz), 2.74 (1£1H, dd, J1¼9.6 Hz, J2¼14.1 Hz),
2.60 (2£1H, dd, J1¼9.6 Hz, J2¼14.1 Hz); 13C NMR
(75 MHz, CDCl3) d 172.5, 172.1, 155.8, 155.7, 137.5,
137.4, 136.4, 136.1, 133.8 (2C), 133.6, 133.4, 133.0, 132.8
(2C), 132.7, 132.6, 128.6 (2C), 128.4 (2C), 128.3 (2C),
128.2 (2C), 128.1, 128.0, 127.8, 127.74, 127.2, 127.1, 127.0,
126.9, 126.7, 126.6, 126.4, 126.3, 126.2, 126.0, 125.8,
125.6, 67.1, 66.9, 55.0, 54.7, 52.7, 52.4, 36.3, 36.1; HRMS
(FAB) calcd for C32H28NO4 (MþH) 490.2018; found
490.2024.
4.3.5. (R )-N a-Benzyloxycarbonyl-1-(1-phenyl)-2-
naphthylalanine methyl ester 11a. 78% yield,
[a ]2D4¼213.9 (c 0.91, CHCl3); 1H NMR (300 MHz,
CDCl3) d 7.79–7.85 (2H, m), 7.21–7.47 (14H, m), 4.92–
5.05 (3H, m), 4.55 (1H, m), 3.62 (3H, s), 3.14 (1H, dd,
J1¼5.4 Hz, J2¼13.8 Hz), 2.91 (1H, dd, J1¼9.0 Hz,
J2¼13.8 Hz); 13C NMR (75 MHz, CDCl3) d 172.6, 155.7,
139.7, 138.8, 136.4, 133.2, 132.6, 131.4, 130.6, 130.4,
128.7, 128.6, 128.2, 128.0, 127.9, 127.6, 127.4, 126.9,
126.2, 125.7, 66.9, 55.0, 52.5, 36.2; HRMS (FAB) calcd for
C28H26NO4 (MþH) 440.1826; found 440.1857.
4.3.2. (S )-N a-tert-Butoxycarbonyl-1-(1-naphthyl)-2-
naphthylalanine methyl ester 10c. 98% yield, two isomers
1
(ca. 1:2 ratio), H NMR (600 MHz, CDCl3) d 7.87–7.98
(3£4H, m), 7.54–7.64 (3£2H, m), 7.39–7.48 (3£3H, m),
7.08–7.29 (3£4H, m), 4.69 (2£1H, d, J¼8.4 Hz), 4.61
(1£1H, d, J¼8.4 Hz), 4.55 (1£1H, dd, J1¼8.4 Hz,
J2¼13.8 Hz), 4.46 (1£1H, dd, J1¼8.4 Hz, J2¼13.8 Hz),
3.54 (1£3H, s), 3.52 (2£3H, s), 3.02 (2£1H, dd, J1¼4.8 Hz,
J2¼13.8 Hz), 2.92 (1£1H, dd, J1¼4.8 Hz, J2¼13.8 Hz),
2.71 (2£1H, dd, J1¼9.0 Hz, J2¼13.8 Hz), 2.58 (1£1H, dd,
J1¼9.6 Hz, J2¼13.8 Hz), 1.32 (1£9H, s), 1.30 (2£9H, s);
13C NMR (75 MHz, CDCl3) d 172.9, 172.7, 155.3, 155.2,
137.4, 137.3, 136.5, 136.3, 133.9, 133.6, 133.1, 133.0,
132.9, 132.7, 132.6, 128.7, 128.6, 128.5, 128.4, 128.3,
128.0, 127.8, 127.3, 127.2, 127.0, 126.9, 126.7, 126.6,
126.3, 126.1, 126.0, 125.8, 125.6, 80.0, 79.9, 54.6, 54.3,
52.4, 52.3, 36.3, 36.2, 28.41, 28.36; HRMS (FAB) calcd for
C29H29NO4 (MþH) 455.2097; found 455.2088.
4.3.6. (R )-N a-Benzyloxycarbonyl-1-(1-naphthyl)-2-
naphthylalanine methyl ester 11b. 100% yield, two
isomers (ca. 1:2 ratio), 1H NMR (300 MHz, CDCl3) d
7.85–7.95 (12H, m), 7.50–7.59 (6H, m), 7.35–7.46 (9H,
m), 7.06–.27 (27H, m), 4.89–5.07 (9H, m), 4.51–4.66 (3H,
m), 3.53, (1H, s), 3.50 (2H, s), 3.06 (2H, dd, J1¼5.1 Hz,
J2¼14.1 Hz), 2.96 (1H, dd, J1¼5.1 Hz, J2¼14.1 Hz), 2.74
(1H, dd, J1¼9.3 Hz, J2¼14.1 Hz), 2.60 (2H, dd, J1¼9.3 Hz,
J2¼14.1 Hz); 13C NMR (75 MHz, CDCl3) d 172.5, 172.1,
155.8, 155.7, 137.5, 137.3, 136.4, 136.1, 133.8, 133.7,
133.5, 133.4, 132.9, 132.8 (2C), 132.7, 132.6, 128.6, 128.5,
128.4, 128.3 (2C), 128.2 (2C), 128.1 (2C), 127.9, 127.8,
127.7, 127.3, 127.2, 126.9 (2C), 126.7, 126.6, 126.3, 126.2
(2C), 125.9, 125.8, 125.6, 67.0, 66.9, 54.9, 54.7, 52.5, 52.4,
36.2, 36.1; HRMS (FAB) calcd for C32H28NO4 (MþH)
490.2018; found 490.2027.
4.3.3. (S )-N a-Actyl-1-(1-naphthyl)-2-naphthylalanine
methyl ester 10d. 96% yield, two isomers (ca. 1:3 ratio),
1H NMR (300 MHz, CDCl3) d 7.85–7.98 (4£4H, m), 7.37–
7.64 (4£5H, m), 7.06–7.30 (4£4H, m), 5.75 (3£1H, d,
J¼7.8 Hz), 5.59 (1H, d, J¼8.1 Hz), 4.80 (1£1H, m), 4.71
(3£1H, m), 3.54 (1£3H, s), 3.52 (3£3H, s), 3.05 (3£1H, dd,
4.3.7. 1-tert-Butoxycarbonyl-3-formyl-2-phenylindole
17. 3-Formyl-2-phenylindole 16 (1.1 g, 5 mmol) in pyridine
(15 mL) was treated with di-tert-butyldicarbonate (1.42 g,
6.5 mmol, 1.3 equiv.) at room temperature under argon for
5 h. After removal of solvent under reduced pressure, the