10222
A. S. P. Cardoso et al. / Tetrahedron 63 (2007) 10211–10225
control) CH Cl (15 ml) was added and the resulting solu-
2
117.8, 117.1, 106.6, 106.4, 85.1, 82.6, 55.7, 46.9, 44.5,
37.1, 25.9, 25.8, 22.9, 18.0, 17.8; acc. mass: 382.23162,
C H N O requires 382.23580.
2
tion washed twice with ice cold aq NaOH (1 M) and then
water. Evaporation of solvent under reduced pressure fur-
nished a yellow oil which was purified by column chromato-
2
2 30 2
graphy (protected from light by aluminium foil, Et O) to
4.4.10. N-Acetylcarbinolamine 21a from Barton ester 19a
and Sb(SPh) . Compound 19a (130 mg, 0.265 mmol) in
2
ꢁ
25
D
give pure 19a (336 mg, 25%); mp (Et O): 28–30 C; [a]
2
3
ꢀ1
ꢀ
185.1 (c 0.50, CH Cl ); IR (film): nmax/cm
[
CDCl ): d 7.79 (1H, d, J 6.7 Hz, Ar-H), 7.66 (1H, d, J
1810
C(O)ON], 1648s (amide C]O); H NMR (400 MHz,
Et O (25 ml) was treated with Sb(SPh) (304.0 mg,
2
2
2
3
1
ꢁ
(1/2 h). The yellow solid (Sb O ) that formed was filtered and
0.677 mmol) in ice–salt bath (ꢀ18 C) with vigorous stirring
3
H
2 3
8
7
.9 Hz, Ar-H), 7.23–7.08 (3H, m, Ar-H), 6.82 (1H, t, J
.4 Hz, Ar-H), 6.62 (1H, dt, J 6.8, 1.2 Hz, Ar-H), 6.56
the filtrate taken to dryness under reduced pressure. The re-
sulting residue was purified by PTLC (Et O) to furnish 21a
2
2
6
(1H, d, J 7.8 Hz, Ar-H), 5.28 (1H, s, NCHN), 5.16 [1H, br
s, NCH CH]C(CH ) ], 5.06 [1H, t, J 7.0 Hz, CCH CH]
C(CH ) ], 4.46 (1H, t, J 7.9 Hz, CHCO N), 3.92 [2H, ddd,
3
(60.2 mg, 64%); [a] ꢀ174.8 (c 0.85, CH Cl ); IR (film):
D
2
2
ꢀ
1
1
nmax/cm 3320 (O–H), 1661s (C]O);
(400 MHz, CDCl ): dH 7.12 (1H, t, J 7.5 Hz, Ar-H), 7.06
H NMR
2
3 2
2
2
2
3
J 16.7, 7.1, 3.6 Hz, NCH CH]C(CH ) ], 2.80 (1H, dd, J
2
(1H, d, J 7.2 Hz, Ar-H), 6.70 (1H, t, J 7.3 Hz, Ar-H), 6.47
(1H, d, J 7.8 Hz, Ar-H), 5.47 (1H, s, NCHN), 5.36 (1H, br
s, CHOH), 5.19 [1H, br s, NCH CH]C(CH ) ], 5.01 [1H,
3 2
1
CCH CH]C(CH ) ], 2.61 (1H, dd, J 13.5, 8.6 Hz,
3.3, 7.6 Hz, CH CHCO N), 2.67 [1H, dd, J 15.1, 9.5 Hz,
2 2
2
3 2
2
3 2
CH CHCO N), 2.45 [1H, dd, J 14.6, 5.4 Hz, CCH CH]
2
t, J 6.7 Hz, CCH CH]C(CH ) ], 4.28 [1H, dd, J 16.0,
2 3 2
2
2
C(CH ) ], 2.33 (3H, s, NCOCH ), 1.71 [3H, s, C(CH ) ],
3 2
7.3 Hz, NCH CH]C(CH ) ], 4.04 [1H, dd, J 16.1, 5.1 Hz,
2 3 2
3
2
3
1
C(CH ) ]; C NMR: d 170.7, 149.4, 138.3, 137.2, 136.0,
.70 [3H, s, C(CH ) ], 1.69 [3H, s, C(CH ) ], 1.56 [3H, s,
NCH CH]C(CH ) ], 2.33–2.28 [4H, m, 2H of
2 3 2
CCH CH]C(CH ) and 2H of CH CHOH], 2.19 (3H, s,
2 3 2 2
3
2
3 2
1
3
3
2
C
1
1
2
35.4, 133.8, 133.5, 128.7, 122.8, 120.4, 119.9, 119.4,
12.7, 109.9, 86.8, 58.0, 57.6, 46.2, 39.3, 34.7, 25.7, 25.5,
1.8, 18.0, 17.9, and 19b, (671 mg, 49%) as a yellow solid;
NCOCH ), 1.77 [3H, s, C(CH ) ], 1.68 [6H, s, C(CH ) ],
3 3 2 3 2
1
3
1.53 [3H, s, C(CH ) ]; C NMR: d 170.9, 148.5, 135.3,
C
3
2
134.3, 133.6, 128.9, 122.9, 121.2, 118.6, 117.9, 108.0, 83.8,
83.3, 54.1, 45.1, 45.0, 37.1, 26.0, 25.8, 22.4, 18.2, 18.1; acc.
mass: 354.23170, C H N O requires 354.23071.
ꢁ
25
mp (Et O): 30–32 C; [a] +248.2 (c 0.83, CH Cl ); IR
2
D
2
2
ꢀ
1
(
film): nmax/cm 1801 [C(O)ON], 1660s (amide C]O);
H NMR (400 MHz, CDCl ): d 7.55 (1H, d, J 8.8 Hz, Ar-
H), 7.13–7.07 (2H, m, Ar-H), 7.04 (1H, d, J 7.1 Hz, Ar-H),
22
28 2
1
3
H
4.4.11. N-Acetylcarbinolamine 21b from Barton ester
19b and Sb(SPh) . Compound 19b similarly furnished
6
6
.64 (1H, t, J 7.3 Hz, Ar-H), 6.42–6.36 (2H, m, Ar-H),
.31 (1H, br s, Ar-H), 5.62 (1H, s, NCHN), 5.20 [1H, br s,
3
2
6
21b (36.4 mg, 74%); [a] +176.0 (c 0.48, CH Cl ); IR
D 2 2
ꢀ1
1
NCH CH]C(CH ) ], 5.09 [1H, br s, CCH CH]C(CH ) ],
3 2
(film): nmax/cm 3318 (O–H), 1660s (C]O), 1634s; H
NMR (400 MHz, CDCl ): d 7.12 (1H, t, J 7.5 Hz, Ar-H),
2
3 2
2
4
7
5
.99 (1H, d, J 8.2 Hz, CHCO N), 4.31 [1H, dd, J 16.0,
2
3
H
.1 Hz, NCH CH]C(CH ) ], 4.02 [1H, dd, J 16.0,
2
7.06 (1H, d, J 7.2 Hz, Ar-H), 6.70 (1H, t, J 7.3 Hz, Ar-H),
6.47 (1H, d, J 7.8 Hz, Ar-H), 5.47 (1H, s, NCHN), 5.36
(1H, br s, CHOH), 5.19 [1H, br s, NCH CH]C(CH ) ],
3 2
.1 Hz, NCH CH]C(CH ) ], 2.84 (1H, d, J 13.0 Hz,
2
3 2
CH CHCO N), 2.54 (1H, dd, J 13.1, 8.5 Hz, CH CHCO N),
2
2
2
2
2
3 2
2
NCOCH ), 1.75 [3H, s, C(CH ) ], 1.71 [3H, s, C(CH ) ],
.43–2.37 [2H, m, CCH CH]C(CH ) ], 2.36 (3H, s,
5.01 [1H, t, J 6.7 Hz, CCH CH]C(CH ) ], 4.28 [1H, dd,
2 3 2
J 16.0, 7.3 Hz, NCH CH]C(CH ) ], 4.04 [1H, dd, J 16.1,
2 3 2
5.1 Hz, NCH CH]C(CH ) ], 2.33–2.28 [4H, m, 2H of
2 3 2
CCH CH]C(CH ) and 2H of CH CHOH], 2.19 (3H, s,
2 3 2 2
2
3 2
3
3 2
3 2
1
3
1
dC 171.2, 150.6, 137.8, 136.9, 135.9, 134.1, 133.6, 131.2,
.65 [3H, s, C(CH ) ], 1.54 [3H, s, C(CH ) ]; C NMR:
3
2
3 2
1
5
29.0, 124.0, 121.2, 118.2, 116.8, 112.4, 106.3, 83.2, 60.3,
5.7, 43.9, 39.4, 36.8, 25.9, 25.7, 23.1, 18.0, 17.9.
NCOCH ), 1.77 [3H, s, C(CH ) ], 1.68 [6H, s, C(CH ) ],
3 3 2 3 2
1
3
1.53 [3H, s, C(CH ) ]; C NMR: d 170.9, 148.5, 135.3,
3
2
C
1
34.3, 133.6, 128.9, 122.9, 121.2, 118.6, 117.9, 108.0,
4
.4.9. Decarboxylation of Barton ester 19b to 20. Barton
ester 19b (200 mg, 0.52 mmol) in CH Cl (10 ml) on UV
83.8, 83.3, 54.1, 45.1, 45.0, 37.1, 26.0, 25.8, 22.4, 18.2,
18.1; acc. mass: 354.23170, C H N O requires 354.23071.
2
2
22 28 2
irradiation (HP, 125 W) for 30 min in the presence of excess
of t-BuSH (0.6 ml, 5.32 mmol) furnished on purification
4.4.12. Enamide 28b. Compound 21b (60 mg, 0.17 mmol)
in xylene (3 ml) was heated under reflux (10 h). The solvent
was evaporated and the residue obtained was purified by
(
7
(
(
PTLC; Et O/n-hexane, 25%) compound 20 (124.7 mg,
2
2
5
1%) as a yellow oil; [a] +237.9 (c 0.63, CH Cl ); IR
2
D
2
ꢀ
1
1
film): nmax/cm 1643s (amide C]O);
400 MHz, CDCl ): dH 7.11–7.05 (1H, m, Ar-H), 7.03 (1/
H
NMR
PTLC (Et O/n-hexane 20%) to give 28b (42.6 mg, 75%)
2
2
5
as a colourless oil; [a] +223.0 (c 0.83, CH Cl ); IR
D 2 2
3
ꢀ
1
1
4
H, d, J 7.7 Hz, Ar-H), 6.98 (3/4H, d, J 7.1 Hz, Ar-H), 6.69
(film): nmax/cm 3049 (O–H), 1662s (C]O); H NMR
(400 MHz, CDCl ): d 7.07 (1H, t, J 7.5 Hz, Ar-H), 7.01
(
(
1/4H, t, J 7.3 Hz, Ar-H), 6.64 (3/4H, t, J 7.2 Hz), 6.38
1H, d, J 7.7 Hz), 5.54 (3/4H, s, NCHN), 5.23 (1/4H, s,
3
H
(1H, d, J 7.2 Hz, Ar-H), 6.68 (1H, t, J 7.3 Hz, Ar-H), 6.48
(1H, d, J 7.9 Hz, Ar-H), 6.46 (1H, d, J 4.3 Hz, NCH]CH),
5.75 (1H, s, NCHN), 5.20 (1H, d, J 4.3 Hz, NCH]CH),
5.13 [1H, br s, NCH CH]C(CH ) ], 4.96 [1H, t,
NCHN), 5.15 [1H, br s, NCH CH]C(CH ) ], 5.05 [1H, t,
3 2
2
J 7.2 Hz, CCH CH]C(CH ) ], 4.22 [1H, dd, J 15.6,
2
3 2
7
NCH CH]C(CH ) ], 3.61–3.57 (1H, m, NCH CH ), 3.25
.0 Hz, NCH CH]C(CH ) ], 3.99 [1H, dd, J 15.7, 4.4 Hz,
2 3 2
2
3 2
J 6.7 Hz, CCH CH]C(CH ) ], 4.34 [1H, dd, J 15.9,
2 3 2
2
3 2
2
2
(
1H, dd, J 17.0, 10.3 Hz, NCH CH ), 2.45 [1/2H, d, J
2
8.1 Hz, NCH CH]C(CH ) ], 4.04 [1H, dd, J 15.9,
2 3 2
2
6
CCH CH]C(CH ) ], 2.09–2.07 (2H, m, NCH CH ), 2.05
.9 Hz, CCH CH]C(CH ) ], 2.37 [3/2H, d, J 6.8 Hz,
3.7 Hz, NCH CH]C(CH ) ], 2.50 [1H, dd, J 14.9, 7.5 Hz,
2 3 2
CCH CH]C(CH ) ], 2.44 [1H, dd, J 15.0, 7.6 Hz,
2 3 2
2
3 2
2
3 2
2
2
(
C(CH ) ], 1.54 [3H, s, C(CH ) ]; C NMR: dC 169.7,
3H, s, NCOCH ), 1.76 [3H, s, C(CH ) ], 1.67 [6H, s,
CCH CH]C(CH ) ], 2.15 (3H, s, NCOCH ), 1.79 [3H, s,
2 3 2 3
3
3 2
1
3
C(CH ) ], 1.68 [3H, s, C(CH ) ], 1.66 [3H, s, C(CH ) ],
3 2 3 2 3 2
3
2
3 2
1
3
1
50.4, 134.8, 134.1, 133.1, 128.3, 122.7, 121.2, 120.4,
1.59 [3H, s, C(CH ) ]; C NMR: d 168.0, 150.3, 135.1,
3 2 C