2106
E. Palombo et al.
LETTER
(6) (a) Audran, G.; Galano, J.-M.; Monti, H. Eur. J. Org. Chem.
2001, 2293. (b) Palombo, E.; Audran, G.; Monti, H.
Tetrahedron Lett. 2003, 44, 6463.
(15) Griffith, W. P.; Ley, S. V. Aldrichimica Acta 1990, 23, 13.
(16) Lindgren, B. O.; Nilsson, T. Acta Chem. Scand. 1973, 27,
888.
(7) Audran, G.; Uttaro, J.-P.; Monti, H. Synlett 2002, 1261.
(8) Details of the X-ray structure can be obtained from the
Cambridge Crystallographic Data Centre: CCDC 271170.
(9) Corey, E. J.; Venkateswarlu, A. J. Am. Chem. Soc. 1972, 94,
6190.
(10) Haroutounian, S. A. In Encyclopedia of Reagents for
Organic Synthesis, Vol. 6; Paquette, L. A., Ed.; John Wiley
and Sons, Inc.: Chichester, 1995, 4208–4213.
(17) Kraus, G. A.; Taschner, M. J. J. Org. Chem. 1980, 45, 1175.
(18) Preparation and Spectroscopic Data of (+)-11.
To a stirred solution of (–)-10 (300 mg, 1.21 mmol) in a
mixture of t-BuOH (20 mL) and 2-methyl-2-butene (2.5
mL), a solution of 80% NaClO2 (683 mg, 6.04 mmol) and
NaH2PO4 (1.16 g, 9.67 mmol) in H2O (10 mL) was added at
r.t. The resulting mixture was stirred for 15 min then diluted
with brine. The aqueous phase was saturated with NaCl and
extracted thoroughly three times with EtOAc. The combined
organic phases were washed with brine, dried, filtered, and
concentrated. The residue was purified by silica gel column
chromatography to give 260 mg (81% yield) of pure acid
(+)-11 as white crystals; mp 130 °C; [a]D25 +7.9 (c 1.0,
CHCl3). IR (KBr): n = 3426, 1702, 1668, 1162 cm–1. 1H
NMR (300 MHz, CDCl3): d = 9.58 (br s, 1 H), 8.02 (br s, 1
H), 7.39 (t, J = 1.8 HZ, 1 H), 6.73 (dd, J = 1.8, 0.6 HZ, 1 H),
2.78 and 2.64 (ABX, J = 17.0, 4.9, 4.4 Hz, 2 H), 2.32 (m, 2
H), 1.90 (m, 1 H), 1.65–1.25 (m, 5 H), 0.89 (s, 3 H), 0.85 (s,
3 H). 13C NMR (75 MHz, CDCl3): d = 194.3 (C), 181.6 (C),
146.9 (CH), 143.9 (CH), 127.6 (C), 108.7 (CH), 46.2 (CH),
42.5 (CH), 41.2 (CH2), 40.9 (CH2), 33.6 (C), 30.5 (CH3),
30.1 (CH2), 20.9 (CH2), 20.0 (CH3). Anal. Calcd for
C15H20O4: C, 68.16; H, 7.63. Found: C, 67.89; H, 7.67.
(19) Gemal, A. L.; Luche, J.-L. J. Am. Chem. Soc. 1981, 103,
5454.
(11) Barton, D. H. R.; McCombie, S. W. J. Chem. Soc., Perkin
Trans. 1 1975, 1574.
(12) Preparation and Spectroscopic Data of (+)-7.
To a stirred solution of cyanohydrin 6 (1.41 g, 4.30 mmol) in
dry CH2Cl2 (40 mL) was added at 0 °C DMAP (4.20 g, 34
mmol) and phenyl chlorothionoformate (2.40 mL, 17.2
mmol) under an argon atmosphere. After 12 h at r.t., the
reaction mixture was poured into H2O and extracted with
Et2O. The combined organic extracts were washed with
H2O, dried, filtered and concentrated. To a stirred solution of
the crude phenoxythiocarbonyl ester in toluene (30 mL) was
added tri-n-butyltin hydride (4.56 mL, 17.2 mmol) and a
catalytic amount of AIBN in toluene (20 mL) under an argon
atmosphere. The reaction mixture was stirred under reflux
for 1 h, cooled and concentrated. The resulting oily residue
was purified by silica gel column chromatography to give
25
827 mg of pure (+)-7 (65% yield for the two steps); [a]D
+19.8 (c 1.0, CHCl3). IR (neat): n = 2958, 2243, 1168 cm–1.
1H NMR (300 MHz, CDCl3): d = 3.67 and 3.56 (ABX,
J = 10.4, 4.2, 3.0 Hz, 2 H), 2.47 and 2.40 (ABX, J = 17.5,
5.1, 3.9 Hz, 2 H), 1.73–1.60 (m, 2 H), 1.53–1.32 (m, 4 H),
1.25–1.10 (m, 2 H), 0.96 (s, 3 H), 0.94 (s, 3 H), 0.87 (s, 9 H),
0.03 (s, 6 H). 13C NMR (75 MHz, CDCl3): d = 120.1 (C),
65.6 (CH2), 44.1 (CH), 41.9 (CH2), 38.9 (CH), 34.1 (C), 30.8
(CH3), 30.3 (CH2), 25.8 (3 × CH3), 21.4 (CH2), 20.2 (CH3),
18.2 (C), 15.3 (CH2), –5.6 (2 × CH3). Anal. Calcd for
C17H33NOSi: C, 69.09; H, 11.25. Found: C, 68.92; H, 11.28.
(13) Preparation and Spectroscopic Data of (–)-8.
A suspension of nitrile (+)-7 (800 mg, 2.71 mmol) and para-
toluenesulfonic acid monohydrate (1.13 g, 5.94 mmol) in
toluene (20 mL) was placed in an oil bath at 120 °C. After
3.5 h, the solution was cooled to r.t. and filtered through a
pad of Celite. The solvent was evaporated and a silica gel
column chromatography gave 420 mg (85% yield) of (-)-8;
[a]D25 –33.9 (c 1.0, CHCl3). IR (neat): n = 2958, 1726, 1146
cm–1. 1H NMR (300 MHz, CDCl3): d = 4.24 and 3.74 (ABX,
J = 11.0, 11.0, 4.7 HZ, 2 H), 2.62 and 2.16 (ABX, J = 18.1,
12.4, 5.7 Hz, 2 H), 1.75–1.36 (m, 6 H), 1.32 (td, J = 11.5, 5.5
Hz, 1 H), 1.16 (td, J = 13.4, 4.3 Hz, 1 H), 0.84 (s, 3 H), 0.79
(s, 3 H). 13C NMR (75 MHz, CDCl3): d = 171.5 (C), 74.3
(CH2), 44.6 (CH), 40.8 (CH2), 32.7 (CH), 31.9 (C), 30.9
(CH2), 29.1 (CH3), 27.5 (CH2), 20.4 (CH2), 19.0 (CH3).
Anal. Calcd for C11H18O2: C, 72.49; H, 9.95. Found: C,
72.76; H, 9.97.
(20) Preparation and Spectroscopic Data of (+)-Ricciocarpin
A (1).
A solution of (+)-11 (160 mg, 0.60 mmol) and CeCl3·7H2O
(450 mg, 1.21 mmol) in MeOH (20 mL) was stirred 12 h at
r.t. The solution was cooled to –18 °C, NaBH4 (204 mg, 5.40
mmol) was added in three portions (3 × 1 h) and the mixture
was slowly allowed to rise to r.t. After 12 h, the reaction
mixture was poured into ice-water, acidified (HCl 6 N,
pH = 1) and stirred for 30 min at r.t. The solution was
saturated with NaCl and extracted with EtOAc. The
combined organic extracts were washed with brine, dried
and filtered. Concentration of the filtrate followed by silica
gel column chromatography gave 127 mg (85% yield) of a
6:1 mixture of (+)-1 and the C-3 epimer. Two
recrystallizations from MeOH afforded pure (+)-
ricciocarpin A(1) as white needles; mp 109 °C [lit.4 mp
110 °C]; [a]D25 +17.5 (c 1.0, CH2Cl2). IR (KBr): n = 2963,
1722, 1162, 1029 cm–1. 1H NMR (300 MHz, CDCl3): d =
7.43 (br s, 1 H), 7.40 (m, 1 H), 6.39 (m, 1 H), 5.27 (dd,
J = 9.5, 4.5 Hz, 1 H), 2.40 (td, J = 12.1, 3.5 Hz, 1 H), 2.24–
2.14 (m, 1 H), 2.06 and 1.93 (ABMX, JAB = 14.5 Hz,
JAX = JAM = 9.5 Hz, JBM = 7.0 Hz, JBX = 4.5 Hz, 2 H), 1.68–
1.23 (m, 5 H), 1.15 (td, J = 13.8, 4.3 Hz, 1 H), 0.91 (s, 6 H).
13C NMR (75 MHz, CDCl3): d = 175.1 (C), 143.6 (CH),
139.6 (CH), 124.8 (C), 108.5 (CH), 71.7 (CH), 42.3 (CH),
40.4 (CH2), 38.9 (CH), 33.7 (C), 29.8 (CH2), 29.7 (CH3),
27.2 (CH2), 21.0 (CH2), 18.5 (CH3). Anal. Calcd for
C15H20O3: C, 72.55; H, 8.12. Found: C, 72.31; H, 8.09.
(14) (a) Mangoni, L.; Adinolfi, M.; Laonigro, G.; Caputo, R.
Tetrahedron 1972, 28, 611. (b) Bock, I.; Bornowski, H.;
Ranft, A.; Theis, H. Tetrahedron 1990, 46, 1199.
Synlett 2005, No. 13, 2104–2106 © Thieme Stuttgart · New York