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275
After heating the mixture for 15 min, it was cooled to 0°C
and diluted with 2 ml of ice-cold H2O. After extraction with
ethyl acetate (EtOAc) (3 ϫ 5 ml), the organic phase was
dried with anhydrous MgSO4 and concentrated in vacuo.
Preparative thin-layer chromotography (TLC) (15% EtOAc/
the organic phase was extracted with EtOAc and dried over
anhydrous MgSO4, and the solvent was removed in vacuo.
Preparative TLC (15% EtOAc/Hexane) gave 20.6 mg
(64%) of compound 2a. 1H NMR: ␦ 0.55 (3H, s), 0.87 (6H,
d, J ϭ 6.5 Hz), 0.93 (3H, d, J ϭ 6.2 Hz), 1.04–2.42 (m), 4.9
(5H, m), 5.05 (1H, broad s). 13C NMR: ␦ 12.01, 14.00,
18.09, 22.61, 22.90, 23.65, 23.84, 25.55, 25.58, 27.90,
28.01, 30.10, 30.98, 35.95, 39.60, 40.06, 40.97, 45.89,
56.02, 56.56, 75.56, 105.6, 114.20, 124.70, 140.09, 144.29,
152.65.
1
hexane) gave 170 mg (74%) of the product as an oil. H
NMR: ␦ 0.54 (3H, s), 0.88 (6H, d, J ϭ 6.6 Hz), 0.92 (3H, d,
J ϭ 6.1 Hz), 3.80–3.980 (4H, m), 4.82 (1H, t, J ϭ), 4.9 (2H,
bs), 5.19 (1H, s). 13C NMR: ␦ 12.0, 14.56, 19.0, 22.29, 23.0,
23.9, 24.0, 25.0, 26.5, 27.5, 27.7, 27.9, 29.4, 31.3, 34.5,
36.4, 39.2, 40.9, 45.9, 56.5, 65.2, 76.1, 105, 106, 124, 142,
151.0. IR: 3480 cmϪ1
.
2.4. 6-Cyanomethyl-5Z-vitamin D3-3-formate (3c)
In a similar fashion, 6(S)-[3-(2-tetrahydro-2H-pyranyl)
propoxy-3,5-cyclovitamin D3 (2d) [1H NMR: ␦ 0.54 (3H,
s), 0.87 (6H, d, J ϭ 6.9 Hz), 0.92 (3H, d, J ϭ 6 Hz),
1.05–2.33 (m), 3.25–3.90 (4H, m), 4.60 (1H, t, J ϭ 6.8 Hz),
4.89 (2H, bs), 5.18 (1H, s)], and 6(S)-benzyl-3,5-cyclovita-
min D3 (2b) (mixed with ϳ20% of 6(R)-isomer) [1H NMR:
␦ 0.524 (3H, s), 0.88, (6H, d, J ϭ 6.7 Hz), 0.93 (3H, d, J ϭ
6.1 Hz), 1.06–2.3 (m), 3.15 (m), 5.01 (2H, bs), 5.29 (1H),
[␦ 5.45 and 5.52 for the 6(R)-diastereoisomer], and 7.2 (m)
were obtained in 78.5% and 94.4% yields, respectively, by
reaction of ketone 1 (R1 ϭ H, 100 mg, 0.26 mmol) with
2-(3-bromopropoxy)tetrahydro-2H-pyran (81.2 mg, 0.4
mmol) and Mg (12.5 mg, 0.5 mmol), and ketone 1 (R1 ϭ H,
30 mg, 0.08 mmol) with benzylbromide (18.6 mg, 0.1
mmol) and Mg (3.7 mg, 0.15 mmol), respectively.
A solution of 2c (10 mg) and 97% HCOOH (250 l) was
heated at 55°C for 15 min, and then diluted by addition of
H2 (5 ml). The reaction mixture was extracted with ether
(3 ϫ 5 ml); the combined organic phase was dried over
anhydrous MgSO4 and concentrated in vacuo. Chromatog-
raphy of the crude mixture using 20% EtOAc/hexane gave
1
4.5 mg (42.2%) of compound 3c. H NMR: ␦ 0.64 (3H, s),
0.85 (6H, d, J ϭ 6.6 Hz), 0.92 (3H, d, J ϭ 6 Hz), 1.12–2.48
(m), 3.11–3.44 (2H, m), 4.89 (1H, s), 5.09 (1H, m), 5.19
(1H, s), 5.33 (1H, s), 7.99 (1H, s). 13C NMR: ␦ 11.96, 18.81,
22.33, 22.55, 22.60, 22.80, 23.24, 23.28, 23.89, 27.59,
27.99, 29.89, 31.83, 31.91, 36.10, 37.15, 39.49, 40.19,
45.62, 55.55, 56.58, 70.78, 76.86, 77.0, 77.47, 113.53,
116.94, 118.55, 123.22, 136.53, 145.71, 146.62, 160.29.
2.2. 6(S)-Cyanomethyl-3,5-cyclovitamin D3 (2c)
2.5. 6-Cyanomethyl-5E-vitamin D3-formate (4c, ϳ4%
yield)
n-BuLi (1 M solution in hexane, 195 l, 0.2 mmol) was
added to a solution of acetonitrile, freshly distilled from
CaH2 (13.5 l, 0.26 mmol) in anhydrous THF (2.7 ml) in a
round-bottomed flask equipped with a stir bar at Ϫ78°C in
a N2 atmosphere. The solution was stirred at Ϫ78°C for 30
min, and the ketone 1 (R1 ϭ H, 50 mg, 0.13 mmol, in 2.7
ml THF) was added to this lithio-acetonitrile solution via a
cannula. The reaction mixture was allowed to warm from
Ϫ78°C to 25°C in 2 h. Water (5 ml) was added to the
reaction mixture, and the organic phase was extracted with
EtOAc (3 ϫ 5 ml). The combined organic phase was dried
over anhydrous MgSO4 and concentrated in vacuo. Prepar-
ative TLC (5% EtOAc/hexane) produced 30.5 mg (55%) of
compound 2c. 1H NMR: ␦ 0.55 (3H, s), 0.87 (6H, d, J ϭ 6.6
Hz), 0.93 (3H, d, J ϭ 6.2 Hz), 2.91–2.93 (2H, d), 4.98 (1H,
1H NMR: ␦ 0.56 (3H, s), 0.89 (6H, d, J ϭ 6.6 Hz), 0.96 (3H,
d, J ϭ 6.2 Hz), 1.04–2.31 (m), 2.95–3.15 (2H, m), 4.96 (1H,
s), 5.06 (1H, m), 5.11 (1H, s), 5.34 (1H, s), 8.02 (1H, s).
2.6. 6-[2-(1,3-Dioxolanyl)ethyl]vitamin D3-acetate (3e)
A solution of 6(S)-[2-(1,3-dioxolanyl)ethyl]-3,5-cyclovi-
tamin D3 (2e, 10 mg) in 400 l of glacial HOAc was heated
at 60°C for 15 min, and then gently quenched with an
ice-cold saturated NaHCO3 solution. The neutralized mix-
ture was extracted with EtOAc (3 ϫ 5 ml). The combined
organic extract was dried over anhydrous MgSO4 and con-
centrated in vacuo. Preparative TLC (5% EtOAc/hexane)
1
produced 5.4 mg (50%) of compound 3e. H NMR: ␦ 0.55
bs), 5.09 (1H, bs), 5.15 (1H, bs). IR: 2245 and 3400 cmϪ1
.
(3H, s), 0.87 (6H, d, J ϭ 6.8 Hz), 0.94 (3H, d, J ϭ 6.1 Hz),
1.15–1.75 (m), 1.98, (3H, s), 2.10–2.57 (m), 3.88 (4H, m),
4.71–4.89 (2H, m), 4.94, (1H, s), 5.24 (1H, s). Correlation
spectroscopy (COSY) spectrum of 3e confirmed the assign-
ment of ␦ 4.71 and 4.94 as the C19-geminal protons. The
5,6-Z-stereochemistry of this compound was further con-
firmed by irradiation at ␦ 5.24 (C7-H), which showed nu-
clear Overhauser effect with one of the C19 protons. 13C
NMR: ␦ 12.04, 18.86, 21.32, 22.40, 22.54, 22.81, 23.88,
27.82, 27.98, 28.95, 30.02, 30.20, 32.58, 32.01, 38.82,
39.46, 40.31, 45.32, 55.51, 56.54, 64.06, 72.79, 76.51,
Mass spectrum (MS) calculated for C29H45NO: 423.68,
observed 424.6 [M ϩ H]ϩ.
2.3. 6(S)-Vinyl-3,5-cyclovitamin D3 (2a)
To a mixture of ketone 1 (R1 ϭ H, 30 mg, 0.08 mmol)
and excess Mg (7.5 mg, 0.3 mmol) in 1.0 ml THF at room
temperature was added vinyl bromide (0.2 ml of 1 M solu-
tion in THF, 0.2 mmol). The reaction mixture was allowed
to stir at 25°C for 30 m. After quenching with H2O (4 ml),