S. K. Gadakh, A. Sudalai / Tetrahedron: Asymmetry 26 (2015) 118–123
121
4.49–4.51 (m, 1H), 7.16–7.30 (m, 5H); 13C NMR (50 MHz, CDCl3): d
32.5, 37.1, 41.7, 72.6, 75.2, 77.3, 125.8, 128.4, 141.9, 151.5; Anal.
Calcd for C13H15IO3: C, 45.11; H, 4.37. Found: C, 45.10; H, 4.35.
4.2.8. (2S,4S)-4-((tert-Butyldimethylsilyl)oxy)-6-phenylhexane-
1,2-diol 13
20 = +30.7 (c 1, CHCl3); 96% ee by chiral HPLC analysis (Chiral-
[a]
D
cel OD-H column, n-hexane/iPrOH, 90:10, 0.5 mL/min) retention
time 13.512 (98.02%) and 13.020 (1.98%) chiral diol 13. IR (CHCl3,
cmÀ1): mmax 702, 1061, 1108, 1427, 1456, 2858, 2932, 3024,
3068, 3359; 1H NMR (200 MHz, CDCl3): d À0.02 (s, 6H), 0.82 (s,
9H), 1.55–1.79 (m, 4H), 2.41–2.61 (m, 2H), 3.31–3.54 (m, 2H),
3.72–3.79 (m, 1H), 3.90–4.05 (m, 1H), 7.02–7.21 (m, 5H); 13C
NMR (50 MHz, CDCl3): d À4.4, 18.1, 25.9, 32.0, 39.1, 40.1, 46.6,
49.2, 70.0, 125.8, 128.3, 128.4, 142.4; Anal. Calcd for C18H32O3Si:
C, 66.62; H, 9.94. Found: C, 66.61; H, 9.90.
4.2.5. 1-(Oxiran-2-yl)-4-phenylbutan-2-ol 11
To a solution of iodolactone 10 (4 g, 11.56 mmol) in anhydrous
MeOH (50 mL) at 0 °C was added K2CO3 (4.8 g, 34.68 mmol) and
the reaction mixture was stirred for 1 h. Next, MeOH was removed
under vacuum and the mixture was diluted with ethyl acetate. The
organic layer was washed with brine and the aqueous phase was
extracted with ethyl acetate (3 Â 20 mL), dried over anhydrous
Na2SO4, and filtered. The solvent was removed under vacuum
and the crude product was purified by flash chromatography
(petroleum ether/ethyl acetate 6:4) to afford 11 (1.87 g, 84%) as a
colorless oil. IR (CHCl3, cmÀ1): mmax 770, 957, 1010, 1230, 1440,
1560, 2857, 2928, 3048, 3350; 1H NMR (200 MHz, CDCl3): d
1.47–1.87 (m, 4H), 2.15 (s, 1H), 2.47–2.84 (m, 4H), 3.02–3.15 (m,
1H), 3.85–3.92 (m, 1H), 7.16–7.21 (m, 5H); 13C NMR (50 MHz,
CDCl3): d 31.8, 39.0, 39.8, 46.5, 50.5, 69.8, 125.8, 128.4, 141.8; Anal.
Calcd for C12H16O2: C, 74.97; H, 8.39. Found: C, 75.01; H, 8.40.
4.2.9. (3S,5R)-3,5-Dihydroxy-7-phenylheptanenitrile 15
To a mixture of sodium cyanide (0.16 g, 3.27 mmol) and the
silylated epoxide 14 (0.5 g, 1.63 mmol) in ethanol (6 mL) was
added trifluoroacetic acid (0.019 g, 0.16 mmol) and the resulting
bright yellow solution was refluxed under nitrogen at 60 °C for
4 h. After completion of the reaction (monitored by TLC), it was
cooled to room temperature and the excess cyanide was quenched
with aqueous NaClO2, diluted with water (3 mL) and EtOAc
(10 mL). The organic layer was separated and the aqueous layer
was extracted with EtOAc (3 Â 5 mL). After extraction the aqueous
layer was poured into aqueous KMnO4 solution before disposal.
The combined organic extracts were washed with brine, dried over
anhydrous Na2SO4, and concentrated under reduced pressure to
give a crude product, which was purified by column chromatogra-
phy with petroleum ether/ethyl acetate (7:3) to give 15 (0.3 g, 84%)
4.2.6. tert-Butyldimethyl((1-(oxiran-2-yl)-4-phenylbutan-2-yl)-
oxy)silane 12
To a solution of secondary alcohol 11 (1.5 g, 7.81 mmol) in dry
CH2Cl2 (30 mL) at 0 °C were added imidazole (1.1 g, 15.63 mmol)
and tert-butyldimethylsilyl chloride (1.77 g, 11.72 mmol). The
reaction mixture was then stirred at 0 °C for 1 h. After completion
of the reaction (monitored by TLC), it was diluted with CH2Cl2,
washed with water, brine and dried over anhydrous Na2SO4.
Removal of the solvent under reduced pressure gave the crude
product, which was then purified by column chromatography over
silica gel with petroleum ether/ethyl acetate (9:1) to give 12
(2.15 g, 90%) as a colorless viscous liquid. IR (CHCl3, cmÀ1): mmax
1062, 1108, 2856, 2928, 3048; 1H NMR (200 MHz, CDCl3): d
À0.03 (s, 6H), 0.83 (s, 9H), 1.53–1.84 (m, 4H), 2.34–2.42 (m, 1H),
2.51–2.73 (m, 3H), 2.91–2.95 (m, 1H), 3.80–3.91 (m, 1H), 7.05–
7.22 (m, 5H); 13C NMR (50 MHz, CDCl3): d À4.6, 18.0, 25.9, 31.2,
39.2, 66.8, 70.6, 71.2, 125.8, 128.2, 128.4, 141.9; Anal. Calcd for
as a colorless liquid. [
a
]
20 = À5.1 (c 0.1, CHCl3); IR (CHCl3, cmÀ1):
D
mmax 700, 906, 1453, 1640, 2127, 2857, 2927, 3026, 3070, 3379;
1H NMR (200 MHz, CDCl3): d 1.21–1.80 (m, 6H), 2.66–2.80 (m,
2H), 3.53–3.85 (m, 4H), 7.17–7.28 (m, 5H); 13C NMR (50 MHz,
CDCl3): d 31.0, 32.6, 33.5, 33.7, 49.7, 73.1, 120.9, 126.8, 128.3,
128.9, 139.9; Anal. Calcd for C13H17NO2: C, 71.21; H, 7.81. Found:
C, 71.15; H, 7.90.
4.2.10. (+)-(4R,6R)-4-Hydroxy-6-(2-phenylethyl)-tetrahydro-2H-
pyran-2-one 3
C
18H30O2Si: C, 70.53; H, 9.87. Found: C, 70.55; H, 9.83.
To a solution of cyano diol 15 (0.2 g, 0.91 mmol) in MeOH
(5 mL) was added aq HCl (2 mL). The reaction mixture was stirred
at 50 °C for 12 h. The solvent was removed under reduced pressure,
the residue extracted with ethyl acetate, and organic layer was
washed with brine. The aqueous layer was extracted with ethyl
acetate (3 Â 5 mL). The combined organic layers were dried over
anhydrous Na2SO4, concentrated under reduced pressure, and
purified by silica gel column chromatography using petroleum
ether/ethyl acetate (6:4) as eluent to afford lactone 3 (0.158 g,
79%) as a colorless solid, mp: 106–107 °C (lit.4e mp 108 °C).
4.2.7. tert-Butyldimethyl(((R)-1-((R)-oxiran-2-yl)-4-phenyl-
butan-2-yl)oxy)silane 14
To a solution of (R,R)-(salen)Co(II) complex (0.043 g, 0.1 mmol)
in toluene (4.0 mL) was added acetic acid (0.04 g, 7.3 mmol). It was
then allowed to stir at 0 °C in the open air for 30 min over which
time the color of the solution changed from orange-red to dark
brown. It was then concentrated in vacuo to obtain the (R,R)-(sale-
n)Co(III) complex as a brown solid. To a solution of Co–salen com-
plex (0.02 g, 0.5 mol %) and racemic epoxide 12 (2 g, 6.55 mmol) in
THF (1 mL) at 0 °C was added H2O (0.059 g, 3.27 mmol) slowly over
5 min. The reaction mixture was allowed to warm to 0 °C and stir-
red for 14 h. After completion of the reaction (monitored by TLC),
the solvent was removed in vacuo. The crude product was purified
by column chromatography over silica gel. The solvent system was
petroleum ether/ethyl acetate (19:1) for chiral epoxide 14 (0.96 g,
48%) and petroleum ether/ethyl acetate (7:3) for chiral diol 13
[a] [a]
20 = +67.5 (c 2, CHCl3) {lit.4h 20 = +68.8 (c 2.29, CHCl3)}; IR
D D
(CHCl3, cmÀ1): mmax 1036, 1135, 1370, 1435, 1650, 1730, 2980,
3442; 1H NMR (200 MHz, CDCl3): d 1.73–2.01 (m, 4H), 2.61–2.86
(m, 4H), 3.05 (s, 1H), 4.32–4.39 (m, 1H), 4.68–4.72 (m, 1H), 7.16–
7.28 (m, 5H); 13C NMR (50 MHz, CDCl3): d 31.1, 35.8, 37.6, 38.6,
62.5, 75.3, 126.1, 128.4, 128.5, 141.0, 171.0; Anal. Calcd for
C13H16O3: C, 70.89; H, 7.32. Found: C, 70.85; H, 7.30.
(0.98 g, 47%). [
a]
D
20 = À5.5 (c 1, CHCl3); 98% ee by chiral HPLC anal-
4.2.11. Yashabushidiol A 4
ysis (Chiralcel OD-H column, n-hexane/iPrOH, 97:03, 0.5 mL/min)
retention time 17.517 (99.02%) and 15.747 (0.98%) for chiral epox-
ide 14. IR (CHCl3, cmÀ1): mmax 702, 1063, 1108, 1427, 2858, 2932,
3048; 1H NMR (200 MHz, CDCl3): d À0.03 (s, 6H), 0.83 (s, 9H),
1.53–1.84 (m, 4H), 2.34–2.42 (m, 1H), 2.51–2.73 (m, 3H), 2.91–
2.95 (m, 1H), 3.80–3.91 (m, 1H), 7.05–7.22 (m, 5H); 13C NMR
(50 MHz, CDCl3): d À4.6, 18.0, 25.9, 31.2, 39.2, 66.8, 70.6, 71.2,
125.8, 128.2, 128.4, 141.9; Anal. Calcd for C18H30O2Si: C, 70.53;
H, 9.87. Found: C, 70.55; H, 9.83.
To a suspension of Mg (0.06 g, 2.45 mmol) in anhydrous THF
(5 mL) at 25 °C taken in a round bottomed flask equipped with a
condenser (cool water circulation) was added benzyl bromide
(0.29 mL, 2.45 mmol) in a dropwise manner followed by CuI
(0.031 mg, 0.16 mmol) and the mixture was allowed to stir for
0.5 h. The mixture was then cooled to 0 °C and chiral epoxide 13
(0.5 g, 1.63 mmol) in THF (3 mL) was added. The reaction mixture
was warmed to 25 °C and stirred for 1 h. Upon completion, the
reaction was quenched with saturated NH4Cl solution (10 mL)