A Convenient Synthesis of (+/-)-talo-Quercitol (1-Deoxy-neo-Inositol) and (+/-)-vibo-Quercitol (1-Deoxy-myo-Inositol) via Ene Reaction of Singlet Oxygen

Full text of DOI:10.1021/jo971978q

J . Org. Chem. 1998, 63, 2039-2041
2039
Notes
gala-quercitol.10 Here with we describe a short and
efficient synthesis of (()-talo-quercitol and (()-vibo-
quercitol starting from commercial 1,3-cyclohexadiene
where we used again ene reaction of singlet oxygen.11
A Con ven ien t Syn th esis of
(()-ta lo-Qu er citol (1-Deoxy-n eo-In ositol)
a n d (()-vibo-Qu er citol
(1-Deoxy-m yo-In ositol) via En e Rea ction of
Sin glet Oxygen
Resu lts a n d Discu ssion
Ahmet Maras¸,† Hasan Sec¸en,† Yas¸ar Su¨tbeyaz,*,† and
Metin Balcı*,‡
1,4-Cyclohexadiene 1 was used as the starting material
for the synthesis of talo-quercitol. OsO4-catalyzed NMO
oxidation12 of 1 afforded diol 2. The resulting cis-diol 2
was protected by ketal formation with 1,2-dimethoxypro-
pane. Tetraphenylporphyrin-sensitized photooxygen-
ation of ketal 3 in methylene chloride at room tempera-
ture gave the hydroperoxide 4 in high yield, via ene
reaction of singlet oxygen, as the sole product (Scheme
1). The peroxide linkage is highly susceptible to reduc-
tive cleavage by a variety of reductants.13 Selective
reduction of peroxide linkage was performed with thio-
urea under very mild conditions to give the alcohol 5a .
Since the only oxygen-oxygen bond breaks in this
reaction, it preserves the configuration at the peroxide-
bonded carbon atom. For further structural proof, 5a was
converted to the corresponding acetate 5b which has been
fully characterized on the basis of the spectroscopic data.
Proton and carbon NMR studies of 5b indicated the
formation of an unsymmetrical compound as expected.
The proton adjacent to the acetoxy group appears as a
multiplet at 5.28 ppm, the alkoxy protons at 4.32 ppm
as a multiplet, and the methylene protons appear as an
AB system at 2.31 and 1.65 ppm. An 11-line 13C NMR
spectrum is also in agreement with the proposed consti-
tution. However, on the basis of NMR data alone we
were not able to assign the correct configuration of the
acetoxy group. The configuration of the acetoxyl group
was confirmed by observation of NOE effects. Irradiation
at the resonance signals of alkoxy protons at δ ) 4.32
caused signal enhancement at the resonances of the
adjacent double bond proton, methylenic protons, and
especially the methyl resonance (acetyl group) at δ )
1.92. These observations clearly indicate the anti-con-
figuration of acetoxyl group in 5b. Singlet oxygen is quite
sensitive to steric consideration and approaches the
substrate predominantly, if not exclusively, from the less
congested side.14 The pronounced stereoselectivity of this
Department of Chemistry, Faculty of Arts and Sciences,
Atatu¨rk University, 25240 Erzurum, Turkey, and
Department of Chemistry, Faculty of Arts and Sciences,
Middle East Technical University, 06531 Ankara, Turkey
Received October 28, 1997
The polyhydroxy cyclohexanes have been an interest
to those concerned with carbohydrates1 . The first known
cyclohexanepentol was a dextrorotatory cyclitol obtained
from the acorns of Quercus species (oaks)2 , hence the
name (+)-proto-quercitol. “Quercitol” has been used as
a generic term for cyclohexanepentols. Ten diastereoi-
somers are predicted for the quercitols. All 10 are known
and only the (+)-proto,2 (-)-proto,3 and (-)-vibo4 stereo-
isomers have been found in nature. Methods which have
been used for quercitol synthesis include reduction
(hydrogenation) of inososes, inosos oximes, or deoxyino-
soses; hydrogenation of bromoquercitols; reduction of
anhydroinositols; and transformation of conduritols.5
Meanwhile, synthesis of talo-quercitol and vibo-quercitol
was described by McCasland6 and Nakajima7 starting
from haloinositols and conduritol-E, respectively. In all
previously reported syntheses, starting materials have
been natural products or compounds which required
many steps to synthesize. Recently we described a
simple route leading to the synthesis of quercitols where
we applied for the first time a singlet oxygen ene reaction
combined with the singlet oxygen [2 + 4] addition8
successively to the synthesis of proto-quercitol9,10 and
† Atatu¨rk University
‡ Middle East Technical University
(1) Anderson. L. In The Carbohydrates, Chemistry and Biochemistry;
Pigman, W.; Horton, D., Eds.; Academic Press: New York, 1972; Vol.
IA, pp 519-579.
(2) Braconnot, H. Ann. Chem. Phys. 1849, 27, 392.
(3) Plouvier, V. C. R.. Seances. Acad. Sci. Paris 1961, 253, 3047.
(4) Posternak, T. The Cyclitols, 1st ed.; Hermann: Paris, 1965; pp
103-107.
(5) For characterization and synthesis of cyclitols, see: Hudlicky,
T.; Cebulak, M. Cyclitols and Derivatives; VCH: New York, 1993; pp
134-150.
(6) (a) McCasland, G. E.; Furuta, S.; J ohnson, L. F.; Shoolery, J . N.
J . Am. Chem. Soc. 1961, 83, 2335. (b) McCasland, G. E.; Furuta, S.;
Bartuska, V. J . Org. Chem. 1963, 28, 2096.
(7) Nakajima, M.; Kurihara, N., Chem. Ber. 1961, 94, 515-523.
(8) For application of singlet oxygen [2 + 4] addition to the synthesis
of conduritols, see: (a) Su¨tbeyaz, Y.; Sec¸en, H.; Balcı, M. J . Chem. Soc.,
Chem. Commun.. 1988, 1330. (b) Sec¸en, H.; Su¨tbeyaz, Y.; Balcı, M.
Tetrahedron Lett. 1990, 31, 1323. (c) Balcı,, M.; Su¨tbeyaz, Y.; Sec¸en,
H. Tetrahedron 1990, 46, 3715. (d) Sec¸en, H.; Gu¨ltekin, S.; Su¨tbeyaz,
Y.; Balcı, M. Synth. Commun. 1994, 24, 2103.
(11) (a) Wasserman, H. H., Ives, J . L. Tetrahedron 1981, 37, 1825.
(b) Carless, H. A. J .; Billinge, J . R.; Oak, O. Z. Tetrahedron Lett. 1989,
30, 3113. (c) Carless, H. A. J .; Oak, O. Z. Tetrahedron Lett. 1989, 30,
1719. (d) Carless, H. A. J .; Busia, K. Tetrahedron Lett. 1990, 31, 1617.
(e) Hudlicky, T.; Price, J . D.; Luna, H.; Andersen, C. M. Synlett 1990,
309. (f) Hudlicky, T.; Rulin, F.; Tsunoda, T.; Luna, H.;, Andersen, C.;
Price, J . D. Isr. J . Chem. 1991, 31, 229. (g) Hudlicky, T.; Luna, H.;
Olivo, H. F.; Andersen, C.; Nugent, T.; Price, J . D. J . Chem. Soc., Perkin
Trans. 1 1991, 2907. (h) Carless, H. A. J .; Malik, S. S.; Tetrahedron
Asymmetry 1992, 3, 1135. (i) Adam, W.; Schuhmann, R. M. J . Org.
Chem. 1996, 61, 874. (j) Balcı, M. Pure Appl. Chem. 1997, 69, 97.
(12) (a) VanRheenen, V.; Kelly, R. C.; Cha, D. Y. Tetrahedron Lett.
1976, 23, 1973. (b) VanRheenen, V.; Cha, D. Y.; Hartley, W. M. Organic
Synthesis; Wiley: New York, 1988; Collect. Vol. 6, p 342.
(9) Sec¸en, H., Salamcı, E., Su¨tbeyaz, Y., Balcı, M. Synlett 1993, 609.
(10) Salamcı, E.; Sec¸en, H.; Su¨tbeyaz, Y.; Balcı, M. J . Org. Chem.
1997, 62, 2453.
(13) Balcı, M. Chem. Rev. (Washington, D.C.) 1981, 81, 91.
(14) Frimer, A. A. In The Chemistry of Functional Groups, Peroxides;
Patai, S., Ed.; J ohn Wiley: New York, 1983.
S0022-3263(97)01978-6 CCC: $15.00 © 1998 American Chemical Society
Published on Web 02/28/1998

2040 J . Org. Chem., Vol. 63, No. 6, 1998
Notes
Sch em e 1
Sch em e 2
peracid.16 The isolated epoxide 8 was submitted to acid-
catalyzed ring-opening reaction in acetic anhydride and
we have isolated a mixture consisting of talo-penta-
acetates 7b and vibo-pentaacetate 915 in a ratio of 4:1.
The resulting mixture has been separated on a silica gel
column. Ammonolysis of 7b and 9 furnished the corre-
sponding quercitols.
Exp er im en ta l Section
Gen er a l P r oced u r e. Melting points were determined on a
melting apparatus. Infrared spectra were obtained from KBr
pellets on an infrared spectrophotometer. 1H NMR spectra were
recorded on 200 MHz spectrometer and reported in δ units with
SiMe4 as internal standard. All column chromatography was
performed on silica gel (60 mesh).
ene reaction is rationalized by the strong steric effect
between the incoming singlet oxygen and bulky methyl
groups. In the next step, the double bond has to be
oxidized in a cis fashion. The oxidation of olefins with
permanganate is not commonly used as a preparative
method because of its typically low selectivity. However,
we chose to examine the oxidation of acetate 5b with
permanganate with the intention of introducing the two
hydroxyl groups in a cis configuration to the double bond
to complete the synthesis of talo-quercitol. Treatment
of 5b with KMnO4 (-5 °C) gave to our surprise only one
diol 6a in an isolated yield of 56%. Careful NMR studies
did not reveal the formation of any trace of the other
diastereomer. For characterization of the product, 6a
was converted to the corresponding triacetate 6b, which
upon hydrolysis gave talo-quercitol 7a (Scheme 1). For
further characterization of 7a we prepared the corre-
sponding pentaacetate in 85% yield. The spectral data
of 7a and 7b were identical with those reported in the
literature.6
4-Cycloh exen e-cis-1,2-d iol (2). The reported procedure12
was used for the synthesis of 4-cyclohexene-cis-1,2-diol 2 in 65%
yield: mp 69-70 °C, colorless crystals from ethyl acetate:hexane
1
(3:1); H NMR (200 MHz, CDCl3) δ 5.55 (m, 2H), 3.91 (m, 2H),
2.28 (m, 4H); 13C NMR (50 MHz, CDCl3) δ 125.70, 70.90, 32.93.
(3a R,7a S)-2,2-Dim et h yl-3a ,4,7,7a -t et r a h yd r ob en zo-1,3-
d ioxole (3). The described ketalization procedure in the
literature8a,17 was applied to the synthesis of 3 (colorless liquid,
1
96%); H NMR (200 MHz, CDCl3) δ 5.80 (m, 2H), 4.35 (m, 2H),
2.25 (m, 4H), 1.41 (s, 3H), 1.32 (s, 3H); 13C NMR (CDCl3, 50 MHz)
δ 126.00, 107.97, 73.56, 28.78, 27.49, 25.35.
(1a ,4b,6a )-8,8-Dim eth yl-7,9-d ioxa -bicyclo[4.3.01,6]n on -2-
en -4-yl h yd r op er oxid e 4. To a stirred solution of ketal 3 (1.0
g, 6.4 mmol) in 150 mL of CH2Cl2 was added 20 mg of
tetraphenylporphyrin (TPP). The resulting mixture was irradi-
ated with a tungsten halogen projection lamp (500 W) while
oxygen was being passed through the solution and the mixture
was stirred at room temperature for 12 h. Evaporation of the
solvent (30 °C, 20 mmHg) and chromatography of the residue
on a Florisil column (30 g) eluting with n-hexane/ CH2Cl2 (7:4)
gave pure hydroperoxide 4 (1.15 g, 95%, colorless liquid): 1H
NMR (200 MHz, CDCl3) δ 8.15 (s, 1H), 6.06 (dm, A part of AB
system, J ) 10.4 Hz, 1H), 5.95 (dm, B part of AB system, J )
10.4 Hz, 1H), 4.70 (m, 1H), 4.68 (m, 2H), 2.45 (dt, A part of AB
system, J ) 13.6, 3.9 Hz, 1H), 1.95 (ddd, B part of AB system,
J ) 13.6, 8.8, 2.8 Hz, 1H), 1.37 (s, 3H), 1.36 (s, 3H); 13C NMR
(CDCl3, 50 MHz) δ 129.72, 129.46, 109.29, 77.21, 72.85, 71.85,
30.15, 28.24, 26.82; IR (KBr, cm-1) 3462, 3387, 3004, 2953, 1651,
1472, 1395, 1242, 1165, 1063, 859.
For the synthesis of vibo-quercitol 10, one should
introduce two hydroxyl group to the double bond in 5 in
a trans fashion (Scheme 2). Therefore, we have submit-
ted 5b to epoxidation reaction15 with m-chloroperbenzoic
acid in an ultrasonic bath and obtained the epoxide in
94% yield as the sole product 8, whose exact configuration
was determined on the basis of NMR spectral data and
NOE experiments. The directive effect of the hydroxyl
group has been suggested to arise because of hydrogen
bonding between the hydroxyl group and the attacking
(1a ,4b ,6a )-8,8-Dim e t h yl-4-h yd r oxy-7,9-d ioxa -b icyclo-
[4.3.01.6]n on -2-en e 5a . To a magnetically stirred slurry of 0.82
g (10.7 mmol) of thiourea in 25 mL of methanol was added a
solution of 1.00 g (5.37 mmol) of anti-hydroperoxide 4 in 50 mL
of methanol at 25 °C. After complete of addition (ca. 10 min),
(16) House, H. O. In Modern Synthetic Reactions, 2nd ed.; Benjamin/
Cummings, Menlo Park, CA, 1972; p 303.
(15) Sec¸en, H.; Maras¸, A.; Su¨tbeyaz, Y.; Balcı, M. Synth. Commun.
1992, 22, 2613.
(17) Yang, N. C.; Chen, M. J .; Chen, P. J . Am. Chem. Soc. 1984,
106, 7310.

Notes
J . Org. Chem., Vol. 63, No. 6, 1998 2041
the mixture was stirred for 1 h, the solid was removed by
filtration, methanol was evaporated (35 °C, 20 mmHg), and the
residue purified by column chromatography on silica gel (10 g)
eluting with chloroform afforded pure 5a (0.82 g, 90%, colorless
liquid): 1H NMR (200 MHz, CDCl3) δ 5.86 (dm, A part of AB
system, J ) 11.4 Hz, 1H), 5.65 (ddd, B part of AB system, J )
11.4, 4.3, 2.4 Hz, 1H), 4.45 (m, 3H), 2.44 (ddm, A part of AB
system, J ) 13.8, 3.7 Hz, 1H), 1.95 (ddd, B part of AB system,
J ) 13.8, 9.5, 2.4 Hz, 1H), 1.32 (s, 6H); 13C NMR (CDCl3, 50
MHz) δ 135.34, 129.10, 109.30, 73.40, 71.91, 63.82, 35.83, 28.12,
26.35; IR (KBr, cm-1) 3438, 3004, 2953, 2902, 1472, 1395, 1242,
1089, 1038, 885. Anal. Calcd for C9H14O3: C, 63.51; H, 8.29.
Found: C, 63.30; H, 8.12.
J ) 10.8, 2.72 Hz, 1H), 5.21 (dd, B part of AB system, J ) 10.8,
3.2 Hz, 1H), 5.25 (m, 1H), 2.14 (s, 3H), 2.13 (s, 3H), 2.04 (m,
2H), 2.00 (s, 9H); 13C NMR (CDCl3, 50 MHz) δ 170.72, 170.52,
170.45, 170.20, 70.07, 69.51, 68.20, 67.31, 66.56, 29.36, 21.45,
21.28, 21.19, 21.13; IR (KBr, cm-1) 2995, 1745, 1370, 1230, 1045.
(1a ,2b ,4b ,5b ,7a )-9,9-Dim et h yl-5-h yd r oxy-3,8,10-t r ioxa -
tr icyclo[5.3.02.4.01.7]d eca n e 8. To a solution of alkene 5a (1
g, 5.8 mmol) in 5 mL of CH2Cl2 were added 2 g of Na2CO3 and
1.7 g (6.96 mmol) of m-chloroperbenzoic acid (m-CPBA). The
mixture was sonicated in an ultrasonic bath (50 kHz) for 3 h.
The precipitate was filtered and washed with 50 mL of CH2Cl2.
The combined CH2Cl2 solutions were filtered from a silica gel
column (5 g) eluting with CH2Cl2. Evaporation of the solvent
gave 8 (1.01 g, 94%): mp 60-61 °C, colorless solid from CH2-
Cl2; 1H NMR (200 MHz, CDCl3) δ 4.31 (m, 3H), 3.39 (br.d, A
part of AB system, J ) 4.00 Hz, 1H), 3.20 (dt, B part of AB
system, J ) 4.0, 1.1 Hz, 1H,), 2.15(ddd, J ) 14.3, 5.6, 2.4 Hz,
1H), 1.61 (ddd, J ) 14.3, 10,8, 1.4 Hz, 1H,), 1.40 (s, 3H), 1.33 (s,
3H); 13C NMR (CDCl3, 50 MHz) δ 109.66, 73.93, 70.35, 64.39,
56.38, 55.72, 27.98, 27.58, 25.72; IR (KBr, cm-1) 3438, 3004,
2978, 1421, 1395, 1268, 1191. Anal. Calcd for C9H14O4: C, 63.68;
H, 8.25. Found: C,63.42; H, 8.11.
Acetolysis of Ep oxy Keta l 8. Ketal 8 (500 mg, 2.68 mmol)
was dissolved in 5 mL of acetic anhydride, to it was added 50
mg of concentrated H2SO4, and the resulting mixture was
refluxed for 6 h. The mixture was added to 50 mL of water,
extracted with ethyl acetate (3 × 50 mL), and dried (Na2SO4).
Evaporation of the solvent under reduced pressure gave a
mixture consisting of talo-quercitol pentaacetate 7b and vibo-
quercitol pentaacetate 9 in a ratio of 80:20 determined by 1H
NMR (0.8 g, combined yield 80%). Pentaacetates 7b and 9 were
separated by column chromatography using silica gel and eluting
with hexane:ethyl acetate (solvent composition was gradated
from starting 85:15 to 75:25) to give talo-quercitol pentaacetate
7b (0.508 g, 50%) and vibo-quercitol pentaacetate 9 (0.103 g,
10%): mp for 9, 113-114 °C (lit. mp 126 °C,19 114 °C,6a 112-
113 °C18) from ethanol; 1H NMR (200 MHz, CDCl3) δ 5.46 (dd, J
) 3.4, 6.5 Hz, 1H,), 5.44 (t, J ) 9.7 Hz, 1H), 5.28 (dd, J ) 1.8,
4.3 Hz, 1H), 5.15 (q, J ) 9.7 Hz, 1H), 4.94 (dd, J ) 3.2, 10.3 Hz,
1H), 2.28 (dt, J ) 4.3, 8.6 Hz, 1H), 2.14 (s, 3H), 2.01 (s, 6H),
2.00 (s, 3H), 1.98 (s, 3H), 1.75 (m, 1H); 13C NMR (50 MHz, CDCl3)
δ 171.79, 171.85, 171.72, 171.79, 171.66, 75.21, 73.43, 71.67,
70.37, 68.80, 32.74, 22.86, 22.76, 22.52; IR (KBr, cm-1) 3489,
3029, 2953, 1753, 1446, 1395, 1242.
(1a,4b,6a)-8,8-Dimethyl-4-acetoxy-7,9-dioxa-bicyclo[4.3.01.6]-
n on -2-en e 5b. To a magnetically stirred solution of alcohol 5a
(0.6 g, 3.50 mmol) in 3 mL of pyridine was added acetic
anhydride (0.428 g, 4.2 mmol). The reaction mixture was stirred
at room temperature for 8 h and cooled to 0 °C. After addition
of 100 mL of water, the water phase was extracted with ether
(3 × 50 mL). The combined organic extracts were washed with
NaHCO3 solution (10 mL) and water (5 mL) and then dried (Na2-
SO4). Removal of the solvent under reduced pressure gave
acetate 5b (0.59 g, 78%, colorless liquid): 1H NMR (200 MHz,
CDCl3) δ 5.71 (dm, A part of AB system, J ) 10.8 Hz, 1H), 5.65
(dm, B part of AB system, J ) 10.8 Hz, 1H), 5.28 (m, 1H), 4.32
(m, 2H), 2.31 (ddt, A part of AB system, J ) 13.8, 5.5, 1.1 Hz,
1H), 1.65 (ddd, B part of AB system, J ) 13.8, 9.1, 2.8 Hz, 1H),
1.92 (s, 3H), 1.23 (s, 3H), 1.21 (s, 3H); 13C NMR (CDCl3, 50 MHz)
δ 171.15, 130.05, 129.10, 109.12, 72.22, 71.83, 66.52, 31.80, 28.12,
27.82, 22.05; IR (KBr, cm-1) 2990, 1740, 1370, 1240, 1040. Anal.
Calcd for C11H16O4: C, 62.25; H, 7.60. Found: C, 61.93; H, 7.46.
(1a ,2b,3b,4b,6a )-8,8-Dim eth yl-2,3,4-tr ia cetoxy-7,9-d ioxa -
bicyclo[4.3.01.6]n on a n e 6b. To a magnetically stirred ethanol
solution (100 mL) of alkene 5b (2.5 g, 11.79 mmol) was added a
solution of KMnO4 (1.86 g, 11.79 mmol) and MgSO4 (1.41 g, 11.79
mmol) in water (40 mL) at -5 °C during 7 h. After the addition
was completed, the reaction mixture was stirred for an ad-
ditional 15 h at the given temperature and then filtered. The
precipitate was washed several times with hot water. The
combined filtrates were concentrated to 20 mL by rotoevapora-
tion. The aqueous solution was extracted with ethyl acetate (3
× 30 mL), and the extracts were dried (Na2SO4). Evaporation
of the solvent gave diol 6a (1.630 g, 56%), which was submitted
to acetylation as described above to give 6b (1.92 g, 88%,
colorless liquid): 1H NMR (200 MHz, CDCl3) δ 5.41(m, 1H), 5.15
(ddd, J ) 11.9, 5.5, 1.75 Hz, 1H), 4.95 (dd, J ) 8.4, 2.5 Hz, 1H),
4.35 (m, 1H), 4.16 (dd, J ) 11.9, 8.4 Hz, 1H), 2.30 (dd, A part of
AB system, J ) 14.2, 5.0 Hz, 1H), 2.13 (dd, B part of AB system,
J ) 14.2, 4.8 Hz,1H), 2.06 (s, 3H), 1.99 (s, 3H), 1.94 (s, 3H), 1.44
(s, 3H), 1.29 (s, 3H); 13C NMR (CDCl3, 50 MHz) δ 170.42, 170.37,
170.16, 109.92, 75.48, 73.09, 72.41, 70.92, 67.07, 28.47, 27.04,
26.54, 21.27; IR (KBr, cm-1) 2993, 1740, 1435, 1360, 1250, 1060.
Anal. Calcd for C15H22O8: C, 54.54; H, 6.71. Found: C, 54.81;
H, 6.54.
(1a ,2a ,3b ,4b ,5a )-P en t a h yd r oxycycloh exa n e [(()-vibo-
Qu er citol] 10. A 100 mg (0.26 mmol) portion of vibo-quercitol
pentaacetate 9 was dissolved in 15 mL of methanol. While dry
NH3 was passed through the solution, the mixture was stirred
for 2 h at room temperature. Evaporation of methanol and
acetamide gave vibo-quercitol 10 (43 mg, quantitative): mp 161-
162 °C (lit. mp 163 °C,6a 161-163 °C,16 159 °C7) from EtOH; 1H
NMR (200 MHz, D2O) δ 4.07 (br q, J ) 3.0 Hz, 1H), 3.77 (ddd,
J ) 12.0, 9.4, 4.8 Hz, 1H), 3.57 (t, J ) 9.2 Hz, 1H), 3.50 (dd, J
) 3.0, 9.2 Hz, 1H), 3.25 (t, J ) 9.2 Hz, 1H), 2.10 (dt, J ) 14.1,
3.9 Hz, 1H), 1.56 (ddd, J ) 14.3, 12.1, 2.5 Hz, 1H); 13C NMR (50
MHz, D2O) δ 81.80, 78.12, 77.11, 72.77, 72.77, 39.44; IR (KBr,
cm-1) 3361, 2927, 1421, 1114, 1038, 987, 680.
(1a ,2a ,3a ,4b,5b)-Cycloh exa n ep en tol [(()-ta lo-Qu er citol]
7a . Ketal triacetate 6b (1.5 g, 4.5 mmol) was dissolved in 5 mL
of 1 N H2SO4 and the resulting mixture was stirred at room
temperature for 3 h. The acid was neutralized with BaCO3.
Filtration of the precipitate and evaporation of the solvent under
reduced pressure gave talo-quercitol 7a (0.7 g, 95%): mp 245-
Ack n ow led gm en t. The authors are indebted to the
Department of Chemistry (Atatu¨rk University) and the
TBAG-DPT-6 for financial support of this work and
State Planning Organization of Turkey (DPT) for pur-
chasing a 200 MHz NMR spectrometer.
1
247 °C (lit.6a mp 246-248 °C) from EtOH; H NMR (200 MHz,
D2O) δ 4.0 (m, 3H), 3.85 (m, 2H), 1.80 (dd, J ) 9.7, 3.1, Hz, 2H);
13C NMR (50 MHz, D2O) δ 75.72, 73.38, 72.69, 70.82, 68.75,
35.17; IR (KBr, cm-1) 3395, 2905, 2500, 1350, 1090, 1000, 845.
(1a,2a,3a,4b,5b)-P en taacetoxycycloh exan e [(()-ta lo-Qu er -
citol P en ta a ceta te] 7b. talo-Quercitol 7a was submitted to
acetylation as described above to give talo-quercitol pentaacetate
7b (colorless solid, 85%): mp 169-171 °C (lit. mp 182-183 °C,6
169.5-171.5 °C7) from EtOH; 1H NMR (200 MHz, CDCl3) δ 5.61
(m, 1H), 5.51 (q, J ) 3.2 Hz, 1H), 5.27 (dd, A part of AB system,
J O971978Q
(18) McCasland, G. E.; Horswill, E. C. J . Am. Chem. Soc. 1953, 75,
4020.
(19) Posternak, T.; Schopfer, W. H. Helv. Chim. Acta 1950, 33, 343-
349.