Second example for the heterocomplexation of chiral diols and complete disproportionation of enantiomers for non-racemic 2,3-O-cyclohexylidene-1,1,4,4-tetraphenylthreitols

Article abstract of DOI:10.1016/j.jfluchem.2009.10.017

Inclusion complexation of a tricyclic dipeptide derived from (S)-proline toward several chiral diols was examined, and observed that inclusion complexation behavior depended strongly on the composition of diol. For 2,3-O-alkylidene-1,1,4,4-tetraphenylthreitols, the derivatives of cyclohexanone and acetone reacted with the dipeptide to generate a 1:2 inclusion complex; however, the former is achiroselective, affording the second heterocomplex known to date. Based on the heterocomplexation, complete disproportionation of enantiomers of non-racemic 2,3-O-cyclohexylidene-1,1,4,4-tetraphenylthreitol was successfully realized, leading to highly effective separation of the excess enantiomer from the racemate. On the other hand, inclusion complexation did not occur between the dipeptide and rac-pinanediol or (4R,5R)-4-diphenylhydroxymethyl-5-hydroxy-2,6,6-triphenyl-1,3,2-dioxabor olane.

Full text of DOI:10.1016/j.jfluchem.2009.10.017

Journal of Fluorine Chemistry 131 (2010) 505–509
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Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Second example for the heterocomplexation of chiral diols and complete
disproportionation of enantiomers for non-racemic 2,3-O-cyclohexylidene-
1,1,4,4-tetraphenylthreitols
*
Xiaoyun Hu, Zixing Shan , Wei Li
Department of Chemistry, Wuhan University, Luojia Mountain, Wuhan 430072, China
A R T I C L E I N F O
A B S T R A C T
Article history:
Inclusion complexation of a tricyclic dipeptide derived from (S)-proline toward several chiral diols was
examined, and observed that inclusion complexation behavior depended strongly on the composition of
diol. For 2,3-O-alkylidene-1,1,4,4-tetraphenylthreitols, the derivatives of cyclohexanone and acetone
reacted with the dipeptide to generate a 1:2 inclusion complex; however, the former is achiroselective,
affording the second heterocomplex known to date. Based on the heterocomplexation, complete
disproportionation of enantiomers of non-racemic 2,3-O-cyclohexylidene-1,1,4,4-tetraphenylthreitol
was successfully realized, leading to highly effective separation of the excess enantiomer from the
racemate. On the other hand, inclusion complexation did not occur between the dipeptide and rac-
pinanediol or (4R,5R)-4-diphenylhydroxymethyl-5-hydroxy-2,6,6-triphenyl-1,3,2-dioxaborolane.
ß 2009 Elsevier B.V. All rights reserved.
Received 7 October 2009
Received in revised form 26 October 2009
Accepted 30 October 2009
Available online 12 November 2009
Keywords:
Chirality separation
Complete disproportionation of
enantiomers
Hetercomplexation
2,3-O-Cyclohexylidene-1,1,4,4-
tetraphenylthreitol
1. Introduction
enantiomer cumulation may be achieved in a great degree, even
species of up to >99% ee was obtained; however, practical yield of
It is well known, a racemate is very difficult to experience
enantiomeric separation in achiral environment, while enantio-
meric purity of non-racemic compound can be frequently
upgraded through recrystallization in suitable solvent. However,
in general, the optical purification technology can only offer
enantiomer-enriched sample or enantiomerically pure species in
lower yield; furthermore, the search for practical solvents
frequently is very time consuming. Since 1980s, it has been
continuously observed that some non-racemic chiral compounds
could offer species with different enantiomeric purity through
chromatography on an achiral stationary phase. In 2006, Solosho-
nok [1–3] first proposed the concept of enantiomer self-
disproportionation (or self-disproportionation of enantiomers)
based on the observation on chromatographic separation in an
achiral silica gel for non-racemic fluoroorganic compounds. Fig. 1 is
a model for self-disproportionation of enantiomers. In the cases of
self-disproportionation of enantiomers (SDEs) [4–5], cumulation
of the excess enantiomer would occur; in certain cases, the
the enantiomerically pure species is not acceptably satisfactorily. If
under a certain condition, disproportionation of enantiomer is
complete, theoretically, quantitative separation of the excess
enantiomer from the racemate should be achieved; that is to say, it
should afford the excess enantiomer of 100% ee and the racemate
in calculated amount (Fig. 2).
In the course of our investigation on interaction between chiral
host and racemic guest, we observed that a tricyclic dipeptide
(3S,6S)-1 [6–10] generated from (S)-proline was refluxed with rac-
1,10-bi-2-naphthol (BINOL) in benzene, then cooled to afford a
1:2:3 heterocomplex [11] consisting of the dipetide, rac-BINOL and
benzene, possessing an indefinite chain structure (Scheme 1). This
is the first observation on heterocomplexation phenomenon in
chiral supramolecular chemistry. ‘‘Heterocomplexation’’ means
achiroselective complexation between chiral host and racemic
guest, where both the enantiomers of a racemic guest are
synchronously bound to a chiral host. The heterocomplexation
strategy has been successfully applied to quantitative separation
[11] of the excess enantiomer from the racemate. In order to
explore the universality of heterocomplexation phenomenon,
interaction between some racemic diols and (3S,6S)-1 was
examined, finding that occurrence of the heterocomplexation
* Corresponding author.
E-mail address: zxshan@whu.edu.cn (Z. Shan).
0022-1139/$ – see front matter ß 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2009.10.017

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X. Hu et al. / Journal of Fluorine Chemistry 131 (2010) 505–509
spectral analyses indicate that they are all a 1:2 supramolecular
complex consisting of the dipetide and CHTTOL. The complex was
worked up in a mixture of water and ethyl acetate to offer (3S,6S)-1
and rac-CHTTOL from the water phase and the organic phase,
respectively, revealing that
a heterocomplexation occurred
Fig. 1. Model for self-disproportionation of enantiomer (SDE).
between (3S,6S)-1 and rac-CHTTOL (Scheme 2). This is the second
example for heterocomplexation of chiral diols known to date.
Attempts for obtaining single crystal suitable for X-ray
crystallographic analysis via recrystallization in benzene or
toluene have not met with success.
Interestingly, complexation reaction between enantiomerically
pure
(4R,5R)-2,3-O-cyclohexylidene-1,1,4,4-tetraphenylthreitol
Fig. 2. Model for complete disproportionation of enantiomers (CDE).
and (3S,6S)-1 can also take place in toluene, but furnished a 1:1
supramolecular complex (Scheme 3).
depends strongly on the composition of reactants and solvents
used. In the present paper, we report intermolecular interaction
between (3S,6S)-1 and several chiral 1,4-, 1,3- and 1,2-diols
(Fig. 3), including rac- and (4R,5R)-2,3-O-cyclohexylidene-1,1,4,4-
tetraphenylthreitol (CHTTOL), rac- and (4R,5R)-2,3-O-isopropyli-
dene-1,1,4,4-tetraphenylthreitol (IPTTOL), (4R,5R)-4-diphenylhy-
droxymethyl-5-hydroxy-2,6,6-triphenyl-1,3,2-dioxaborolane
(DHTDB) or rac-pinanediol (PADOL), the second example for
heterocomplexation of chiral diols and complete disproportiona-
tion of enantiomers in non-racemic CHTTOL.
The above facts show that between (3S,6S)-1 and rac-CHTTOL,
enantioselective inclusion complexation cannot occur, though
(3S,6S)-1 can form inclusion complex with an enantiomer of
CHTTOL. It appears that existent form of chiral diols influences
considerably its complexation property.
Taking into account of the previous result [11], heterocom-
plexation of (3S,6S)-1 to rac-CHTTOL has been also attempted to
apply to separation of the excess enantiomer from the racemate in
non-racemic CHTTOLs. For a non-rac-CHTTOL, the amount of the
rac-CHTTOL included can be readily calculated based on the ee
value of the non-rac-CHTTOL, thus the appropriate (3S,6S)-1
loading requested for the formation of a 1:2 complex with the rac-
CHTTOL can be readily determined. When a stoichiometric (3S,6S)-
1 was added to a benzene or toluene solution of the non-rac-
CHTTOL, refluxed, and then cooled, the rac-CHTTOL contained in
the non-rac-CHTTOL was isolated out of the solution as a
crystalline inclusion complex, while the excess enantiomer
remained in benzene or toluene solution. The mother liquor
removed from the inclusion complex was concentrated and
2. Results and discussion
(3S,6S)-1 was allowed to reflux with racemic 2,3-O-cyclohex-
ylidene-1,1,4,4-tetraphenylthreitol (CHTTOL) [12–14] in benzene
or toluene in a 1:1–3 molar ratio to form a homogeneous solution;
cooled to room temperature, a white solid was isolated out of the
system; after recrystallization in the same solvent as used in the
reaction, a colorless crystal was obtained, respectively. The
Scheme 1. Heterocomplexation of (3S,6S)-1 to rac-BINOL in benene.
Fig. 3. Chiral diols examined in the present work.
Scheme 2. Heterocomplexation of (3S,6S)-1 to rac-CHTTOL in benzene or toluene.

X. Hu et al. / Journal of Fluorine Chemistry 131 (2010) 505–509
507
Scheme 3. Inclusion complexation of (3S,6S)-1 to (4R,5R)-CHTTOL in toluene.
Scheme 4. Complete disproportionation of enantiomers of non-racemic CHTTOLs via heterocomplexation.
Scheme 5. Inclusion complexation between (3S,6S)-1 and (4R,5R)-IPTTOL.
Fig. 4. Numbering scheme and molecular assembly for the inclusion complex of (3S,6S)-1 and (4R,5R)-IPTTOL. Hydrogen bonding: O10 H10 O7, 0.82 1.82 2.635(2) 174.5; O6
H6 O21, 0.82 2.08 2.891(3) 172.2; O3 H3 O6, 0.82 1.92 2.709(2) 162.4.

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X. Hu et al. / Journal of Fluorine Chemistry 131 (2010) 505–509
crystallized to furnish enantiomerically pure (4R,5R)- or (4S,5S)-
CHTTOL (Scheme 4). For example, a mixture of (4R,5R)-CHTTOL of
80% ee and 0.1 equivalent of (3S,6S)-1 was dissolved in benzene or
toluene (20 mL) under heating and refluxed for 2 h, and then
cooled to ambient temperature to isolate a 1:2 colorless crystalline
complex of (3S,6S)-1 and rac-CHTTOL, ca. 60% yield. The solution
removed from the crystal was evaporated to ca. half of the original
volume to afford second crop, combined with the above together,
ca. 85% yield. The mother liquor separated from the above
inclusion complex was further concentrated to isolate a colorless
crystal of enantiomerically pure (4R,5R)-CHTTOL in more than 80%
yield. Finally, the solution was evaporated to dryness to furnish
(4R,5R)-CHTTOL contaminated by the heterocomplex.
was prepared by an improved Weber and Shepherd method [17].
Non-racemic (4R,5R)-CHTTOL was formed through mixing stoi-
chiometrically rac- and (4R,5R)-CHTTOL. IR spectra were record on
a Testscan Shimadzu FTIR 8000 in KBr. 1H and 13C NMR spectra
were taken in CDCl3 solutions at 300 or 400 MHz and 75 or
100 MHz, respectively, on a Varian Mercury VX 300 or Bruker AV
400, and all chemical shifts were reported as
d values (ppm)
relative to Me4Si. Melting points were determined on a VEB
Wa¨getechnik Rapido PHMK 05 instrument and were not corrected.
Optical rotations were measured in CHCl3 on a PerkinElmer 341 Mc
polarimeter.
4.2. Heterocomplexation of (3S,6S)-1 to rac-CHTTOL
It presents a striking contrast to the above, an analog of
rac-CHTTOL, rac-2,3-O-isopropylidene-1,1,4,4-tetraphenylthreitol
(IPTTOL) [13] did not undergo heterocomplexation under similar
condition to the above. However, between enantiomerically pure
(4R,5R)-IPTTOL and (3S,6S)-1, an inclusion complexation took
place and furnished a 1:2 crystalline complex (Scheme 5), which
has been characterized by the single crystal X-ray diffraction
analysis. The perspective view of the inclusion complex of (3S,6S)-
1 and (4R,5R)-IPTTOL showing the numbering scheme were shown
in Fig. 4. The data [15] showed that only an inclusion complex
molecule was included in a unit cell, where the configuration of the
dipeptide is retentive, namely it still is cis-(3S,6S). It was also
observed that in this supramolecular assembly, there are two types
of H bonding, including an internal H bond between both the
hydroxyl groups in per diol molecule and an intermolecular H bond
between the hydroxyl group of the diol and the carbonyl group of
(3S,6S)-1, and one carbonyl group of the dipeptide merely bonded
to one diol molecule.
A mixture of rac-CHTTOL (0.304 g, 0.6 mmol) and (3S,6S)-1
(0.058 g, 0.3 mmol) was dissolved in benzene (10 mL) with heating
and refluxed for 2 h, and then cooled to ambient temperature to
isolate a 1:2 colorless crystalline complex (0.337 g) of (3S,6S)-1 and
rac-CHTTOL, yield: 93%. mp 215–228 8C, [
a
]
25 = ꢀ21.2 (c 1.1,
D
CHCl3). 1H NMR (400 MHz, CDCl3):
d
1.11–1.29 (m, 12H,
cyclohexylidene of diol), 1.37–1.47 (m, 8H, cyclohexylidene of
diol), 1.87–2.36 (m, 8H, 2CH2CH2 of dipeptide), 3.52–3.55 (dd,
J = 8.8 Hz, J = 5.6 Hz, 4H, 2NCH2 of dipeptide), 4.11 (s, 4H, OH,
disappeared after adding D2O), 4.16 (t, J = 8.4 Hz, 2H, NCHC55O of
dipeptide), 4.56 (s, 4H, CH, framework of diol), 7.22–7.35 (m, 24H,
Ph-H), 7.37–7.41 (m, 8H, Ph-H), 7.50–7.55 (m, 8H, Ph-H). 13C NMR
(75 MHz, CDCl3):
d 146.1, 142.7, 128.5, 128.1, 127.7, 127.2, 109.9,
80.5, 78.1, 60.5, 45.2, 36.5, 27.7, 23.9.
The spectra of a 1:2 inclusion complex isolated in toluene are
very similar to those in benzene. 1H NMR (400 MHz, CDCl3):
d
1.14–1.27 (m, 12H, cyclohexylidene of diol), 1.40–1.44 (m, 8H,
cyclohexylidene of diol), 1.83–2.36 (m, 8H, 2CH2CH2 of dipeptide),
3.49–3.53 (dd, J = 8.8 Hz, J = 5.6 Hz, 4H, 2NCH2 of dipeptide), 4.14
(t, J = 8.0 Hz, 2H, NCHC55O of dipeptide), 4.22 (s, 4H, OH,
disappeared after adding D2O), 4.54 (s, 4H, CH, framework of
diol), 7.20–7.33 (m, 24H, Ph-H), 7.35–7.40 (m, 8H, Ph-H), 7.49–7.54
(m, 8H, Ph-H).
Similar investigation indicated that no inclusion complexation
occurred between (3S,6S)-1 and chiral pinanediol [16] or (4R,5R)-
4-diphenylhydroxylmethyl-5-hydroxy-2,6,6-triphenyl-1,3,2-
dioxa-borolane [17].
3. Conclusion
The mother liquor was concentrated to offer second crop of the
inclusion complex, combined with the above together, 0.55 g, 85%
yield. The above obtained crystalline complex was worked up with
a mixture of water and diethyl acetate to afford (3S,6S)-1 [mp 143–
In summary, intermolecular interaction between (3S,6S)-1 and
some chiral diols has been examined, finding that the composition
of diols is one of the most important factors influencing
complexation property of the diols to (3S,6S)-1. Formation of
the complex between (3S,6S)-1 and (4R,5R)-2,3-O-cyclohexyli-
dene-1,1,4,4-tetraphenylthreitol or (4R,5R)-2,3-O-isopropylidene-
1,1,4,4-tetraphenylthreitol does not mean that enantioselective
inclusion complexation can take place between (3S,6S)-1 and the
racemic diols. For the chiral diols examined here, only rac-2,3-O-
cyclohexylidene-1,1,4,4-tetraphenylthreitol can undergo hetero-
complexation to (3S,6S)-1, and realized highly effective separation
of the excess enantiomer from the racemate in non-racemic 2,3-O-
cyclohexylidene-1,1,4,4-tetraphenylthreitol via complete dispro-
portionation of enantiomers.
145 8C [
a
]
]
25 = ꢀ44.2 (c 1, in CH3OH)] and rac-CHTTOL [mp 211–
D
214 8C [
a
25 = 0 (c 1, in CHCl3)] from water phase and the organic
D
phase, respectively.
4.3. A representative procedure for complete disproportionation of
enantiomers for non-racemic CHTTOL
According to similar procedure to the above, rac-CHTTOL
(0.525 g, 1.04 mmol)) of 80% ee was allowed to mix with (3S,6S)-1
(0.03 g, 0.104 mmol) in benzene or toluene (20 mL), dissolved,
refluxed, then cooled to isolate a 1:2 colorless crystalline inclusion
complex of (3S,6S)-1 and rac-CHTTOL. The solution removed from
the inclusion complex crystal was concentrated to afforded
crystals of (4R,5R)-CHTTOL (0.32 g, 75% yield), mp 195–197 8C,
4. Experimental
4.1. General
[
a
]
25 = ꢀ75 (c 1, CHCl3). 1H and 13C NMR spectra are in
D
conformance with those of the authorized sample. The mother
liquor was further concentrated to furnish the second crystalline
crop of (4R,5R)-CHTTOL, combined with the first crop, over 80%
yield.
All the reagents and solvents are purchased (CP or AR grade).
(3S,6S)-1 was prepared according to the literature [10], mp 144–
146 8C [
a
]
D
25 = ꢀ44.5 (c 1, in CH3OH). IR: 1650 s. 1H NMR (CDCl3,
300 MHz): 1.82–2.37 (m, 8H), 3.51–3.55 (dd, J = 4.8 Hz, J = 7.8 Hz,
4H); 4.17 (t, J = 9.0 Hz, 2H). MS: 389 (6, [Mdimer+1]+), 195 (100,
[M+1]+). rac- and (4R,5R)-CHTTOLs as well as rac- and (4R,5R)-
IPTTOLs were synthesized referring to the literature [13], (4R,5R)-
DHTDB was prepared according to the literature [16], and rac-
PADOL were formed through mixing (+)- and (ꢀ)-PADOL, which
4.4. Inclusion complexation of (3S,6S)-1 to (4R,5R)-CHTTOL
Similar to the above, a mixture of (4R,5R)-CHTTOL (0.304 g,
0.6 mmol) and (3S,6S)-1 (0.058 g, 0.3 mmol) was treated in toluene
under reflux and then cooled to isolate a 1:1 colorless crystalline

X. Hu et al. / Journal of Fluorine Chemistry 131 (2010) 505–509
509
complex (0.332 g, 92% yield) of (3S,6S)-1 and (4R,5R)-CHTTOL. Mp
(9), b = 11.7937(11), c = 14.2641 (13),
a
= 87.127 (2)8,
b
= 76.0290
205–212 8C, [
a
]
D
25 = ꢀ99.1 (c 0.22, CHCl3). 1H NMR (400 MHz,
(10)8, = 79.9710 (10)8; absorption coefficient (m ;
g
), 0.083 mmꢀ1
CDCl3):
d
1.08–1.26 (m, 12H, cyclohexylidene of diol), 1.35-1.44 (m,
index ranges, ꢀ11 ꢂ h ꢂ 11, ꢀ14 ꢂ k ꢂ 14, ꢀ17 ꢂ l ꢂ 10; F(000),
8H, cyclohexylidene of diol), 1.84–2.38 (m, 8H, 2CH2CH2 of
dipeptide), 3.49–3.53 (dd, J = 8.8 Hz, J = 5.2 Hz, 4H, 2NCH2 of
dipeptide), 4.12 (s, 4H, OH, disappeared after adding D2O), 4.14 (t,
J = 8.0 Hz, 2H, NCHC55O of dipeptide), 4.52 (s, 4H, CH, framework of
diol), 7.20–7.32 (m, 24H, Ph-H), 7.34–7.37 (m, 8H, Ph-H), 7.48–7.52
600; GOF, 1.025.
Acknowledgment
We thank the National Natural Science Foundation of China
(20672083 and 20872115) for financial support.
(m, 8H, Ph-H). 13C NMR (100 MHz, CDCl3):
d 145.8, 142.4, 128.3,
127.8, 127.4, 127.2, 126.9, 109.6, 80.2, 77.9, 60.3, 44.9, 36.2, 27.4,
23.7, 23.1.
Appendix A. Supplementary data
4.5. Inclusion complexation of (3S,6S)-1 to (4R,5R)-IPTTOL
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jfluchem.2009.10.017.
Similar to the above, a mixture of (4R,5R)-IPTTOL (0.935 g,
2.0 mmol) and (3S,6S)-1 (0.295 g, 1.0 mmol) was dissolved in
toluene, refluxed for 2 h, and then cooled to isolate a 1:2, colorless
crystalline complex (0.487 g, 93% yield) of (3S,6S)-1 and (4R,5R)-
References
IPTTOL. 1H NMR (400 MHz, CDCl3):
d 1.06 (s, 12H, methyls of the
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[2] V.A. Soloshonok, D.O. Berbasov, J. Fluorine Chem. 127 (2006) 597.
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[4] V.J. Mayani, S.H.R. Abdi, R.I. Kureshy, N.H. Khan, S. Agrawal, R.V. Jasra, Chirality 21
(2009) 255.
[5] V. Soloshonok, Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA,
United States, April 6–10, 2008, FLUO-005.
[6] J. Kapfhammer, A. Matthes, Z. Physiol. Chem. 223 (1933) 43.
[7] N. Daisuke, K. Kiyomi, K. Kenji, S. Ryuichi, Org. Lett. 8 (2006) 6139.
[8] A. Friedrich, M. Jainta, M. Nieger, S. Braese, Synlett (2007) 2127.
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[10] B.D. Harri, K.L. Bhat, Hetereocycles 24 (1986) 1045.
diol), 2.34–1.91 (m, 8H, 2CH2CH2), 3.55–3.51 (m, 4H, 2NCH2), 4.14
(t, J = 8.0 Hz, 2H, 2NCHC55O), 4.27 (s, 4H, OH of the diol,
disappeared after adding D2O), 4.61 (s, 4H, framework C–H of
the diol), 7.39–7.32 (m, 32H, Ph-H of the diol), 7.57–7.55 (m, 8H,
Ph-H of the diol). 13C NMR (100 MHz, CDCl3):
d 166.4, 146.0, 142.7,
128.6, 128.1, 127.7, 127.5, 127.3, 127.2, 109.5, 81.0, 78.1, 60.5, 45.2,
27.7, 27.1, 23.3. After treatment with a mixture of water and
diethyl acetate, (4R,5R)-IPTTOL was obtained from the organic
phase, mp 192–194 8C, [
a
]
25 = ꢀ60.5 (c 1, CHCl3); Lit. [12]:
[11] Z.X. Shan, Y. Xiong, J. Yi, X.Y. Hu, J. Org. Chem. 73 (2008) 9158.
[12] F. Toda, K. Tanaka, Tetrahedron Lett. 29 (1988) 551.
[13] D. Seebach, A.K. Beck, R. Imwinkelried, S. Roggo, A. Wonnacott, Helv. Chim. Acta
70 (1987) 954.
D
[a
]
D
25 = ꢀ60.6 (c 1, CHCl3), 100% ee. 1H and 13C NMR spectral data
are identical to those cited in Ref. [13].
After standing for 3 months at ambient temperature (25–38 8C),
the toluene solution of the inclusion complex of (3S,6S)-1 and
(4R,5R)-IPTTOL furnished a colorless single crystal suitable for X-
ray diffraction analysis.
[14] A.K. Beck, P. Gysi, L. La Vecchia, D. Seebach, Org. Synth. 76 (1999) 12.
[15] Final atomic coordinates of the crystal, along with lists of anisotropic thermal
parameters, hydrogen coordinates, bond lengths, and bond angles, have been
deposited with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-748884. Data can be obtained, on request, from the Direc-
tor, Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ,
UK (fax: (+44) 1223 336 033; e-mail: deposit@ccdc.cam.cn; web: http://
www.ccdc.cam.ac.uk).
Crystallographic data of (3S,6S)-1ꢁ2 (4R,5R)-IPTTOL: empirical
formula,
C72H74N2O10; formula weight, 1127.33; calculated
3
3
˚
density, 1.253 g/cm ; volume (V), 1493.6 (2) A ; crystal system,
[16] Y. Zhou, Z.X. Shan, Tetrahedron Lett. 48 (2007) 3531.
triclinic; space group, P1; Z = 1; unit cell dimensions, a = 9.2916
[17] W.P. Weber, J.P. Shepherd, Tetrahedron Lett. 13 (1972) 4907.