Expanding Synthetic Utilities of Asymmetric Dihydroxylation Reaction: Conversion of syn-Diols to syn-Amino Alcohols

Full text of DOI:10.1021/jo991079x

J . Org. Chem. 1999, 64, 8745-8747
8745
Sch em e 1
Exp a n d in g Syn th etic Utilities of
Asym m etr ic Dih yd r oxyla tion Rea ction :
Con ver sion of syn -Diols to syn -Am in o
Alcoh ols
Gae Y. Cho and Soo Y. Ko*
Department of Chemistry and Center for Cell Signaling
Research, Ewha Womans University, Seoul 120-750, Korea
Received J uly 6, 1999
Sharpless’s asymmetric dihydroxylation (AD) is among
the most efficient asymmetric transformations available
to synthetic chemists.1 Its rapid acceptance to the syn-
thetic arsenal testifies the power of the process: high
enantioselectivities, substrate generality, easy operation,
etc. Equally important is the rich chemistry that one can
do with the initial products of the process. Selective
transformations of vicinal diols further expand the
synthetic utility of the AD process. Their discoveries,
therefore, have been much sought after. Toward this end,
conversions of vicinal diols to cyclic sulfates, halohydrin
esters, and epoxides and subsequent transformations
have been reported.2
Our interest in this area has been mainly centered on
the inability of the AD process to produce anti(erythro)-
diols in high enantioselectivity. This inherent weakness
of the AD process, which results from the fact that
disubstituted (Z)-olefins are poor substrates for AD, has
limited the synthetic utilities to only half of the all the
possible stereoisomers as far as disubstituted vicinal diols
and derivatives thereof are concerned.3 As a solution to
this, we have reported a “cyclic sulfate rearrangement-
opening process” and shown that anti-diols as well as cis-
epoxides are now accessible via the AD process.4 We have
also reported a rearrangement process of vicinal-diol
cyclic thionocarbonates, which proceeds with net retention
of stereochemistry (eq 1, Scheme 1). This process provides
an access to syn(threo)-hydroxy thiols from AD products,
syn-diols, not a straightforward transformation other-
wise.5 Expanding on this cyclic thionocarbonate rear-
rangement chemistry, we envisaged that cyclic iminocar-
bonates would undergo a similar tandem displacement
(rearrangement) with net retention of stereochemistry (eq
2).6 The overall process, after necessary protective and
deprotective steps, would be a conversion of syn-diols (AD
products) to syn-amino alcohols. As most of the presently
known protocols (e.g., via cyclic sulfates or epoxides)
convert the AD products to anti-amino alcohols, the
iminocarbonate rearrangement process, if successful,
would complement the current methodology and greatly
expand the synthetic utility of the AD process. Amino
alcohol functional groups are often found in many bio-
active compounds, and their stereoselective synthesis is
of interest.7
Resu lts a n d Discu ssion
Using a tartrate ester as our model syn-diol and
following the literature procedure, we prepared the cyclic
iminocarbonate.8 Thus, the starting diol was activated
via tin ketal and then, without the isolation of the tin
intermediate, treated with an isothiocyanate.8d An elec-
tron-withdrawing substituent (R′′) on the nitrogen was
expected to facilitate the subsequent tandem displace-
ment step. Also the lability of the group in the final
deprotection step was taken into consideration; the com-
mercially available benzoyl isothiocyanate was used
throughout this initial study. The cyclic N-benzoyl imino-
carbonate thus prepared proved too unstable to be
chromatographed; therefore, it was treated directly with
a bromide nucleophile (Bu4NBr). Following reflux for 2
h, the desired N-benzoyloxazolidin-2-one (cyclic N-ben-
zoylcarbamate) was obtained in 81% overall yield. The
three-step sequence from the starting diol to the rear-
ranged product (N-benzoyloxazolidin-2-one)stin ketal-
ization, iminocarbonate formation, and rearrangements
was conducted in a single reaction vessel.
The same three-step sequence was tried on a variety
of diol substrates. As the significance of this transforma-
tion is the retention of configuration of both carbinol
carbons, and as this process would, in practice, often be
utilized following an AD reaction, only syn-diols, i.e., the
AD products of (E)-disubstituted olefins, were chosen as
the substrates. All the diol substrates tried provided the
desired N-benzoyloxazolidin-2-ones in good yields, al-
though certain substrates required minor modifications
from the standard reaction conditions described above.
The results are summarized in Table 1.
The rearrangement proceeded in a regioselective man-
ner. The nitrogen functionality was incorporated either
at the R to carbonyl or benzylic sites. When there is a
competition between these two activating groups, a
mixture of regioisomers was obtained as determined by
(1) (a) J acobsen, E. N.; Marko, I.; Mungall, W. S.; Schroder, G.;
Sharpless, K. B. J . Am. Chem. Soc. 1988, 110, 1968. (b) Kolb, H. C.;
VanNieuwenhze, M. S.; Sharpless, K. B. Chem. Rev. 1994, 94, 2483.
(2) (a) Gao, Y.; Sharpless, K. B. J . Am. Chem. Soc. 1988, 110, 7538.
(b) Kolb, H. C.; Sharpless, K. B. Tetrahedron 1992, 48, 10515. (c)
Fleming, P. R.; Sharpless, K. B. J . Org. Chem. 1991, 56, 2869.
(3) Wang, L.; Sharpless, K. B. J . Am. Chem. Soc. 1992, 114, 7568.
(4) (a) Ko, S. Y.; Malik, M. Tetrahedron Lett. 1993, 34, 4675. (b) Ko,
S. Y.; Malik, M.; Dickinson, A. F. J . Org. Chem. 1994, 59, 2570. (c)
Ko, S. Y.; Lerpiniere, J . Tetrahedron Lett. 1995, 36, 2101. (d) Ko, S. Y.
Tetrahedron Lett. 1994, 35, 3601.
(7) For a recent survey on â-amino alcohols, see: Reddy, K. S.; Sola,
L.; Moyano, A.; Pericas, M. A.; Riera, A. J . Org. Chem. 1999, 64, 3969.
(8) (a) Yano, K.; Baba, A.; Matsuda, H. Chem. Ber. 1991, 124, 1881.
(b) Baba, A.; Seki, K.; Matsuda, H. J . Org. Chem. 1991, 56, 2684. (c)
Baba, A.; Seki, K.; Matsuda, H. J . Heterocycl. Chem. 1990, 27, 1925.
(d) As noted in ref 8a, addition of Et3N may accelerate the iminocar-
bonate formation but is not essential for the reaction.
(5) Ko, S. Y. J . Org. Chem. 1995, 60, 6250.
(6) (a)Barton, D. H. R.; Motherwell, W. J . Nouv. Chim. 1978, 2, 301.
(b) Barton, D. H. R.; Motherwell, W. J . Chem. Soc., Perkin Trans. 1
1980, 1124.
10.1021/jo991079x CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/22/1999

8746 J . Org. Chem., Vol. 64, No. 23, 1999
Notes
Ta ble 1. Con ver sion of syn -Diols to P r otected syn -Am in o
Combining with the AD process, the present methodol-
ogy, therefore, introduces a syn-amino alcohol functional-
ity in two steps from (E)-disubstituted olefins in a
stereoselective manner. In this regard, it is interesting
to compare the present chemistry with the latest asym-
metric process from Sharpless group, namely the asym-
metric aminohydroxylation (AA) process.10 The AA pro-
cess provides protected amino alcohols from olefins in a
single step. Perhaps as it is relatively new and still to be
further developed, the enantioselectivities are not yet
invariably high.11 The present methodology owes the
absolute stereocontrol to the AD, so it enjoys generally
higher enantioselectivities, albeit in two separate opera-
tions. More importantly, the two processes complement
each other in terms of the regioselection. In crotonate-
and cinnamate-type substrates, the AA process prefer-
entially introduces a nitrogen function at â to the
carbonyl and an oxygen at the R site, while the present
chemistry yields regioisomeric R-amino-â-hydroxy deriva-
tives.12
Alcoh ols via Cyclic Im in oca r bon a tesa
entry
diol (R,R′)
M-X
yieldb
i
i
1
2
3
4
5
6
CO2 Pr, CO2 Pr
CH3, CO2Etc
Ph, CO2Etc
Bu4NBr
Bu4NBrd
Bu4NBr
Bu4NBr
LiI
81
74
77e
83f
73
c
CO2Et, p-MeOC6H4
Ph, Phg
g
CH3, p-MeOC6H4
LiI
58
a
b
Refer to the Experimental Section for details. Overall yield
from the diol. c Racemic diol was used. The BzNCS step and the
d
Bu4NBr step were conducted concurrently. e A mixture of the
regiosiomers (2.7:1) was obtained. The major isomer was the one
shown above. f A mixture of the regiosiomers (1.4:1) was obtained.
g
The major isomer was the one shown above. The enantiomer
antipodal to the structure given was used.
In conclusion, the chemistry described in this paper
allows one to convert syn-diols to syn-amino alcohols. As
most of the previously known diols transformations are
usually accompanied by an inversion of a stereocenter,
the iminocarbonate rearrangement process described
herein is unique in retaining the diol configurations. Also,
it effects the regioselection opposite to what the AA
brings about. Therefore, the present chemistry comple-
ments the existing methodologies for amino alcohol
synthesis.
NMR (entries 3 and 4). In general, the rearrangement
proceeded more smoothly with the diol substrates con-
taining a carbonyl activating group than with aryl-
activated diols. Thus, poor yields were initially observed
with stilbenediol and anetholediol following the standard
procedure. When the halide nucleophile was changed
from bromide to iodide (LiI), however, satisfactory yields
were obtained from these aryl diols (entries 5 and 6).
Although the halide nucleophile is thought to be regener-
ated at the end of the tandem displacement and therefore
should be required in a catalytic amount, less than 1
equiv of Br- or I- has so far resulted in lower yields. The
iminocarbonate formation step and the tandem displace-
ment may be conducted in situ. Thus, the diol prepared
from a crotonate ester was activated via tin ketal and it
was treated with BzNCS and Bu4NBr in the presence of
Et3N to yield the desired N-benzoyloxazolidin-2-one in
overall 74% (enty 2). With some diols (for example,
stilbenediol and tartrate), however, the in situ procedure
resulted in lower yields of the products, a concurrent
monobenzoylation of the diols being a major side reaction
under these conditions. Dichloroethane is in general
preferred to toluene as the reaction solvent.
Exp er im en ta l Section
Rea r r a n gem en t of a Ta r tr a te Ester to th e Cor r esp on d -
in g N-Ben zoyloxa zolid in -2-on e. Diisopropyl L-tartrate (242
mg, 1.03 mmol) was dissolved in dichloroethane (15 mL).
Dibutyltin oxide was added and the mixture heated to reflux
for 4 h under nitrogen with a concomitant removal of water
(Dean-Stark trap). Benzoyl isothiocyanate (0.228 mL, 1.73
mmol) and triethylamine (0.167 mL, 1.2 mmol) were added, and
the mixture was heated to reflux. After 1 h, tetrabutylammo-
nium bromide (332 mg, 1.03 mmol) was added and heating was
continued for a further 2 h. The reaction mixture was partitioned
between ethyl acetate and water. The organic phase was
separated, washed with brine, and dried (Na2SO4). The concen-
trated crude product was chromatographed on a silica column
(hexane:EtOAc ) 2.2:1) to yield the pure product (304 mg,
81%): [R]D -47.7 (c 0.80, EtOH); mp 115-116 °C; 1H NMR
(CDCl3) δ 7.70 (2H, d, J ) 7.0 Hz), 7.58 (1H, m), 7.45 (2H, m),
5.23-5.12 (2H, m), 5.02 (1H, d, J ) 3.7 Hz), 4.87 (1H, d, J ) 3.6
Hz), 1.55-1.30 (12H, m); IR 2993 (m), 1809 (b), 1741 (s), 1688
(s), 1387 (m) cm-1; MS m/e 364 (MH+). Anal. Calcd for
C18H21NO7: C, 59.50; H, 5.83; N, 3.85. Found: C, 59.71; H, 5.85;
N, 3.80.
The N-benzoyloxazolidin-2-ones thus obtained may be
deprotected to amino alcohols in the following manner.
Basic or acidic solvolysis (Cs2CO3, LiOH, DBU, or Ti-
(OiPr)4 in alcoholic solvents) removes the benzoyl group
first (an ester functional group present in the product
may undergo a transesterification). The remaining ox-
azolidin-2-one ring (cyclic carbamate) may be most
conveniently cleaved in a three-step sequence of N-Boc
protection [(Boc)2O, DMAP], basic solvolysis cleaving the
carbamate ring (Cs2CO3), and Boc-deprotection (TFA).9
Rea r r a n gem en t of a Cr oton a te Diol to th e Cor r esp on d -
in g N-Ben zoyloxa zolid in -2-on e. Ethyl crotonate diol (racemic,
92.9 mg, 0.63 mmol) was activated via tin ketal as described
above. Benzoyl isothiocyanate (0.116 mL, 0.88 mmol), triethyl-
The nature of the stereochemistry during the rear-
rangement step has been confirmed to be net retention
(double-inversion) by a chemical correlation. Thus, a
threonine ester was converted first to the oxazolidin-2-
one (phosgene), which was then N-benzoylated (BzCl,
DMAP). The N-benzoylated product as well as the
intermediate oxazolidin-2-one each proved identical to
those derived from the crotonate diol as described above.
(10) (a) Li, G.; Sharpless, K. B. Angew. Chem., Int. Ed. Engl. 1996,
35, 451. (b) Rudolph, J .; Sennhenn, P. C.; Vlaar, C. P.; Sharpless, K.
B. Angew. Chem., Int. Ed. Engl. 1996, 35, 2810. (c) Li, G.; Angert, H.;
Sharpless, K. B. Angew. Chem., Int. Ed. Engl. 1996, 35, 2813. (d)
Reddy, K. L.; Dress, K. D.; Sharpless, K. B. Tetrahedron Lett. 1998,
39, 3667. (e) Bruncko, M.; Schlingloff, G.; Sharpless, K. B. Angew.
Chem., Int. Ed. Engl. 1997, 36, 1483. (f) Reiser, O. Angew. Chem., Int.
Ed. Engl. 1996, 35, 1308. (g) O’Brien, P. Angew. Chem., Int. Ed. Engl.
1999, 38, 326.
(11) Enantioselectivities of the AA process range typically 80-90%
ee for disubstituted (E)-olefins,10g while anything below 90% ee would
be a rare exception for the AD process.
(12) Cf.: Tao, B.; Schlingloff, G.; Sharpless, K. B. Tetrahedron Lett.
1998, 39, 2507.
(9) (a) Knapp, S.; Kukkola, P. J .; Sharma, S.; Murali Dhar, T. G.;
Naughton, A. B. J . J . Org. Chem. 1990, 55, 5700. (b) Ishibuchi, T.;
Ishibuchi, S.; Kunieda, T. Tetrahedron 1993, 49, 1841.

Notes
J . Org. Chem., Vol. 64, No. 23, 1999 8747
amine (0.104 mL, 0.75 mmol) and tetrabutylammonium bromide
(203 mg, 0.63 mmol) were added, and the mixture was heated
to reflux overnight. The reaction mixture was partitioned
between ethyl acetate and water. The organic phase was
separated, washed with brine, and dried (Na2SO4). The concen-
trated crude product was chromatographed on a silica column
(hexane:EtOAc ) 2.2:1) to yield the pure product (166 mg,
74%): mp 95-97 °C; 1H NMR (CDCl3) δ 7.73 (2H, d, J ) 7.7
Hz), 7.58 (1H, m), 7.45 (2H, m), 4.71-4.64 (2H, m), 4.30 (2H, q,
J ) 7.1 Hz), 1.65 (3H, d, J ) 5.9 Hz), 1.31 (3H, t, J ) 7.2 Hz);
IR 2989 (m), 2940 (m), 1802 (s), 1753 (s), 1686 (s) cm-1; MS m/e
278 (MH+). Anal. Calcd for C14H15NO5: C, 60.64; H, 5.45; N,
5.05. Found: C, 60.67; H, 5.37; N, 4.94.
Rea r r a n gem en t of a Cin n a m a te Diol to th e Cor r e-
sp on d in g N-Ben zoyloxa zolid in -2-on e. Ethyl cinnamate diol
(racemic, 167 mg, 0.79 mmol) was converted to the corresponding
cyclic N-benzoyliminocarbonate (the benzoyl isothiocyanate step
took 2 h), which was then treated with tetrabutylammonium
bromide (274 mg, 0.85 mmol) as described above for the reaction
with a tartrate ester (reflux overnight). The reaction mixture
was partitioned between ethyl acetate and water. The organic
phase was separated, washed with brine, and dried (Na2SO4).
The concentrated crude product was chromatographed on a silica
column (hexane:EtOAc ) 2.5:1) to yield the product as a 2.7:1
mixture of regioisomers (205.5 mg, 77%). The regioisomers were
separated by crystallization (hexanes-EtOAc). R-N-isomer (ma-
jor): mp 95-96 °C; 1H NMR (CDCl3) δ 7.73 (2H, d, J ) 7.7 Hz),
7.59 (1H, m), 7.49-7.44 (7H, m), 5.55 (1H, d, J ) 5.2 Hz), 5.01
(1H, d, J ) 5.1 Hz), 4.36 (2H, q, J ) 7.0 Hz), 1.34 (3H, t, J ) 7.1
Hz); IR 2993 (m), 1787 (s), 1751 (s) cm-1; MS m/e 340 (MH+).
Anal. Calcd for C19H17NO5: C, 67.20; H, 5.05; N, 4.13. Found:
C, 66.86; H, 5.06; N, 4.01. â-N-isomer (minor): mp 165-167 °C;
1H NMR (CDCl3) δ 7.68 (2H, d, J ) 7.8 Hz), 7.55 (1H, m), 7.47-
7.38 (7H, m), 5.63 (1H, d, J ) 4.6 Hz), 4.87 (1H, d, J ) 4.6 Hz),
4.38 (2H, q, J ) 7.1 Hz), 1.38 (3H, t, J ) 7.1 Hz); IR 3058 (m),
1800 (s), 1768 (s) cm-1; MS m/e 340 (MH+). Anal. Calcd for
(m), 3035 (m), 1793 (s), 1681 (s) cm-1; MS m/e 344 (MH+). Anal.
Calcd for C22H17NO3: C, 76.95; H, 4.99; N, 4.08. Found: C, 76.91;
H, 5.00; N, 4.00.
Rea r r a n gem en t of An eth oled iol to th e Cor r esp on d in g
N-Ben zoyloxa zolid in -2-on e. (R,R)-Anetholediol (210 mg, 1.15
mmol) was converted to the corresponding cyclic N-benzoylimino-
carbonate (the benzoyl isothiocyanate step took 2 h), which was
then treated with lithium iodide (140 mg, 1.0 mmol) as described
above for the reaction with stilbenediol (reflux for 2 h). The
reaction mixture was partitioned between ethyl acetate and
water. The organic phase was separated, washed with brine, and
dried (Na2SO4). The concentrated crude product was chromato-
graphed on a silica column (hexane:EtOAc ) 2.2:1) to yield the
pure product (206.4 mg, 58%): [R]D -61.2 (c 0.69, CHCl3); mp
1
155-156 °C; H NMR (CDCl3) δ 7.72 (2H, d, J ) 7.9 Hz), 7.55
(1H, m), 7.42 (2H, m), 7.36 (2H, d, J ) 8.6 Hz), 6.92 (2H, d, J )
8.6 Hz), 5.06 (1H, d, J ) 7.8 Hz), 4.62-4.53 (1H, m), 3.79 (3H,
s), 1.53 (3H, d, J ) 6.2 Hz); IR 2839 (b), 1798 (s), 1681 (s), 1517
(s) cm-1; MS m/e 312 (MH+). Anal. Calcd for C18H17NO4: C,
69.44; H, 5.50; N, 4.50. Found: C, 69.28; H, 5.55; N, 4.49.
Dep r otection of th e N-Ben zoyloxa zolid in -2-on es to th e
Cor r esp on d in g Am in o Alcoh ols: Rep r esen ta tive P r oce-
d u r e. The N-benzoyloxazolidin-2-one derived from (S,S)-stil-
benediol (70 mg, 0.2 mmol) was dissolved in absolute ethanol (7
mL), and Cs2CO3 (84 mg, 0.25 mmol) was added. The mixture
was stirred at room temperature for 2 h. It was concentrated,
and the residue was chromatographed on a silica column (3:2
hexanes-EtOAc) to yield the debenzoylated product (48 mg,
99%) as a white solid: mp 127-130 °C; 1H NMR (CDCl3) δ 7.40
(6H, m), 7.32 (4H, m), 5.42 (1H, brs), 5.31 (1H, d, J ) 7.4 Hz),
4.75 (1H, d, J ) 7.4 Hz); IR 3264 (b), 1754 (s), 1723 (s) cm-1
;
MS m/e 239 (MH+).
The oxazolidin-2-one obtained as above (48 mg, 0,2 mmol) was
dissolved in THF (6 mL) and treated with (Boc)2O (90 mg, 0.41
mmol) and DMAP (12 mg, 0.2 mmol) at room temperature for
1.5 h. Aqueous workup (water-EtOAc) was followed by a column
chromatography (7:2 hexanes-EtOAc) to yield the N-Boc-
oxazolidin-2-one (53 mg, 78%) as a white solid: mp 78∼80 °C;
1H NMR (CDCl3) δ 7.42 (6H, m), 7.29 (4H, m), 5.26 (1H, d, J )
5.9 Hz), 4.98 (1H, d, J ) 5.8 Hz), 1.25 (9H, s); IR 2981 (m), 2931
C
19H17NO5: C, 67.20; H, 5.05; N, 4.13. Found: C, 67.13; H, 4.73;
N, 3.96.
Rea r r a n gem en t of a p-Meth oxycin n a m a te Diol to th e
Cor r esp on d in g N-Ben zoyloxa zolid in -2-on e. Ethyl p-meth-
oxycinnamate diol (racemic, 214 mg, 0.89 mmol) was converted
to the corresponding cyclic N-benzoyliminocarbonate (the ben-
zoyl isothiocyanate step took 1 h), which was then treated with
tetrabutylammonium bromide (370 mg, 1.15 mmol) as described
above for the reaction with a tartrate ester (reflux for 9 h). The
reaction mixture was partitioned between ethyl acetate and
water. The organic phase was separated, washed with brine, and
dried (Na2SO4). The concentrated crude product was chromato-
graphed on a silica column (hexane:EtOAc ) 2:1) to yield the
product as a 1.4:1 mixture of regioisomers (271 mg, 83%). The
regioisomers were partially separated by column chromatogra-
phy (hexane:EtOAc ) 2:1). R-N-isomer (minor): 1H NMR (CDCl3)
δ 7.74 (2H, d, J ) 7.1 Hz), 7.59 (1H, t, J ) 7.4 Hz), 7.46 (2H, t,
J ) 7.4 Hz), 7.36 (2H, d, J ) 8.7 Hz), 6.98 (2H, d, J ) 8.7 Hz),
5.49 (1H, d, J ) 5.5 Hz), 5.01 (1H, d, J ) 5.5 Hz), 4.33 (2H, q,
J ) 7.1 Hz), 3.85 (3H, s), 1.31 (3H, t, J ) 7.1 Hz). â-N-isomer
(major): 1H NMR (CDCl3) δ 7.67 (2H, d, J ) 7.2 Hz), 7.55 (1H,
t, J ) 7.4 Hz), 7.42 (2H, t, J ) 7.8 Hz), 7.38 (2H, d, J ) 8.7 Hz),
6.94 (2H, d, J ) 8.7 Hz), 5.58 (1H, d, J ) 4.7 Hz), 4.87 (1H, d,
J ) 4.7 Hz), 4.36 (2H, q, J ) 7.1 Hz), 3.80 (3H, s), 1.35 (3H, t,
J ) 7.1 Hz).
(m), 1826 (s), 1735 (s) cm-1
.
The N-Boc-oxazolidin-2-one (163 mg, 0.48 mmol) was then
treated with Cs2CO3 (163 mg, 0.5 mmol) in absolute ethanol (10
mL) at room temperature. The mixture was concentrated and
the residue chromatographed on a silica column (2:1 hexanes-
EtOAc) to yield the N-Boc-amino alcohol (117 mg, 78%): mp
112-113 °C; 1H NMR (CDCl3) δ 7.29 (10H, m), 5.40 (1H, d, J )
7.5 Hz), 4.82 (2H, m), 2.72 (1H, brs); IR 3317 (b), 2981 (m), 1672
(s), 1521 (s) cm-1
.
The final N-Boc deprotection was performed with the N-Boc-
amino alcohol (117 mg, 0.37 mmol) in a 1:1 mixture (v/v) of
trifluoroacetic acid-dichloromethane (10 mL). After being stirred
at room temperature for 1 h, the mixture was concentrated and
the residue partitioned between 10% aqueous Na2CO3 and
EtOAc. The organic phase was separated, dried (Na2SO4), and
chromatographed on a silica column (EtOAc) to yield (S,S)-2-
amino-1,2-diphenylethan-1-ol (60 mg, 77%) as a white solid: [R]D
-99.7 (c 0.8, EtOH);13 mp 104-108 °C; 1H NMR (CDCl3) δ 7.26
(10H, m), 4.67 (1H, d, J ) 6.5 Hz), 3.99 (1H, d, J ) 6.5 Hz), 1.85
(3H, br); IR 3367 (s), 3086 (b), 1448 (s) cm-1
.
Ack n ow led gm en t. This work was supported by the
Korea Research Foundation (Grant 1998-001-D00521).
The authors gratefully acknowledge the generous gift
of enantiomerically pure diols from Prof. Sharpless and
Dr. Gao.
Rea r r a n gem en t of Stilben ed iol to th e Cor r esp on d in g
N-Ben zoyloxa zolid in -2-on e. (R,R)-Stilbenediol (208 mg, 0.97
mmol) was converted to the corresponding cyclic N-benzoylimino-
carbonate as described above (the benzoyl isothiocyanate step
took 1 h). Lithum iodide (160 mg, 1.2 mmol) was added and the
entire mixture heated to reflux overnight. The reaction mixture
was partitioned between ethyl acetate and water. The organic
phase was separated, washed with brine, and dried (Na2SO4).
The concentrated crude product was chromatographed on a silica
column (hexane:EtOAc ) 3:1) to yield the pure product (243.4
J O991079X
(13) (a) The observed optical rotation of this compound is comparable
to the literature value ([R]D -106.7 (c 0.72, EtOH)),13b confirming that
little, if any, racemization has taken place during the entire transfor-
mations and the course of the stereochemistry is indeed retention at
both carbinol carbons. (b) Shimizu, M.; Tsukamoto, K.; Matsutani, T.;
Fujisawa, T. Tetrahedron 1998, 54, 10265.
1
mg, 73%): [R]D 13.1 (c 0.82, CHCl3); mp 168-170 °C; H NMR
(CDCl3) δ 7.8 (2H, d, J ) 7.8 Hz), 7.58 (1H, m), 7.49-7.29 (12H,
m), 5.46 (1H, d, J ) 8.0 Hz), 5.42 (1H, d, J ) 7.9 Hz); IR 3068