Novel α-Hydroxy-α-(2-hydroxy-1-naphthyl)acetic Acid and its Derivatives. Preparation and Optical Resolution

Article abstract of DOI:10.1055/s-2004-815953

A facile preparation of novel α-hydroxy-α-(2-hydroxy-1- naphthyl)acetic acid by a base-catalyzed condensation of 2-naphthol with glyoxylic acid is described. One of its derivatives, α-methoxy-α-(2- methoxy-1-naphthyl)acetic acid, has successfully been resolved.

Full text of DOI:10.1055/s-2004-815953

PAPER
341
Novel -Hydroxy- -(2-hydroxy-1-naphthyl)acetic Acid and its Derivatives.
Preparation and Optical Resolution
N
ovel -Hydroxy--(2-hy
a
droxy-1-na
k
phthyl)aceti
o
c
Acidand it
t
s
D
eriv
o
atives Yamaye,*a Hirotaka Okano,a Yoshiko Motoyanagi,a Namiko Cho (Toh),a Tetsutaro Yoshinaga,b
Toshiaki Tsuru,c Katsuya Mukaec
a
Faculty of Engineering, Kyushu Kyoritsu University, 1-8 Jiyugaoka, Yahatanishi, Kitakyushu 807-8585, Japan
Fax +81(93)6038186; E-mail: yamaye@kyukyo-u.ac.jp
b
Department of Applied Chemistry, Kyushu Institute of Technology, 1-1 Sensuicho, Tobata, Kitakyushu 804-8550, Japan
c
Department of Industrial Chemistry, Kyushu Sangyo University, 3-1 Matsukadai, 2-Chome, Higashiku, Fukuoka 813-8503, Japan
Received 30 October 2003; revised 24 December 2003
Abstract: A facile preparation of novel -hydroxy- -(2-hydroxy-
1-naphthyl)acetic acid by a base-catalyzed condensation of 2-naph-
thol with glyoxylic acid is described. One of its derivatives, -meth-
oxy- -(2-methoxy-1-naphthyl)acetic acid, has successfully been
resolved.
Key words: -hydroxy- -(2-hydroxy-1-naphthyl)acetic acid
-
methoxy- -(2-methoxy-1-naphthyl)acetic acid, 2-naphthol, glyox-
ylic acid, optical resolution
Scheme 1 Preparation of 1 and its derivatives.
Mandelic acid finds a wide variety of applications in me-
dicinal, agricultural, and other compounds.1 One of its de-
rivatives, o-hydroxymandelic acids have been prepared Treatment of 1 with MeOH in the presence of a catalytic
via electrophilic substitution of phenols.2,3 However, con- amount of H2SO4 at room temperature for 3 hours was
densation of phenols with glyoxylic acid, for example, conducted, yielding methyl -hydroxy- -(2-hydroxy-1-
usually gives a mixture of isomeric products and much ef-
naphthyl)acetate (2), with the -hydroxyl group intact. On
fort has focused on regioselective substitution of phenols.2 the other hand, when heated in boiling MeOH for 3 hours,
Recently, an increasing number of stereoselective synthe- 1 was transformed into methyl -methoxy- -(2-hydroxy-
ses of the corresponding optically active -hydroxy acids 1-naphthyl)acetate (3) in 96% yield. Reactions with other
have also been reported.3
alcohols including EtOH also gave the similar results
(Scheme 1).
To our surprise, however, there have been no reports on
condensation of naphthols with glyoxylic acid (and its de-
rivatives), producing the corresponding -hydroxy acids.
Controlled regioselective substitution should be compara-
tively easy for naphthols. Stereoselective preparation of
the corresponding optically active -hydroxy acids will
also thus be accessible. Here we report a convenient prep-
aration of racemic -hydroxy- -(2-hydroxy-1-naph-
thyl)acetic acid (1) and the optical resolution of one of its
derivatives, together with a few examples of utilization.
+
CHCOOR
O
CHCOOR
OH
R = Me, Et
Figure 1 Possible intermediates.
These types of ‘simultaneous esterification-etherification’
(and failure of the optical resolution of 1) could be ex-
plained by a possible intervention of an o-quinone me-
thide or a benzylic cation intermediate shown in Figure 1.
o-Quinone methides are regarded as well-known reactive
intermediates and a number of methods for their forma-
tion have been reported.4 The pyrolysis of o-hydroxyben-
zyl alcohols and related compounds formed the
corresponding o-quinone methides as common intermedi-
ates and their MS spectra were observed.5 In our present
study, too, fragment peaks corresponding to the o-quinone
methide intermediate (EI mode) were detected: m/z (%)
200 (80) for 1, 214 (7) for 2, 214 (17) for 3, 200 (3) for 4,
and 228 (2) for 6. However, attempts to trap a prospective
A base-catalyzed condensation of 2-naphthol with glyox-
ylic acid at room temperature for 4 hours yielded racemic
1 in 98% yield. Such easy accessibility to racemic 1 and
its structural analogy to mandelic acid prompted us to de-
velop a possible use of 1 as a resolving agent, a chiral aux-
iliary, and so forth. Attempted resolutions of racemic 1,
however, have so far not been successful, presumably due
to possible racemization under the resolving conditions.
On the other hand, derivatization of 1 was easy as shown
in Scheme 1.
SYNTHESIS 2004, No. 3, pp 0341–0344
x
x
.
x
x
.2
0
0
4
Advanced online publication: 03.02.2004
DOI: 10.1055/s-2004-815953; Art ID: F10203SS
© Georg Thieme Verlag Stuttgart · New York

342
M. Yamaye et al.
PAPER
o-quinone methide using a couple of dienophiles have so Utilization of (+)-4 as a resolving agent was demonstrated
far been unsuccessful.
by optical resolution via diastereomeric salt formation.
Thus, ( )- -(1-naphthyl)ethylamine (NEA) was smoothly
resolved into (+)-NEA (89%, 81% ee) and (–)-NEA (94%,
88% ee). Other racemic amines, such as PEA and 1-(p-
tolyl)ethylamine, were also resolved in a similar manner
(see experimental).
-Methoxy- -(2-methoxy-1-naphthyl)acetic acid (4) was
obtained from 3 in 98% yield. One-pot two-step reaction
was effective for the preparation of 4; methoxylation of
the 2-hydroxyl group of 3 using dimethyl sulfate in the
presence of LiOH, followed by ester hydrolysis with an
additional LiOH in the same flask. The first-step of the re- In summary, starting from commercially available re-
action was monitored by TLC to confirm the disappear- agents, a simple and convenient procedure for preparing a
ance of the spot corresponding to 3. It was found difficult promising chiral -hydroxy acid derivative has been de-
to obtain the corresponding ester in a pure state in the first veloped and its preliminary application to optical resolu-
step, because further hydrolysis occurred to form 4. An at- tion has been presented.
tempted one-step reaction to accomplish both methoxyla-
tion and methyl ester hydrolysis by addition of the
All reagents were of commercial grade. Melting points were deter-
combined amount of LiOH resulted in unsatisfactory
yields of 4. Use of such bases as NaOH and KOH instead
of LiOH also gave 4 in less than 30% yield.
mined on a Yanaco MP-500D and are uncorrected. IR spectra were
recorded on a Jasco FT/IR-230 spectrophotometer as KBr pellets.
UV-visible spectra were measured on a Perkin-Elmer Lambda 20
spectrophotometer at r.t. 1H and 13C NMR spectra were obtained on
Joel JNM-A500 and JNM-AL400 spectrometers. Chemical shifts
are expressed in ppm relative to TMS as internal standard. Mass
spectra (MS) were obtained on a Joel JMS-SX102A. Microanalyses
Optical resolution of ( )-4 was performed via diastereo-
meric salt formation. Unlike ( )-1, ( )-4 was expected to
be less prone to possible formation of the corresponding
o-quinone methide or benzylic ion and in fact underwent were carried out on a Yanaco CHN corder MT-5. HPLC analysis
was performed on a Jasco HPLC chromatograph (Gulliver series)
a smooth resolution. Diastereomeric salts of ( )-4 with ei-
with a UV detector operating at 240 nm using an ODS column (Jas-
ther (+)- or (–)-1-phenylethylamine (PEA) were formed in
co CrestPak C18T-5) and MeOH–H2O as the mobile phase. Chiral
acetone. Separation and recrystallization of the less sol-
chromatography was performed with a Daicel Chiralcel OD-H col-
umn with n-hexane–2-propanol–TFA or -diethylamine as the mo-
bile phase and a Daicel Crownpak column with aqueous perchloric
acid as the mobile phase. The optical rotations were measured on a
uble salt and its subsequent decomposition with 2 M
KOH afforded (+)-4 ([ ]D20+162, 99% ee) and (–)-4
([ ]D20–161, 97% ee) (Table 1).
Jasco P-1010 polarimeter using the sodium D line at 589 nm. CD
spectra were recorded on a Jasco J-720 spectropolarimeter.
would be expected (Figure 2).
Their CD spectra showed mirror images of one another as
-Hydroxy- -(2-hydroxy-1-naphthyl)acetic Acid (1)
To a suspension of 2-naphthol (5.8 g, 40 mmol) and glyoxylic acid
monohydrate (5.8 g, 60 mmol) in H2O (20 mL) was added 2 M
KOH (50 mL, 0.10 mol) under cooling.
The mixture was stirred at r.t. for 4 h, then neutralized with 2 M HCl
(50 mL, 0.10 mol), extracted with Et2O (3 × 40 mL), the combined
extracts were washed with H2O, and dried (MgSO4). Evaporation of
the solvent gave crude 1 as a yellowish solid (8.6 g, 98%). An ana-
lytical sample was obtained by recrystallization from Et2O–toluene
(20:80); mp 133–135 °C.
IR (KBr): 3530, 3420, 3280, 1725 (C = O), 1630, 810 cm–1.
1H NMR (500 MHz, DMSO-d6): = 5.71 (br s, 1 H, CHOH), 5.95
(s, 1 H, CHCOOH), 7.16–8.10 (m, 6 H, ArH), 9.84 (br s, 1 H,
ArOH), 12.3 (br s, 1 H, COOH).
Figure 2 CD spectra of (+)-4 and (–)-4 in MeOH at 30 °C.
Table 1 Resolution of ( )-4 via the Corresponding Diastereomeric Salts
No. of
Recrystallizations
PEA
Separated Diastereomeric Salts
4
Yield (%)a
[ ]D
Mp (°C)
103–105
103–105
[ ]D
ee (%)c
>99
20,b
20,b
Mp (°C)
(–)
(+)
1
1
177–179
177–179
51
49
+119
–118
+162
–161
97
a Based on half the amount of ( )-4.
b c 0.2, MeOH.
c Determined by HPLC [column: Chiralcel OD-H; eluent: n-hexane–2-propanol-TFA=95:5:0.5; flow rate: 0.5 mL/min; detection: UV (280 nm),
OR].
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Novel Hydroxy- -(2-hydroxy-1-naphthyl)acetic Acid and its Derivatives
343
13C NMR (125.65 MHz, DMSO-d6): = 65.0 (CHCOOH), 117.8,
118.2, 122.4, 124.1, 125.9, 128.1, 128.3, 129.2, 132.8, 152.8, 175.5
(COOH).
MS (FAB): m/z (%) = 218 (M+, 79), 202 (29), 201 (100), 200 (5),
183 (81), 173 (87), 127 (22). Direct introduction of a solid sample
in EI mode at 31.6 °C gave a relative intensity of 80% of the frag-
ment peak at m/z 200.
MS (EI): m/z (%) = 274 (M+, 19), 228 (2), 201 (100), 173 (35), 127
(23).
Anal. Calcd for C16H18O4: C, 70.06; H, 6.61. Found: C, 70.04; H,
6.62.
-Methoxy- -(2-methoxy-1-naphthyl)acetic Acid (4)
To a solution of 3 (5.0 g, 20 mmol) in THF (50 mL) at <5 °C was
added LiOH·H2O (3.5 g, 83 mmol) in H2O (30 mL) and then dime-
thyl sulfate (6.0 mL, 60 mmol) in THF (10 mL). The mixture was
refluxed for 2 h until the spot corresponding to 3 disappeared by
monitoring on TLC, and then cooled to r.t. Additional LiOH·H2O
(5.0 g, 0.12 mol) in H2O (40 mL) was added, and the mixture was
refluxed for an additional 2 h, acidified, and extracted with Et2O (3
× 40 mL). The combined extracts were washed with H2O, dried
(MgSO4), and evaporated in vacuo to remove the solvent. The resi-
dual oil was dissolved in toluene (10 mL) and evaporated in vacuo
to give 4.9 g (98%) of solid as the crude product. Recrystallization
from toluene gave needles; mp 135–137 °C
UV (MeOH): max (log ) = 229 (5.15) nm.
Anal. Calcd for C12H10O4: C, 66.05; H, 4.62. Found: C, 65.81; H,
4.70.
Methyl -Hydroxy- -(2-hydroxy-1-naphthyl)acetate (2)
A solution of 1 (2.5 g, 11 mmol) in MeOH (20 mL), with a few
drops of concd H2SO4, was stirred at r.t. for 3 h, then neutralized
with sat. NaHCO3 solution. Addition of H2O (100 mL) resulted in
the formation of a precipitate, which was collected, washed with
H2O, and dried, giving 1.9 g (74%) of crude product. Recrystalliza-
tion from toluene gave an analytical grade sample of 2; mp 113–
115 °C.
IR (KBr): 3080, 2940, 1720 (C=O), 1620, 815 cm–1.
1H NMR (400 MHz, DMSO-d6): = 3.31 (s, 3 H, CHOCH3), 3.93
(s, 3 H, ArOCH3), 5.70 (s, 1 H, CHCOOH), 7.35–8.18 (m, 6 H,
ArH), 12.6 (br s, 1 H, COOH).
13C NMR (100.4 MHz, DMSO-d6): = 56.9 (CHOCH3), 57.0
(ArOCH3), 73.6 (CHCOOH), 114.0, 118.0, 123.4, 124.1, 126.4,
128.1, 128.8, 130.3, 131.9, 155.1, 172.4 (COOH).
MS (EI): m/z (%) = 246 (M+, 90), 204 (94), 201 (100), 200 (3), 185
(66), 171 (67), 169 (41), 141 (52), 128 (44), 127 (52), 126 (41), 115
(75).
IR (KBr): 3510, 3160, 2940, 1730 (C=O), 1625, 820 cm–1.
1H NMR (400 MHz, DMSO-d6): = 3.53 (s, 3 H, COOCH3), 5.88
(s, 1 H, CHOH), 6.01 (s, 1 H, CHCOOCH3), 7.15–8.05 (m, 6 H,
ArH), 9.93 (s, 1 H, ArOH).
13C NMR (100.4 MHz, DMSO-d6): = 51.6 (COOCH3), 64.8
(CHCOOCH3), 117.1, 118.0, 122.3, 123, 6, 126.0, 128.0, 128.1,
129.4, 132.5, 152.5, 174.3 (COOCH3).
MS (EI): m/z (%) = 232 (M+, 63), 215 (10), 214 (7), 174 (20), 173
(100), 172 (23), 171 (33), 145 (39), 144 (26), 127 (84), 126 (20),
117 (23), 115 (62).
UV (CH3CN): max (log ) = 229 (4.67) nm.
Anal. Calcd for C14H14O4: C, 68.28; H, 5.73. Found: C, 68.19; H,
5.78.
Anal. Calcd for C13H12O4: C, 67.23; H, 5.21. Found: C, 67.34; H,
5.25.
-Methoxy- -(2-hydroxy-1-naphthyl)acetic Acid (5)
Methyl -Methoxy- -(2-hydroxy-1-naphthyl)acetate (3)
A solution of 1 (5.0 g, 23 mmol) in MeOH (50 mL), with concd
H2SO4 (2.0 mL), was heated under reflux for 3 h, then neutralized
with sat. NaHCO3 solution. Addition of H2O (100 mL) resulted in
the formation of a precipitate, which was collected, washed with
H2O, and dried, giving 5.4 g (96%) of crude product. Recrystalliza-
tion from toluene–hexane (50:50) gave an analytical grade sample
of 3; mp 116–118 °C
To a solution of 3 (3.0 g, 12 mmol) in THF (40 mL) at <5 °C was
added LiOH·H2O (1.5 g, 36 mmol) in H2O (20 mL). After stirring
for 10 h at r.t., the mixture was neutralized with 2 M HCl (13 mL),
and extracted with toluene (3 × 50 mL). The combined extracts
were washed with H2O, dried (MgSO4), and evaporated in vacuo.
The residual oil was dissolved in toluene (10 mL) and evaporated in
vacuo to leave 2.3 g (84%) of a solid product.
IR (KBr): 3380, 2940, 1700 (C=O), 1630, 815 cm–1.
IR (KBr): 3370, 2950, 1715 (C=O), 1630, 815 cm–1.
1H NMR (400 MHz, DMSO-d6): = 3.30 (s, 3 H, CHOCH3), 5.66
(s, 1 H, CHCOOH), 7.17–8.07 (m, 6H, ArH), 9.96 (s, 1 H, ArOH),
12.5 (br s, 1 H, COOH).
13C NMR (100.4 MHz, DMSO-d6): = 56.8 (CHOCH3), 73.8
(CHCOOH), 114.4, 117.7, 122.3, 123.7, 125.9, 127.9, 128.0, 129.6,
132.3, 153.3, 172.5 (COOH).
1H NMR (400 MHz, DMSO-d6): = 3.31 (s, 3 H, CHOCH3), 3.54
(s, 3 H, COOCH3), 5.76 (s, 1 H, CHCOOCH3), 7.18–8.00 (m, 6 H,
ArH), 10.1 (s, 1 H, ArOH).
13C NMR (125.65 MHz, DMSO-d6): = 51.7 (COOCH3), 56.8
(CHOCH3), 73.9 (CHCOOCH3), 114.0, 117.9, 122.6, 123, 4, 126.4,
128.2, 128.3, 130.2, 132.6, 153.7, 171.9 (COOCH3).
MS (EI): m/z (%) = 246 (M+, 15), 214 (17), 187 (100), 186 (20), 172
(25), 171 (85), 144 (17), 127 (23), 115 (40).
Resolution of ( )-4
To a solution of ( )-4 (6.0 g, 24 mmol) in acetone (280 mL) at 50 °C
was added (–)-PEA (1.6 mL, 12 mmol) in acetone (20 mL). The
mixture was allowed to stand overnight at <5 °C. Needles precipi-
tated and these were collected, washed with acetone, and dried to af-
ford the less soluble salt (3.2 g, 72%). Recrystallization from
acetone gave 2.3 g (51%) of (+)-4·(–)-PEA; mp 177–179 °C. The
salt was decomposed by the addition of an equimolar amount of 2
M KOH and the amine liberated was removed by extraction with
Et2O. The resulting solution was neutralized with 2 M HCl, and ex-
tracted with Et2O (3 × 20 mL). The combined extracts were washed
with H2O, dried (MgSO4), and evaporated in vacuo to remove the
solvent. The residue was allowed to stand overnight at <5 °C to give
Anal. Calcd for C14H14O4: C, 68.28; H, 5.73. Found: C, 68.31; H,
5.76.
Ethyl -Ethoxy- -(2-hydroxy-1-naphthyl)acetate (6)
IR (KBr): 3400, 2980, 1710 (C=O), 1625 cm–1.
1H NMR (500 MHz, DMSO-d6): = 1.01 (t, J = 7.02 Hz, 3 H,
CHOCH2CH3), 1.09 (t, J = 7.02 Hz, 3 H, COOCH2CH3), 3.41–3.64
(m, 2 H, CHOCH2CH3), 3.99–4.08 (m, 2 H, COOCH2CH3), 5.84 (s,
1 H, CHCOOC2H5), 7.17–8.07 (m, 6 H, ArH), 10.0 (s, 1 H, ArOH).
13C NMR (125.65 MHz, DMSO-d6): = 14.0 (COOCH2CH3), 15.1
(CHOCH2CH3), 60.2 (COOCH2CH3), 64.4 (CHOCH2CH3), 72.4
(CHCOOCH2CH3), 114.4, 117.7, 122.3, 123.4, 126.0, 127.9, 128.0,
129.8, 132.3, 153.1, 171.3 (COOCH2CH3).
20
crystals of (+)-4 (99% ee); mp 103–105 °C. [ ]D +162 (c 0.2,
MeOH). CD (c 8.70 × 10–6 M, MeOH):
(
) 235 (+21), 218
max
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344
M. Yamaye et al.
PAPER
nm (–17). The filtrate obtained after removal of the needles was re-
duced in vacuo to one-half of its initial volume and allowed to stand
overnight to precipitate optically impure amine salts, which were
removed by filtration. Acetone was added to the resulting filtrate to
a total volume of 280 mL. The mixture was heated to 50 °C and,
upon addition of (+)-PEA (1.6 mL, 12 mmol) in acetone (20 mL),
was stirred for 5 min and filtered. Standing overnight resulted in
precipitation of needles, which were collected and recrystallized
once from acetone to give 2.2 g (49%) of (–)-4·(+)-PEA; mp 177–
179 °C. Decomposition of the salt gave (–)-3 (97% ee); mp 103–
105 °C. [ ]D20 –161 (c 0.2, MeOH). CD (c 8.98 × 10–6 M, MeOH):
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max
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A solution of (+)-4 (1.0 g, 4.0 mmol) in EtOH (10 mL) was added
to ( )-NEA (1.4 g, 7.9 mmol) in EtOH (50 mL) at 70 °C. The mix-
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equimolar amount of 2 M KOH was added to liberate (–)-NEA,
which was extracted with Et2O (2 × 10 mL). The combined extracts
were washed with H2O, dried (MgSO4), and evaporated to give (–)-
NEA (0.63 g, 94%, 88% ee). The filtrate left after removal of the
less soluble salt was concentrated under reduced pressure to half its
volume and the deposited impure salt filtered. The resulting filtrate
was evaporated to leave unreacted (+)-NEA (0.60 g, 89%, 81% ee).
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Synthesis 2004, No. 3, 341–344 © Thieme Stuttgart · New York