Highly Deoxygenated Sugars. II. Synthesis of Chiral Cyclopentenes via Novel Carbocyclization of C-4 Branched Deoxysugars

Article abstract of DOI:10.1081/CAR-120025324

Tri-O-acetyl-D-glucal (1) was converted via Ferrier type II rearrangement with high α-selectivity to 2,3-unsaturated methyl glycosides 2a and 2b using ferric chloride as the catalyst. Palladium induced allylic substitution with sodium tert-butylacetoacetate as a nucleophile leads to C-4 branched sugars. Subsequent hydrogenation followed by treatment with trifluoroacetic acid affords the highly functionalized chiral cyclopentene derivative 5a as a versatile chiral building block for cyclopentanoids.

Full text of DOI:10.1081/CAR-120025324

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Highly Deoxygenated Sugars. II. Synthesis of Chiral
Cyclopentenes via Novel Carbocyclization of C‐4
Branched Deoxysugars
Karsten Krohn a , Dietmar Gehle a , Oliver Kamp a & Teunis van Ree a
a Department of Chemistry , University of Paderborn , Warburger Str. 100, Paderborn, 33098,
Germany
Published online: 23 Aug 2006.
To cite this article: Karsten Krohn , Dietmar Gehle , Oliver Kamp & Teunis van Ree (2003) Highly Deoxygenated Sugars.
II. Synthesis of Chiral Cyclopentenes via Novel Carbocyclization of C‐4 Branched Deoxysugars , Journal of Carbohydrate
Chemistry, 22:6, 377-383, DOI: 10.1081/CAR-120025324
To link to this article: http://dx.doi.org/10.1081/CAR-120025324
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JOURNAL OF CARBOHYDRATE CHEMISTRY
Vol. 22, No. 6, pp. 377–383, 2003
Highly Deoxygenated Sugars. II. Synthesis of Chiral
Cyclopentenes via Novel Carbocyclization
of C-4 Branched Deoxysugarsy
*
Karsten Krohn, Dietmar Gehle, Oliver Kamp, and Teunis van Ree
Department of Chemistry, University of Paderborn, Paderborn, Germany
ABSTRACT
Tri-O-acetyl-D-glucal (1) was converted via Ferrier type II rearrangement with high a-
selectivity to 2,3-unsaturated methyl glycosides 2a and 2b using ferric chloride as the
catalyst. Palladium induced allylic substitution with sodium tert-butylacetoacetate as a
nucleophile leads to C-4 branched sugars. Subsequent hydrogenation followed by
treatment with trifluoroacetic acid affords the highly functionalized chiral cyclopen-
tene derivative 5a as a versatile chiral building block for cyclopentanoids.
Key Words: Deoxygenated sugars; Ferrier type II rearrangement; Pd-catalyzed
allylic substitution; Carbocyclization; Cyclopentene.
yDedicated to Professor Dr. Hans Paulsen on the occasion of his 80th birthday.
*
Correspondence: Karsten Krohn, Department of Chemistry, University of Paderborn, Warburger
Str. 100, 33098 Paderborn, Germany; E-mail: kk@chemie.uni-paderborn.de.
377
DOI: 10.1081/CAR-120025324
0732-8303 (Print); 1532-2327 (Online)
www.dekker.com
Copyright D 2003 by Marcel Dekker, Inc.

378
Krohn et al.
INTRODUCTION
In a first communication on the utilization of sugars as chiral building blocks, we
synthesized highly deoxygenated carbohydrate derivatives starting from commercially
available tri-O-acetyl-D-glucal (1).[1] In the present study, we wanted to investigate a
new type of carbocyclization in an aldol-type reaction of the protected anomeric
aldehyde with reactive functional groups, attached to the deoxygenated sugar core.
RESULT AND DISCUSSION
To achieve deoxygenation in only a few steps, we started from glucal acetate (1),
which was converted to a mixture of the 2,3-deoxygenated a,b-methyl-O-glycosides 2a
and 2b,[2] employing the ferric chloride catalyzed Ferrier type II rearrangement.[3]
Using this catalyst, much milder reaction conditions were possible than with the
previously used boron trifluoride etherate[4] or other catalysts (review [5]). In addition,
the yields were much better (91%) and the a,b-ratio (8:1) was shifted in favor of the a-
anomer 2a (Scheme 1). It was possible to purify the a-anomer 2a to a factor of ca. 50:1
by flash chromatography on silica gel.
The key step in the attachment of a keto ester at C-4 was the palladium-catalyzed
allylic substitution starting from 2a. Palladium-catalyzed allylic substitutions are
widely employed in organic synthesis, particularly in carbon-carbon bond formation
(reviews [6,7]). In carbohydrate chemistry for instance, Baer and Hanna used the
reaction in the synthesis of aminated and alkylated 2,3-unsaturated sugars with amines or
reactive methylene compounds such as sodium dimethyl malonate as the nucleophiles.[8]
Surprisingly, b-keto esters have not yet been employed to attach carbon side chains at C-
4 of sugars. In contrast to the malonate alkylation, a new stereogenic center is formed at
the C-H acidic center of the keto ester, with little stereoselectivity expected in the
formation of this new chiral center. However, this stereochemical problem was not
relevant because the stereogenic center was removed later in the sequence by
decarboxylation of the b-keto ester to a ketone.
More important concerns of the palladium catalyzed allylic substitution were the
stereoselectivity of the incoming nucleophile and the regioselectivity of the process,
e.g. a- or g-addition with respect to the two allylic leaving groups in 2a. The
assumed transition state A of the process is shown in Scheme 2. In the initial step,
the allylic acetate forms intermediate p-allylpalladium complexes in the presence of tet-
rakis(triphenylphosphine) palladium. The reactive catalyst is regenerated after substitu-
tion of the leaving group by the nucleophile in the presence of excess triphenylphosphine.
Scheme 1. Ferric chloride-catalyzed a-selective Ferrier type II reaction of tri-O-acetyl-D-glucal (1).

Highly Deoxygenated Sugars. II
379
Scheme 2. Regio- and stereoselectivity of the palladium-catalyzed allylic substitution starting
from allylic acetate 2.
Both the regioselectivity and stereoselectivity of the nucleophile addition depend on the
formation of the Z3-palladium-allyl complex.
In the present case, the nearly pure a-anomer 2a was reacted in the initial ex-
periments with sodium tert-butylacetoacetate as the nucleophile and tetrakis(triphenyl-
phosphine)palladium/triphenylphosphine as the catalyst (Scheme 2). In later reactions,
the 8:1 mixture of 2a and 2b was also used without any losses in selectivity or yield.
The resulting keto ester 3, with the keto ester attached to a deoxygenated sugar moiety,
was obtained in 88% yield. As expected, an approximately 1:1 ratio of diastereomers
was formed at the C-H acidic keto ester function as deduced from the NMR spectra of
3. However, the reaction was entirely stereoselective with respect to the attack of the
nucleophile at C-4 of the Z3-palladiumallyl complex A. In addition, the completely
regioselective a-substitution was secured by the better leaving group capability of the
acetate versus the anomeric methoxy group. These results are in agreement with
literature precedence as described in a review by Frost et al.[9]
In the next step, the C-4 alkylated unsaturated sugar derivative 3 was hydrogenated
under standard conditions with 5% Pd/C and hydrogen in ethanol to obtain the
saturated branched deoxy sugar 4 in 95% yield (Scheme 3).
Five transformations were still needed to arrive at the anticipated cyclization
product via aldol-type reaction starting from 4: saponification and decarboxylation of
the ester group, cleavage of the anomeric methyl glycoside, and aldol reaction followed
by water elimination of the terminal methyl ketone with the aldehyde at the anomeric
center. All these reactions might proceed under acidic catalysis and, therefore,
Scheme 3. Acid-catalyzed transformation of keto ester 4 to either the cyclopentene 5a or the
lactone 6.

380
Krohn et al.
compound 4 was treated for 30 minutes with trifluoroacetic acid in dichloromethane
solution (Scheme 3). To our delight, only two major products were formed in this
multistep sequence: the chiral cyclopentene 5a and the bridged seven-membered
lactone 6. Evidently, cleavage of the tert-butyl ester in 4 was the initial step, followed
by the decarboxylation and subsequent aldol condensation with the intermediate
aldehyde, derived from cleavage of the methyl glycoside 4.
In a systematic study to improve the yields of either cyclopentene 5a or lactone 6,
we found that the reaction at room temperature afforded the desired cyclopentene 5a as
essentially the only product in 71% yield. At lower temperatures (0°C), the rate of
decarboxylation was apparently slower than the opening of the hemiacetal and the
bicyclic lactone 6 was formed predominantly (68%). It has to be stressed that the five
membered carbocycle 5a has two clearly defined chiral centers determined by the
stereochemistry of the sugar core. One stereogenic center is located at the ring position
and the other one in the side chain. The compound possesses an array of highly
condensed functional groups and the primary hydroxyl group is selectively protected as
an acetate. These functional groups can all be easily used for further transformations.
For instance, saponification of the primary acetate proceeds quantitatively to yield the
diol 5b, opening the way to an aldehyde functionality after periodate glycol cleavage.
To the best of our knowledge, this is the first example, possibly extendable to other
sugar glycals, in which a keto side chain and the anomeric aldehyde are condensed
in an aldol-type condensation to form a cyclopentene. The product may prove to be an
easily available chiral starting material for cyclopentanoid natural products of
biological importance which have been synthetic targets over the years (e.g. pros-
taglandins, thromboxanes).[10,11]
In summary, this paper describes the synthesis of the chiral cyclopentene 5a in only
four steps and 54% overall yield, starting from commercially available glucal acetate 1.
A separation of stereoisomeric intermediates is not required at any stage of the synthesis.
EXPERIMENTAL
General remarks and instrumentation. Silica gel 60 F254 coated plates from
Merck AG Darmstadt were used for TLC. Spots were detected by UV light (l = 254
and 366 nm), spraying and heating with 8% ethanolic sulfuric acid or the
cerium(IV)molybdato phosphoric acid reagent (Merck AG). Preparative LC was
performed using silica gel plates (1 mm) from Macherey and Nagel. Melting points
were recorded with a Gallenkamp Melting Point apparatus (uncorrected); IR spectra:
NICOLET 510 P; optical rotations: Perkin-Elmer polarimeter 241 (589 nm); elemental
analyses: Perkin-Elmer Elementar Analysator 240; mass spectra: FINNEGAN MAT
8200 and FISON MD 800, relative intensities in brackets; NMR spectra: Bruker ARX
200 (200/50 MHz) and Bruker AMX 300 (300/75 MHz) spectrometer. GC: Hewlett
Packard 5890 Series II, column: FS-SE-52.
- and -Methyl 4,6-di-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranoside (2a
and 2b).[2] To a solution of 3,4,6-tri-O-acetyl-D-glucal (2.00 g, 7.3 mmol) and
methanol (1.1 equiv) in dried CH2Cl2 was added a 0.1 M solution of FeCl3 (0.01 equiv
in CH2Cl2).[3] The reaction was monitored by TLC [pentane: ethyl acetate = 7:3; ca. 30
min] and then quenched by addition of saturated aqueous NaHCO3 solution (120 mL).

Highly Deoxygenated Sugars. II
381
The phases were separated, the aqueous phase was extracted twice with CH2Cl2, and
the combined organic phases were washed with brine (50 mL), dried (MgSO4), and the
solvent removed under reduced pressure. The crude mixture was analyzed by GC
(130°C to 200°C; 10°C/min) to show an 8:1 ratio of the anomeric isomers. The mixture
was filtered over a short column of silica gel to afford the methyl-4,6-di-O-acetyl-2,3-
dideoxy-D-erythro-hex-2-enopyranoside 2a and 2b in 91% yield (a/b ratio 8:1). 1H
NMR (200 MHz, CDCl3) (mixture of anomers): d = 2.02, 2.03 (2 Â s, 2 Â 3 H,
2 Â Ac-CH3), 3.37 (s, 3 H, OCH3), 3.94–4.04 (m, 1 H, 5-H), 4.06–4.23 (m, 2 H,
2 Â 6-H), 4.85–4.96 (m, 1 H, 1-H), 5.08–5.25 (m, 1 H, 4-H), 5.77–5.90 (m, 2 H, 2-H,
3-H). 13C NMR (50 MHz, CDCl3) (mixture of anomers): d = 20.6, 20.8 (2 Â q,
2 Â Ac-CH3), 55.7 (q, OCH3), 62.8 (t, C-6), 65.1, 66.7 (2 Â d, C-4, C-5), 95.2 (d, C-
1), 127.5, 129.06 (2 Â d, C-2, C-3), 170.1, 170.6 (2 Â s, 2 Â Ac-C=O).
Methyl 6-O-acetyl-2,3,4-trideoxy-4-[acetyl(tert-butoxycarbonyl)methyl]- -D-ery-
thro-hex-2-enopyranoside (3) (mixture of isomers). tert-Butyl acetoacetate (6.3 mL,
38 mmol) was deprotonated under argon at 0°C in dry THF (50 mL) by addition of sodium
hydride (2.8 g, 42 mmol). The clear solution of the anion was added dropwise under argon
via a Teflon tube into a flask containing 2a and 2b (6.18 g, 25.3 mmol), triphenylphos-
phine (0.17 g, 0.63 mmol) and tetrakis(triphenylphosphine)palladium (0.07 g, 0.06 mmol,
1/400 equiv) in dry THF (100 mL). The solution was refluxed for 8 h (TLC and GC and
monitoring). The reaction was then quenched by addition of ammonium chloride (100
mL), the aqueous phase was extracted with CH2Cl2 (3 Â 60 mL), the combined organic
layers were washed with brine, and dried over MgSO4. After evaporation of the solvent,
the crude product was purified by column chromatography (PE:EtOAc = 9:1 to 3:1) to
yield the branched sugar 3 (7.6 g, 88%) as a 1:1 mixture of diastereomers.
1
[a]D = + 103.9°, (c 1.0, CHCl3). H NMR (200 MHz, CDCl3) (mixtures of isomers):
d = 1.37–1.46 (m, 9 H, OC(CH3)3), 1.94–2.06, 2.15–2.20 (2 Â m, 6 H, Ac-CH3, 3 Â 4’-
H), 2.79–2.98, 3.28–3.48 (2 Â m, 5 H, 4-H, 1-OCH3, 2’-H), 3.84–4.40 (m, 3 H, 5-H,
2 Â 6-H), 4.48–4.97 (m, 1 H, 1-H), 5.62–5.91 (m, 2 H, 2-H, 3-H). 13C NMR (50 MHz,
CDCl3) (mixture of isomers): d = 20.5 (q, Ac-CH3), 27.6 (3 Â s, OC(CH3)3), 29.1 (d, C-
4’), 33.6 (d, C-4), 54.9 (q, OCH3), 58.3 (d, C-2’), 63.6 (t, C-6), 66.4 (d, C-5), 82.7 (q,
OC(CH3)3), 95.1 (d, C-1), 125.3 (d, C-2), 129.5 (d, C-3), 167.0 (s, C-1’), 170.6 (s, Ac-
C=O), 201.1 (s, C-3’). IR (Film): n = 2979 cmÀ1 (m, C–H), 2938 (m, C–H), 2829 (w, C–
H), 1740 (s, C=O, ester), 1716 (s, C=O, ketone), 1654 (w, C=C), 1629 (w, C=C), 1454 (m,
C–H), 1394 (m, C–H), 1369 (s, C–H), 1241 (s, C–O), 1147 (s, C–O), 1049 (s, C–O),
966 (m), 843 (w). MS (CI, isobutane): m/z (%) = 343 (1) [M+ + H], 311 (18), 269 (4), 255
(100), 237 (11), 213 (9), 195 (16), 151 (5), 103 (3), 57 (43) [C3H5O+], 43 (10) [CH3CO+].
Anal. Calcd for C17H26O7: C, 59.64; H, 7.65. Found: C, 59.14; H, 7.79.
Methyl 6-O-acetyl-2,3,4-trideoxy-4-[acetyl(tert-butoxycarbonyl)methyl]- -D-
erythro-hexopyranoside (4) (mixture of isomers). A solution of 3 (2.04 g, 5.97
mmol) in ethanol was hydrogenated with 5% Pd/C (0.07 mg, 0.5 mol, 1 atm hydrogen
pressure). After 5 h, the catalyst was filtered off and the solvent of the filtrate was
evaporated. Compound 4 was isolated as a colorless oil (1.95 g, 95%). [a]D = +89.6°,
1
(c 1.15, CHCl3). H NMR (200 MHz, CDCl3) (mixture of isomers): d = 1.30–1.75 (m,
13 H, OC(CH3)3, 2 Â 2-H, 2 Â 3-H), 1.97–2.04, 2.10–2.41 (2 Â m, 7 H, Ac-CH3,
3 Â 4’-H, 4-H), 3.24–3.32 m, 3 H, 1-OCH3), 3.36–3.50 (m, 1 H, 2’-H), 3.59–4.66 (m,
4 H, 5-H, 2 Â 6-H, 1-H). 13C NMR (50 MHz, CDCl3) (mixture of isomers): d = 19.8

382
Krohn et al.
(t, C-3), 20.4 (q, Ac-CH3), 27.5 (3 Â s, OC(CH3)3), 29.1 (d, C-4’), 29.2 (t, C-2), 34.5
(d, C-4), 53.9 (q, OCH3), 59.7 (d, C-2’), 64.1 (t, C-6), 68.6 (d, C-5), 82.1 (q,
OC(CH3)3), 97.6 (d, C-1), 167.5 (s, C-1’), 170.4 (s, Ac-C=O), 201.3 (s, C-3’). IR
(Film): n = 2976 cmÀ1 (s, C–H), 2936 (s, C–H), 2833 (m, C–H), 1740 (s, C=O, ester),
1721 (s, C=O, ketone), 1630 (m, C=C), 1456 (m, C–H), 1393 (m, C–H), 1369 (s,
C–H), 1238 (s, C–O), 1147 (s, C–O), 1131 (s, C–O), 1055 (s, C–O), 964 (m), 865
(w). MS (CI, isobutane): m/z (%) = 345 (1) [M+ + H], 313 (13), 271 (2), 257 (73), 239
(5), 213 (11), 197 (3), 195 (3), 153 (3), 103 (2), 57 (100) [C3H5O+], 43 (36) [CH3CO+].
Anal. Calcd for C17H28O7: C, 59.29; H, 8.12. Found: C, 59.16; H, 8.12.
1 (R), 5 (R)-1-[5-(2-Acetoxy-1-hydroxyethyl)-cyclopent-1-enyl]-ethanone (5a).
Compound 4 (128 mg, 0.38 mmol) was treated at 0°C with a mixture of CH2Cl2/TFA
(2:1, 3 mL). After the addition, the solution was allowed to warm up to room
temperature within 5 min, and after 30 min at 20°C it was quenched by addition of a
saturated aqueous solution of NaHCO3 (20 mL). The aqueous phase was extracted with
CH2Cl2 (3 Â 5 mL), the combined organic layers were washed twice with brine (each
5 mL), dried over MgSO4, and the solvent was evaporated under reduced pressure.
Chromatography on silica gel (PE:EtOAc = 7:3 to 1:1) afforded the carbocycle 5a (57
1
mg, 71%). [a]D = + 41.5°, (c 0.6, CHCl3). H NMR (200 MHz, CDCl3): d = 1.71–1.88
(m, 1 H, 4’-Ha), 2.00 (s, 3 H, Ac-CH3), 2.03–2.21 (m, 1 H, 4’-Hb), 2.32 (s, 3 H, 3 Â 2-
H), 2.42–2.64 (m, 2 H, 2 Â 3’-H), 3.14–3.26 (m, 1 H, 5’-H), 3.76 (dd, J = 11.7 Hz,
J = 8.7 Hz, 1 H, 1@-H), 3.95–4.00 (m, 2 H, 2 Â 2@-H), 6.87–6.91 (m, 1 H, 2’-H). 13C
NMR (50 MHz, CDCl3): d = 20.9 (q, Ac-CH3), 25.7 (t, C-4’), 27.0 (q, C-2), 32.6 (t, C-
3’), 48.1 (d, C-5’), 66.7 (t, C-2@), 71.1 (d, C-1@), 145.0 (s, C-1’), 149.9 (d, C-2’), 171.3
(s, Ac-C=O), 198.7 (s, C-1). IR (Film): n = 3430 cmÀ1 (s, O–H), 2951 (m, C–H),
2921 (m, C–H), 2848 (w, C–H), 1735 (s, C=O, Ester), 1659 (s, C=O, a,b-unsaturated
ketone), 1631 (w, C=C), 1431 (m, C–H), 1373 (s, C–H), 1242 (s, C–O), 1040 (s, C–
O). MS (CI, isobutane): m/z (%) = 213 (37) [M+ + H], 195 (100) [M+ + H–H2O], 153
(15), 135 (8), 125 (3), 110 (2), 91 (2), 57 (30) [C3H5O+], 43 (17) [CH3CO+].
Anal. Calcd for C11H16O4: C, 62.25; H, 7.60 Found: C, 61.44; H, 7.79.
1@(R), 5’(R)-1-[5-(1,2-Dihydroxyethyl)-cyclopent-1-enyl]-ethanone (5b). Carbo-
cycle 5a (140 mg, 0.66 mmol) was dissolved in absolute methanol (10 mL) and to this
solution a small piece of sodium was added. After 4 h the mixture was neutralized to
pH = 7 with Amberlite 120. The resin was filtered off and the solvent was evaporated
to afford the crude product, which was passed over silica to yield 5b (105 mg, 0.62
1
mmol) in 95% yield. [a]D = + 38.3°, (c 0.6, CHCl3). H NMR (200 MHz, CDCl3):
d = 1.95–2.05 (m, 2 H, 4’-H), 2.37 (s, 3 H, 3 Â 2-H), 2.50–2.66 (m, 2 H, 2 Â 3’-H),
3.05–3.16 (m, 1 H, 5’-H), 3.31–3.51 (m, 2 H, 2 Â 2@-H), 3.81–3.91 (m, 1 H, 1@-H),
4.28 (br, 2 Â OH), 26.97–6.99 (m, 1 H, 2’-H). 13C NMR (50 MHz, CDCl3): d = 25.3
(t, C-4’), 27.1 (q, C-2), 3.1 (t, C-3’), 47.0 (d, C-5’), 65.0 (t, C-2@), 72.9 (d, C-1@), 145.7
(s, C-1’), 150.2 (d, C-2’), 199.4 (s, C-1). IR (Film): n = 3394 cmÀ1 (s, O–H), 2929 (m,
C–H), 2921 (m, C–H), 1651 (s, C=O, a,b-unsaturated ketone), 1629 (w, C=C), 1429
(m, C–H), 1377 (s, C–H), 1289 (s, C–O), 1067 (s, C–O).
Anal. Calcd for C9H14O3: C, 63.51; H, 8.29 Found: C, 62.70; H, 8.33.
4-Acetyl-6-acetoxymethyl-2,7-dioxabicyclo[3.2.2]nonan-3-one (6). Keto ester 4
(256 mg, 0.76 mmol) was dissolved at 0°C in a mixture of CH2Cl2/TFA (2:1, 6 mL).

Highly Deoxygenated Sugars. II
383
The mixture was stirred at 0°C for 2 h and then a saturated solution of NaHCO3 (20
mL) was added. The aqueous phase was extracted with CH2Cl2 (3 Â 5 mL), the
combined organic layers were washed with brine, dried over MgSO4, and the solvent
was evaporated under reduced pressure. Chromatography (PE:EtOAc = 7:3 to 1:1)
1
afforded the lactone 7 (113 mg, 58%); mp = 51°C. [a]D = + 55.5°, (c 0.93, CHCl3). H
NMR (200 MHz, CDCl3): d = 1.37–1.56, 1.83–1.94 (2 Â m, 4 H, 2 Â 8H, 2 Â 9H),
2.03 (s, 3 H, AcCH3), 2.42 (s, 3 H, 3 Â 2’-H), 2.84–2.92 (m, 1 H, 5-H), 3.62 (d, J =
11.6 Hz, 1 H, 4-H), 3.65–3.73 (m, 1 H, 6-H), 3.95–4.11 (m, 2 H, 2 Â 1@-H), 5.46 (d, J
= 4.0 Hz, 1 H, 1-H). 13C NMR (50 MHz, CDCl3): d = 20.8 (q, AcCH3), 21.2, 21.7
(2 Â t, C-8, C-9), 30.1 (q, C-2’), 35.4 (d, C-5), 52.7 (d, C-4), 65.8 (t, C-1@), 72.7 (d, C-
6), 98.4 (d, C-1), 170.8, 171.3 (2 Â s, C-3, Ac-C=O), 199.9 (s, C-1’). IR (Film):
n = 2950 cmÀ1 (s, C–H), 2867 (m, C–H), 1786 (s, C=O, lactone), 1793 (s, C=O,
ester), 1734 (s, C=O, ketone), 1377 (m, C–H), 1248 (s, C–O), 1160 (s, C–O), 1098 (s,
C–O), 1036 (s, C–O). MS (EI, 70 eV): m/z (%) = 214 (5) [M+], 213 (10) [M+–H], 196
(26) [M+–H2O], 154 (18), 136 (8), 123 (24), 107 (15), 67 (6), 43 (100) [CH3CO+].
Anal. Calcd for C10H14O5: C, 56.07; H, 6.59 Found: C, 56.22; H, 6.52.
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Received December 10, 2002
Accepted May 1, 2003