(-)-Daucic acid: Proof of D-lyxo configuration, synthesis of its D-ribo, D-xylo, L-arabino and L-lyxo analogs, and biosynthetic implications

Article abstract of DOI:10.1016/j.tetasy.2003.10.007

The dimethyl esters of the 2,6-anhydro-3-deoxy-hept-2-enaric acids with D-xylo, D-lyxo, L-arabino, L-lyxo- and D-ribo-configuration were synthesized from D-galactose and D-mannose, respectively, and further characterized by their di-O-acetyl and di-O-benz

Full text of DOI:10.1016/j.tetasy.2003.10.007

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 14 (2003) 3973–3986
(−)-Daucic acid: Proof of
-ribo, -xylo, -arabino and
implicationsꢀ
D
-lyxo configuration, synthesis of its
D
D
L
L
-lyxo analogs, and biosynthetic
Frieder W. Lichtenthaler,* Ju¨rgen Klotz and Katsumi Nakamura
Clemens-Scho¨pf-Institut fu¨r Organische Chemie und Biochemie, Technische Universita¨t Darmstadt,
D-64287 Darmstadt, Germany
Received 26 September 2003; accepted 14 October 2003
Abstract—The dimethyl esters of the 2,6-anhydro-3-deoxy-hept-2-enaric acids with
-ribo-configuration were synthesized from -galactose and -mannose, respectively, and further characterized by their di-O-ace-
tyl and di-O-benzoyl derivatives. Comparison of their physical data with those of Daucus carota derived products revealed
(−)-daucic acid to have -lyxo-configuration 46 rather than the previously assigned -xylo stereochemistry 1. Dimethyl daucate
D-xylo, D-lyxo, L-arabino, L-lyxo- and
D
D
D
D
D
43 could be converted by acid-induced ring contraction and dehydration into naturally occurring (+)-osbeckic acid 47, thereby
proving its (S)-configuration. Configurational identity in the pyranoid rings of (−)-daucic acid and KDO, together with available
biosynthetic evidence on chelidonic acid 4, a leaf closing factor, suggests a joint, KDO 8-P-based pathway for their biosynthesis
in plants.
© 2003 Elsevier Ltd. All rights reserved.
dimethyl daucate 2 and its di-O-acetyl derivative,3 and
comparisons with NMR data of certain 3,4-unsaturated
hexuronates4a which on close inspection prove unreli-
1. Introduction
(−)-Daucic acid, a seven-carbon sugar–dicarboxylic acid
widely distributed across a range of plant families such
as carrots (Daucus carota), wheat, sunflower, sugar
beet, and tobacco, was first isolated from mature car-
rots in 19712 and shown later to be a 2,6-anhydro-3-
deoxy-
D
-hept-2-enaric acid of
D
-xylo configuration 1.3
The assignment of a dihydropyran structure was based
on the oxidative conversion of its dimethyl ester into
dimethyl chelidonate (2“3), its affiliation to the
D-
series of sugars, i.e. configuration at C-6, convincingly
followed from the high positive rotation of the furanoid
rearrangement product 5 (+79.3 in CHCl3) which corre-
lated well with the equally high negative rotation of the
synthetically prepared L
-enantiomer (Scheme 1).3
Less conclusive were the configurational assignments at
C-4 and C-5, as they were inferred from low resolution
(60 MHz) 1H NMR couplings for H-4 and H-5 in
Scheme 1. Reactions of Daucus carota-derived (−)-daucic
acid leading to the structure of a 2,4-anhydro-2-deoxy-hept-2-
enaric acid and, on the basis of 60 MHz 1H NMR data, to the
ꢀ Part 31 of the series ‘Sugar-Derived Building Blocks’. For Part 30,
see Ref. 1.
* Corresponding
author.
Fax:
+49-6151-166674;
e-mail:
D
-xylo configuration.3
lichtenthaler@chemie.tu-darmstadt.de
0957-4166/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2003.10.007

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F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
able.4b In view of the proclivity of sugar-derived dihy-
dropyrans to give complex, hardly predictable confor-
mational equilibria between the respective half-chair
forms, resulting in intricate coupling patterns with little
bearing on the actual configuration, a verification of the
stereochemistry at C-4 and C-5 of (−)-daucic acid
appeared imperative.
These implications, together with the notion that daucic
acid is a possible biosynthetic precursor of chelidonic
acid 4, a leaf-closing factor of Cassia mimosoides,5
prompted us to devise a stereocontrolled synthesis,
practical enough to furnish sufficient amounts for bio-
logical studies. Accordingly, we report herein expedient
syntheses of the daucic acids with
bino, -lyxo, and -lyxo configuration, from
tose and -mannose, respectively, entailing assignment
of the -lyxo stereochemistry to the Daucus carota-
derived product.6
D
-xylo,
D
-ribo,
L
-ara-
L
D
D-galac-
D
D
2. Results and discussion
Our conceptual approach for developing a stereochemi-
cally unambiguous access to the -xylo-heptenaric acid
D
2—as well as the three alternate configurations conceiv-
able for 2—was based on the anomeric one-carbon
homologation of suitable
D-hexoses, subsequent oxida-
tion at either terminus to the respective pyranoid C7-
dicarboxylic acids, and controlled b-elimination into
the pyranoid ring to be effected by the judicious choice
of leaving groups.
Scheme 2. Elaboration of
D-xylo-heptenarates from D-galac-
tose. Reagents and conditions: (a) HCONH2, Me2CO, hw, 3
days, rt, 54%;8 (b) 8% HCl/MeOH, reflux, 3 h, 86%; (c) Pt/O2,
water (pH 8), 70°C, 4 h; then HCl/MeOH, rt, 1 h, 56%; (d)
BzCl, pyridine, −40°C, 2 h; then MsCl, −40°C to rt, 2 h, 58%;
(e) Ac2O, pyridine rt, 14 h, 85%; (f) BzCl, pyridine, rt, 12 h,
87%; (g) HCl satd MeOH, reflux, 14 h, 73%; (h) 0.1N
NaOMe/MeOH, rt, 1 h, 77%; (i) NaOAc/Ac2O, 100°C, 1 h,
59%.
2.1.
D
-xylo-Heptenarate 2
As outlined in Scheme 2, synthesis of 2 started from
tri-O-acetyl-2-acetoxy- -galactal 6, readily accessible
from -galactose in a three-step/one-pot procedure
D
D
involving acetylation, treatment with HBr/HOAc7a and
dimethylamine-promoted elimination of HBr.7b,c The
acetone-initiated photoaddition of formamide to 6,
albeit complex,8 is a-selective to give heptonamide 7 as
the major product (54%), which was then converted
into methyl heptonate 8 by vigorous methanolysis. Oxi-
dation of the primary hydroxyl was smoothly effected
by oxygen in the presence of Adams catalyst to afford,
after esterification with methanolic HCl, dimethyl hep-
tarate 9. Despite of its 5-OH group being axial suggest-
ing a preferential 5,6-elimination in the tri-O-acetyl
derivative 10, exposure to NaOAc/Ac2O at 70°C led to
complex mixtures. The tribenzoate 11, however, when
heated in NaOAc/Ac2O at 100°C, preferentially dis-
12 by briefly heating in NaOAc/Ac2O to afford the
dibenzoate 15 (79%), or, more smoothly, in its de-O-
benzoylation product 13 through exposure to NaOMe/
MeOH, which directly provided the OH-free dimethyl
D
-xylo-heptenarate 2 (77%). Except for the di-O-acetyl
14 and di-O-benzoyl derivatives 15, all products of this
reaction sequence were obtained in readily characteriz-
able, crystalline form.
The melting point for 2 thus obtained proved to be
close to that of the Daucus carota-derived product (cf.
Table 1), yet its specific rotation, albeit similar in
numerical value, was opposite in sign. The notion that
the natural product could thus have the enantiomeric
placed the axial 5-benzoyloxy group to afford the D5,6
unsaturated dibenzoate 15 in fair yield (59%). Acid
-
de-O-benzoylation then led to the
2.
D-xylo-heptenarate
L
-xylo-configuration, was clearly invalidated by the dis-
tinct differences in the 1H NMR data of synthetic 2 and
15 as compared to those reported for the respective
products of natural origin: chemical shifts for H-4, H-5
and H-6 are 0.3–0.6 ppm apart, and the J3,4 and J4,5
couplings have significantly different values (Table 1).
An alternate possibility to generate 2 from dimethyl
heptarate 9 comprised the introduction of a better
leaving group at O-5, implemented by low temperature-
benzoylation of the equatorial hydroxyls and subse-
quent treatment with methanesulfonyl chloride (“12).
Now, 5,6-dimination could cleanly be effected, either in
Thus, a
D-xylo or L-xylo configuration for natural
(−)-daucic acid can unequivocally be dismissed.

F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
3975
Table 1. Relevant physicochemical data of dimethyl 2,6-anhydro-3-deoxy-hept-2-enarates of
D
-xylo,
D-ribo, L-arabino and
D
-lyxo configuration and their diacetates as compared with those reported3 for the carrot-derived daucic acid derivatives
stantially smaller negative value for the Daucus carota-
2.2. Heptenarates of
D
-ribo and -lyxo configuration
L
derived product. As distinct differences also prevail in
1
Of the remaining configurational possibilities for car-
rot-derived (−)-daucic acid— -ribo, -lyxo and -ara-
bino—the synthesis of the -ribo-analog 22 was
addressed next, taking advantage of the a- -mannosyl-
cyanide 16, readily accessible from -mannose by
the respective H NMR data (cf. Table 1),
D
-ribo as
D
D
D
well as
L
-ribo stereochemistry for natural (−)-daucic
D
acid can also be eliminated.
D
D
The a-
D
-mannosyl-cyanide 16, unexpectedly, could also
-lyxo-heptenarates 29–31
acetylation9 and anomeric cyanation.10 Acid hydrolysis
followed by esterification with methanol smoothly pro-
vided the mannosyl-C-carboxylate 17. As the Pt/O2-
oxidation of the primary hydroxyl group in 17 proved
unusually capricious, its conversion into the 1,7-dicar-
boxylate was effected by TEMPO-catalyzed sodium
hypochlorite oxidation—a reagent that had given excel-
lent results in various other sugar oxidations11—to
provide, upon esterification with methanolic HCl, the
dimethyl heptarate 18 in high yield. Subsequent protec-
tion of O-3 and O-4 by acetonation (“19), followed by
mesylation (“20) set the stage for 5,6-elimination of
methanesulfonate, which was simply realized by brief
exposure to Al2O3/lutidine at 40°C (“21). Finally,
removal of the isopropylidene group in 21 with aqueous
be used to generate the
L
(Scheme 3). Quite in contrast to its acidic hydrolysis
leading to the C-mannosyl-a-carboxylate (16“17),
alkaline saponification—sodium methoxide/methanol
for deacetylation (1 h, rt) and 12.5% aqueous sodium
hydroxide (4 h, reflux) for nitrile hydrolysis—was
accompanied by an unprecedented epimerization at the
pseudo-anomeric C-2, to provide the C-mannosyl-b-
carboxylic acid 25 in high yield (90%). The subsequent
oxidation and esterification 25“26 followed standard
methodology, as did the introduction of a mesyl group
at O-5 after prior protection of the 3,4-diol grouping
(26“27“28). Aluminum oxide/lutidine-induced 5,6-
elimination of mesylate in 28 proceeded smoothly (“
29) and acid removal of the isopropylidene group gave
trifluoroacetic acid smoothly delivered the desired
D
-
the well-crystallizing dimethyl
with physicochemical data highly relevant to the
L
-lyxo-heptenarate 30
ribo-heptenarate 22, and, after acetylation, its di-O-ace-
tyl derivative 23. Both were obtained as syrups of
distinctly high positive rotation in contrast to the sub-
configuration of daucic acid: melting point (127–
1
128°C), H NMR chemical shifts and coupling patterns

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F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
2.3.
D
-lyxo- and -arabino-heptenarates
L
Finally to gain access to the
cic acid, we focused on a synthetic pathway starting
from C-b- -galactosyl-cyanide 32, because it would
also provide the respective -arabino analogs by con-
D
-lyxo configured (−)-dau-
D
L
verting alternatively the 3-OH and the 5-OH in
dimethyl heptarate 34 into displaceable leaving groups.
The key intermediate 34 could straightforwardly be
prepared by base hydrolysis of 32, esterification (“33)
and TEMPO/NaOCl oxidation, the three steps being
performable in an overall yield of 64% (Scheme 4).
For generation of L-arabino analogs of daucic acid, the
protocol used for the successful conversion of 9 into 12
was evaluated first, comprising selective 3,4-di-O-ben-
zoylation and mesylation at O-5. In the case of 34,
however, this approach failed due to distinctly different
OH groups reactitivites of 34 as compared to 9: Reac-
tion of 34 with 2.1 molar equiv. of benzoyl chloride in
pyridine at −40°C resulted in mixtures mainly consist-
ing of the 3,5- and 4,5-dibenzoates. This course was
somewhat unexpected, as the dimethyl heptarates 9 and
34 are 2-epimeric C-(galacturonyl)carboxylates in
which the axial 5-OH would anticipated to be least
reactive towards acylation. As an alternate, albeit less
direct route to the desired 3,4-di-O-benzoyl-5-O-mesyl-
heptarate 38, the cis-diol grouping in 34 was blocked
by isopropylidenation (“35, the key intermediate for
generation of the
D-lyxo compounds, cf. below), fol-
lowed by benzoylation (“36) and acid hydrolysis of the
acetonide. The resulting 3-benzoate of 34—unlike 34
itself—could readily be mono-acylated at the 4-OH by
low temperature benzoylation, the ensuing in situ mesyl-
ation delivering the appropriately blocked 38 in a toler-
able overall yield of 40% for the five steps from 34.
Introduction of the D5,6-unsaturation towards the
L-
Scheme 3.
D-Mannose-derived D-ribo and L-lyxo hepte-
narates. Reagents and conditions: (a) Ac2O, pyridine,9 then
Me3SiCN, BF3·Et2O, CH3NO2, 35°C, 2 h;10 (b) 25% aqueous
HCl, 50°C, 24 h; then HCl satd MeOH, rt, 2 h, 85%; (c)
TEMPO/NaOCl, H2O/CH2Cl2, 0°C, 20 h, then HCl/MeOH,
rt, 2 h, 83%; (d) Me2CO/H2SO4, rt, 4 h, 75%; (e) MsCl,
pyridine, 0°C, 3 h, 94%; (f) Basic Al2O3, lutidine, 40°C, 30
min, 75%; (g) CHCl3–TFA–H2O (50:10:1), rt, 1 h, 86%; (h)
Ac2O/pyridine, rt, 5 h, 90%; (i) BzCl, pyridine, rt, 12 h, 87%;
(k) NaOMe/MeOH, 1 h, rt, then 12.5% aqueous NaOH,
reflux, 4 h, 90%; (l) conc. HNO3, 55°C, 1 h, then 8% HCl/
MeOH, 67%.
arabino heptenarate was most readily effected in the
de-O-benzoylated heptarate 39 to give 40, the actual
L
-arabino analog of dimethyl daucate, as a syrup; its
diacetate 41, however, crystallized well. As anticipated,
both, 40 and 41 had 1H NMR data (cf. Table 1)
distinctly different in chemical shifts and coupling pat-
terns from those observed for the carrot-derived
products.
The
D
-lyxo-heptenarates 42–45, all derivatives of natu-
ral (−)-daucic acid, were also prepared from the 4,5-O-
isopropylidene-heptarate 35 by a similar sequence of
reactions: mesylation (“37) and Al2O3/lutidine-induced
elimination gave 42, in which the isopropylidene group
was removed by exposure to aqueous trifluoroacetic
acid (“43).
(cf. Table 1,
D-lyxo data) correlated exceedingly well
with the carrot-derived dimethyl daucate, only the spe-
cific rotation (+96.7), albeit identical in magnitude, was
of opposite sign. Similarly congruent proved to be the
1H NMR data of the diacetate 31 and the natural
dimethyl daucate derivative (Table 1). The conclusion
In their physicochemical data, 43 and its di-O-acetyl
derivative 44 are in nearly perfect agreement with those
of the carrot-derived products, not only in sign and
magnitude of rotation but, most notably, in the chemi-
cal shifts and coupling patterns (Table 1). The slight
deviations in the coupling constants undoubtedly result
to be drawn is obvious: the
31 are enantiomers to the respective carrot-derived
L
-lyxo-heptenarate 30 and
1
from comparing H NMR data obtained at different
resolution (603 versus 300 MHz) and, conceivably, dif-
products, that is, (−)-daucic acid must have
configuration.
D-lyxo
5
ferent temperatures which affect the H6 X 6H5 equi-

F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
3977
Scheme 4. Dimethyl heptenarates of L-arabino and D-lyxo configuration from D-galactose. Reagents and conditions: (a) NaOAc,
Ac2O, 100°C, 2 h,12a then Me3SiCN, BF3·Et2O in CH3NO2, 35°C, 2 h,12b 79%; (b) (i) NaOMe/MeOH, 2 h, rt, (ii) 6N NaOH, 4
h, reflux, (iii) HCl–satd MeOH, rt, 2 h, 85%; (c) TEMPO/NaOCl, H2O/CH2Cl2, 0°C, 20 h, then satd HCl/MeOH, rt, 2 h, 76%;
(d) Me2CO, H2SO4, rt, 4 h, 76%; (e) BzCl, pyridine, rt, 12 h, 90%; (f) MsCl/pyridine, 0°C, 3 h, 85%; (g) 0.2N NaOMe/MeOH,
15 min, rt, 77%; (h) CHCl3–TFA–water (50:10:1), rt, 1 h, 83%; (i) Ac2O/pyridine, rt, 12 h, 90%; (k) (i) TFA–CHCl3–H2O, rt, 30
min, (ii) BzCl (1.2 equiv.), pyridine, −40°C, 2 h, (iii) MsCl, pyridine, rt, 3 h, 53%; (l) HCl–satd MeOH, reflux, 24 h, 86%; (m) basic
Al2O3–lutidine, 40°C, 30 min, 74%.
librium of the respective halfchair forms, and, hence, the
NMR patterns. Notwithstanding, this evidence is cogent
enough as to unambiguously assign carrot-derived (−)-
L., and hence named osbeckic acid,13 it may well be
generated from daucic acid in the plant.
daucic acid the
D-lyxo-configuration.
2.4. Biosynthetic implications
The synthetic (−)-dimethyl daucate 43 could readily be
de-esterified by aqueous trifluoroacetic acid to give the
free acid 46 in crystalline form. Slightly more vigorous
acid conditions elicited the pyran“furan rearrangement
observed previously for the carrot-derived product:3
when exposed to methanolic HCl, 43 was converted into
5 (60%), heating in water in the presence of a strongly
acidic ion exchange resin gave the free acid 47 (81%). As
47 has been isolated from the shrub Osbeckia chinensis
Not only is the biosynthetic origin of (−)-daucic acid
intriguing—sedoheptulose-7-phosphate 48 and DAH 7-P
49, both established intermediates of the pentose phos-
phate and shikimic acid pathways, respectively, may be
conjectured as precursors—but the close structural anal-
ogy to chelidonic acid 4 with only oxidation of the allylic
OH group in daucic acid and ensuing elimination of
water being required to effect the chemical conversion.

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F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
14C-Labeling studies on the biosynthesis of chelidonic
acid have uniformly demonstrated that -glucose and,
still better,
-ribose is well incorporated,14,15 whilst 48
substrate,
phosphate (
D
-erythrose 4-phosphate, but to
-Rib 5-P) and
D-ribose 5-
D
D
D
-Ara 5-P as well,21 may
D
tentatively be taken as evidence that an octulosonate
8-phosphate-based pathway is also operative in plants.
is not.14 The postulation, that, hence, DAH 7-P 49 is
the likely precursor15 persisted for 30 years, yet was
convincingly disproved recently by quantitative carbon
flux analyses of 13C-labeled sugars, suggesting a biosyn-
thetic assembly of chelidonic acid from one molecule of
pentose phosphate and phosphoenolpyruprate (PEP).16
Such a biosynthetic process, de facto, is well established
Relying on the newly established
istry of (−)-daucic acid—48 and 49 as precursors would
elaborate -arabino configuration—and on the conjec-
ture that daucic acid is a precursor of chelidonic acid, a
biosynthetic pathway towards both readily unfolds as
depicted in Scheme 5: D-Ara 5-P and PEP undergo an
aldol-type condensation to KDO 8-P 50, whose stereo-
chemistry in the pyranoid ring, notably, correlates per-
D-lyxo stereochem-
D
in Gram-negative bacteria, where PEP and
5-phosphate ( -Ara 5-P), in turn generated from
ribulose 5-phosphate by isomerization, undergo an
D
-arabinose
D
D
-
aldol-type condensation to 3-deoxy-
D
-manno-octulo-
fectly with the
-Rib 5-P would be involved in the aldol addition step,
the eight-carbon sugar phosphate would have -altro
D-lyxo configuration of daucic acid. If
sonate 8-phosphate (KDO 8-P), 50.17,18 Thereby, the
D
KDO 8-P synthase involved stereoselectively elaborates
D
the 4R isomer, hence,
D
-manno configuration for 50, as
configuration entailing an (‘unnecessary’) epimerization
at some later stage.
the aldol addition proceeds with exclusive si attack of
PEP to the re face of the sugar carbonyl.19 Although
the existence of such a KDO 8-P-based mechanism has,
as of now, not been detected in plants, the fact that
DAH 7-P synthase—a key enzyme of the shikimic acid
pathway20 and abundantly present in higher plants—
not only catalyzes aldol addition of PEP to its natural
Unlike bacterial systems where the eight-carbon chain
of KDO 8-P is incorporated into cell wall lipopolysac-
charides, here, the terminal carbon obviously is
removed by dephosphorylation and oxidative decar-
boxylation. Although the resulting intermediate 51
Scheme 5. Conceivable mechanism for the biosynthesis of C7-dicarboxylic acids in plants from common precursors, based on the
striking configurational identity of daucic acid 46 and KDO 8-P 50 in their pyranoid rings, the smooth chemical conversions of
46 into chelidonic 4 and osbeckic acid 47, and available evidence on the biosynthesis of 4. Meconic acid 54, plentiful in the latex
of Papaveracea, may be arrived at merely by oxidation of conjectural intermediate 53.

F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
3979
requires only loss of water to reach daucic acid, a
direct 3,2-elimination is unlikely—‘cells obey the laws
of chemistry’22—as the hydrogen atom involved (H-3)
is not activated. This is usually effected by a vicinal
3.2.
D
-Galactose“
D
-xylo analogs of dimethyl daucate
3.2.1. 3,4,5,7-Tetra-O-acetyl-2,6-anhydro- -glycero-L-
D
gluco-heptonamide [C-(tetra-O-acetyl-a- -galactopyran-
D
carbonyl group—the
D
-glucose“kojic acid conver-
osyl)formamide] 7. 2,3,4,6-Tetra-O-acetyl-1,5-anhydro-
sion23 has been rationalized on this basis24—hence,
oxidation of 51 at C-4 appears most plausible, the
ensuing dehydration 52“53 now being readily com-
prehensible. From the central dihydropyranone inter-
mediate 53, elaboration of daucic acid merely requires
D
-lyxo-hex-1-enitol 6, readily accessible from
D-galac-
tose by acetylation,7a treatment with HBr/HOAc7b and
diethylamine-promoted elimination of HBr7c (75%
overall yield on a 0.1 molar scale when refraining
from purification of intermediates), was subjected to
photoaddition of formamide to afford 7 in 54% yield;8
mp 187–189°C; [h]D20=+57 (c 0.9, CHCl3) [lit.8 mp
186–189°C; [h]2D0=+53.3 (CHCl3)].
a
reduction,
and
generation
of
chelidonic
acid the elimination of another molecule of water.
Meconic acid may be conjectured to arise by a dehy-
drogenation step (53“54), the furanoid osbeckic acid
47 from daucic acid via ring contraction and twofold
dehydration.
3.2.2. Methyl 2,6-anhydro-
[methyl C-(a- -galactopyranosyl)formate] 8. A suspen-
D
-glycero- -gluco-heptonate
L
D
sion of 7 (5.42 g, 15 mmol) in 100 mL of 8% HCl in
MeOH was refluxed for 3 h. The then clear solution
was taken to dryness in vacuo and the resulting
residue was purified by elution from a short silica gel
column with CHCl3–MeOH (4:1). Evaporation of the
appropriate eluates left a syrup which crystallized from
MeOH/CHCl3: 2.87 g (86%) of 8; mp 141–142°C;
[h]2D0=+106 (c 0.7, MeOH). Anal. calcd for C8H14O7
(222.2): C, 43.24; H, 6.35. Found: C, 62.07; H, 7.32.
The tempting consistency of this metabolic scheme,
most notably the configurational identity of KDO 8-P
and daucic acid in their pyranoid rings, clearly calls
for a systematic scrutiny of higher plants for the
occurrence of an eight-carbon sugar phosphate path-
way with the likely intermediates 51–53, especially in
those species, in which these C7-dicarboxylic acids
have been detected: daucic acid in carrots, sugar beet,
wheat, sun flower, and tobacco,3 osbeckic acid in
Osbeckia chinensis,13 meconic acid in Papaveraceae25
and chelidonic acid in a plethora of plant families.26
Also conducive towards unravelement of the biosyn-
thesis of these plant acids will be the eleven-step-syn-
3.2.3. Dimethyl 2,6-anhydro-
D
-glycero- -gluco-heptarate
L
9. Freshly reduced Adams catalyst (1.0 g) was added
to an aqueous solution of 8 (2.20 g, 10 mmol, in 50
mL), and O2 was passed through the suspension with
vigorous stirring for 4 h at 70°C, maintaining pH 8 by
gradual addition of solid NaHCO3. After filtration,
the solution was taken to dryness in vacuo, the residue
was suspended in methanolic HCl (40 mL of saturated
solution), and stirred for 1 h at ambient temperature.
Filtration of insolubles, removal of the solvent from
the filtrate, purification of the resulting syrup by elu-
tion from a silica gel column (2×20 cm) with CHCl3–
MeOH (6:1), and evaporation of the eluates
containing 9 gave 1.40 g (56%) of a colorless syrup,
uniform by TLC (Rf=0.42 in CHCl3–MeOH, 4:1); MS
(FD) m/z 251 (M++1), 250 (M+). Anal. calcd for
C9H14O8 (250.2): C, 43.20; H, 5.64. Found C, 43.08,
H, 5.60.
thesis of (−)-daucic acid from
since the first six from -galactose to dimethyl
ero- -manno-heptarate 34 can be performed in three
D
-galactose described
D
D
-glyc-
L
consecutive one-pot operations on fairly large scale
(51%). The synthesis is also flexible enough to readily
prepare the postulated intermediates 51–53 in labeled
form. Synthetic and biosynthetic studies along these
veins are being implemented.
3. Experimental
3.1. General remarks
3.2.4. Dimethyl 3,4,5-tri-O-acetyl-2,6-anhydro-
D
-glyc-
ero- -gluco-heptarate 10. A mixture of heptarate 9 (50
L
Melting points were determined with a Bock hot-stage
microscope and are uncorrected. Optical rotations
were measured on a Perkin–Elmer 241 polarimeter at
20°C using a cell of 1 dm path length; concentration
(c) in g/100 mL and solvent are given in parentheses.
1H and 13C NMR spectra were recorded on a Bruker
ARX-300 spectrometer in the solvents indicated. Mass
spectra were acquired on Varian MAT 311 and MAT
212 spectrometers. Microanalyses were determined on
a Perkin–Elmer 240 elemental analyzer. Analytical
thin-layer chromatography (TLC) was performed on
precoated Merck plastic sheets (0.2 mm silica gel 60
mg, 0.2 mmol), pyridine (2 mL) and Ac2O (1 mL) was
kept at rt overnight, subsequently diluted with EtOAc
and washed with satd aqueous NaHCO3 and water,
and dried (Na2SO4). Concentration of solution to dry-
ness gave a crystalline mass, which was recrystallized
from EtOH to afford 70 mg (90%) of 10; mp 151–
152°C; [h]2D0=+173 (c 0.7, CHCl3). 1H NMR (300
MHz, CDCl3) l 2.02, 2.05, 2.10 (3 s, 3H each, 3 Ac),
3.76, 3.77 (two 3H-s, 2 OMe), 5.05 (d, 1H, J=6.0 Hz),
5.38 (d, 1H, J=2.7 Hz), 5.39 (dd, 1H, J=2.9, 9.8 Hz),
5.77 (dd, 1H, J=2.7, 2.9 Hz); MS (FD) m/z 378
(M++2), 334 (M+−Ac). Anal. calcd for C15H20O11
(376.3): C, 47.88; H,5.36. Found: C, 47.79; H, 5.19.
F254) with detection by UV (254 nm) and/or spraying
with H2SO4 (50%) and heating. Column and flash
chromatography was carried out on Fluka silica gel 60
(70–230 mesh) using the specified eluents.
3.2.5. Dimethyl 3,4,5-tri-O-benzoyl-2,6-anhydro-
D
-glyc-
ero- -gluco-heptarate 11. Benzoyl chloride (1.8 mL, 15
L

3980
F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
mmol) was added to a solution of dimethyl heptarate 9
(150 mg, 0.6 mmol) in pyridine (12 mL), and the mixture
was stirred at rt overnight. Dilution with EtOAc, succes-
sive washings with satd aqueous NaHCO3 and water,
drying (Na2SO4), and evaporation to dryness in vacuo
gave a syrup which was purified by elution from a short
silica gel column with n-hexane–acetone (2:1). Removal
of the solvents from the product-containing eluates
(TLC: Rf=0.28 in n-hexane–acetone, 2:1) gave a solid
residue which crystallized from EtOH: 295 mg (87%) of
11 as colorless crystals; mp 136–137°C; [h]2D0=+217 (c
residue was purified by elution from a short silica gel
column with acetone–CHCl3 (1:1). Eluates containing
product of Rf=0.40 (TLC in CHCl3–acetone, 2:1) were
concentrated to a syrup, which crystallized from
EtOAc/hexane: 180 mg (77%) of 2; mp 133–135°C;
[h]2D0=+106.0 (c 0.6, acetone). 1H NMR (300 MHz,
CDCl3) l 3.85, 3.88 (two 3H s, 2 OMe), 4.19 (m, 2H),
4.60 (m, 1H), 6.20 (dd, 1H, J=1.3, 4.8 Hz); MS (FD
m/z 232 (M+), 233 (M++1). Anal. calcd for C9H12O7
(232.2): C, 46.55; H, 5.21. Found C, 46.48; H, 5.25
1
1.1, CHCl3). H NMR (300 MHz, CDCl3) l 3.63, 3.69
3.2.9. Dimethyl 4,5-di-O-acetyl-2,6-anhydro-3-deoxy-D-
(two 3H-s, 2 OMe), 5.46 (d, 1H, J=5.5 Hz), 5.57 (d, 1H,
J=3.6 Hz), 5.85 (dd, 1H, J=5.4, 8.5 Hz), 6.04 (dd, 3.1,
8.5 Hz), 7.50, 7.95 (2 m, 9H and 6H, 3 C6H5); MS (FD)
m/z 563 (M++1). Anal. calcd for C30H26O11 (562.5): C,
64.06; H, 4.66. Found: C, 63.96; H, 4.58.
xylo-hept-2-enarate 14. A solution of heptenarate 2 (60
mg, 0.26 mmol) in a mixture of Ac2O (1 mL) and
pyridine (3 mL) was stirred at rt overnight and subse-
quently taken to dryness in vacuo. The resulting residue
purified on a short silica gel column by elution with
CHCl3–MeOH (20:1) to give 68 mg (82%) of 14 as a
clear syrup; [h]2D0=+146.0 (c 0.8, CHCl3). 1H NMR (300
MHz, CDCl3) l 2.06, 2.11 (two 3H-s, 2 Ac), 3.84, 3.86
(two 3H-s, OMe), 4.61 (m, 1H), 5.13 (ddd, 1H, J=0.8,
2.2, 5.3 Hz), 5.38 (ddd, 1H, J=1.4, 1.5, 2.2 Hz), 6.23
3.2.6.
mesyl-
Dimethyl
-glycero-
2,6-anhydro-3,4-di-O-benzoyl-5-O-
-gluco-heptarate 12. A solution of
D
L
heptarate 9 (810 mg, 3.2 mmol) in pyridine (10 mL) was
cooled to −40°C and a mixture of benzoyl chloride (0.8
mL, 0.69 mmol) and pyridine (5 mL) was added drop-
wise with vigorous stirring. After 2 h at −40°C,
methanesulfonyl chloride (0.25 mL, 3.2 mmol) was
added and stirring was continued at −40°C (1 h) fol-
lowed by allowing the mixture warm to rt (2 h). Subse-
quent extraction with satd aqueous NaHCO3 and water,
drying (Na2SO4), and removal of the solvent in vacuo
gave a residue, which was purified by elution from a
silica gel column with n-hexane–acetone (2:1). The first
fraction (Rf=0.49, TLC in n-hexane–acetone, 3:2) con-
tained 320 mg (18%) of tribenzoate of 11. The fractions
eluted next, with product of Rf=0.39, were combined
and evaporated to a syrup which crystallized from
EtOH: 930 mg (53%) of 12 as colorless crystals; mp
1
(dd, J=1.5, 5.3 Hz; H NMR (300 MHz, C6D6) l 1.49,
1.50 (two 3H-s, 2 Ac), 3.27, 3.34 (two 3H-s, 2 OMe),
4.41 (m, 1H), 5.20 (ddd, 1H, J=0.8, 2.2, 5.3 Hz), 5.57
(ddd, 1H, J=1.4, 1.5, 2.2 Hz), 6.38 (dd, 1H, J=1.5, 5.3
Hz); MS (FD) m/z 316 (M+), 257 (M+−COOMe).
3.2.10. Dimethyl 4,5-di-O-benzoyl-2,6-anhydro-3-deoxy-
D
-xylo-hept-2-enarate 15. (a) By benzoylation of 2.
Benzoyl chloride (0.2 mL, 0.7 mmol) was added solution
of 2 (60 mg, 0.26 mmol) in pyridine (2 mL), and the
mixture was stirred at rt overnight. Dilution with
EtOAc, washing with satd NaHCO3 and water, drying
(Na2SO4), and removal of the solvent in vacuo left a
syrup, which was purified on a short silica gel column
(n-hexane–acetone, 2:1). Eluates with Rf=0.63 (TLC,
CHCl3–EtOAc, 20:1) were concentrated to give 95 mg
(83%) of 15 as colorless syrup; [h]2D0=+127.0 (c 0.9,
1
158–160°C; [h]2D0=+174 (c 0.5, CHCl3). H NMR (300
MHz, CDCl3) l 3.04 (s, 3H, SO2Me), 3.64, 3.85 (2 s, 3H
each, 2 OMe), 5.22 (d, 1H, J=6.7 Hz), 5.62 (d, 1H,
J=1.8 Hz), 5.76 (dd, 1H, J=1.8, 2.9 Hz), 5.84 (dd, 1H,
J=6.7, 10.3 Hz), 5.93 (dd, 1H, J=2.9, 10.3 Hz), 7.50,
8.00 (2 m, 2 C6H5); MS (FD) m/z 537 (M++1). Anal.
calcd for C24H24O12S (536.5): C,53.73; H, 4.51. Found:
C,53.68; H, 454.
1
CHCl3). H NMR (300 MHz, CDCl3) l 3.82, 3.88 (two
3H-s, 2 OMe), 4.86 (m, 1H), 5.56 (ddd, 1H, J=0.8, 2.4,
5.2 Hz), 5.78 (ddd, 1H, J=1.5, 1.8, 2.4 Hz), 6.41 (dd,
J=1.5, 5.2 Hz), 7.46, 7.60, 8.03 (3 m, 10H, 2 C6H5); MS
(FD) m/z 440 (M+). Anal. calcd for C23H20O9 (440.4): C,
62.72; H, 4.58. Found: C, 62.65; H, 4.50.
3.2.7. Dimethyl 2,6-anhydro-5-O-mesyl-
D
-glycero-L-
gluco-heptarate 13. A suspension of 805 mg (1.5 mmol)
of dibenzoate 12 in satd methanolic HCl (25 mL) was
refluxed for 14 h. The clear solution was then taken to
dryness in vacuo and the residue was purified on a short
silica gel column by elution with aceton–CHCl3 (1:1).
Removal from the solvents in vacuo afforded a syrup,
which crystallized from CHCl3/n-hexane to yield 425
mg (73%) of 13; mp 149–150°C; [h]2D0=+92 (c 0.7,
CHCl3); MS (FD) m/z 388 (M+). Anal. calcd for
C15H16O16S (388.4): C, 46.39; H, 4.15. Found: C, 46.30;
H, 4.03.
(b) By elimination of benzoic acid from 11. A solution
of 11 (200 mg, 0.35 mmol) in Ac2O (5 mL) was heated
in the presence of NaOAc (150 mg) at 100°C for 1 h.
The reaction mixture was diluted with EtOAc, washed
with water, satd aqueous NaHCO3 and water, and then
dried over Na2SO4. The solution was concentrated and
purified on a silica gel column (CHCl3–EtOAc, 30:1) to
afford 90 mg (59%) of 15 as a syrup, identical with the
product described above.
3.3.
24)
D
-Mannose“products of
D
-ribo configuration (21–
3.2.8. Dimethyl 2,6-anhydro-3-deoxy- -xylo-hept-2-
D
enarate 2. A methanolic solution of mesylate 13 (390
mg, 1 mmol, in 10 mL) was added to 20 mL of 0.1N
methanolic NaOMe, the mixture was stirred for 1 h, and
subsequently concentrated in vacuo. The amorphous
3.3.1. Methyl 2,6-anhydro-
[methyl C-(a- -mannopyranosyl)formate] 17. A solution
of 4.0 g (11.2 mmol) of C-(tetra-O-acetyl-a- -manno-
D
-glycero- -talo-heptonate
D
D
D

F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
3981
syl)cyanide 1610 in water (40 mL) and conc. HCl (80
mL) was stirred at 50°C for 24 h followed by concen-
tration in vacuo and repeated coevaporation with
MeOH. Drying in vacuo afforded the free heptonic acid
(17, H instead of Me, 2.2 g) as a uniform syrup (TLC:
Rf=0.49 in EtOAc–HOAc–water, 3:2:1), which was
dissolved in anhydrous MeOH (20 mL) followed by
addition of 20 mL of HCl–satd MeOH. The solution
was stirred at rt for 2 h, followed by removal of the
solvent to dryness in vacuo and three coevaporations
with dry MeOH. Purification of the residue by elution
from a silica gel column (3×30 cm) with CHCl3–MeOH
(5:1) and concentration of the eluates in vacuo gave
2.14 g (86%) of 17 as a syrup; [h]2D0=+39.6 (c 1.1,
MeOH); Rf=0.64 (TLC in EtOAc–EtOH–water,
Rf=0.72 (TLC in EtOAc–EtOH–water, 30:3:1) and
crystallization of the residue from EtOH–n-hexane gave
1.16 g (75%) of 19 as cubic crystals; mp 91°C; [h]2D0=
+12.5 (c 1.0, acetone); 1H NMR (300 MHz, [D4]MeOH)
l 1.34, 1.45 (2 s, 3H each, CMe2), 3.75, 3.77 (2 s, 3H
each, 2 OMe), 4.14 (dd, 1H, J=5.2, 5.4 Hz), 4.20 (dd,
1H, J=5.4, 5.5 Hz), 4.31 (d, 1H, J=5.2 Hz), 4.54 (dd,
1H, J=4.3, 5.4 Hz), 4.67 (d, 1H, J=4.3 Hz); MS (FD)
m/z 291 (M++1), 290 (M+). Anal. calcd for C12H18O8
(290.3): C, 49.65; H, 6.25. Found: C, 49.66; H, 6.25.
3.3.4. Dimethyl 2,6-anhydro-3,4-O-isopropylidene-5-O-
mesyl-
D
-glycero- -talo-heptarate 20. To a cooled (0°C)
D
solution of 19 (1.0 g, 3.4 mmol) in pyridine (12 mL) was
added methanesulfonyl chloride (0.7 mL, 9 mmol), and
the mixture was stirred for 3 h at 0°C. After addition of
solid NaHCO3 and stirring for another 30 min, the
reaction mixture was diluted with satd aqueous
NaHCO3, extracted with EtOAc, dried (Na2SO4), and
taken to dryness in vacuo: 1.19 g (94%) of 20 as
colorless syrup; [h]2D0=+9.7 (c 1.0, CHCl3); Rf=0.57
(TLC in toluene–EtOAc, 1:1). 1H NMR (300 MHz,
CDCl3) l 1.32, 1.48 (two 3H-s, CMe2), 3.08 (s, 3H,
SO2Me), 3.76, 3.77 (two 3H-s, 2 OMe), 4.30 (dd, 1H,
J=5.4, 5.7 Hz), 4.46 (d, 1H, J=6.4 Hz), 4.52 (dd, 1H,
J=4.2, 5.4 Hz), 4.74 (d, 1H, J=4.2 Hz), 4.99 (dd, 1H,
J=5.7, 7.4 Hz); MS (FD) m/z 369 (M++1), 368 (M+).
Anal. calcd for C13H20O10S (368.4): C, 42.39; H, 5.47.
Found: C, 42.23; H, 5.38.
1
14:6:3). H NMR (300 MHz, [D4]MeOH) l 3.45 (dd,
1H, J=3.0, 8.9 Hz), 3.68 (m, 2H, H-5, H-6), 3.72 (m,
1H, H-7), 3.84 (dd, 1H, J=1.8, 11.8 Hz, H-7), 4.28 (dd,
1H, J=2.2, 3.0 Hz), 4.52 (d, 1H, J=2.2 Hz); MS (FD)
m/z 223 (M++1), 222 (M+). Anal. calcd for C8H14O7
(222.2) C, 43.23; H, 6.35. Found: C, 43.29; H, 6.41.
3.3.2. Dimethyl 2,6-anhydro-
D
-glycero- -talo-heptarate
D
18. To a mixture of 17 (2.14 g, 9.6 mmol) in satd
aqueous NaHCO3 (16 mL) containing KBr (90 mg) and
n-Bu4NCl (120 mg) was added a solution of 50 mg of
2,2,6,6-tetramethyl-1-piperidinyloxy (‘TEMPO’) in
CH2Cl2 (20 mL). The mixture was cooled to 0°C and a
solution of NaOCl (13%, 56 mL) and satd aqueous
NaHCO3 (8.8 mL) was added dropwise over 1 h.
Stirring was continued at 0°C for 20 h, followed by
separation of the two layers and washing of the organic
phase with water (3×15 mL). The combined aqueous
extracts were acidified with 2N HCl and concentrated
in vacuo to a syrup which was dissolved in water and
passed through an ion-exchanger column (Amberlite
IR-120 H+, 3×30 cm). After removal of the solvent the
syrup was dissolved in anhydrous MeOH (30 mL) and
treated with a satd solution of dry HCl in anhydrous
MeOH (30 mL) at ambient temperature for 2 h, and
then concentrated. The residue was purified on a silica
gel column (3×30 cm) by elution with CHCl3–MeOH
(5:1). Product-containing eluates (Rf=0.91, TLC in
EtOAc–EtOH–water, 14:6:3) were concentrated to give
1.33 g (55%) of 18 as a colorless syrup; [h]2D0=+61.4 (c
3.3.5. Dimethyl 2,6-anhydro-4,5-O-isopropylidene-3-
deoxy- -ribo-hept-2-enarate 21. To a solution of 1.0 g
D
(2.7 mmol) 20 in 100 mL of lutidine was added 10 g of
basic Al2O3 (Fluka type 5016A, basic) and the mixture
was warmed to 40°C for 30 min, followed by evapora-
tion to dryness in vacuo. The residue was applied to a
silica gel column (3×30 cm) and eluted with CH2Cl2–
acetone 110:1. Removal of the solvent from the eluates
with Rf=0.74 (TLC in toluene–EtOAc, 1:1) in vacuo
yielded 540 mg (73%) of 21 as a colorless syrup; [h]2D0=
1
+41.9 (c 1.0, CHCl3); H NMR (300 MHz, CDCl3) l
1.41, 1.48 (2 s, 3H each, CMe2), 3.83, 3.84 (2 s, 3H
each, 2 OMe), 4.46 (m, 2H, 5-H, 6-H), 4.63 (dd, 1H,
J=4.0, 4.9 Hz, 6.23 (d, 1H, J=4.0 Hz); 13C NMR (75.5
MHz, CDCl3) l 25.9, 28.1 (CMe2), 52.7, 52.9 (2 OMe),
67.2 (C-4), 71.7, 75.0 (C-5, C-6), 108.9 (C-3), 110.4
(CMe2), 144.6 (C-2), 161.9, 168.3 (2 CO). Anal. calcd
for C12H16O7 (272.3): C, 52.94; H, 5.92. Found: C,
53.06; H, 5.79.
1
1.5, MeOH); H NMR (300 MHz, D2O, 32°C) l 3.74,
3.78 (two 3H-s, 2 OMe), 3.75 (dd, 1H, J=2.9, 5.8 Hz),
4.11 (dd, 1H, J=2.2, 3.0 Hz), 4.18 (dd, 1H, J=4.5, 5.8
Hz), 4.11 (dd, 1H, J=2.9, 5.8 Hz), 4.18 (dd, 1H,
J=4.5, 8.9 Hz), 4.29 (d, 1H, J=4.5 Hz), 4.66 (d, 1H,
J=7.3 Hz). Anal. calcd for C9H14O8 (250.2): C, 43.20;
H,5.64. Found: C, 43,10; H, 5.62.
3.3.6. Dimethyl 2,6-anhydro-3-deoxy- -ribo-hept-2-
D
enarate 22. Treatment of 21 (540 mg, 2.0 mmol) with 20
mL of a mixture of CHCl3–TFA–water (50:10:1) at
30°C for 1 h and removal of the solvent afforded a
syrup, which was purified by elution from a silica gel
column (2×20 cm) with CH2Cl2–acetone (2:1). Concen-
tration of the eluates gave 390 mg (85%) of 22 as a
colorless syrup; [h]2D0=+150.4 (c 1.0, acetone); Rf=0.57
(TLC in CHCl3–acetone, 1:1). 1H NMR (300 MHz,
CDCl3) l 3.07, 3.45 (two 1H-d, 2 OH), 3.83, 3.84 (two
3H-s, 2 OMe), 4.12 (ddd, 1H, J=4.3, 5.7, 7.6 Hz), 4.32
(ddd, 1H, J=4.3, 4.4, 5.2 Hz), 4.63 (d, 1H, J=7.6 Hz),
6.10 (d, 1H, J=4.4 Hz); 13C NMR (75.5 MHz, CDCl3)
3.3.3. Dimethyl 2,6-anhydro-3,4-O-isopropylidene-
D-
glycero- -talo-heptarate 19. A suspension of 18 (1.33 g,
D
5.3 mmol) in dry acetone (40 mL) and conc. H2SO4 (0.1
mL) was stirred at rt for 4 h. The reaction mixture was
carefully neutralized with ion-exchange resin (Amberlite
IR-400, OH−) and concentrated to syrup, which was
dissolved in dry acetone (30 mL). After addition of 6 g
of silica gel and removal of the solvent, the residue was
applied to a silica gel column (3×30 cm) and eluted with
toluene–EtOAc (1:1). Evaporation of the fractions with

3982
F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
l 52.7, 53.0 (2 OMe), 61.5 (C-4), 66.7 (C-5), 74.7 (C-6),
109.9 (C-3), 143.8 (C-2), 162.1, 169.2 (2 CO); MS (FD)
m/z 233 (M++1), 232 (M+). Anal. calcd for C9H12O7
(232.2): C, 46.56; H, 5.21. Found: C, 44.91; H, 5.15.
oxidation (“26); Rf=0.34 (TLC in EtOAc–HOAc–
1
H2O, 3:2:1); [h]2D0=−2.4 (c 1.0 MeOH); H NMR (300
MHz, D2O) l 3.41 (ddd, 1H, J=2.3, 6.4, 9.6 Hz, H-6),
3.59 (t, 1H, J=9.6 Hz), 3.72 (dd, 1H, J=3.4, 9.6 Hz),
3.75 (dd, 1H, J=6.4, 12.4 Hz), 3.93 (dd, 1H, J=2.3,
12.4 Hz), 4.31 (dd, 1H, J=1.4, 3.4 Hz), 4.37 (d, 1H,
J=1.4 Hz); MS (FD) m/z 208 (M+).
3.3.7. Dimethyl 4,5-di-O-acetyl-2,6-anhydro-3-deoxy-D-
ribo-hept-2-enarate 23. Stirring of 22 (63 mg, 0.27
mmol) in a mixture of Ac2O (2 mL) and pyridine (4
mL) for 5 h at rt, evaporation to dryness in vacuo, and
elution of the residue from a silica gel column (1.5×20
cm) with CH2Cl2–acetone (60:1) afforded 78 mg (91%)
of 23 as a colorless syrup; [h]2D0=+171.1 (c 0.9, CHCl3);
3.4.2. Dimethyl 2,6-anhydro-
D
-glycero- -galacto-hep-
D
tarate 26. Solid 25 (7.00 g, 33.7 mmol) was gradually
added (30 min) to a stirred, warmed (55–60°C) mixture
of conc. HNO3–fuming HNO3 (1:1, 12 mL) containing
9 mg of NaNO2. Stirring at 55–60°C was continued for
1.5 h, followed by dilution with water (80 mL), neutral-
ization with 25% aqueous NaOH (to pH 8) and filtra-
tion of insolubles. Removal of the solvent in vacuo left
a syrup, which was dissolved in H2O (20 mL), then
MeOH (200 mL) was added and the mixture was stored
at 5°C for 12 h. The solid mass was separated, dissolved
with H2O (80 mL) and applied to a column of Amber-
lite IR-120 (H+-form) (140 mL). Acidic eluates were
collected, treated with active carbon, and then taken to
dryness in vacuo. Treatment of the residue with 8%
HCl–MeOH (40 mL) at rt for 2 h and concentration to
dryness gave a syrup, which was purified by elution
from a silica gel column (4.5×30 cm) with CHCl3–
MeOH (6:1). Eluates of Rf=0.40 (TLC in CHCl3–
MeOH, 4:1) were evaporated to dryness in vacuo and
the residue was crystallized from MeOH–CHCl3: 4.65 g
(55%) of 26 as needles; a second crop (0.98 g, 12%) was
obtained from the mother liquor; mp 163°C; [h]2D0=
−22.7 (c 1.0, MeOH); 1H NMR (300 MHz, D2O) l 3.76
(dd, 1H, J=3.0, 9.5 Hz), 3.81, 3.84 (two 3H-s, 2 OMe),
3.83 (dd, 1H, J=9.2, 9.5 Hz), 3.99 (d, 1H, J=9.2 Hz),
4.34 (dd, 1H, J=1.2, 3.0 Hz), 4.49 (d, 1H, J=1.2 Hz);
MS (FD) m/z 252 (M++2), 251 (M++1), 250 (M+). Anal.
calcd for C9H14O8 (250.2): C, 43.20; H,5.64. Found: C,
42.98; H, 5.56.
1
Rf=0.69 (TLC in toluene–EtOAc 1:1); H NMR (300
MHz, CDCl3) l 2.08, 2.09 (two 3H-s, 2 Ac), 3.82, 3.85
(two 3H-s, 2 OMe), 4.84 (m, 1H), 5.52 (m, 2H), 6.01
1
(m, 1H); H NMR (C6H6): 1.68, 1.69 (two 3H-s, 2 Ac),
3.28, 3.25 (two 3H-s, 2 OMe), 4.74 (d, 1H, J=6.3 Hz),
5.62 (dd, 1H, J=3.8, 4.2 Hz), 5.71 (ddd, 1H, J=0.7,
4.2, 5.6 Hz), 6.02 (dd, 1H, J=0.7, 3.8 Hz); (FD) m/z
317 (M++1), 316 (M+). Anal. calcd for C13H16O9
(316.3): C, 49.37; H, 5.10. Found: C, 48.95; H, 5.04.
3.3.8. Dimethyl 2,6-anhydro-4,5-di-O-benzoyl-3-deoxy-
D
-ribo-hept-2-enarate 24. A mixture of 22 (58 mg, 0.25
mmol), 4 mL of pyridine, and benzoyl chloride (0.1
mL, 0.86 mmol) was stirred for 4 h at 0°C and then
diluted with EtOAc. The solution was successively
washed with satd aqueous NaHCO3 (3×10 mL) and
water (10 mL), dried (Na2SO4), and then concentrated
in vacuo. The residue was purified by elution from a
silica gel column (1.5×20 cm) with CH2Cl2–acetone
(60:1). Removal of the solvents from the eluates in
vacuo gave 81 mg (74%) of 24 as a colorless syrup;
[h]2D0=+177.0 (c 0.9, CHCl3); Rf=0.56 (TLC in tolu-
1
ene–EtOAc, 1:1). H NMR (300 MHz, CDCl3) l 3.75,
3.79 (two 3H-s, 2 OMe), 5.02 (m, 1H), 5.81 (m, 2H,
H-4, H-5), 6.16 (m, 1H), 7.30, 7.45, 7.87 (3 m, 10 H, 2
C6H5); 1H NMR (C6H6) l 3.23, 3.26 (two 3H s, 2
OMe), 4.93 (d, 1H, J=6.4 Hz), 5.98 (dd, 1H, J=4.0,
4.3 Hz), 6.09 (ddd, 1H, J=0.9, 4.2, 6.4 Hz), 6.22 (dd,
1H, J=0.9, 4.0 Hz), 6.94, 7.04, 7.99 (3 m, 10H, 2
C6H5). Anal. calcd for C23H20O9 (440.4): C, 62.73; H,
4.58. Found: C, 62.72; H, 4.68.
3.4.3. Dimethyl 2,6-anhydro-3,4-O-isopropylidene-
D-
glycero- -galacto-heptarate 27. To a suspension of 26
D
(2.0 g, 8 mmol) in dry acetone (50 mL) containing 0.15
mL of conc. sulfuric acid was added. The reaction
mixture was stirred for 4 h at 20°C followed by stirring
with Amberlite IR-400 (OH−-form), filtration washing
with water and evaporation of the combined filtrates to
dryness. The residue was applied to a silica gel column
(3×30 cm) and eluted with toluene–EtOAc (1:1). Evapo-
ration of the fractions with Rf=0.72 (TLC in EtOAc–
EtOH–water, 30:3:1) left a syrup that crystallized from
EtOH–n-hexane: 1.80 g (75%) of 27 as colorless
needles; mp 139°C; [h]2D0=−31.1 (c 1.0, Me2CO); 1H
NMR (300 MHz, [D4]MeOH) l 1.32, 1.45 (2 s, 3H
each, CMe2), 3.76, 3.77 (2 s, 3H each, 2 OMe), 3.98 (m,
2H, H-5, H-6), 4.23 (dd, 1H, J=6.0, 6.2 Hz), 4.55 (dd,
1H, J=6.0, 6.2 Hz), 4.67 (d, 1H, J=2.4 Hz); 13C NMR
(75.5 MHz, [D4]MeOH) l 26.6, 27.9 (CMe2), 52.9 (2
OMe), 70.6, 79.4 (C-5, C-6), 75.6 (C-2, C-3), 111.9
(CMe2), 170.2, 171.5 (2 CO); MS (FD) m/z 292 (M++
2), 291 (M++1), 290 (M+). Anal. calcd for C12H18O8
(290.3): C, 49.65; H, 6.25. Found: C, 49.74; H, 6.28.
3.4.
D-Mannose“L-lyxo products 29–31 (ent-daucic
acid derivatives)
3.4.1. 2,6-Anhydro-
[C-(b- -mannopyranosyl)formic acid] 25. To a solution
of a-
-mannosyl-cyanide 1610 in MeOH (30 mL) was
D
-glycero- -galacto-heptonic acid
D
D
D
added 17 mL of 0.1N NaOMe in MeOH, and the
mixture was kept at rt for 1 h followed by evaporation
to dryness in vacuo. The residue was dissolved in 12.5%
aqueous NaOH (50 mL) and refluxed for 4 h. Dilution
with H2O (150 mL), neutralization by stirring with
Amberlite IR-120 (H+-form, 100 mL), filtration with
several washings with water, and evaporation of the
combined filtrates to dryness in vacuo gave a solid
mass, which was purified by passing it, dissolved in 60
mL of water, through an Amberlite IR 120 column (100
mL) and rinsed with water. Evaporation of the com-
bined eluates to dryness in vacuo gave 7.34 g (90%) of
25 as a syrup, which was directly used for the ensuing

F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
3983
3.4.4. Dimethyl 2,6-anhydro-3,4-O-isopropylidene-5-O-
mesyl- -glycero- -galacto-heptarate 28. To a cooled
was stirred at ambient temperature for 2 h, followed by
removal of the solvent in vacuo. The residue was
dissolved in 12.5% aqueous NaOH (50 mL) and the
solution was refluxed for 4 h, subsequently diluted with
water (150 mL) and neutralized by stirring with Amber-
lite IR-120 (H+-form, 120 mL). Filtration, several wash-
ings with water and evaporation of the combined
filtrates to dryness in vacuo gave the free heptonic acid
(33, H instead of Me) as a crystalline mass, which was
directly subjected to esterification by stirring with HCl–
satd MeOH (50 mL) at rt overnight. The mixture was
then taken to dryness in vacuo providing 7.4 g (85%) of
33 as a syrup, sufficiently pure (1H NMR) for the
ensuing oxidation (“34).
D
D
(0°C) solution of 27 (600 mg, 2 mmol) in pyridine (10
mL) was added methanesulfonyl chloride (0.4 mL, 5.2
mmol), and the mixture was stirred for 3 h at 0°C. Solid
NaHCO3 was then added and stirring was continued
for another 30 min at 0°C. The reaction mixture was
diluted with satd aqueous NaHCO3, extracted with
EtOAc, and dried over Na2SO4. Removal of the solvent
in vacuo gave a crystalline mass, which was recrystal-
lized from i-PrOH to afford 645 mg (85%) of 28 as
colorless needles; mp 163°C; [h]2D0=−17.9 (c 1.0,
1
CHCl3); H NMR (300 MHz, CDCl3): l 1.37, 1.55 (2 s,
3H each, CMe2), 3.14 (s, 3H, MsMe), 3.83, 3.84 (2 s,
3H each, 2 OMe), 4.17 (d, 1H, J=7.3 Hz), 4.45 (dd,
1H, J=6.0, 6.2 Hz), 4.48 (d, 1H, J=2.2 Hz), 4.63 (dd,
1H, J=6.0, 6.2 Hz), 4.99 (dd, 1H, J=6.2, 7.3 Hz); MS
(FD) m/z 369 (M++1), 368 (M+). Anal. calcd for
C13H20O10S (368.4): C, 42.39; H,5.47. Found: C, 42.03;
H,5.42.
Syrupy 33, of Rf=0.40 (TLC in EtOAc–i-PrOH–water
5:2:1), can be crystallized by trituration with EtOAc:27
mp 121–123°C, [h]2D0=−32.0 (c 0.2, H2O).
3.5.2. Dimethyl 2,6-anhydro-
D
-glycero- -manno-hep-
L
tarate 34. To a solution of syrupy 33 as obtained above
(7.2 g, 32 mmol) in satd aqueous NaHCO3 (50 mL)
containing KBr (300 mg) an nBu4NCl (350 mg) was
added a solution of TEMPO in CH2Cl2 (150 mg in 60
mL) followed, after cooling to 0°C, by the dropwise
addition of a mixture of aqueous 13% NaOCl (150
mL), satd aqueous NaCl (50 mL) and satd aqueous
NaHCO3 (25 mL) over the period of 1 h. Stirring was
continued for 12 h at 0°C and the mixture was allowed
to warm to ambient temperature. Separation of the two
layers, washing of the organic phase with water (3×25
mL), acidification of the combined aqueous layer and
extracts with 2N HCl, and concentration in vacuo left a
syrup which was dissolved in water (80 mL) and passed
through an Amberlite IR-120 column (H+-form, 140
mL). Acidic eluates were collected, treated with active
carbon, and then taken to dryness in vacuo. The result-
ing syrup was exposed to 8% HCl–MeOH (40 mL) for
2 h at ambient temperature. Removal of the solvent,
purification of the residue by elution from a silica gel
column with CHCl3–MeOH (6:1) and evaporation of
the combined eluates with Rf=0.40 in CHCl3–MeOH
(4:1) to dryness in vacuo gave a syrup which crystal-
lized on trituration with MeOH–CHCl3: 6.65 g (70%) of
34 as colorless needles; mp 163–164°C; [h]2D0=+23.0 (c
3.4.5. Dimethyl 2,6-anhydro-4,5-O-isopropylidene-3-
deoxy- -lyxo-hept-2-enarate 29. To a solution of 324
L
mg (0.9 mmol) 28 in 30 mL of lutidine was added 3 g
of basic Al2O3 (Fluka type 5016 A basic) and the
mixture was warmed to 40°C for 30 min followed by
evaporation in vacuo to dryness. The residue was
applied to a silica gel column (1.5×30 cm) and eluted
with CH2Cl2–Me2CO (110:1). Removal of the solvent
from the eluates with Rf=0.53 (TLC in vacuo yielded
165 mg (69%) as 29 as a syrup; [h]2D0=+20.6 (c 0.9,
1
CHCl3); H and 13C NMR data were identical to those
of its
D
-lyxo enantiomer 41. Anal. calcd for C12H16O7
(272.3): C, 52.94; H, 5.92. Found: C, 51.44; H, 5.86.
3.4.6. Dimethyl 2,6-anhydro-3-deoxy- -lyxo-hept-2-
L
enarate (ent-dimethyl daucate) 30. Exposure of 29 to 6
mL of CHCl3–TFA–H2O (50:10:1) for 1 h at 30°C and
evaporation to dryness in vacuo gave a semi-crystalline
residue, which was purified by elution from a silica gel
column (2×20 cm) with CH2Cl2–Me2CO (2:1) Removal
of the solvent and crystallization from EtOAc–n-hexane
afforded 95 mg (73%) of 30; mp 126°C; [h]2D0=+94.1 (c
1
0.3, acetone); H and 13C NMR data duplicated those
of the enantiomeric (carrot-derived) (−)-dimethyl dau-
cate 42 (vide infra). Anal. calcd for C9H12O7 (232.2): C,
46.56; H, 5.21. Found: C, 45.92; H, 5.15.
1
1.0, MeOH). H NMR (300 MHz, D2O) l 3.76 (dd,
J=3.0 Hz, 9.6 Hz, 1H), 3.81, 3.84 (2 s, 3H each), 3.83
(dd, J=9.2, 9.6 Hz, 1H), 4.00 (d, J=9.2 Hz, 1H), 4.34
(dd, J=1.3, 3.0 Hz, 1H), 4.50 (d, J=1.3 Hz, 1H); 13C
NMR (75.5 MHz, D2O) l 55.9, 56.0,70.6, 72.5, 75.7,
80.3, 80.8, 173.2, 173.7; MS (FD) m/z 251 (M++1), 250
(M+). Anal. calcd for C9H14O8 (250.2): C, 43.20;
H,5.64. Found C, 43.24; H,5.60.
3.4.7. Dimethyl 4,5-di-O-acetyl-2,6-anhydro-3-deoxy-L-
lyxo-hept-2-enarate 31. Stirring of 30 (30 mg) in 4 mL
of pyridine–acetic anhydride (4:1) for 5 h at rt, followed
by work-up as described for the
D
-lyxo product 43 (cf.
below) afforded 31 (27 mg, 88%) as a syrup of [h]2D0=
1
+53.6 (c 1.0, CHCl3). H NMR data were identical to
those of 44.
3.5.3. Dimethyl 2,6-anhydro-4,5-O-isopropylidene-
D-
glycero- -manno-heptarate 35. suspension of
L
A
3.5.
D
-Galactose“
L
-arabino analogs of daucic acid
dimethyl heptarate 34 (3.40 g, 13.6 mmol) in dry ace-
tone (70 mL) containing 0.2 mL of conc. H2SO4 was
stirred for 4 h at ambient temperature, and subse-
quently neutralized with basic ion-exchange resin
(Amberlite IR-400, OH−). Evaporation to dryness gave
a syrup which was applied to a silica gel column
(4.5×30 cm) and eluted with toluene–EtOAc (1:1).
3.5.1. Methyl 2,6-anhydro- -glycero- -manno-heptonate
D
L
[methyl C-(b- -galactopyranosyl)formate] 33. To a solu-
D
tion of 14.0 g (39.2 mmol) of C-(tetra-O-acetyl-b-D-
galactosyl)cyanide 3212b in dry MeOH (30 mL) was
added 17 mL of 0.1N NaOMe–MeOH and the mixture

3984
F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
Evaporation of the fractions with Rf=0.72 (TLC in
EtOAc–EtOH–water 30:3:1) and crystallization of the
residue from EtOH–n-hexane gave 3.25 g (83%) of 35
as colorless needles; mp 139°C; [h]2D0=+38.7 (c 0.7,
CHCl3). (300 MHz, CDCl3) l 1.31, 1.47 (2 s, 3H each),
3.49 (bs, 1H), 3.79, 3.80 (2 s, 3H each), 3.88 (d, J=8.2
Hz, 1H), 4.04 (m, 1H), 4.20 (dd, J=5.8, 5.8 Hz, 1H),
4.51 (m, 2H); 13C NMR (75.5 MHz, CDCl3) l 26.1,
27.4 (CMe2), 52.7, 52.9 (2 OMe), 69.7, 73.4, 74.8, 76.7,
77.4, 110.9, 167.6, 169.9 (2 COOMe); MS (FD) m/z 291
(M++1), 290 (M+), 275 (M+−CH3). Anal. calcd for
C12H18O8 (290.3): C, 49.65; H, 6.25. Found C, 49.71; H,
6.22.
Aside 38, 40 mg (10%) of dimethyl 2,6-anhydro-3,5-di-
O-benzoyl-4-O-mesyl- -glycero- -manno-heptarate was
D
L
obtained from the fractional crystallization; mp 226–
228°C; [h]2D0=+104.8 (c 0.5, CHCl3); 1H NMR (300
MHz, CDCl3) l 3.05 (s, 3H, MsMe), 3.72, 3.73 (two
3H-s, 2 OMe), 4.26 (d, 1H, J=9.9 Hz), 4.52 (m, 1H,
6-H), 5.29 (dd, 1H, J=3.5, 9.9 Hz), 5.76 (t, 1H, J=9.9
Hz), 6.22 (dd, 1H, J=1.3, 3.5 Hz), 7.35 and 8.10 (2 m,
6 and 4H, 2 C6H5); MS (FD) m/z 537 (M++1), 536
(M+).
3.5.6. Dimethyl 2,6-anhydro-5-O-mesyl-
D
-glycero-L-
manno-heptarate 39. A suspension of 38 (180 mg, 0.33
mmol) in 16% HCl–MeOH (10 mL) was refluxed for 2
days. The clear solution was concentrated to a syrup
which was purified on a silica gel column (CHCl3–ace-
tone, 1:1). Product-containing eluates (Rf=0.25, TLC
in CHCl3–acetone, 1:1) were concentrated to afford 95
mg (86%) of 39 as a crystalline mass; mp 144–145°C;
MS (FD) m/z 329 (M++1), 328 (M+).
3.5.4. Dimethyl 2,6-anhydro-3-O-benzoyl-4,5-O-iso-
propylidene-
D
-glycero- -manno-heptarate 36. A solution
L
of 35 (490 mg, 1.7 mmol) in pyridine (10 mL) contain-
ing 400 mL (3.5 mmol) of benzoyl chloride was stirred
at rt overnight and then poured onto an approximate
1:1 mixture of ice and satd aqueous NaHCO3. The solid
material was filtered off, washed with water, and recrys-
tallized from EtOH to afford 585 mg (90%) of 36; mp
3.5.7. Dimethyl 2,6-anhydro-3-deoxy- -arabino-hept-2-
L
enarate 40. To a solution of 39 in MeOH (80 mg in 2
mL) was added 1.7 mL of 0.1N NaOMe in MeOH and
the mixture was stirred at rt for 15 min. Removal of the
solvent in vacuo and purification by elution from a
silica gel column with CHCl3–acetone (1:1) afforded 52
mg (90%) of 40 as a syrup; [h]2D0=+30.0 (c 1.0, acetone);
1H NMR (300 MHz, CDCl3) l 3.80, 3.85 (two 3H s, 2
OMe), 4.19 (m, 1H), 4.25 (m, 1H), 4.73 (dd, 1H, J=0.9,
5.4 Hz), 6.13 (dd, 0.9, 4.3 Hz), MS (FD) m/z 233
(M++1), 232 (M+). Anal. calcd for C9H12O7 (232.2): C,
46.56; H, 5.21. Found: C, 46.50; H, 5.14.
1
160–162°C; [h]2D0=+6.3 (c 0.8, CHCl3); H NMR (300
MHz, CDCl3) l 1.36, 1.56 (two 3H-s, CMe2), 3.76, 3.87
(two 3H-s, 2 OMe), 4.36 (d, 1H, J=5.4 Hz), 4.57 (dd,
1H, J=5.4, 6.4 Hz), 4.61 (d, 1H, J=2.3 Hz), 4.68 (dd,
1H, J=2.3, 6.4 Hz), 5.72 (t, 1H, J=5.4 Hz), 7.55, 8.05
(2 m, 3H and 2H, C6H5); MS (FD) m/z 395 (M++1),
394 (M+). Anal. calcd for C19H22O9 (394.4): C, 57.87;
H, 5.62. Found: C, 57.80; H, 5.55.
3.5.5.
mesyl-
Dimethyl
-glycero-
2,6-anhydro-3,4-di-O-benzoyl-5-O-
-manno-heptarate 38. A solution of 36
D
L
3.5.8. Dimethyl 4,5-di-O-acetyl-2,6-anhydro-3-deoxy-L-
(320 mg, 0.8 mmol) in 6 mL of CHCl3–TFA–water
(50:10:1) was stirred at ambient temperature for 30 min,
then concentrated to a syrup and purified on a silica gel
column by elution with acetone–CHCl3 (2:1). Eluates
with Rf=0.26 (TLC in acetone–CHCl3, 2:1) were con-
centrated to a syrup, which was dissolved in pyridine (3
mL), cooled to −35 to −40°C, followed by addition of a
mixture of benzoyl chloride (0.12 mL, 1 mmol) and
pyridine (1 mL). Stirring at −40°C was continued for 2
h whereafter methanesulfonyl chloride (0.15 mL, 2
mmol) was then added, and the mixture was allowed to
warm to rt (3 h). Subsequent dilution with EtOAc (20
mL), washing with satd aqueous NaHCO3 and water,
drying (Na2SO4), and concentration in vacuo gave a
syrup which was purified on a silica gel column
(CHCl3–EtOAc, 5:1). Eluates with Rf=0.60 (TLC in
CHCl3–acetone, 5:1) were concentrated to give a crys-
talline mass consisting of a 5:1 mixture (1H NMR) of
38 and its 4-O-mesylated isomer. Fractional crystalliza-
tion from EtOH afforded 230 mg (53%) of 38; mp
arabino-hept-2-enarate 41. Exposure of 40 (23 mg, 0.1
mmol) to a mixture of Ac2O (0.3 mL) and pyridine (1.5
mL) for 12 h at rt, evaporation to dryness in vacuo and
purification of the residual syrup by elution from a
short silica gel column with n-hexane–acetone (2:1)
gave 27 mg (90%) of 41 as a syrup, which gradually
crystallized by standing at 5°C; mp 104–106°C; [h]2D0=
1
+72.0 (c 0.6, CHCl3); H NMR (300 MHz, CDCl3) l
2.01, 2.11 (two 3H-s, 2 Ac), 3.79, 3.88 (two 3H s, 2
OMe), 5.06 (dd, 1H, J=2.1, 2.2 Hz), 5.14 (ddd, 1H,
J=1.6, 2.1, 5.4 Hz), 5.44 (m, 1H), 6.18 (dd, 1H, J=1.5,
1
5.4 Hz); H NMR (C6H6) l 1.44, 1.46 (two 3H s, 2 Ac),
3.20, 3.25 (two 3H s, 2 OMe), 4.89 (dd, 1H, J=1.6, 2.6
Hz), 5.22 (ddd, 1H, J=1.6, 2.3, 5.3 Hz), 5.58 (m, 1H),
6.37 (dd, J=1.5, 5.3 Hz); 13C NMR (75.5 MHz,
CDCl3) l 20.8 (2 Ac), 52.6, 52.9 (2 OMe), 62.5 (C-4),
66.9 (C-5), 73.2 (C-6), 104.6 (C-3), 145.2 (C-2), 161.9,
166.4, 169.9, 169.4 (4 CO); MS (FD) m/z 316 (M+).
3.6. D-Galactose“(−)-dimethyl daucate and derivatives
42–45
1
189–190°C; [h]2D0=+89.0 (c 0.6, CHCl3); H NMR (300
MHz, CDCl3) l 3.05 (s, 3H, SO2Me), 3.72, 3.86 (two
3H s, 2 OMe), 4.30 (d, 1H, J=10.0 Hz), 4.55 (m, 1H),
5.55 (dd, 1H, J=3.1, 10.2 Hz), 5.73 (dd, 1H, J=0.7, 3.1
Hz), 5.91 (dd, 1H, J=10.0, 10.2 Hz), 7.50, 8.00 (2 m,
6H and 4H, 2 C6H5); MS (FD) m/z 537 (M++1), 536
(M+). Anal. calcd for C24H24O12S (536.5): C, 53.73; H,
4.51. Found: C, 53.63; H, 4.45.
3.6.1. Dimethyl 2,6-anhydro-4,5-O-isopropylidene-3-O-
mesyl- -glycero- -manno-heptarate 37. To a cooled
solution of 35 (1.0 g, 3.4 mmol) in pyridine (12 mL),
methanesulfonyl chloride (0.7 mL, 9 mmol) was added.
The mixture was stirred for 3 h at 0°C. After stirring
with solid NaHCO3 for 30 min at 0°C, the reaction
D
L

F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
3985
mixture was diluted with satd aqueous NaHCO3, then
extracted with EtOAc, and dried over Na2SO4. The
solution was concentrated to give a crystalline mass,
which was recrystallized from i-PrOH to afford 1.1 g
(85%) of 37 as colorless needles; mp 163°C; [h]2D0=
+17.2 (c 1.1, CHCl3); Rf=0.34 (toluene–EtOAc, 1:1);
1H NMR (300 MHz, CDCl3) l 1.37, 1.56 (2 s, 3H each,
CMe2), 3.15 (s, 3H, SO2Me), 3.84, 3.85 (two 3H-s, 2
OMe), 4.17 (d, J=7.4 Hz, 1H), 4.46 (dd, J=6.0, 6.3
Hz, 1H), 4.49 (d, J=2.3 Hz, 1H), 4.64 (dd, J=2.3, 6.0
Hz, 1H), 4.98 (dd, J=6.0, 6.3 Hz, 1H); 13C NMR (75.5
MHz, CDCl3) l 26.1, 27.1 (CMe2), 39.0 (SO2Me), 52.9,
53.1 (2 OMe), 73.7, 74.6, 75.3, 75.7, 77.2, 111.8 (CMe2),
167.0, 167.1 (2 CO); MS (FD) m/z 369 (M++1), 368
(M+), 353 (M+−Me). Anal. calcd for C13H20O10S
(368.4): C, 42.39; H, 5.47. Found: C, 42.48; H, 5.37.
50 mg (91%) of 44 as a colorless syrup, uniform by
TLC (Rf=0.60 in toluene–EtOAc, 1:1); [h]2D0=−54.1 (c
1
0.6, CDCl3); H NMR (300 MHz, CHCl3) l 2.05, 2.10
(2 s, 3H each, 2 AcMe), 3.82, 3.86 (2 s, 3H each, 2
OMe), 4.84 (1H, d, J=1.4 Hz, H-6), 5.73 (2H, m, H-4,
H-5), 5.98 (1H, dd, J=1.7, 2.3 Hz, H-3). 1H NMR (300
MHz, C6D6) l 1.65, 1.66 (2 s, 3H each, 2 AcMe), 3.31
(s, 6H, 2 OMe), 4.27 (1H, d, J=1.7 Hz, H-6), 5.56 (1H,
ddd, J=1.2, 2.3, 4.5 Hz, H-4), 5.81 (1H, ddd, J=1.2,
1.7, 1.7 Hz, H-5), 6.00 (1H, dd, J=1.7, 2.3 Hz, H-3);
13C NMR (75.5 MHz, CDCl3) l 20.5, 20.6 (2 AcMe),
52.8, 53.0 (2 COOMe), 63.5, 64.2 (C-4, C-5), 74.5 (C-6),
107.5 (C-3), 144.6 (C-2), 161.4, 166.4, 169.8, 169.9 (4
CO); MS (FD) m/z 316 (M+). Anal. calcd for C13H16O9
(316.3): C, 49.37; H, 5.10. Found: C, 49.31; H, 5.03.
3.6.5. Dimethyl 2,6-anhydro-4,5-di-O-benzoyl-3-deoxy-
3.6.2. Dimethyl 2,6-anhydro-4,5-O-isopropylidene-3-
D
-lyxo-hept-2-enarate 45. Dimethyl daucate 43 (21 mg,
deoxy-
D
-lyxo-hept-2-enarate (dimethyl 4,5-O-isopropyli-
0.09 mmol) was benzoylated with benzoyl chloride (0.1
mL, 0.86 mmol) and 3 mL of pyridine. The reaction
mixture was stirred for 4 h at ambient temperature and
then diluted with EtOAc. The solution was washed with
satd aqueous NaHCO3 (3×10 mL) and H2O (10 mL),
dried (Na2SO4), and concentrated in vacuo to a residue,
which was purified by elution from a silica gel column
(1.5×20 cm) with CH2Cl2–acetone (60:1). Removal of
the solvent from the eluates in vacuo and trituration of
the syrup with little MeOH resulted in crystallization:
30 mg (76%) of 45; mp 112–113°C [lit.3 mp 112°C for
the carrot-derived product]; [h]2D0=−88.9 (c 0.5,
dene-daucate) 42. To a solution of mesylate 37 (1.0 g,
2.7 mmol) in 100 mL of lutidine was added 10 g of
basic Al2O3 (Fluka type 5016) and the suspension was
stirred for 30 min at 40°C and subsequently evaporated
to dryness. The residue was applied to a silica gel
column (3×30 cm) and eluted with CH2Cl2–acetone
(110:1). Removal of the solvent from the eluates with
Rf=0.51 (TLC in toluene–EtOAc 1:1) in vacuo yielded
565 mg (77% of 42 as a syrup; [h]2D0=−19.1 (c 1.0,
1
CHCl3); H NMR (300 MHz, CDCl3) l 1.37, 1.41 (2 s,
3H each, CMe2), 3.83, 3.90 (2 s, 3H each, 2 OMe), 4.67,
(1H, d, J=1.5 Hz, H-6), 4.69 (1H, ddd, J=1.3, 1.5, 5.9
Hz), 4.89 (dd, 1H, J=3.3, 5.9 Hz), 6.08 (dd, 1H,
J=1.3, 3.3 Hz). Anal. calcd for C12H16O7 (272.3): C,
52.94; H, 5.92. Found: C, 53.10; H, 5.87.
1
CHCl3); H NMR (300 MHz, CDCl3) l 3.76, 3.90 (2 s,
3H each, 2 OMe), 5.06 (1H dd, J=1.4, 2.0 Hz, H-6),
6.07 (2H, m, H-4, H-5), 6.21 (1H, dd, J=1.6, 3.0 Hz,
H-3), 7.26–8.14 (10 H, m, 2 C6H5); 1H NMR (300
MHz, C6H6) l 3.17, 3.32 (2 s, 3H each, 2 OMe), 4.31
(1H, dd, J=1.2, 1.7 Hz, H-6), 5.83 (1H, ddd, J=1.2,
1.7, 4.3 Hz, H-4), 6.11 (1H, ddd, J=1.5, 1.7, 4.3 Hz,
H-5), 6.17 (1H, dd, J=1.5, 2.8 Hz, H-3), 6.8-7.1, 7.9
−8.1 (2 m, 10 H, 2 C6H5); 13C NMR (75.5 MHz,
CDCl3) l 53.0, 53.1 (2 OMe), 64.6, 64.9 (C-4, C-5), 74.3
(C-6), 107.5 (C-3), 128.5–133.9 (12 C, 2 C6H5), 145.1
(C-2), 161.7, 165.3, 165.6, 166.7 (4 CO); MS (FD) m/z
440 (M+). Anal. calcd for C23H20O9 (440.4): C, 62.72;
H, 4.58. Found: C, 62.66; H, 4.49.
3.6.3. (−)-Dimethyl daucate (dimethyl 2,6-anhydro-3-
deoxy- -lyxo-hept-2-enarate) 43. Exposure of 42 (475
D
mg, 1.7 mmol) to a stirred mixture of 20 mL of
CHCl3–TFA–water (50:10:1) gave after 1 h at rt and
evaporation to dryness a semi-crystalline residue, which
was purified by elution from a silica gel column (2×20
cm) with CH2Cl2–acetone (2:1). Concentration of the
eluate and crystallization from EtOAc–n-hexane
afforded 335 mg (83%) of 43 as a colorless powder; mp
128–129°C; [h]2D0=−97.3 (c 0.6, acetone); Rf=0.38
(TLC in CHCl3–acetone 1:1). 1H NMR (300 MHz,
CDCl3) l 3.84, 3.86 (2 s, 3H each, 2 OMe), 4.30 (1H,
ddd, J=1.2, 2.4, 4.4 Hz, H-5), 4.50 (1H, ddd, J=0.7,
3.3, 4.4 Hz, H-4), 4.67 (1H, dd, J=0.7, 2.4 Hz, H-6),
6.05 (1H, dd, J=1.2, 3.3 Hz, H 3; 13C NMR (75.5
MHz, CDCl3) l 52.8, 53.1 (2 OMe), 63.8 (C-4), 66.0
(C-5), 75.6 (C-6), 111.5 (C-3), 143.3 (C-2), 162.2, 168.8
(2CO); MS (FD) m/z 234 (4%, M++2), 233 (39%.
M++1), 232 (100%, M+); UV (EtOH) umax 242 nm (m
5470). Anal. calcd for C9H12O7 (232.3): C, 46.56;
H,5.21. Found: C, 46.49; H, 5.19.
3.6.6. (−)-Daucic acid [2,6-anhydro-3-deoxy- -lyxo-hept-
D
2-enaric acid; IUPAC: (2S,3R,4R)-3,4-dihydro-3,4-dihy-
droxy-2H-pyran-2,6-dicarboxylic acid] 46. To an
aqueous solution of dimethyl daucate 43 (60 mg, 0.3
mmol, in 4 mL) was added TFA (1 mL) and the
mixture was stirred for 3 days at 30°C. Evaporation of
the solution to dryness in vacuo afforded a syrup,
which gave a crystalline mass on trituration with ace-
tone–n-hexane: 42 mg (79%) of 46; mp 87–88°C; [h]2D0=
−85.0 (c 1.2, MeOH); Rf=0.25 (TLC in EtOAc–
1
HOAc–water, 3:2:1); [lit.3 mp 85–87°C]. H NMR (300
MHz, [D4]MeOH) l 4.28 (dt, 1H, J=1.6, 1.6, 4.5 Hz,
H-5), 4.60 (ddd, 1H, J=0.9, 2.0, 4.5 Hz, H-4), 4.74 (dd,
1H, J=0.9, 1.6 Hz), 5.93 (dd, 1H, J=1.6, 2.0 Hz); 13C
NMR (75.5 MHz, [D4]MeOH) l 67.4 (C-4), 68.2 (C-5),
79.6 (C-6), 115.4 (C-3), 145.7 (C-2), 166.8, 173.4 (2
CO). Anal. calcd for C7H8O7 (204.1): C, 41.14; H, 3.95.
Found: C, 41.12; H, 3.87.
3.6.4. Dimethyl 4,5-di-O-acetyl-2,6-anhydro-3-deoxy-D-
lyxo-hept-2-enarate 44. Stirring of dimethyl daucate 43
(40 mg, 0.17 mmol) with Ac2O (1 mL) and pyridine (4
mL) at 20°C for 5 h, evaporation to dryness in vacuo,
and elution of the syrupy residue from a silica gel
column (1.5×20 cm) with CH2Cl2–acetone (60:1) gave

3986
F. W. Lichtenthaler et al. / Tetrahedron: Asymmetry 14 (2003) 3973–3986
3.6.7. (+)-Dimethyl osbeckate [methyl 2S-hydroxy-2-(5-
carbomethoxy-2-furyl)acetate] 5. Refluxing 43 (50 mg,
0.21 mmol) in methanol satd. with HCl (5 mL) for 4 h
was followed by evaporation to dryness in vacuo and
several coevaporations from MeOH. Purification of the
residue by elution from a silica gel column (1×15 cm)
with CH2Cl2–MeOH (20:1), removal of the solvents
from the eluates and trituration of the residues with
acetone–n-hexane yielded 28 mg (62%) of 5 as colorless
crystals; mp 134°C; [h]2D0=+78.9 (c 0.5, acetone) [lit.13
for the Osbeckia chinensis-derived product: mp 134–
135°C; [h]2D0=+79.3 (c 0.2, acetone)]; 1H NMR (300
MHz, CDCl3) l 3.56 (bs, 1H, OH), 3.82, 3.87 (two
3H-s, 2 OMe), 5.25 (s, 1H), 6.48, 7.13 (2 d, J=3.5 Hz);
MS (FD) m/z 215 (M+1)+, 214 (M+). Anal. calcd for
C9H10O6 (214.2): C, 50.47; H, 4.71. Found: C, 50.50; H,
4.74.
C-H3 torsional angle of ꢀ130°, and hence, a J2,3 of 7.5
Hz. By consequence, the utility of these data for compar-
ative purposes is futile.
5. (a) Miyoshi, E.; Shizuri, Y.; Yamamura, S. Chem. Lett.
1987, 511–514; (b) Ueda, M.; Shigemori, H.; Sata, N.;
Yamamura, S. Phytochemistry 2000, 53, 39–44.
6. For a preliminary report of part of this work, see:
Lichtenthaler, F. W.; Nakamura, K.; Klotz, J. Angew.
Chem., Int. Ed. 2003, 43, in press.
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3.6.8. (+)-Osbeckic acid [2S-hydroxy-2-(5-carboxy-2-
furyl)acetic acid] 47. A solution of dimethyl daucate 43
(50 mg, 0.2 mmol) in water (5 mL) was stirred with
Amberlite IR-120 (H+-form, 1 g) and the mixture was
refluxed for 5 h. Filtration and evaporation of the
combined filtrate and washings to dryness in vacuo
gave 35 mg (85%) of 47 as a colorless syrup; Rf=0.59
(TLC in EtOAc–HOAc–water, 3:2:1); [h]2D0=+79.6 (c
10. Kini, G. D.; Petrie, C. R.; Hennen, W. J.; Dalley, N. K.;
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81–94.
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1
0.8, MeOH) [lit.13 oil, [h]2D0=+83.5 (c 0.2, MeOH)]; H
NMR (300 MHz, D2O) l 5.47 (s, 1H), 6.70 (d, J=3.5
Hz), 7.31 (d, 1H, J=3.5 Hz); 13C NMR (75.5 MHz,
D2O) l 69.4 (C-2), 114.4, 122.9 (C-3%, C-4%), 147.5,
158.1, 164.8, 176.2 (C-2%, C-5%, 2 CO).
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Acknowledgements
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We are pleased to acknowledge the support of this
investigation by the Deutsche Forschungsgemeinschaft,
the Fonds der Chemischen Industrie, and the Alexan-
der von Humboldt Foundation (fellowship to K.N.)
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