Efficient Production of Biomass-Derived C4 Chiral Synthons in Aqueous Solution

Article abstract of DOI:10.1002/cctc.201700944

Carbohydrates are expected to replace petroleum and to become the base of industrial chemistry. Chirality is one particular area in which carbohydrates have a special potential advantage over petroleum resources. Herein, we report a catalytic approach for the direct production of d-tetroses [i.e., d-(?)-erythrose and d-(+)-erythrulose] from d-hexoses through a fast retro-aldol process at 190 °C that achieves a yield of 46 % and completely retains the chiral centers in the final chiral synthon. The d-tetrose products were further converted into their derivatives, thereby accomplishing transfer of chirality from natural chiral hexoses to high-value-added chiral chemicals. Our results also suggest that the product distribution for the conversion of d-hexoses was determined by their isomerization and epimerization trends that competed with their corresponding retro-aldol condensation processes.

Full text of DOI:10.1002/cctc.201700944

Accepted Article
Title: Efficient Production of Biomass-derived C4 Chiral Synthons in
Aqueous Solution
Authors: Shaoying Lin, Xiao Guo, Kai Qin, Lei Feng, Yahong Zhang,
and Yi Tang
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.201700944
Link to VoR: http://dx.doi.org/10.1002/cctc.201700944
A Journal of
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10.1002/cctc.201700944
ChemCatChem
COMMUNICATION
Efficient Production of Biomass-derived C4 Chiral Synthons in Aqueous Solution
Shaoying Lin, Xiao Guo, Kai Qin, Lei Feng, Yahong Zhang* and Yi Tanga
Abstract: Carbohydrates are expected to replace petroleum and
substantially become the base of the industrial chemistry. The
utilization of chirality is one particular area in which carbohydrates
have a special potential advantage over petroleum resources. We
report a catalytic approach for the direct production of D-tetroses (i.e.,
D-(−)-erythrose and D-(+)-erythrulose) from D-hexoses via a fast
retro-aldol process at 190 oC that achieves 46% yield while completely
retaining the chiral centers in the final chiral synthon. The D-tetrose
products were further converted into their derivatives, thereby
accomplishing the chiral transfer from natural chiral hexoses to high
value-added chiral chemicals. Our results also suggested that the
product distribution for the conversion of D-hexoses was determined
by their isomerization and epimerization trends that compete with their
corresponding retro-aldol condensation processes.
a chiral synthon for further applications.[15–21] For example, lactol 8
as an important chiral synthon, which can be obtained from the
16]
methylenation of 2,3-O-isopropylidene-D-erythronolactone,[9,
and can be readily dehydrated to a mixture of isomeric α,β-
unsaturated esters.[16] (2-azaallyl) stannane 10 is
a key
intermediate in the synthesis of (−)-amabiline.[17] Additionally, D-
tetrose is a natural C4 back-bone which can be used to synthesize
various achiral C4 chemicals such as α-hydroxyl butyric acids[22, 23]
and α-hydroxy-γ-butyrolactone (α-HBL).[24] However, the synthesis
of C4 skeleton compounds from significantly more abundant C6
sugars have been scarcely published the literature. Obviously, high
efficient production of D-tetrose is imperative for developing its
diverse applications. Recently, retro-aldol process have been used
to reduce the size of hexoses, and C3 products such as lactic acid or
lactates were obtained from both D-(−)-fructose and D-(+)-
glucose.[5-7] Although D-tetrose can be theoretically obtained from
D-(+)-glucose via a retro-aldol process, its dehydration products
such as methyl vinylglycolate (MVG), methyl-4-methoxy-2-
hydroxybutanoate (MMHB), vinylglycolate (VG), and α-HBL were
observed as byproducts only in trace amounts in such systems.[6, 22,
As a result of the diminishing availability of needed petro-
chemical resources, carbohydrates are emerging as a potential
renewable alternative to these fossil fuel-based resources.
Accordingly, several routes have been developed to convert
carbohydrate-derived sugars into a few flexible, general-
purpose molecules for the production of renewable fuels[1–4]
and chemicals.[5–8] Compared to fossil fuels, carbohydrates are
characterized by their multiple chiral centers and structural
variations. Chirality at molecular level is one of the major
issues when developing chemicals and advanced materials.[9]
In this sense, the “chiral pool” approach (i.e., chiral
substructures derived from readily available, renewable
materials are used as synthons and directly integrated into
target molecules) is a very valuable strategy.[10] The optimum
size for a chiral synthon is 3–4 carbon atoms.[9] Although
carbohydrates are the most prominent members of the chiral
pool, the most abundant and generally accessible
25]
Additionally, its natural chirality is completely lost during the
conversion process. Therefore, the development of a new catalytic
system able to produce chiral tetrose product with excellent yield
is of high interest.
Herein, we report for the first time the direct production of
D-tetrose from D-hexose (aldose) in the presence of tungstic
or molybdic species. In this process, the predominant
production of C4 compounds greatly depended on the relative
isomerization and epimerization rates of D-(+)-glucose, D-(−)-
fructose, and D-(+)-mannose, with the highest yield of D-
tetrose reaching 46%. This catalytic system demonstrated the
feasibility of the retro-aldol process in accumulating chiral
monosaccharides derived from carbohydrates are C5–C6 tetrose while also allowing further conversion of the as-
sugars. Therefore, methods for decreasing the size of the
carbohydrate skeleton have to be developed.
prepared D-tetrose into erythronic acid via in situ oxidation.
Thus, this route allows the transformation of C6 aldoses into
value-added chiral synthons.
Interconvertible D-(−)-erythrose and D-(+)-erythrulose are
two ideal chiral synthons possessing a C4 skeleton. As shown
in Scheme 1, D-(−)-erythrose as a chiral synthon exhibits a
strong potential for the pharmaceutical industry. Thus, it can
be readily converted into non-natural L-(+)-erythrose 2 via
To efficiently obtain tetrose, various Lewis acid catalysts
were used herein to carry out the transformation of D-(+)-
glucose into C4 and C2 compounds. Fig. 1 summarizes the
yields of the main tetroses (i.e., erythrose (ERO) and
erythrulose (ERU)) in aqueous solutions containing various
homogeneous Lewis acid catalysts. Herein, therose (THO), the
counterpart epimer of ERO, is not included owing to its yield
lower than 1.0 mol% in these catalytic systems. We found that
tungstic and molybdic compounds converted D-(+)-glucose
into tetrose and glycolaldehyde (GA) (Fig. 1 and Table S1,
entries 1–10). A tetrose yield of 46.1% was attained in the
presence of ammonium tungstate (AT) (Fig. 1). Tetrose
dehydration products (i.e., α-HBL and VG) as well as traces of
C3 species were observed (Table S1, entries 1–10). Among
them, the main tetrose product catalyzed by a series of
erythritol
1 [11]
,
(+)-tanikolide
3,[12]
2,4-di-O-benzyl-1-
deoxymannojirimicyn 4[13] and epi-muricatacin 5[14] products.
Moreover, after oxidation of its aldehyde group and subsequent
lactonization, we can obtain D-(−)-erythronolactone, widely used as
[a]
S. Lin, X. Guo, K. Qin, L. Feng, Prof. Y. Zhang, Prof. Y. Tanga
Department of Chemistry, Shanghai Key Laboratory of Molecular
Catalysis and Innovative Materials, Laboratory of Advanced
Materials, Collaborative Innovation Centre of Chemistry for Energy
Materials, Fudan University, Shanghai 200433, china, E-mail:
zhangyh@fudan.edu.cn; Fax: +86-21-65641740.
Supporting information for this article is given via a link at the end of
the document.
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10.1002/cctc.201700944
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Scheme 1. Schematic representation of the reaction sequence used to produce chiral synthons (D-tetrose and D-(−)-erythronolactone) via catalytic processing of
D-hexose as well as various potential target chiral chemicals, providing a platform for the retention and the transfer of the chirality of natural carbohydrates. 1:
erythritol; 2: L-(+)-erythrose; 3: (+)-tanikolide; 4: 2,4-di-O-benzyl-1-deoxymannojirimicyn; 5: epi-muricatacin (−)-2; 6: isopropyildene-2,2-dimethyl-3-O-trimeth-ylsilyl-
α-D-erythro-3,6-furanoso-3-hexulosonate; 7: (−)-semigl-abrin; 8: lactol; 9: loracarbef; 10: (2-azaallyl) stannane; and 11: (−)-swainsonine.
tungstic compounds was ERO, whereas ERU was obtained with LAA), C6 (5-hydroxymethylfurfural, HMF), and C5 (levulinic
systems containing molybdic species as a catalyst (Fig. 1 & Fig acid, LA) compounds, as shown in Table S1, entries 11–20.
S1). In more detail, the reaction activities depended on the
The production of erythrose and its chirality was confirmed
tungstic compound used. For example, except AT, ammonium by mass spectrometry (MS), 1H and 13C nuclear magnetic
paratungstate (APT) achieved more than 38% of tetrose within resonance (NMR) spectra, and specific rotation of the product
10 s (Fig. 1), whereas the yield of tetrose reached up to 40%
(Fig. 2). Two strong signals at m/z = 119 and 239,
after 60 s in the presence of tungstic acid (TA) and ammonium corresponding to the theoretical m/z of D-tetrose and its
metatungsten (AMT) (Fig. S2). However, unlike tungstic dimer under the negative ionization mode, respectively, were
species, molybdic compounds can catalyze the retro-aldol clearly observed from the crude product mixture (Fig. 2a) as
condensation of D-(+)-glucose at low temperature and long well as a separate erythrose product (Fig. S4). The change of
reaction time. Thus, ammonium molybdate (AM) required 90 the specific rotation from +50.9 to +1.4o after reaction
s to reach the highest tetrose yield (37.8%, Table S2). However, revealed the formation of levorotatory products from the
it is clear that other metal salt catalysts including Pb(II), Sn(II),
Zr(IV), Al(III), Bi(III), and Cr(II) showed poor yield of tetrose as
dextrorotatory D-(+)-glucose. Moreover, the specific rotation
(-13.7o) of the erythrose separated from the reaction mixture
compared to tungstic and molybdic catalysts (Fig. 1 & Fig. S3 ), was very close to the theoretical value (-14.5o) for this
as they dominantly converted D-(+)-glucose into C3 (lactic acid, compound as well as that of commercial D-(−)-erythrose (Fig.
1
2b). Furthermore, its H and 13C NMR spectra (Fig. 2c and d,
respectively) perfectly matched with those of commercial D-
(−)-erythrose (Fig. S5). The resonance intensity ratio for its α-
and β-furanose structures (i.e., α:β ratio of ca. 2:1) further
confirmed the existence of D-(−)-erythrose.[26] In addition, D-
(+)-erythrulose (i.e., the counterpart isomer of D-(−)-erythrose
separated from the reaction mixture catalyzed by ammonium
1
phosphomolybdate (APM)) displayed m/z signal and H NMR
spectrum similar to commercial erythrulose (Figs. S6, S7).
Furthermore, the change of specific rotation from +50.9 to
+4.9o after reaction in the presence of APM revealed the
formation of D-(+)-erythrulose in larger amounts as compared
to the AT-catalytic system (Fig. 2b).
Figure 1. Yield of D-tetrose (ERO and ERU) obtained from D-(+)-glucose in the
presence of various catalysts. Reaction conditions: 100 mg of D-(+)-glucose and
20 mg of catalyst were added into 10 mL of H2O, and the reaction was carried
It is worthy to mention that ERO during the retro-aldol
process of glucose can sequentially transformed into GA (R2,
out at 190 oC for 10 s under microwave irradiation. AT: ammonium tungstate;
APT: ammonium paratungstate; PT: potassium tungstate; TA: tungstenic acid;
AMT: ammonium metatungsten; APM: ammonium phosphomolybdate; AM:
ammonium molybdate; MA: molybdic acid; PMA: phosphomolybdic acid.
Scheme S1) whereas the generated GA can also go through an
aldol condensation to produce ERO again (R-2, Scheme S1).
However, according to the results in Table S1, the yields of GA
in all the experiments during the retro-aldol of glucose are
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Figure 2. (a) MS analysis results of the reaction solution catalyzed by AT under the negative ionization mode; (b) specific rotation of the resulting reaction solution,
erythrose separated from the reaction mixture after reaction catalyzed by AT, and various referenced sugar aqueous solutions. The concentration of all the aqueous
solutions was fixed at 1.0 wt%. The data in parenthesis represent the theoretical values. (c) 1H NMR and (d) 13C NMR spectra of the erythrose separated from the
reaction mixture catalyzed by AT. They were recorded on a 500 MHz NMR spectrometer in D2O. AT: ammonium tungstate.
always higher than that of tetrose as well as that of C4
converted D-(+)-mannose into tetrose and GA, with AT
products in the presence of various tungstic and molybdic showing the highest yield of tetrose.
catalysts, which means that the reaction rate of ERO towards
GA (R2) is much higher than that of GA converted into ERO (R-
2) under our experimental conditions. This trend is in
accordance with their thermodynamic analyses. Because the
retro-aldol process of ERO toward GA is a process of entropy
increasing whereas the aldol process of GA toward tetrose is a
entropy decreasing one, such high reaction temperature is in
favor of retro-aldol process of ERO according to G = H –TS.
Therefore, we believe that the tetrose products derive from D-
glucose rather than GA under such experimental condition.
Since AT showed the best yield of tetrose, the reaction
conditions were optimized for glucose conversion in the
presence of AT. The yield of D-tetrose increased with the
reaction temperature (Fig. S8). However, further retro-aldol
splitting of D-tetrose took place at temperatures higher than
190 oC, and the yield of GA greatly increased as a result.
Similarly, extension of reaction time also led to further
transformation of D-tetrose into GA. Simultaneously, the
dehydration product VG noticeably increased with the
prolonging time (Table S3). Furthermore, only trace amounts
of D-tetrose were obtained in the absence of catalyst (Fig. 1).
The addition of AT significantly promoted the reaction, and the
highest yield of D-tetrose was obtained at an AT/D-(+)-glucose
weight ratio of 0.2 (Fig. S9a). Under optimal conditions,
changes in the D-(+)-glucose concentration from 0.5 to 2.0 wt%
did not significantly affected the yield of D-tetrose, and nearly
30% of D-tetrose was obtained even at a high D-hexose
concentration of 9.1 wt% (Fig. S9b). Moreover, expanding
substrate from glucose to mannose resulted in similar product
distributions in the presence of different catalysts (Fig. S10
and Table S4). Thus, tungstic and molybdic compounds
Figure 3. Carbon yield for retro-aldol and dehydration products obtained from
(a) D-(+)-glucose and (b) D-(+)-mannose in the presence of various catalysts.
(c) 100% stacked column for epimerization and isomerization products of D-(+)-
glucose/D-(+)-mannose in the presence of AT and Pb(II) at 120 oC for 40 min.
(a) and (b) Reaction conditions: 100 mg of D-(+)-glucose/D-(+)-mannose and
20 mg of catalyst were added into 10 mL of H2O, and the reaction was carried
out at 190 oC for 10 s under microwave irradiation. (c) Reaction conditions: 100
mg of D-hexose and 20 mg of catalyst were added into 10 mL of H2O, and the
reaction was carried out at 120 oC for 40 min under microwave irradiation.
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According to the total conversion results of D-(+)-glucose/D- respectively. The produced D-(−)-erythrose was isomerized
(+)-mannose (Fig. 3a, 3b and Tables S1, S4), nearly all catalysts into D-(+)-erythrulose and also further transformed into GA
selectively catalyzed C–C bond cleavage reactions over D- and achiral HBL and VG via retro-aldol and dehydration
hexose. Thus, tungstic and molybdic catalysts converted D-(+)- reactions, respectively. Therefore, only under optimal
glucose/D-(+)-mannose into C2 and C4 sugars, whereas the
rest of metal salt catalysts predominantly converted these
conditions, the chiral tetrose can be sufficiently accumulated
in the reaction system. In contrast, the rest of metal ion
sugars into C3, C6, and C5 compounds. Additionally, as catalytic systems dominantly isomerized D-(+)-glucose into D-
indicated in Tables S1 and S4, isomerization and epimerization (−)-fructose, which readily transformed into triose. However,
of D-(+)-glucose/D-(+)-mannose took place in competition chiral triose immediately turned into racemic LAA via 1,2-
with the retro-aldol condensation process. It is known that C3
intramolecular hydride shift. Also, D-(−)-fructose formed HMF
and C5/C6 products generally originate from D-(−)-fructose and LA at high temperature via dehydration and rehydration
retro-aldol and dehydration processes,[6,7] respectively, processes. Therefore, the accumulation of C3–C4 sugars
whereas C2 and C4 sugars can be obtained by retro-aldol during the conversion of D-hexose is key to retain the chirality
splitting of D-(+)-glucose/D-(+)-mannose (Scheme 1). of carbohydrates.
Therefore, the D-(+)-glucose/D-(+)-mannose product
distribution under the presence of Lewis acid catalysts fully
depended on the isomerization and epimerization rates. The
results given in Fig. 3a and 3b indicated that tungstic and
molybdic compounds favoured epimerization between D-(+)-
glucose and D-(+)-mannose, while other metal ions catalyzed
isomerization to D-(−)-fructose. This difference became more
prominent at low reaction temperatures (Fig. 3c and Table S5).
Thus, D-(+)-glucose/D-(+)-mannose were predominantly
transformed into their epimerized product in the presence of
AT at low temperature. In contrast, these sugars were mainly
isomerized to D-(−)-fructose in the presence of Pb(II)-
containing catalysts.
In other words, ketose was produced via H1-H2 hydride shift
rather than C1-C2 carbon shift in the presence of Pb(II) ions,
which is in excellent agreement with previous reports.[6, 27, 28]
Also, a previous study has reported the catalytic effect of Pb(II),
Sn(II), and Al(III) salts during the conversion of D-(+)-glucose
Figure 4. Reaction routes of D-hexoses in the presence of various Lewis
acid catalysts. GA: glycolaldehyde; ERO: D-(−)-erythrose; ERU: D-(+)-
erythrulose; VG: vinylglycolate; HBL: α-hydroxy-γ-butyrolactone; DHA:
into LAA via fructose,[6] further supporting their role in the
glucose to fructose isomerization process. In addition, the
product distributions for the catalytic conversion of fructose
and sucrose with AT, APM, and Pb(II) further support the
above hypothesis (i.e., fructose mainly converted into C3
products even in the presence of AT and APM, while sucrose
displayed an average C3 and C4 product distribution, Table S6).
However, different from the isomerization/epimerization
tendency of D-(+)-glucose/D-(+)-mannose, the produced ERO
during the retro-aldol process of hexoses was inclined to
isomerize into ERU rather than epimerize into THO in the
presence of tungstic or molybdic compounds, which can be
further demonstrated by the transformation of ERO in the
presence of AT and APM (Table S7).
Finally, we confirmed that product distribution for D-hexose
conversion via retro-aldol process was determined by the
tendency to isomerization and epimerization among D-(+)-
glucose, D-(−)-fructose, and D-(+)-mannose. The proposed
reaction pathway for the conversion of D-hexose with the
above catalytic systems is depicted in Fig. 4. In the case of
catalysts containing tungstic or molybdic compounds, D-(+)-
glucose was preferably epimerized to D-(+)-mannose via
forming anionic complexes between glucose and
dimolybdate/ditungstate,[29-31] with both D-(+)-glucose and D-
(+)-mannose being converted into D-(−)-erythrose and GA,
dihydroxyacetone; GLA: D-(+)-glyceraldehyde; LAA: lactic acid; LA:
levulinic acid; and HMF: 5-hydroxymethylfurfural.
Retro-aldol condensation is an important reaction to
selectively tailor C3–C4 compounds preserving the chirality of
biomass-derived hexoses. However, previous studies reported
retro-aldol degradation of C6 sugars in integration with a
tandem reaction to convert the as-prepared C3 or C2 sugars
32]
into downstream more stable products.[6,
For example,
achiral glycol was obtained via retro-aldol and hydrogenation
tandem processes,[32] while racemic lactic acid was
synthesized by combining retro-aldol degradation and hydride
shift processes.[6] To date, these processes were rarely used to
directly prepare C4 sugar from significantly more abundant C6
sugars, because of the instability of tetrose[33] and the
competition of parallel reactions such as aldose–ketose
interconversion. Our results demonstrate, for the first time,
that the retro-aldol process is a highly efficient strategy for
controllably transforming D-(+)-glucose and D-(+)-mannose
into D-tetrose under optimum conditions.
Additionally, as shown in Scheme 1, both D-(−)-erythrose
and D-(−)-erythronolactone can be used as synthons to
introduce chirality in various potential molecules. In previous
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solution with a pH meter (PHS-3E, Leici Instruments Co., Ltd) before being
analyzed by high-performance liquid chromatography (HPLC, Shimadzu
LC-20AD).
reports,[34, 35] D-(−)-erythrose was prepared by degrading D-
arabinose oxime through the acetylated aldononitrile,[34]
while D-(−)-erythronolactone was obtained by oxidation of D-
ascorbic acid with hydrogen peroxide and a base.[35] Our
results provided a new synthetic route to convert D-hexose to
D-tetrose, such that D-(−)-erythronolactone can be obtained
by oxidation of D-(−)-erythrose. Therefore, we further
attempted the conversion of D-tetrose, and most of the as-
prepared D-(−)-erythrose was oxidized to D-(−)-erythronic acid
(ERA) over an Au-hydrotalcite (Au/HT) catalyst at 1.7 MPa of
O2 (Fig. S11). In this case, D-(−)-erythronolactone can be easily
achieved via acidification of the above solution with HCl, and
subsequently separated from water by extraction with ethyl
acetate.[32] These results demonstrated the maintaining and
transferring of natural chirality derived from C6 sugars via a
one-pot process. Nevertheless, although this catalytic system
involves an epimerization-driven reaction route, how to
efficiently prevent and control of the aldose-ketose
interconversion in the presence of a Lewis acid, which finally
determines the yield of single tetrose, still remains an issue.
Accordingly, further improvements can be expected through
the use of multi-functional catalysts or structural stabilizers.
In conclusion, we have proposed an efficient strategy to
produce D-tetrose from biomass-derived C6 aldoses via a fast
retro-aldol process at mild conditions. In such catalytic system,
chiral D-tetrose was readily obtained with the yield up to 46%
and identified from D-(+)-glucose/D-(+)-mannose in the
presence of tungstic or molybdic catalysts. We noted that
tungstic or molybdic compounds can selectively achieve
epimerization of aldose–aldose (D-(+)-glucose and D-(+)-
mannose) while decreasing the extent of aldose–ketose
isomerization, which is key to successfully accumulate D-
tetrose rather than triose or their mixtures in the reaction
mixture. Moreover, we tried the further transformation of as-
prepared chiral D-tetrose toward its oxidative product
erythronic acid by a one-pot cascade catalytic process. These
results obtained in the current work not only demonstrate the
production of chiral C4 skeleton from C6 sugars but also
provide an achievable platform for the complete retainment
and delivery of its natural chirality.
Inter-conversion among the three D-hexoses at low temperature: D-
hexose (0.1 g) without any pretreatment and 20 mg of AT/Pb(NO3)2 were
dissolved in 10 mL of water to obtain a certain concentration of the reaction
solution. The mixture solution was placed in the microwave-assisted
reactor for 5–40 min at 100–160 oC. The reaction mixture was cooled and
subsequently analyzed by HPLC at certain time intervals. Prior to the
analysis, the pH value of the solution was accurately adjusted to 7.0 by
using a 0.25 mol∙L-1 NaOH solution.
Preparation of the Au-loaded hydrotalcite (Au/HT) catalyst:
Hydrotalcite (HT) with a Mg/Al molar ratio of 4.0 was prepared by
hydrothermal synthesis at 140 oC for 20 h. Typically, 20.51 g of Mg(NO3)2
∙6H2O, 7.5 g of Al(NO3)3∙6H2O, and 24 g of urea were added to 200 g of
deionized water with an ultrasonic bath. The mixture was subsequently
placed into a Teflon-lined autoclave. After reacting at 140 oC for 20 h, the
mixture was filtered and washed with deionized water. Then the as-
prepared HT solids were subsequently dried overnight at 60 oC and
grinded for further use. Furthermore, 100 g of a HAuCl4 aqueous solution
(1.0 wt%), with a pH value pre-adjusted to 8–9 by ammonium hydroxide,
was added drop by drop to the grinded HT aqueous solution (1.0 wt%, 100
g). Five grams of a 1.0 wt% NaBH4 aqueous solution were subsequently
added to the mixture and stirred at room temperature for 10 h. Once filtered,
dried, and grinded, the Au/HT sample was activated in a hydrogen furnace
at 300 oC for 3 h before used.
Conversion of D-hexose into D-(−)-erythronic acid (ERA): The
activated Au/HT catalyst (85 mg) was added to 4 g of the above reaction
mixture, and the solution pH value was adjusted to 10.0 by using a 2.0 wt%
NaOH solution. The mixture solution was subsequently stirred at an
oxygen pressure of 1.7 MPa and room temperature for 40 h. The reaction
mixture was analyzed by HPLC at certain time intervals. Before being
analyzed by HPLC, the pH value of the solution was accurately adjusted
to 7.0 by using a 0.25 mol∙L-1 H2SO4 solution. The corresponding details
about the product analysis see the Supporting Information.
Acknowledgements
Experimental Section
This work was supported by NSFC (21673045, U1463206,
21473037, 21433002 and 21573046), 973 Program
(2013CB934101), Sinopec (X514005).
Conversion of D-hexose towards D-tetrose: All the catalytic reactions
were carried out in a 30 mL reactor under microwave irradiation. The
microwave field was provided by a single-mode microwave instrument
(Nova-2s, Preekem Scientific Instruments Co., Ltd). The used radiation
frequency was 2.45 GHz while the highest output power was 500 W. The
temperature of the reaction system was measured by an infrared (IR)
detector assembled in the microwave instrument. D-hexose (0.1–1.0 g)
without any pretreatment and various catalysts (5–100 mg) were dissolved
in 10 mL of water to obtain a certain concentration in the reaction solution.
The mixture solution was placed in the microwave-assisted reactor for 5 s
Keywords: biomass conversion • D-tetrose • retro-aldol reaction
• chiral synthon • epimerization
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–
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10.1002/cctc.201700944
ChemCatChem
COMMUNICATION
COMMUNICATION
Chiral D-tetrose is readily obtained
with considerable yield and
identified from D-(+)-glucose/D-
(+)-mannose in the presence of
tungstic or molybdic catalysts
through an epimerization-driven
reaction route.
S. Lin, X. Guo, K. Qin, L. Feng, Y.
Zhang* and Y. Tanga
Page No. – Page No.
Efficient Production of Biomass-
derived C4 Chiral Synthons in
Aqueous Solution
This article is protected by copyright. All rights reserved.