An alternative approach for the synthesis of sulfoquinovosyldiacylglycerol

Article abstract of DOI:10.3390/molecules26144275

Sulfoquinovosyldiacylglycerol (SQDG) is a glycolipid ubiquitously found in photosyn-thetically active organisms. It has attracted much attention in recent years due to its biological ac-tivities. Similarly, the increasing demand for vegan and functional foods has led to a growing interest in micronutrients such as sulfolipids and their physiological influence on human health. To study this influence, reference materials are needed for developing new analytical methods and providing enough material for model studies on the biological activity. However, the availability of these materials is limited by the difficulty to isolate and purify sulfolipids from natural sources and the unavailability of chemical standards on the market. Consequently, an alternative synthetic route for the comprehensive preparation of sulfolipids was established. Here, the synthesis of a sulfolipid with two identical saturated fatty acids is described exemplarily. The method opens possibilities for the preparation of a diverse range of interesting derivatives with different saturated and unsatu-rated fatty acids.

Full text of DOI:10.3390/molecules26144275

molecules
Article
An Alternative Approach for the Synthesis
of Sulfoquinovosyldiacylglycerol
Tobias Sitz 1 , Hendrik Domey , Judith Fischer 1 and Sascha Rohn 1,2,
1
*
1
Institute of Food Chemistry, Hamburg School of Food Science, University of Hamburg, Grindelallee 117,
0146 Hamburg, Germany; tobias.sitz@chemie.uni-hamburg.de (T.S.);
2
hendrik.domey@googlemail.com (H.D.); judith.fischer@chemie.uni-hamburg.de (J.F.)
Institute of Food Technology and Food Chemistry, Technische Universität Berlin, Gustav-Meyer-Allee 25,
2
13355 Berlin, Germany
*
Correspondence: rohn@tu-berlin.de; Tel.: +49-30-314-72583
Abstract: Sulfoquinovosyldiacylglycerol (SQDG) is a glycolipid ubiquitously found in photosynthet-
ically active organisms. It has attracted much attention in recent years due to its biological activities.
Similarly, the increasing demand for vegan and functional foods has led to a growing interest in
micronutrients such as sulfolipids and their physiological influence on human health. To study this
influence, reference materials are needed for developing new analytical methods and providing
enough material for model studies on the biological activity. However, the availability of these
materials is limited by the difficulty to isolate and purify sulfolipids from natural sources and the
unavailability of chemical standards on the market. Consequently, an alternative synthetic route for
the comprehensive preparation of sulfolipids was established. Here, the synthesis of a sulfolipid
with two identical saturated fatty acids is described exemplarily. The method opens possibilities for
the preparation of a diverse range of interesting derivatives with different saturated and unsaturated
fatty acids.
ꢀ
ꢁꢂꢀꢃꢄꢅꢆꢇ
ꢀ
ꢁꢂꢃꢄꢅꢆ
Citation: Sitz, T.; Domey, H.; Fischer,
J.; Rohn, S. An Alternative Approach
for the Synthesis of
Keywords: SQDG; sulfoquinovosyldiacylglycerol; sulfolipids; sulfur; total synthesis
Sulfoquinovosyldiacylglycerol.
Molecules 2021, 26, 4275. https://
doi.org/10.3390/molecules26144275
1. Introduction
The sulfolipid sulfoquinovosyldiacylglycerol (SQDG), first described in 1959 by Ben-
son et al., is a polar glycolipid characterized by a sulfonic acid head group, a 6-deoxy-6-
Academic Editor: David Barker
sulfo-glucose, referred to as sulfoquinovose [
tosyldiacylglycerols), it is one of the three non-phosphorous glycolipids that form the main
part of the structural lipids in the thylakoid membranes of photosynthetic organisms [ ]. In
1]. Besides galactolipids (mono- and digalac-
Received: 17 June 2021
Accepted: 13 July 2021
Published: 14 July 2021
2
addition to the anionic structures, SQDG derivatives (SQDGs) possess a high diversity of
the diacylglycerol backbone due to the variation in chain length, the degree of saturation,
and the fatty acid functionalization. A recent study reported up to two hundred tentatively
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
identified sulfolipids in cyanobacteria of the genus Arthrospira [
have attracted much attention in recent years because of their biological activities. Accord-
ingly, many studies on their possible pharmacological relevance have been conducted [ ].
3]. Furthermore, SQDGs
4–6
At the same time and due to the growing demand for vegan nutrition and functional food,
the interest in nutritional physiological questions regarding micronutrients like sulfolipids
is increasing. However, the meaning of sulfolipids for human nutrition is still controversial.
On the one hand, some health-promoting effects are attributed to them, e.g., they are
known to have antiviral properties, because of their amphiphilic nature [2]. On the other
hand, sulfur compounds could also have negative effects, as some microorganisms of the
lower gastrointestinal tract can produce hydrogen sulfide as a (toxic) metabolite during
biotransformation in the intestine [7–9]. Therefore, there should be the aim to improve
understanding of the effects of SQDGs on human health. Consequently, it is necessary to
develop new analytical methods and model systems for evaluating possible physiological
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4
.0/).
Molecules 2021, 26, 4275. https://doi.org/10.3390/molecules26144275
https://www.mdpi.com/journal/molecules

Molecules 2021, 26, 4275
2 of 11
effects. For such approaches, it is essential to obtain reference substances in comparatively
high quantities and of appropriate purity. The difficulty here is the availability, restricted
by the difficult isolation and purification of SQDGs from natural sources, and the almost
non-existent commercial availability. For this reason, synthetic preparation is a crucial
step. Based on this fact, it was decided to synthesize SQDGs in order to evaluate different
analysis methods in the further course of research. Several approaches have been reported
for the synthesis of SQDGs, but they are either quite time consuming, do not start with
the simple component D-glucose, or the protecting group strategy does not provide an
approach to the unsaturated lipoform. Moreover, often these synthetic strategies are not
scalable due to expensive catalysts [10–12]. Manzo et al. (2017) developed a chemical
synthesis that seemed to fulfill those criteria. However, the final deprotection of the acetyl
groups required careful tuning of the experimental conditions and led to a significant
decrease in yield, resulting from a partial deacylation of fatty acids by cleavage of the
ester bond [13,14]. For this reason, we aimed at developing an alternative approach. It
was hypothesized that a change in protecting groups after some intermediary steps of
the synthesis enables a more efficient synthesis route. Further, this switch might enable
preservation of the advantage of anchimeric assistance by acetate and allow an easier,
gentle, and selective deprotection of the final product.
2. Results and Discussion
Here, an alternative and versatile strategy for the synthesis of β-sulfoquinovosyl
diacylglycerol is described. The first step was to choose orthogonal protecting groups at the
sugar that would allow selective deprotection without affecting the diacylglycerol moiety
and the glycosidic linkage. Therefore, acetate groups were primarily chosen, which have
already been used in the synthesis of α- and β-SQDGs [13,14]. Unfortunately, the use of
the acetate groups in the presence of the ester linkage of glycerol to the acyl chains proved
to be unsuitable. Deprotection with hydrazine monohydrate under various experimental
conditions resulted in partial cleavage of the ester bond of the acyl chains at position
sn-2. This result was also confirmed by NMR spectra, which showed shielding of the
0
13
H-2 signals and loss of the C signal for carbonyl carbons of the carboxylic acid ester.
Consequently, acetate groups only as temporary protection for the hydroxy functions of
the sugar moiety were used. Further in the synthesis, they were replaced by a levulinyl
ester. On the one hand, acetate groups preserve the advantage of stereoselectivity in the
formation of the β-glycosidic bond by anchimeric assistance [15,16], but, on the other hand,
levulinic acid is more completely and selectively removable by hydrazine under mild
acetate-buffered conditions, which is pushed by the formation of 6-keto-3-methyl-1,4,5,6-
tetrahydro-pyridazine as a by-product [17]. As shown in Scheme 1, the synthesis begins
with the acetylation of D-glucose. The reaction with pyridine as a catalyst results in an
exclusive formation of the
α
-anomer of glucose pentaacetate [18
,19]. The present result
was unexpected, because a mixture of anomers, corresponding to the
α/β-mixture of the
anomers in the starting material, was assumed. However, the reaction conditions enable
an interpretation of the results. Glucose was first dissolved in pyridine, which could have
supported a base-catalyzed mutarotation to the
acetic anhydride and the reaction time of 20 h led to the formation of the thermodynamically
favored -anomer [21]. Additionally, it can be hypothesized that the recrystallization in
water/methanol supports the selectivity. This first step was followed by the selective
deacetylation of the anomeric hydroxyl group with ammonium acetate (compound ) and
conversion to the trichloroacetimidate . Subsequent coupling with 1,2-O-isopropylidene
glycerol under conditions according to Schmidt et al. [22] gave the -glycoside , as
diastereomeric products, determined by the neighboring group participation of the acetate
group (NMR signals of the anomeric protons for both diastereomers: 4.59, 4.60 (d,
α-anomer [20]. The subsequent addition of
α
2
3
β
4
δ
J = 8 Hz)). It was decided to carry out the synthesis with racemic glycerol, as the primary
aim was not to synthesize enantiomerically pure products, but to develop a synthesis using
simple chemicals. This allows a quick and easy building up of a stock of sulfolipids for

Molecules 2021, 26, 4275
3 of 11
general research. Removal of all acyl protecting groups of compound
conditions gave compound
the primary hydroxyl group, resulting in compound
anhydride in pyridine resulted in the fully protected product
of the tosyl group with thioacetate gave the thioacetylglucopyranoside
4
under ZEMPLEN
5
[
23]. This was treated with tosylchloride to selectively protect
. Subsequent treatment with levulinic
. Following the replacement
. The next step
6
7
8
was the removal of the isopropylidene protecting group. Treatment with 80% acetic acid in
aqueous solution provided the diol intermediate 9.
0
0
0
0
Scheme 1. Synthesis of 3-O-[(2 ,3 ,4 -tri-O-levulinyl-6 -thioacetyl)-β-D-glucosyl]-(R/S)-glycerol (9). A precursor for potential
SQDGs.
This intermediate represents the key precursor for subsequent syntheses, as the simple
workflow makes the process conceivable for subsequent up-scaling. This opens the possi-
bility of producing a wide range of SQDGs with mono-, mixed, or unsaturated fatty acids
at the glycerol moiety, starting from the precursor in only a few follow-up steps. In the case
presented here, a simple combination with two identical fatty acids to demonstrate the
feasibility of the system was carried out exemplarily. However, the preparation of mixed
fatty acids by the stepwise introduction of different acyl residues at C-1 and C-2 of glycerol
◦
under STEGLICH conditions at 0 C is also described in the literature [14,24].
As shown in Scheme 2, the diacylglycerol compound 10 was prepared by condensation
of compound 9 with two equivalents of stearic acid under STEGLICH conditions at room
temperature [25]. This was followed by the removal of the levulinyl protecting groups
with buffered hydrazine in acetic acid/pyridine solution at room temperature. The use
of the levulinyl protecting groups showed advantages compared to former studies. The
others used mainly benzyl ether or acetyl groups [10–14]. The removal of levulinyl groups
was complete after 30 min at room temperature, when treating an excess of hydrazine.
Compared to the use of acetyl groups, it was reported that the removal of these groups
was the most difficult step in the synthesis, as it required special tuning of experimental
conditions (temperature, time, equivalents) [13,14]. Moreover, difficulties in purification
and partial deacylation were reported [14]. In contrast, the byproduct of levunyl removal
can be easily separated, because of the water solubility of 4,5-dihydro-6-methyl-3(2H)
pyridazinone. Partial deacylation of the fatty acid was not observed. Another problem
besides the non-specific deacylation that has been reported, when using hydrazine, is the
partial hydrogenation of unsaturated fatty acids [8]. However, Cateni et al. (2008) stated
that treatment with buffered hydrazine is also applicable in the presence of unsaturated
fatty acids [26]. The final step was an oxidation with oxone, leading to the corresponding
sulfonic acid, the final SQDG (compound 12, 69%).

Molecules 2021, 26, 4275
4 of 11
Scheme 2. Synthesis of 1,2-distearoyl-3-O-[
form of 1,2-distearoyl-3-O-[β-D-sulfoquinovosyl]-(R/S)-glycerol with 10% overall yield.
β-D-sulfoquinovosyl]-(R/S)-glycerol (SQDG). Conversion of D
-glucose to the K+
A comparison of the main differences between the new synthesis route and the one
presented by Manzo et al. (2017) is shown in Scheme 3. The synthesis route of the present
study was shorter by two steps and involved a change in protecting groups in some
intermediate steps of the synthesis.
O
O
OH
O
O
C17H35
2 Steps
overall yield 44 %
O
C17H35
1
2 Steps
O
OH
OH
overall yield 8 %
O
O
O
S
O
O
S
K
O
A
B
O
O
O
O
O
HO
AcO
OAc
HO
OH
Deprotection:
Hydrazin (7.2 eq)
in Ethanol (85 %)
at 44 °C, 3 h
OH
OAc
C17H35
OH
C17H35
O
O
O
O
OH
O
O
C17H35
O
C17H35
1
0 Steps
2 Steps
overall yield 52 %
O
S
O
OH overall yield 18 %
O
O
O
O
K
O
S
O
O
O
HO
OH
LevO
OLev
HO
OH
Deprotection:
M Hydrazin buffered in
OH
OLev
C17H35
OH
C17H35
1
acetic acid/pyridine (2/3)
at RT, 0.5 h
Scheme 3. Comparison of the main differences between the synthesis route of (A) Manzo et al. (2017) [13] and (B) the new
route of the present work.
Both routes start with D-glucose and end with the same final product. The route
described by Manzo et al. requires a total of 14 steps. The route of this work requires only
1
2 steps. The shortened route is achieved by direct tosylation, resulting in an overall yield
of 10%. In comparison, Manzo et al. (2017) used a sequence of tritylation–acetylation–
detritylation–tosylation instead, which reduces the overall yield to 4%. However, the
real advantage of the alternative route is the change in protecting group. Manzo et al.
used acetyl protecting groups exclusively. This is a disadvantage, because the reaction
conditions for the final removal of the acetate protecting group lead to partial cleavage
of the fatty acids of the acyl glycerol. When using levulin groups, this problem was not
observed due to the milder reaction conditions, which furthermore allowed an easier and
faster deprotection.
3. Materials and Methods
All reagents were purchased from commercial suppliers (Sigma-Aldrich (Darmstadt,
Germany), Honeywell (Seelze, Germany), Acros (Schwerte, Germany) and used without
further purification. Solvents (DCM, DMF, pyridine, MeOH, toluene) were purchased
as anhydrous over molecular sieves from Acros Organics. Unless otherwise stated, all

Molecules 2021, 26, 4275
5 of 11
reactions were performed in dried glassware with magnetic stirring and under nitrogen
atmosphere. All reactions were monitored with thin-layer chromatography (TLC) using an
aluminum TLC plate (silica gel 60, F254, Merck KGaA, Darmstadt, Germany). Components
on TLC plates were visualized with cerium-based staining (4.5 g ammonium molybdate
tetrahydrate, 0.18 g anhydrous cerium sulfate, 2.5 mL sulfuric acid, and 90 mL H O) or
2
staining with copper (5 g anhydrous copper sulfate, 10 mL o-phosphoric acid 85%, and
9
0 mL H O) followed by heating. Purification of products was carried out with silica
2
gel 60 (particle size 0.040–0.063 mm, Merck KGaA, Darmstadt, Germany) and freshly
distilled solvents were used as eluents. Yields refer to chromatographically purified and
spectroscopically pure compounds. NMR spectra were recorded on Bruker instruments
(Fourier HD 300; Avance I 400 DRX 500, or Avance III 600 at room temperature. Chemical
shift is reported in ppm with the solvent resonance signal as the internal standard:
δ
1
13
1
13
chloroform-d1: 7.26 ( H NMR), 77.16 ( C NMR), methanol-d4: 3.31 ( H NMR), 49.00 ( C
NMR). Coupling constant J is given in Hertz (Hz). Multiplicities are classified as follows:
s = singlet, d = doublet, t = triplet, q = quartet, and combinations thereof; m = multiplet
or br = broad signal. Two-dimensional NMR experiments (COSY, HSQC, HMBC) were
used for the assignment of all NMR signals. The approximately diastereomeric ratio was
determined by taking H and C NMR data into account. High-resolution mass spectra
were recorded on an Agilent 6224 ESI-TOF coupled with an Agilent HPLC 1200 Series. The
spectra can be found in the supplementary materials.
1
13
General procedure for preparation of levulinic acid anhydride: A solution of dicy-
◦
clohexylcarbodiimide (0.5 equiv.) in dry dichloromethane (15 mL) was cooled to 0 C.
Levulinic acid (1 equiv.) dissolved in dry DCM (10 mL) was added dropwise. The reaction
mixture was stirred for 1 h with the formation of a colorless precipitate. The precipitate
was removed by filtration and the solvent evaporated in vacuo to result in a colorless syrup.
The resulting product was used without further purification.
1
,2,3,4,6-Penta-O-acetyl-D-glucopyranose (1): D-glucose (29.6 g, 0.164 mol) was mixed
with 200 mL of anhydrous pyridine. While stirring with a magnetic stirrer, acetic anhydride
240 mL, 2.54 mol) was slowly added. This mixture was kept at room temperature under
(
stirring for 20 h. When the reaction was complete, the solution was mixed with ice and
stirred until all ice melted, whereupon a colorless solid precipitated. The mixture was fil-
tered, and the filtered product was washed with ice-cold water to remove pyridine residues.
The filtered product was recrystallized in a solution of water/methanol (v/v = 50/50) and
1
gave compound
1
as a colorless solid (59.6 g, 92%). H NMR (600 MHz, CDCl ):
δ
6.33
3
(
5
2
1
6
d, J = 3.7 Hz, 1H, H-1
β
), 5.47 (dd, J = 9, J < 1.0 Hz, 1H, H-3), 5.14 (t, J = 9.8 Hz, 1H, H-4),
.10 (dd, J = 10.3, 3.7 Hz, 1H, H-2), 4.29–4.24 (m, 1H, H-6a), 4.18–4.05 (m, 2H, H-5, H-6b),
.18, 2.09, 2.04, 2.02, 2.01 (all s, 15H, 5 171.0,
COCH3). 13C NMR (150 MHz, CDCl3):
C=O), 89.2 (C-1 ), 69.98 (C-3), 69.97 (C-5) 69.3 (C-2) 68.05 (C-4),
×
δ
70.32, 170.28, 169.8, (4
×
α
1.6 (C-6), 21.0, 20.83, 20.80, 20.7, 20.6 (5 × C(O)CH ).
3
2,3,4,6-Tetra-O-acetyl-D-glucopyranose (2): Ammonium acetate (19.8 g, 0.257 mol)
was added to a solution of compound
100 mL). The solution was stirred at room temperature overnight (30 h). After completion
of the reaction (monitored by TLC), the solution was evaporated in vacuo. The residue was
purified by silica gel column chromatography (ethyl acetate) to give compound (43.3 g,
7% yield) as an amber-colored syrup. The product was present as an anomeric mixture in
1 (50.0 g, 0.128 mol) in dry N,N-dimethylformamide
(
2
9
1
a ratio of (
α
:
β
) 3:1. H NMR (500 MHz, CDCl ): main signals
α
-anomer:
), 5.07 (t, J = 9.7 Hz, 1H, H-4). 4.89 (dd, J = 10.2,
), 4.26 (td, J = 3.9, 2.0 Hz, 1H, H-5), 4.23—4.20
δ 5.52 (dd, J = 10.2,
3
9.4 Hz, 1H, H-3), 5.45 (d, J = 3.6 Hz, 1H, H-1
β
3
.6 Hz, 1H, H-2), 4.73 (d, J = 8.0 Hz, 1H, H-1
α
1
3
(
m, 1H, H-6a), 4.14–4.09 (m, 1H, H-6b), 2.08, 2.07, 2.02, 2.01 (all s, 12H, 4
×
COCH3).
C
NMR (125 MHz, CDCl3): 170.8, 170.4, 169.8, 169.5, 168.9 (5 C=O), 95.7 (C-1 β
δ
×
), 90,3
(
(
C-1
α
), 71.2 (C-2), 70.0 (C-3), 68.7 (C-4), 67.4 (C-5), 62,1 (C-6), 20.86, 20.82, 20.80, 20.73
+
4 × C(O)CH ) HRESIMS m/z: 371.096 [M + Na] (calculated for C H O Na, 371.095).
3
14 20 10
2
,3,4,6-Tetra-O-acetyl-D-glucopyranosyl trichloroacetimidate (3): To a solution of
compound (41.9 g, 0.12 mmol) and in dry dichloromethane (120 mL), trichloroacetonitrile
2

Molecules 2021, 26, 4275
6 of 11
◦
(
(
60 mL, 0.6 mol) was added at 0 C. Then, 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU)
1.8 mL, 12 mmol) was added dropwise into the solution and stirred for 1 h. After the
reaction was completed, the reaction mixture evaporated in vacuo. The residue was
purified by silica gel column chromatography (ethyl acetate/cyclohexane, v/v, 50/50)
1
to give compound
2
(48.8 g, 83% yield) as an amber-colored syrup. H NMR (400 MHz,
CDCl ): δ 8.69 (s, 1H, NH), 6.55 (d, J = 3.7 Hz, 1H, H-1β), 5.55 (t, J = 9.9 Hz, 1H, H-3), 5.17
3
(
t, J = 9.9 Hz, 1H, H-4), 5.12 (dd, J = 10.2, 3.7 Hz, 1H, H-2), 4.27 (dd, J = 12.3, 4.1 Hz, 1H,
H-6a), 4.20 (ddd, J = 10.3, 4.2, 2.1 Hz, 1H, H-5), 4.17–4.08 (m, 1H, H-6b), 2.07, 2.04, 2.02,
.01 (all s, 12H, 4 170.7, 170.1, 170.0, 169.6,
COCH3). 13C NMR (100 MHz, CDCl3):
2
×
δ
(
2
4 × C=O), 160.9 (HN=C), 93.0 (C-1), 70.1 (C-5), 70.0 (C-3), 69.8 (C-2), 67.9 (C-4), 61.5 (C-6),
+
0.80, 20.80, 20.7, 20.56 (4
×
C(O)CH ). HRESIMS m/z: 514.002 [M + Na] (calculated for
3
C H Cl NO Na, 514.005).
16
20
3
10
1,2-Isopropylidene-3-O-(β-D-2,3,4,6-tetra-O-acetyl-glucopyranosyl)-(R/S)-glycerol (4):
To a solution of compound
3
(56.3 g, 0.11 mol) in dry dichloromethane (60 mL), 1,2-O-
◦
isopropylidene glycerol (26.0 mL, 0.20 mol) was added and cooled to -10 C. Then, boron
trifluoride etherate (1.6 mL, 13 mmol) was added dropwise into the solution and stirred.
After 2 h, more boron trifluoride etherate (1.0 mL, 8.1 mmol) was added and slowly
warmed until reaching room temperature. After stirring overnight, the reaction mixture
was quenched with triethylamine (2 mL) and mixed with ice and stirred until all ice melted,
whereupon a beige-colored solid precipitated. The mixture was filtered, and the filtered
product was washed with ice-cold water. The filtered product was recrystallized in a
solution of water/methanol (v/v, 50/50) and gave compound
4
as a colorless solid (40.9 g,
1
80%). The product was present as a diastereomeric mixture in a ratio of 7:3. H NMR (600
MHz, CDCl3):
H-2), 4.59 (d, J = 8.0 Hz, 1H, H-1
δ
5.19 (tt, J = 9.5, 6.9 Hz, 1H, H-3), 5.09–5.03 (m, 1H, H-4), 5.01–4.95 (m, 1H,
0
α
), 4.27–4.22 (m, 1H, H-6a), 4.22–4.19 (m, 1H, H-2 ), 4.12
0
(
1
dd, J = 12.3, 2.4 Hz, 1H, H-6b), 4.02 (dd, J = 8.5, 6.4 Hz, 1H, H-3 a), 3.78 (dd, J = 10.3, 5.9 Hz,
H, H-1 a), 3.71 (dd, J = 8.4, 5.8 Hz, 1H, H-3 b), 3.68 (dq, J = 7.4, 2.5 Hz, 1H, H-5), 3.63 (dd, J
0
0
0
=
10.4, 5.7 Hz, 1H, H-1 b), 2.08, 2.04, 2.01, 1.99 (all s, 12H, 4
×
COCH ), 1.39 (s, 3H, CH ),
3
3
.33 (s, 3H, CH3). 1 C NMR (150 MHz, CDCl ):
3
δ
170.8, 170.4, 169.51, 169.47, (4
×
C=O),
1
1
3
0
0
09.7 (C(CH ) , 100.1 (C-1), 74.5 (C-2 ) 72.9 (C-3), 72.0 (C-5), 71.3 (C-2), 70.7 (C-1 ), 68.5
3
2
0
(
C-4), 66.9 (C-3 ), 62.0 (C-6), 26.9 (CH ), 25.5 (CH ), 20.9, 20.8, 20.73, 20.71 (4
×
C(O)CH3).
3
3
+
HRESIMS m/z: 485.159 [M + Na] (calculated for C H O Na, 485.163).
20
30 12
1,2-Isopropylidene-3-O-(β-D-glucopyranosyl)-(R/S)-glycerol (5): Sodium methanolate
(
3.46 g, 64.1 mmol) was added to a suspension of compound (5.00 g, 10.8 mmol) in dry
4
methanol (50 mL). The reaction mixture was stirred at room temperature. After 2 h, the
reaction was completed and the solution was homogeneous. The mixture was neutral-
®
ized with Amberlyst 15 (Merck KGaA), filtered, and evaporated in vacuo. The residue
was purified by silica gel column chromatography (ethyl acetate/methanol (v/v, 70/30)
to give compound
5
(2.95 g, 92% yield) as a colorless syrup. The product was present
1
as a diastereomeric mixture in a ratio of 7:3. H NMR (500 MHz, MeOD): 4.36–4.31 (m,
0
0
1
H, H-2 ), 4.29 (d, J = 7.7 Hz, 1H, H-1
α
), 4.08 (dd, J = 8.5, 6.5 Hz, 1H, H-3 a), 3.90 (dd,
0
J = 10.3, 5.3 Hz, 1H, H-1 a), 3.87 (dd, J = 11.9, 1.7 Hz, 1H, H-6a), 3.77 (dd, J = 8.5, 6.1 Hz,
0
0
1
H, H-3 b), 3.66 (dd, J = 11.9, 5.3 Hz, 1H, H-6b), 3.62 (dd, J = 10.2, 6.2 Hz, 1H, H-1 b),
.38–3.33 (m, 1H, H-3), 3.29–3.26 (m, 2H, overlapped H-4, H-5), 3.18 (dd, J = 9.1, 7.7 Hz, 1H,
3
13
H-2), 1.40 (s, 3H, CH ), 1.34 (s, 3H, CH ). C NMR (125 MHz, MeOD):
δ
110.6 (C(
) ,
CH3 2
3
3
0 0
04.5 (C-1), 78.0 overlapped (C-3, C-5), 76.1 (C-2 ), 75.1 (C-2), 71.59 (C-1 ), 71.57 (C-4), 67.7
1
(
0
C-3 ), 62.7 (C-6), 27.1 (CH ), 25.6 (CH ), HRESIMS m/z: 317.121 [M + Na] (calculated for
3 3
+
C H O Na, 317.121).
12
22
8
1,2-Isopropylidene-3-O-[(6-O-(4-tolylsulfonyl))-β-D-glucopyranosyl]-(R/S)-glycerol (6):
To a solution of compound
5
(900 mg, 3.06 mmol) in dry pyridine (10 mL), p-toluenesulfonyl
◦
chloride (TsCl, 654 mg, 3.43 mmol, 1.1 equiv.) was added at 0 C and stirred overnight
at room temperature. An additional amount of TsCl (100 mg, 0.52 mmol) was added.
After 2 h, the reaction was quenched with EtOH; solvents were evaporated in vacuo and
the residue was purified by flash column chromatography (ethyl acetate/methanol (v/v,

Molecules 2021, 26, 4275
7 of 11
1
00:0
→
90:10)) to give compound 6 (994 mg, 72% yield) as a colorless resin. The product
1
was present as a diastereomeric mixture in a ratio of 7:3. H NMR (300 MHz, CDCl ):
δ
3
7
.77 (d, J = 8.3 Hz, 2H, Ar-H), 7.31 (d, J = 8.1 Hz, 2H, Ar-H), 4.35–4.15 (m, 4H, overlapped
0
0
0
H-2 , H-1, H-6a,b), 4.01 (dd, J = 8.7, 6.6 Hz, 1H, H-3 a), 3.80–3.71 (m, 1H, H1 a), 3.65 (dd,
J = 8.5, 5.8 Hz, 1H, H-3 b), 3.56–3.49 (m, 2H, overlapped H-3, H-1 b), 3.45 3.45–3.37 (m, 2H,
overlapped H-4, H-5), 3.34 (t, J = 8.5 Hz, 1H, H-2), 2.42 (s, 3H, aromatic methyl), 1.39 (s,
0
0
13
3
H, CH ), 1.32 (s, 3H, CH ). C NMR (75 MHz, CDCl3): δ 145.1, Ar, (CCH ), 132.4 Ar,
3
3
3
(
(
(
CSO3), 130.0, 128.1 (4
×
CH, aromatic methynes), 109.9 (C(CH ) , 95.8 (C-1), 76.1 (C-3), 74.7
3 2
0
0
0
C-2 ), 73.6 (C-5), 73,3 (C-2), 71.3 (C-1 ), 69.7 (C-4), 69.2 (C-6), 66.6 (C-3 ), 27.1 (CH ), 25.6
3
+
CH ), 21.2 (Ar, CCH ), HRESIMS m/z: 471.131 [M + Na] (calculated for C H O SNa,
3
3
19 28 10
4
71.130).
0
0
0
0
1
,2-Isopropylidene-3-O-[(2 ,3 ,4 -tri-O-levulinyl-6 -O-(4-tolylsulfonyl))-β-D-glucosyl]-
R/S)-glycerol: (7): To a solution of compound (990 mg, 2.01 mmol) in dry pyridine
10 mL), levulinic anhydride (3.0 mL, 15 mmol) dissolved in dry pyridine (7 mL) was
(
(
6
added dropwise. The reaction was stirred overnight at room temperature. After the
reaction was complete, ice water (50 mL) was added. The mixture was extracted with
chloroform (3
lution of sodium bicarbonate (2
and concentrated in vacuo. The residue was purified by silica gel column chromatography
×
50 mL) and the combined organic layers were extracted with a 10% so-
×
50 mL) first and then with water, dried over Na SO ,
2
4
(
ethyl acetate/cyclohexane (v/v, 50/50
→
100/0)) to give 7 (1.42 g, 87%) as a colorless resin.
1
The product was present as a diastereomeric mixture in a ratio of 7:3. H NMR (400 MHz,
CDCl3):
δ
7.79 (d, J = 8.4 Hz, 2H, Ar-H), 7.34 (d, J = 8.2 Hz, 2H, Ar-H), 5.21 (t, J = 9.6 Hz,
H, H-3), 4.90 (m, 2H, overlapped H-2, H-4), 4.51 (d, J = 7.9 Hz, 1H, H-1 ), 4.24–4.18 (m,
H, H-2 ), 4.15 (dd, J = 11.6, 2.8 Hz, 1H, H-6a), 4.04 (dd, J = 11.6, 6.5 Hz, 1H, H-6b), 4.00 (d,
1
1
α
0
0
0
J = 6.5 Hz, 1H, H-3 a), 3.80–3.69 (m, 2H, overlapped H-5, H-1 a), 3.66 (dd, J = 8.5, 5.9 Hz,
0
0
1
(
H, H-3 b), 3.57 (dd, J = 10.5, 5.4 Hz, 1H, H-1 b), 2.82–2.66 (m, 6H, 3
×
CH OCO), 2.64–2.46
2
m, 6H, 3 CH COCH ), 2.44 (s, 3H, aromatic methyl), 2.15 (s, 3H), 2.15 (s, 3H), 2.13 (s,
×
2
3
13
3
H), (3
×
CH CO), 1.39 (s, 3H, CH ), 1.33 (s, 3H, CH ). C NMR (100 MHz, CDCl3):
δ
3
3
3
2
06.37, 206.34, 206.31 (3
×
CH CO), 172.1, 171.7, 171.3 (3
×
CH OCO), 145.2, (Ar, CCH ),
3
2
3
1
(
32.8 (Ar, CSO ), 130.0, 128.2 (4
C-2 ), 72.0 (overlapped C-3, C-5), 71.01 (C-2), 70.7 (C-1 ), 68.6 (C-4), 68.0 (C-6), 66.9 ( C-3 )
×
CH, aromatic protons), 109.7 (C(CH ) , 100.8 (C-1), 74.5
3
3 2
0
0
0
3
7.90, 37.84, 37.80 (3
×
CH COCH ), 29.86, 29.79, 29.77, (3
×
CH CO), 27.91, 27.88, 27.83
2
3
3
+
(
(
3 × CH OCO), 26.9 (CH ), 25,5 (CH ), 21.8 (Ar, CCH ), HRESIMS m/z: 765.239 [M + Na]
2
3
3
3
calculated for C H O SNa, 765.240).
34
46 16
0
0
0
0
1
,2-Isopropylidene-3-O-[(2 ,3 ,4 -tri-O-levulinyl-6 -thioacetyl)-β-D-glucosyl]-(R/S)-
glycerol: (8) Compound (1.40 g, 1.88 mmol) was dissolved in dry dimethylformamide
10 mL) and potassium thioacetate (646 mg, 5.66 mmol) was added. The reaction was
7
(
◦
stirred at 80 C. After 2 h, the reaction mixture was cooled until reaching room temperature
and further stirred overnight. Subsequently, the solvents were evaporated in vacuo and the
residue was purified by silica gel column chromatography (ethyl acetate) to give compound
8
(926 mg, 76% yield) as a colorless resin. The product was present as a diastereomeric
1
mixture in a ratio of 7:3. H NMR (400 MHz, CDCl3):
δ 5.20 (t, J = 9.7 Hz, 1H, H-3),
5
.00–4.88 (m, 2H, overlapped H-2, H-4), 4.52 (d, J = 8.0 Hz, 1H, H-1
α
), 4.23 (p, J = 5.9
0
0
0
Hz, 1H, H-2 ), 4.03 (dd, J = 8.4, 6.4 Hz, 1H, H-3 a), 3.85–3.68 (m, 2H, overlapped H-1 a,
0
0
H-3 b), 3.63 (dd, J = 10.4, 5.7 Hz, 1H, H-1 b), 3.60–3.53 (m, 1H, H-5), 3.28 (dd, J = 14.3,
.0 Hz, 1H, H-6a), 3.01–2.92 (m, 1H, H-6b), 2.81–2.68 (m, 6H, 3 CH OCO), 2.63–2.50
3
×
2
(
(
2
m, 6H, 3 × CH COCH ), 2.32 (s, 3H, CH C(O)S), 2.16 (s, 3H), 2.15 (s, 3H), 2.13 (s, 3H)
2
3
3
13
3 × CH CO), 1.39 (s, 3H, CH ), 1.33 (s, 3H, CH ). C NMR (100 MHz, CDCl3):
δ 206.6,
3
3
3
06.5, 206.4 (3
×
CH CO), 194.8 (CH C(O)S), 172.1, 171.8, 171.4 (3
×
CH OCO), 109.6
3
3
2
0
0
(
(
(
C(CH ) , 100.8 (C-1), 74.5 (C-2 ), 73.3 (C-5), 72.1 (C-3), 71.3 (C-4), 70.8 (C-2), 70.5 (C-1 ) 67.0
3
2
0
C-3 ), 37.93, 37.87, 37.84 (3 × CH COCH ), 30.5 (CH C(O)S), 30.2 (C-6), 29.9, 29.8, 29.79
2
3
3
3
×
CH CO), 28.02, 27.95, 27.93 (3
×
CH OCO), 26.9 (CH ), 25.5 (CH ). HRESIMS m/z:
42 14
3
2 3 3
+
669.219 [M + Na] (calculated for C H O SNa, 669.219).
2
9

Molecules 2021, 26, 4275
8 of 11
0
0
0
0
3
-O-[(2 ,3 ,4 -tri-O-levulinyl-6 -thioacetyl)-β-D-glucosyl]-(R/S)-glycerol (9): A solu-
◦
tion of compound
8
(876 mg, 1.35 mmol) in 80% aq acetic acid (10 mL) was stirred at 45 C
for 2 h. The mixture was evaporated in vacuo and co-evaporated with toluene three times.
The residue was purified by silica gel column chromatography (ethyl acetate/methanol
(
v/v, 100/0
→
70/30)) to give 9 (730 mg, 89%) as a colorless resin. The product was present
1
as a diastereomeric mixture in a ratio of 7:3. H NMR (300 MHz, CDCl ):
δ 5.22 (t, J = 9.7 Hz,
3
1
H, H-3), 5.01–4.89 (m, 2H, overlapped H-2, H-4), 4.48 (d, J = 8.0 Hz, 1H, H-1
α
), 3.96–3.80
0
0
0
0
0
(
m, 2H, overlapped H-2 , H-1 a), 3.72–3.50 (m, 4H, overlapped H-1 b, H-3 a, H-3 b, H-5),
3
3
2
.29 (dd, J = 14.3, 2.7 Hz, 1H, H-6a), 2.96 (dd, J = 14.3, 7.2 Hz, 1H, H-6b), 2.86–2.67 (m, 6H,
×
CH OCO), 2.64–2.47 (m, 6H, 3 CH COCH ), 2.33 (s, 3H, CH C(O)S), 2.18 (s, 3H),
×
13
2
2
3
3
.16 (s, 3H), 2.13 (s, 3H) (3
×
CH CO). C NMR (75 MHz, CDCl3): δ 208.1, 206.7, 206.5 (3
3
×
CH CO), 195.0 (CH C(O)S), 172.0, 171.8, 171.6 (3
2.2 (C-1 ), 72.0 (C-3), 71.3 (C-4), 70.7 (C-2), 70.6 (C-2 ), 63.4 (C-3 ), 38.0, 37.9, 37.8 (3
×
CH OCO), 101.4 (C-1), 73.2 (C-5),
3
3
2
0
0
0
7
×
CH COCH ), 30.6 (CH C(O)S), 30.1 (C-6), 29.9, 29.81, 29.80 (3
×
CH CO), 28.0, 27.9, 27.8 (3
2
3
3
3
+
×
CH OCO). HRESIMS m/z: 629.188 [M + Na] (calculated for C H O SNa, 629.188).
2 26 38 14
0
0
0
0
1
,2-Distearoyl-3-O-[(2 ,3 ,4 -tri-O-levulinyl-6 -thioacetyl)-β-D-glucosyl]-(R/S)-glycerol
10): To a solution of compound (700 mg, 1.15 mmol) in dry dichloromethane (15.0 mL),
stearic acid (854 mg, 3.00 mmol), dicyclohexylcarbodiimide (608 mg, 2.90 mol), and 4-
Dimethylamino)-pyridine (67 mg, 0.5 mmol) were successively added. The reaction
(
9
(
mixture was stirred overnight for 24 h at room temperature. The precipitate was removed
by filtration and the solvent evaporated in vacuo. The residue was purified by silica gel
column chromatography eluted with ethyl acetate/cyclohexane, v/v, 50/50 to give the
product 10 (1.05 g, 80%) as a colorless waxy solid. The product was present as a diastere-
1
omeric mixture in a ratio of 7:3. H NMR (400 MHz, CDCl ):
δ
5.23–5.13 (m, 2H, overlapped
), 4.28 (dd,
3
0
H-3, H-2 ), 4.98–4.91 (m, 2H, overlapped H-2, H-4), 4.45 (d, J = 8.0 Hz, 1H, H-1
J = 12.0, 3.7 Hz, 1H, H-3 a), 4.07 (dd, J = 12.0, 6.4 Hz, 1H, H-3 b), 3.89 (dd, J = 10.9, 5.3 Hz,
H, H-1 a), 3.65 (dd, J = 10.9, 5.4 Hz, 1H, H-1 b), 3.57 (ddd, J = 10.0, 7.2, 2.9 Hz, 1H, H-5),
α
0
0
0
0
1
3
3
6
.28 (dd, J = 14.3, 2.9 Hz, 1H, H-6a), 2.96 (dd, J = 14.3, 7.2 Hz, 1H, H-6b), 2.87–2.67 (m, 6H,
× CH OCO), 2.66–2.47 (m, 6H, 3
×
CH COCH ), 2.33 (s, 3H, CH C(O)S), 2.29 (dd, J = 9.0,
2 3 3
2
.3 Hz, 4H,
α
-methylene of stearoyl), 2.16 (s, 3H), 2.15 (s, 3H), 2.13 (s, 3H) (3 × CH CO),
3
1.63–1.54 (m, 4H, β-methylene of stearoyl), 1.18 (br s, 56H, aliphatic methylenes of stearoyl),
1
3
0
2
.81 (t, J = 7.2, 6.4 Hz, 6H, 2
×
terminal CH of stearoyl). C NMR (100 MHz, CDCl3): δ
3
06.7, 206.5, 206.4 (3
×
CH CO), 194.7 (CH C(O)S), 173.5, 173.2 (2
CH OCO), 100.7 (C-1), 73.3 (C-5), 72.0 (C-3), 71.1 (C-4), 70.6 (C-2),
×
C(O)O of stearoyl),
3
3
1
72.1, 171.8, 171.3 (3
×
2
0
0
0
69.9 (C-2 ), 67.6 (C-1 ), 62.4 (C-3 ), 37.94, 37.87, 37.84 (3
×
CH COCH ), 34.4, 34.2 (2 × α
C
2
3
-methylene), 30.6 (CH C(O)S), 30.6 (C-6), 30.9, 29.98, 29.94 (overlapped 3
×
CH CO), 32.1,
3
3
2
9.9–29.2, 22.8 (aliphatic methylenes, in part overlapped), 28.0, 27.9, 27.8 28.0, 27.9, 27.8
(
3
×
CH OCO), 25.0 (2 × βC-methylene of stearoyl), 14.3 (2
×
terminal CH of stearoyl).
2
3
−
−
−
HRESIMS m/z: 1183.757 [M + HCOO ] (calculated for C H108O18 , 1183.718).
63
0
1
,2-Distearoyl-3-O-[(6 -thiol)-β-D-glucosyl]-(R/S)-glycerol (11): To a solution of com-
pound 10 (500 mg, 0.44 mmol) in dry pyridine (5 mL), 1 M hydrazine monohydrate in
pyridine/glacial acetic acid (v/v, 3/2) (10 mL) was added. The reaction mixture was stirred
for 30 min at room temperature. After the reaction was completed, ice water (50 mL)
was added. The mixture was extracted with chloroform (3
organic layers were extracted with a 10% solution of sodium bicarbonate (2
and then with water, dried over Na SO , and concentrated in vacuo. The residue was
×
50 mL) and the combined
×
50 mL) first
2
4
purified by silica gel column chromatography (chloroform/methanol, v/v, 97/3
→
92/8)
to give compound 11 (270 mg, 76%) as a colorless solid. The product was present as a
1
diastereomeric mixture in a ratio of 7:3. H NMR (300 MHz, CDCl ):
δ
5.34–5.16 (m, 1H,
3
0
0
H-2 ), 4.42 (dd, J = 12.0, 3.9 Hz, 1H, H-3 a), 4.29 (d, J = 7.7 Hz, 1H, H-1
.2 Hz, 1H, H-3 b), 3.98 (dd, J = 11.0, 5.5 Hz, 1H, H-1 a), 3.70 (dd, J = 11.0, 5.9 Hz, 1H,
H-1 b), 3.58–3.45 (m, 2H, overlapped H-3, H-4), 3.41–3.34 (m, 2H, overlapped H-2, H-5),
α), 4.14 (dd, J = 12.0,
0
0
6
0
2
.97 (ddd, J = 14.1, 9.5, 2.7 Hz, 1H, H-6a), 2.74 (dt, J = 14.3, 7.4 Hz, 1H, H-6b), 2.40–2.23
(
m, 4H, -methylene of stearoyl), 1.66–1.52 (m, 4H, -methylene of stearoyl), 1.37–1.19
α
β

Molecules 2021, 26, 4275
9 of 11
(
m, 56H, aliphatic methylenes of stearoyl), 0.88 (t, J = 6.5 Hz, 6H, 2
×
terminal CH of
3
stearoyl). 13C NMR (75 MHz, CDCl3):
δ
173.9, 173.5 (2
×
C(O)O of stearoyl), 103.1 (C-1),
0
0
0
7
6.33 (C-3), 76.30 (C-5), 73.8 (C-2), 72.2 (C-4), 70.10 (C-2 ), 68.0 (C-1 ), 62.5 (C-3 ), 34.5, 34.3
× αC-methylene), 32.1, 29.9–29.2, 22.8 (aliphatic methylenes, overlapped), 26.4 (C-6),
5.1, 25.0 (2 × βC-methylene), 14.3 (2 terminal CH of stearoyl), HRESIMS m/z: 801.580
(2
2
[
×
3
-
−
9
M − H] (calculated for C H O S , 801.592).
45
85
1
,2-Distearoyl-3-O-[β-D-sulfoquinovosyl]-(R/S)-glycerol-potassium salt (12): To a
solution of compound 11 (170 mg, 0.211 mmol) in glacial acetic acid (5 mL), potassium
acetate (550 mg, 5.60 mmol) and oxone (2 KHSO , KHSO , K SO ) (560 mg, 1.82 mmol,
5
4
2
4
4
2
equiv. KHSO ) were added. The resultant mixture was stirred at room temperature for
4 h. After the reaction was complete, the mixture was evaporated in vacuo and the residue
5
purified by flash chromatography (chloroform/methanol/water, v/v/v, 92/8/0
→
65/25/4)
to give compound 12 (120 mg 69%), as a colorless solid. The product was present as a
1
diastereomeric mixture in a ratio of 7:3. H NMR (300 MHz, CDCl ):
δ 5.30–5.21 (m, 1H,
), 4.14 (dd, J = 12.1,
3
0
0
H-2 ), 4.43 (dd, J = 12.1, 3.1 Hz, 1H, H-3 a), 4.28 (d, J = 7.7 Hz, 1H, H-1
.8 Hz, 1H, H-3 b), 4.01 (dd, J = 11.0, 5.3 Hz, 1H, H-1 a), 3.77–3.66 (m, 2H, overlapped H-1 b,
α
0
0
0
6
H-5), 3.39–3.36 (m, 1H, H-3), 3.36–3.33 (m, 1H, H-6a), 3.26–3.21 (m, 1H, H-2), 3.20–3.16 (m,
H, H-4), 3.04 (dd, J = 14.4, 7.3 Hz, 1H, H-6b), 2.30 (td, J = 7.5, 5.0 Hz, 4H, -methylene of
stearoyl), 1.65–1.52 (m, 4H, -methylene of stearoyl), 1.24 (br s, 56H, aliphatic methylenes
of stearoyl), 0.86 (t, J = 7.2, 6.6 Hz, 6H, 2
1
α
β
1
3
×
terminal CH of stearoyl). C NMR (75 MHz,
3
CDCl3):
7
3
δ
174.5, 174.2 (2
×
C(O)O of stearoyl), 103.5 (C-1), 76.4 (C-3), 73.9 (C-2), 73.6 (C-4),
0
0
0
2.4 (C-5), 70.7 (C-2 ), 68.2 (C-1 ), 63.2 (C-3 ), 54.0 (C-6), 34.6, 34.4 (2 × αC-methylene),
2.2, 30.0–29.4, 22.8 (aliphatic methylenes, in part overlapped), 25.2 (2 × βC-methylene of
−
stearoyl), 14.3 (2
×
terminal CH of stearoyl). HRESIMS m/z: 849.562 [M
−
H] (calculated
3
−
85 12
for C H O S , 849.577).
45
4. Conclusions
The pharmacological and physiological activity of micronutrients such as SQDGs is
of increasing interest. Therefore, new applications are needed for analyzing these minor
components. However, there are challenges in isolating the individual products and ob-
taining reference substances of sufficient purity to evaluate bioactivity. SQDGs can only be
extracted from natural sources as a mixture of lipoformes and, therefore, require methods
for synthesis. Consequently, an alternative approach was proposed, inspired by previous
studies, but using a new protecting group strategy that allows simple and selective depro-
tection. The proposed synthesis route was primarily developed for preparing different
SQDGs as reference compounds. This synthesis did not aim at enantiomerically pure
components to keep it as simple as possible. However, when applying these compounds
as reference substances in food analysis, determination of single diastereomers might only
play a minor role. Nonetheless, further experiments could be used to adapt synthesis
for enantiomerically pure products, e.g., for research questions or pharmacological ap-
plications. The synthesis presented herein achieved an overall yield of 10% and opens
up possibilities for a wide range of SQDGs, containing mono-, mixed, or unsaturated
fatty acids.
Supplementary Materials: The original H and 13C NMR spectra are available in the supplementary
1
material.
Author Contributions: Conceptualization, T.S. and S.R.; Funding acquisition, S.R.; Investigation, T.S.,
H.D. and J.F.; Methodology, T.S. and H.D.; Project administration, S.R.; Resources, S.R.; Supervision,
S.R.; Visualization, T.S.; Writing—original draft, T.S.; Writing—review and editing, T.S., H.D., J.F. and
S.R. All authors have read and agreed to the published version of the manuscript.
Funding: This research was funded by the German Federal Ministry of Food and Agriculture (BMEL)
and the Federal Office for Agriculture and Food (BLE), grant number FKZ 847 596.
Institutional Review Board Statement: Not Applicable.

Molecules 2021, 26, 4275
10 of 11
Informed Consent Statement: Not Applicable.
Data Availability Statement: The data sets presented in this study are available on request from the
corresponding author.
Acknowledgments: We acknowledge support by the Open Access Publication Fund of the TU Berlin.
Conflicts of Interest: The authors declare no conflict of interest.
References
1
2
.
.
Benson, A.A.; Daniel, H.; Wiser, R. A sulfolipid in plants. Proc. Natl. Acad. Sci. USA 1959, 45, 1582–1587. [CrossRef]
Benning, C. Biosynthesis and function of the sulfolipid sulfoquinovosyl diacylglycerol. Annu. Rev. Plant Biol. 1998, 49, 53–75.
[CrossRef] [PubMed]
3.
4.
5.
6.
7.
8.
9.
Antonelli, M.; Benedetti, B.; Cavaliere, C.; Cerrato, A.; La Barbera, G.; Montone, C.M.; Piovesana, S.; Laganà, A. Enrichment
procedure based on graphitized carbon black and liquid chromatography-high resolution mass spectrometry for elucidating
sulfolipids composition of microalgae. Talanta 2019, 205, 120162. [CrossRef]
Sahara, H.; Hanashima, S.; Yamazaki, T.; Takahashi, S.; Sugawara, F.; Ohtani, S.; Ishikawa, M.; Mizushina, Y.; Ohta, K.;
Shimozawa, K.; et al. Anti-tumor Effect of Chemically Synthesized Sulfolipids Based on Sea Urchin’s Natural Sulfonoquinovosyl-
monoacylglycerols. Jpn. J. Cancer Res. 2002, 93, 85–92. [CrossRef]
Matsumoto, Y.; Sahara, H.; Fujita, T.; Shimozawa, K.; Takenouchi, M.; Torigoe, T.; Hanashima, S.; Yamazaki, T.; Takahashi, S.;
Sugawara, F.; et al. An Immunosuppressive Effect by Synthetic Sulfonolipids deduced from Sulfonoquinovosyl Diacylglycerols
of Sea Urchin. Transplantation 2002, 74, 261–267. [CrossRef] [PubMed]
Loya, S.; Reshef, V.; Mizrachi, E.; Silberstein, C.; Rachamim, Y.; Carmeli, S.; Hizi, A. The Inhibition of the Reverse Transcriptase of
HIV-1 by the Natural Sulfoglycolipids from Cyanobacteria: Contribution of Different Moieties to Their High Potency. J. Nat. Prod.
1
998, 61, 891–895. [CrossRef] [PubMed]
Burrichter, A.; Denger, K.; Franchini, P.; Huhn, T.; Müller, N.; Spiteller, D.; Schleheck, D. Anaerobic Degradation of the Plant
Sugar Sulfoquinovose Concomitant With H2S Production: Escherichia coli K-12 and Desulfovibrio sp. Strain DF1 as Co-culture
Model. Front. Microbiol. 2018, 9, 2792. [CrossRef]
Haange, S.-B.; Groeger, N.; Froment, J.; Rausch, T.; Burkhardt, W.; Gonnermann, S.; Braune, A.; Blaut, M.; Von Bergen, M.;
Rolle-Kampczyk, U. Multiplexed Quantitative Assessment of the Fate of Taurine and Sulfoquinovose in the Intestinal Microbiome.
Metabolites 2020, 10, 430. [CrossRef]
Burkhardt, W.; Rausch, T.; Klopfleisch, R.; Blaut, M.; Braune, A. Impact of dietary sulfolipid-derived sulfoquinovose on gut
microbiota composition and inflammatory status of colitis-prone interleukin-10-deficient mice. Int. J. Med Microbiol. 2021, 311,
1
51494. [CrossRef]
1
1
0. Gordon, D.M.; Danishefsky, S.J. Synthesis of a cyanobacterial sulfolipid: Confirmation of its structure, stereochemistry and
anti-HIV-1 activity. J. Am. Chem. Soc. 1992, 114, 659–663. [CrossRef]
1. Hanashima, S.; Mizushina, Y.; Yamazaki, T.; Ohta, K.; Takahashi, S.; Sahara, H.; Sakaguchi, K.; Sugawara, F. Synthesis of
Sulfoquinovosylacylglycerols, Inhibitors of Eukaryotic DNA Polymerase
CrossRef]
2. Gigg, R.; Penglis, A.; Conant, R. Synthesis of 3-O-(6-Deoxy-6-sulpho-
Sulphoquinovosyl Diglyceride. J. Chem. Soc. Perkin Trans. 1980, 2490–2493. [CrossRef]
3. Manzo, E.; Fioretto, L.; Pagano, D.; Nuzzo, G.; Gallo, C.; De Palma, R.; Fontana, A. Chemical Synthesis of Marine-Derived
Sulfoglycolipids, a New Class of Molecular Adjuvants. Mar. Drugs 2017, 15, 288. [CrossRef]
α
and
β. Bioorganic. Med. Chem. 2001, 9, 367–376.
[
1
1
1
1
1
α-D-glucopyranosyl)-l,2-di-O-hexadecanoyl-L-glycerol,
4. Ziaco, M.; Fioretto, L.; Nuzzo, G.; Fontana, A.; Manzo, E. Short Gram-Scale Synthesis of Sulfavant A. Org. Process. Res. Dev. 2020
4, 2728–2733. [CrossRef]
,
2
5. Manzo, E.; Ciavatta, M.L.; Pagano, D.; Fontana, A. An efficient and versatile chemical synthesis of bioactive glyco-glycerolipids.
Tetrahedron Lett. 2012, 53, 879–881. [CrossRef]
6. Pagano, D.; Cutignano, A.; Manzo, E.; Tinto, F.; Fontana, A. Glycolipids synthesis: Improved hydrazinolysis conditions for
preparation of 1,2-polyunsaturated fatty acyl-β-monogalactosyl-glycerols. Carbohydr. Res. 2016, 424, 21–23. [CrossRef]
7. Ho, T.-L.; Wong, C.M. Hydroxyl Protection by Levulinylation. Synth. Commun. 1975, 5, 91–93. [CrossRef]
1
1
8. Huang, G.L.; Gao, H.; Yi, C.; Huang, D.; Han, J. Study on the synthesis of 2,3,4,6-O-tetraacetyl-α-D-glucopyranosyl bromide. Bulg.
Chem. Commun. 2017, 49, 17–19.
1
2
2
9. Behrend, R.; Roth, P. Ueber die Birotation der Glucose. Eur. J. Org. Chem. 1904, 331, 359–382. [CrossRef]
0. Hill, A.; Shallenberger, R. Autocatalytic mutarotation of D-glucose in pyridine. Carbohydr. Res. 1969, 11, 541–545. [CrossRef]
1. Pearson, W.A.; Spessard, G.O.
975, 52, 814–815. [CrossRef]
2. Schmidt, R.; Michel, J. Facile Synthesis of
Chem. Int. Ed. 1980, 19, 731–732. [CrossRef]
3. Wang, Z. Comprehensive Organic Name Reactions and Reagents; Wiley: Hoboken, NJ, USA, 2010; pp. 3123–3125.
α- and β-D-Glucose Pentaacetate An experiment in structure assignment using nmr. J. Chem. Educ.
1
2
2
α- and β-O-Glycosyl Imidates; Preparation of Glycosides and Disaccharides. Angew.

Molecules 2021, 26, 4275
11 of 11
2
4. Chen, J.; Profit, A.A.; Prestwich, G.D. Synthesis of Photoactivatable 1,2-O-Diacyl-sn-glycerol Derivatives of 1-l-Phosphatidyl-
d-myo-inositol 4,5-Bisphosphate (PtdInsP2) and 3,4,5-Trisphosphate (PtdInsP3). J. Org. Chem. 1996, 61, 6305–6312. [CrossRef]
PubMed]
5. Neises, B.; Steglich, W. Simple Method for the Esterification of Carboxylic Acids. Angew. Chem. Int. Ed. 1978, 17, 522–524.
CrossRef]
[
2
2
[
6. Cateni, F.; Bonivento, P.; Procida, G.; Zacchigna, M.; Favretto, L.G.; Scialino, G.; Banfi, E. Chemoenzymatic synthesis and
antimicrobial activity evaluation of monogalactosyl diglycerides. Eur. J. Med. Chem. 2008, 43, 210–221. [CrossRef] [PubMed]