Chemical glucosylation of pyridoxine

Article abstract of DOI:10.1016/j.carres.2020.107929

The chemical synthesis of pyridoxine-5′-β-D-glucoside (5′-β-PNG) was investigated using various glucoside donors and promoters. Hereby, the combination of α4,3-O-isopropylidene pyridoxine, glucose vested with different leaving and protecting groups and the application of stoichiometric amounts of different promoters was examined with regards to the preparation of the twofold protected PNG. Best results were obtained with 2,3,4,6-tetra-O-acetyl-D-glucopyranosyl fluoride and boron trifluoride etherate (2.0 eq.) as promoter at 0 °C (59%). The deprotection was accomplished stepwise with potassium/sodium hydroxide in acetonitrile/water followed by acid hydrolysis with formic acid resulting in the chemical synthesis of 5′-β-PNG.

Full text of DOI:10.1016/j.carres.2020.107929

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Chemical glucosylation of pyridoxine
Thomas Bachmann, Michael Rychlik
PII:
S0008-6215(19)30674-3
DOI:
https://doi.org/10.1016/j.carres.2020.107929
CAR 107929
Reference:
To appear in: Carbohydrate Research
Received Date: 16 November 2019
Revised Date: 27 January 2020
Accepted Date: 27 January 2020
Please cite this article as: T. Bachmann, M. Rychlik, Chemical glucosylation of pyridoxine, Carbohydrate
Research (2020), doi: https://doi.org/10.1016/j.carres.2020.107929.
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Chemical glucosylation of pyridoxine
Thomas Bachmann* and Michael Rychlik
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Chair
of
Analytical
Food
Chemistry,
Technical
University
Munich,
Maximus-von-Imhof-Forum 2, 85354 Freising, Germany; thomas.bachmann@tum.de
* Correspondence: thomas.bachmann@tum.de; Tel.: +49-8161-71-6395
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Abstract: The chemical synthesis of pyridoxine-5'-β-D-glucoside (5'-β-PNG) was
investigated using various glucoside donors and promoters. Hereby, the combination of
α4,3-O-isopropylidene pyridoxine, glucose vested with different leaving and protecting
groups and the application of stoichiometric amounts of different promoters was examined
with regards to the preparation of the twofold protected PNG. Best results were obtained with
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2,3,4,6-tetra-O-acetyl-D-glucopyranosyl fluoride and boron trifluoride etherate (2.0 eq.) as
promoter at 0 °C (59 %). The deprotection was accomplished stepwise with
potassium/sodium hydroxide in acetonitrile/water followed by acid hydrolysis with formic
acid resulting in the chemical synthesis of 5'-β-PNG.
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Keywords: Pyridoxine; Vitamin B6; Chemical Glycosylation; Chemical Synthesis
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1. Introduction
The group of vitamin B6 consists of the three vitamers pyridoxine (PN), pyridoxal (PL),
pyridoxamine (PM) and their respective phosphorylated compounds pyridoxine 5'-phosphate
(PNP), pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP) (Figure 1).[1]
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Figure 1. The group of vitamin B6 unites six substrates sharing a 2-methyl 3-hydroxypyridine
structure.

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Furthermore, a glucosylated derivative, pyridoxine-5'-β-D-glucoside (5'-β-PNG, 1), can be
found in plants as a major fraction of the total vitamin B6 content (Figure 1).[2-4] The
substance was first identified in 1968 during investigations regarding the metabolism of
pyridoxine in microorganisms.[5] In this study, the transglucosylation of glycosyl-moieties -
sucrose was found to be the most efficient as carbon-donor amongst other tested saccharides
- to pyridoxine using intact cells of Sarcina lutea and the isolated enzyme of Micrococcus
resulted in mainly 5'-α-PNG and small amounts of 4'-α-PNG. The molecules were verified
via enzymatic hydrolysis and comparison to a chemically synthesized sample.[6-10] The
latter was prepared and isolated as a hexaacetate derivative according to KOENIGS-KNORR
reaction
using
α4,3-O-isopropylidene
pyridoxine,
2,3,4,6-tetra-O-benzyl-α-
D-glucopyranosyl chloride and silver carbonate followed by
subsequent acetylation.[9] The application of purified α-glucosidase from Mucor javanicus
with dextrin has been reported in 1996 to result in the formation of 4'- and 5'-α-PNG in an
equimolar ratio with 14 % yield.[11] Also, a marine exo-α-glucosidase from the anaspidean
mollusc Aplysia fasciata was tested regarding transglucosylation properties towards
pyridoxine and showed high selectivity towards the 5’ position for both mono- (α-D-glucose)
and disaccharide (α-isomaltose) formation resulting in specifically the α-glycoside.[12]
Next to these microorganisms and isolated enzymes, also fungi of the genus Verticillium
dahliae were found to catalyze a highly selective (99 %) transglucosylation towards
5'-α-PNG with moderate yield (34 %) from maltodextrin using borate as complexing
agent.[13]
Although the α-epimer of 5'-PNG also exhibits nutritional value, the main fraction (5 - 70 %)
of the total vitamin B6 content in plant-derived foods consists of the β-epimer.[14, 15] After
their first identification in 1977 through isolation from rice bran, Yasumoto et al. also
pioneered in the chemical synthesis of 5'-β-PNG preparing the molecule via
KOENIGS-KNORR synthesis with a yield of 3 % using α4,3-O-isopropylidene pyridoxine,
2,3,4,6-tetra-O-acetyl-α- -glucopyranosyl bromide and silver carbonate.[16] Additionally,
D
pyridoxine glycosides were prepared from various glycosyl donors (e.g.
p-nitrophenyl-β-glucoside) utilizing a β-glucosidase, which has been isolated and purified
from rice bran[17] or sweet almond[18] beforehand. With the latter, a mixture of
4’-α/5’-α/5’-β-PNG (20/39/41) was obtained in 36 % (± 10 %) yield.[18] Transglycosylating
properties towards 4'- and 5'-β-PNG were also detected incubating cellobiose and pyridoxine
with β-glucosidase (cellobiase) from wheat bran and using an isolated glucosyltransferase
from popped pea (Pisum sativum) along with UDP-Glucose and PN.[4, 19] In this regard a

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variety of glycosidases were tested in glycosylation reactions using pyridoxine as
substrate.[20]
Various plant seeds, i.e. soybean, cow pea, jack bean, japanese radish, chinese cabbage,
spinach, rice, corn, wheat, trefoil and alfalfa produce PNG during germination.[19, 21-25]
While investigating the formation of β-PNGs in germinating seeds of wheat, barley and rice,
the regioselective preference regarding the 4' and 5'-position of pyridoxine in certain seeds
was noticed. Seeds of wheat and barley produced both the 4' and 5'-β-PNG in the same molar
ratio during the germination. In contrast, rice seeds mainly contained the 5’-glucoside, while
the 4’-glucoside was formed only in small amounts at later stages of germination.[11]
Soybean seeds formed only 5'-β-PNG.[24] Furthermore, alfalfa seeds were reported to create
unlabeled PNG - the yields ranged from 35-60 % -, [2H]- and [3H]-β-PNG.[25-29]
Although there exists a manifold of different methods with regard to the biotechnological
preparation of pyridoxine glycosides, the chemical pathway towards this substrate is not
explored well to this day. Hereby, main approaches rely on the preparation via
KOENIGS-KNORR reaction conditions, but result in rather unsatisfying yields. The aim of this
study was to establish a fundament comprising of various methods regarding the chemical
preparation of β-PNG in order to suggest opportunities in the field of the chemical synthesis
of this molecule as an alternative to the commonly utilized preparation via biotechnological
pathways. To achieve this objective, a strategy was required that would not only compete in
the yield and selectivity of the reaction towards the desired molecule, but also in the
simplicity of the preparation steps and time needed therefor.
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2. Results & Discussion
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2.1. Synthesis of the glucosyl donors and protection of PN
In order to establish this methodology, this study focused on investigations regarding the
chemical glucosylation of pyridoxine. Therefore, the starting materials for the glucosylation
reaction, namely the glucosyl donors (3-18) and acceptor (20), were prepared starting from
glucose (2) and pyridoxine hydrochloride (19) and subsequently implemented in a
glucosylation reaction (Scheme 1).

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Scheme 1. General depiction outlining the strategy for the chemical glucosylation of pyridoxine. P =
protecting group (Ac, Bz, Bn, Piv), LG = leaving group (F, Cl, Br, SEt, SPh, SBox, Imidate).
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The hydrophilicity of pyridoxine (PN) shackles the vitamin to its solubility in water - and
somewhat ethanol -, a solvent not favorable for glycosylation reactions. In order to enhance
its solubility in organic solvents and to improve the selectivity towards 5'-position, the
hydroxyl-groups in 3'- and 4'-position were protected using p-toluenesulfonic acid (pTSA)
and 2,2-dimethoxypropane resulting in the protected pyridoxine (20, 96 %, Scheme 2).[30]
The introduction of the acetonide group in the right position was verified by 2D-NMR
measurements.
OH
O
O
O
HO
O
OH
OH
pTSA, acetone
N
H
N
Cl
19
20
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Scheme 2. The protection of PN proceeded selectively with pTSA and 2,2-dimethoxypropane.
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The synthesis of the glucosyl donors started with the peracetylation of glucose (2, 3;
Scheme 3).[31] Implementation of bromine (4) and chlorine (5) leaving groups was
accomplished with hydrogen bromide (HBr) or thionyl chloride and tin tetrachloride
(SOCl2/SnCl4).[32-34] Deprotection of the anomeric acetate group was achieved with
ethylene diamine and acetic acid.[35] The utilization of benzyl amine as selective
anomeric-deprotection reagent[36] required a longer reaction time and higher effort with
regards to the purification of the product. Continuing from the free hydroxyl functionality (7)
either trichloroacetimidate-glucose (8) could be obtained using trichloroacetonitrile and
DBU or a fluorine leaving group (9) could have been installed using diethylaminosulfur
trifluoride (DAST).[35, 37]
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Scheme 3. Preparation of the glucosyl donors. a) Ac2O, pyridine; b) HBr; c) SOCl2, SnCl4;
d) 2-Mercaptobenzoxazole, K2CO3; e) Ethylene diamine, HOAc; f) DBU, NCCl3; g) DAST; h)
EtSH/EtPh, BF3·OEt2; i) NaOMe, MeOH; j) BnBr, NaH; k) BzCl, pyridine; l) PivCl, pyridine; m)
NBS; n) C2O2Br2; o) DAST.
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Thioglycosylation (10, 11) of a peracetylated saccharide can be accomplished with a variety
of Lewis acids e.g. SnCl4, trimethylsilyl trifluoromethanesulfonate (TMSOTf) or boron
trifluoride etherate (BF3·OEt2).[38-40] Furthermore, a SBox-leaving group (6) was furnished
using 2-mercapto-benzoxazole and potassium carbonate.[41] In order to investigate the
influence of other protecting groups on the glucosylation of PN, the remaining acetate groups
had to be cleaved while leaving the thiol-group intact. Deacetylation (12) was undertaken
according to ZEMPLÉN using sodium methoxide in methanol followed by application of
cation exchange resin (Dowex, H+-form) during workup.[42] Next, the molecule could be
modified with benzyl-protecting groups (15) using benzyl bromide (BnBr) and sodium
hydride (NaH) or benzoyl-groups (13) and pivaloyl-groups (14) using the respective
chlorides (BzCl/PivCl) as starting material with pyridine. After hydrolysis (16) of the thiol
group with N-bromosuccinimide (NBS), a bromine leaving group could be introduced with
oxalyl bromide resulting in the 2,3,4,6-tetra-O-benzyl-α-D-glucopyranoside bromide (18).
DAST aided in the synthesis of the fluorinated benzyl glucoside 17.
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2.2. Glucosylation reactions
As part of a first approach, a promoting system consisting of the combination of
N-iodosuccinimide (NIS) and different acidic/Lewis-acidic reagents, namely TMSOTf,
triflic acid (TfOH), BF3·OEt2, or various silver or rather copper salts, in particular silver
triflate (AgOTf), silver carbonate (Ag2CO3), silver oxide (Ag2O) and copper triflate
(Cu(OTf)2), was examined (Scheme 4). As for the glucosyl donors, thio, imidate and

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bromoglucosides were chosen because of their versatile scope of application, good stability
and simple preparation (Scheme 3).[40, 43-45] In order to enhance the selectivity towards the
β-product, acetate protecting groups represented the first choice due to their neighbouring
group participation.[46-48]
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Scheme 4. General reaction scheme for the first glucosylation-approaches involving
OENIGS-KNORR- and SCHMIDT-conditions as well as glucosylations with thioglucosides and
K
depiction of the expected product (21).
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Variations regarding the reaction conditions focused not only on switching the leaving
groups and promoter systems, i.e. different amounts (0.1 - 0.3 eq.) of promoter with or
without the addition of NIS, but - as further dimensions of variation - additionally on
temperature (− 78, − 30, 0 °C or rt) and time. Unfortunately, this set of experiments ended
exclusively in the formation of the orthoester-structure 22 when NIS was added regardless of
the chosen glucosylation method and reaction conditions (Figure 2, Scheme 5).
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Figure 2. First reaction approaches ended exclusively in the formation of the orthoester 22.
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On the other hand, no conversion of the starting material took place using a promoter-system
without NIS. This was especially salient in the case of KOENIGS-KNORR conditions, where
the acetylated glycopyranosyl bromide 4 was reacted under the addition of silver triflate (0.3
eq.) at 0 °C. Hereby, the orthoester was isolated with a yield of 48 % while adding NIS (3.0
eq.). On the other hand, no conversion occurred without NIS, suggesting a NIS-mediated
formation of the orthoester. The structural discrepancy was verified via the number of
13
carbon-signals related to the acetate-groups in the C-NMR spectra - three in case of the

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orthoester versus four in the desired product - and an erroneous m/z (= 414 vs. the
sought-after 371) after the following basic deprotection of the acetate groups.
The study of orthoesters is profoundly entrenched in the chemistry of glycosylation
reactions, especially in the preparation of 1,2-trans-glycosides where the anchimeric
assistance is utilized in the enhancement of β-selectivity. Furthermore, orthoesters
themselves were already pictured as either intermediates on the way to a desired glycoside or
used as starting materials directly.[49-52] Contrarily, their formation was connected to an
undesired reaction outcome, too.[53, 54] Their origination can be traced to the
activator-assisted heterolytic fission of the C-LG bond with formation of an oxonium ion
leading to the generation of a more stable acyloxonium ion through neighbouring group
participation of the C-2 acyl group and the subsequent attack of the glycosyl acceptor
towards this new electrophilic center (Path A, Scheme 5).[55-57]
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Scheme 5. The formation of orthoesters occurs through neighbouring group participation.
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In this regard, the originally planned utilization of the neighbouring group effect to enhance
the selectivity towards the β-product resulted in an undesired reaction outcome bearing only
the orthoester structure, despite the variation of the reaction conditions and use of Lewis
acids as promoters. In order to circumvent this problem, either the impact of the
neighbouring group effect had to be diminished or a potential transformation of the
orthoester into the desired glucosidic structure evaluated. Regarding the latter, especially
Lewis-acidic reagents such as TMSOTf are commonly applied as aid in the rearrangement
towards the desired product.[49, 50, 58-61] Unfortunately, no procedures helped in our case
resulting either in no conversion of PNG while applying mild conditions (0 °C - rt, 0.1 - 1 eq.
of acidic catalyst) or cleavage of the glucosidic bond in the case of harsh conditions (> rt, > 1
eq. of acidic catalyst, multiple days).

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In order to bypass the neighbouring group effect, a further option that was explored involved
the utilization of the nitrilium effect of acetonitrile (ACN). Through selective coordination
towards the α-face according to the solvent coordination hypothesis, the nucleophilic attack
of the acetate groups can be obviated (Path B, Scheme 5).[62-64] Although this strategy
being useful with regards to the selectivity of the reaction towards the β-product, the
complete substitution of dichloromethane as the reaction solvent was not possible due to
reduction in solubility of the starting materials, making the addition of ACN in stoichiometric
amounts inevitable. Nevertheless, no orthoester formation was observed with this procedure
(AgOTf 0.3 eq./NIS 3.0 eq., − 78 °C) and the desired product could be isolated, even though
in low yields (20 %).
Glycosylation reactions involving pyridine based derivatives show either a scarce
appearance in the literature[65-67] or are mostly studied in conjunction with nucleotide
synthesis.[68-73] Their utilization as part of a protection strategy was also an aspect of
research.[74-76] Optimally, application of low amounts of promoter (0.1 – 0.3 eq.) suffices
with regards to glycosylation reactions, but since the activation is mostly performed in an
acid driven approach, the basicity of pyridine derivatives could exhibit a competing effect
under such conditions.[77, 78] In order to explore this hypothesis, the introductory
experiments leading to the orthoester were revised with a stoichiometric amount of promoter
added to the reaction (Scheme 6).
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Scheme 6. The initial experiments were repeated with an increased amount of promoter.
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Interestingly, this shifted the reaction outcome not only completely from the formation of the
orthoester (22) to the desired PNG (21), but also resulted in a high β-selectivity of the
reaction. Since the mechanism proposedly proceeds via the departure of the leaving group
and the stabilization of the resulting oxonium ion through formation of an acyloxonium ion, a
higher amount of promoter - hereby especially triflate substrates - could have an impact not
only with regards to countering the basicity of PN, but also providing a shielding effect of the
acyloxonium ion, allowing a selective attack of PN on the anomeric position from the
β-side.[46, 79-83] A similar outcome, where an increase (0.1 to 0.25 eq.) of promoter helped
with the conversion of the starting material - although with non-pyridine moieties -, was

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observed with TMSOTf and AgOTf.[58, 84] Furthermore, a dependence of the orthoester
formation on the temperature was described while preparing DON-glycosides under
S
CHMIDT conditions.[85] It additionally has to be noted, that acetonide protecting groups are
unstable against Brønsted acids. Due to the Lewis-acidic properties of the promoters used in
this study, an increase of promoter showed no harm to the acetonide group.
Having found a method for the synthesis of the desired PNG, the process of optimization was
addressed next. For this task, halogen, thio or imidate glucosideswere utilized in analogy to
the introductory tests (Scheme 6).
First, reactions revolving around the activation of trichloroacetimidate functionalities (8)
with Lewis acids in dichloromethane as solvent were investigated (Scheme 7, table 1).[86,
87]
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Scheme 7. First glucosylation reactions were performed with trichloroacetimidate donors.
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Hereby, no formation of PNG was observed with either TMSOTf (1.0 eq.) or Sc(OTf)3 (1.0
eq.) at 0 °C (entry 1/2). Better conversion was obtained with TfOH (1.0 eq., 33 %, entry 3)
and BF3·OEt2 (1.0 eq., 40 %, entry 4), indicating a superior activation of trichloroacetimidate
groups using BF3·OEt2 rather than TMSOTf.[84]
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Table 1. Reaction conditions for the imidate glucosides.
entry substrate
promoter [eq.] T [°C] yield [%]
1
2
3
4
5
6
7
TMSOTf 1.0
Sc(OTf)3 1.0
TfOH 1.0
0
0
-
8
8
8
8
8
8
8
-
0
33
40
11
32
42
BF3·OEt2 1.0
BF3·OEt2 1.0
BF3·OEt2 1.0
BF3·OEt2 1.5
0
rt
− 78
0
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231
Lowering (− 78 °C) and raising (rt) the reaction temperature led to lower yields (32 resp. 11
%, entries 5/6). Furtherly increasing the amount of promoter stimulated no higher reaction
outcome (42 %, entry 7). All performed reactions led selectively to the β-anomer and no
formation of the α-anomer could be detected. Furthermore, monitoring the reactions via TLC

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indicated that most of the reaction took place during the first 12 hours and a prolonged
reaction time did not result in a further change of the reaction mixture.
Thiol derivatives are established leaving groups in chemical glycosylations, having gone
through extensive research and thus making them powerful tools in carbohydrate
chemistry.[88] Hence, they were included in this survey (Scheme 8).
O
OP
Promoter, NIS,
MS 4Â, T, t
OP
PO
O
OP
OP
O
O
O
PO
PO
SPh/SBox
+
20
(CH2Cl2)
OP
N
6, 10, 13 - 15
21, 23 - 25
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Scheme 8. Thioglucosides were investigated next as part of this survey.
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While applying the same reaction conditions (BF3·OEt2 1.0 eq., entry 3, table 2) as with
imidate groups, the glucosylation of phenyl
2,3,4,6-tetra-O-acetyl-1-thio-β- -glucopyranoside (10) proceeded in approximately the
D
same yield (38 %), whereas TfOH (1.0 eq., entry 4) increased the outcome of the reaction (48
%). Also, both raising (rt, entry 5) and lowering (− 78 °C, entry 6) the temperature led to
lower yields (29 and 19 %, respectively) in accordance to imidate donors outlined above and
no activation of the donor was achieved with TMSOTf (1.0 eq., entry 1) or AgOTf (1.0 eq.,
entry 2) at 0 °C.
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Table 2. Reaction conditions for the thioglucosylations.
entry substrate promoter [eq.]a T [°C] yield [%] α/β
1
2
TMSOTf 1.0
AgOTf 1.0
BF3·OEt2 1.0
TfOH 1.0
0
0
-
-
10
10
10
10
10
10
10
15
15
13
14
6
-
-
3
0
38
48
29
19
-
β
4
0
β
5
TfOH 1.0
rt
β
6
TfOH 1.0
− 78
0
β
7
TfOH 1.0
-
8
TfOH 1.0
− 78
0
40
55
15
16
-
76/24
9
TfOH 1.0
74/26
10
11
12
13
14
15
TfOH 1.0
0
β
β
-
TfOH 1.0
0
TMSOTf 1.0
BF3·OEt2 1.0
AgOTf 3.0
TfOH 1.0
0
0
-
-
6
rt
35
47
β
β
6
0
6
248
a all reactions (except 7) were carried out with 3.0 eq. NIS.

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Furthermore, no product could have been isolated utilizing IBr as alternative iodine source
(entry 7).[89] All reactions were carried out with and without the addition of NIS (3.0 eq.) as
additive as part of this survey, although no conversion occurred in the latter case (table 2). In
addition to the electron-withdrawing acetate-groups, also the influence of benzyl- (15),
benzoyl- (13) and pivaloyl-groups (14) in combination with TfOH/NIS as promoter was
examined. In comparison, benzoyl- (15 %, entry 10) and pivaloyl-groups (16 %, entry 11)
hampered the glycosidic bond formation, while the application of benzyl groups, although
generating a bigger amount of PNG at 0 °C (55 %, entry 9), resulted in an anomeric mixture
of approximately α/β = 3/1 independent of the reaction temperature (− 78 / 0 °C).
A modern approach regarding the aspect of versatility in glycosylation reactions was
undertaken by Demchenko introducing SBox-leaving groups, which combine the electronic
effects and activation properties of thiol and imidate groups.[90-95] When integrating them
(6) into this study, the addition of 3.0 eq. AgOTf (35 %, entry 14) at rt and 1.0 eq. TfOH at 0
°C (47 %, entry 15) both formed the product, while no conversion of the starting material was
observed with TMSOTf (1.0 eq., entry 12) or BF3·OEt2 (1.0 eq., entry 13) at 0 °C. Although
being frequently found in the literature as promoter for SBox-leaving groups, the lack of
reactivity utilizing TMSOTf states a common agreement with the reactions involving imidate
and thioglycosides. In this regard, the insufficiency of BF3·OEt2 stands in contrast to the
previous experiments.
After scoping imidate and thiol substrates, halogens represented the third party of leaving
groups investigated during this study (Scheme 9).
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Scheme 9. Halogen glucosides were investigated as last part of this study.
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The first experiments were built around the variation of reaction conditions with bromine (4)
as leaving group. Since a higher amount of promoter hindered the formation of the
orthoester, a preliminary reaction was performed with AgOTf (1.0 eq.) and NIS (3.0 eq.) as
promoter system at 0 °C, resulting in sparse amounts of product (21 %, entry 1, table 3).
Again, in analogy to the activation of the thiol groups, no reaction was observed without NIS
while utilizing bromine as leaving group. On the other hand, a trial using solely NIS as
promoter resulted in no conversion of the starting material, making this reaction type

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interesting, since the addition of NIS as co-promoter is mostly known for thioglycosylations.
Increasing the amount further to three equivalents of promoter led to nearly a duplication of
the obtained yield (40 %, entry 2). Variation of the temperature both to a lower (− 78 °C, 30
%, entry 3) and higher (rt, 32 %, entry 4) degree led to less product in comparison.
283
Table 3. Reaction conditions for the glucosylations with a bromine leaving group.
entry substrate promoter [eq.]c T [°C] yield [%] α/β
1
2
AgOTf 1.0
AgOTf 3.0
AgOTf 3.0
AgOTf 3.0
AgOTf 3.0
AgOTf 3.0
Ag2CO3 3.0
Ag2O 3.0
0
0
21
40
30
32
48
-
β
4
4
β
3
− 78
rt
β
4
4
β
4
5a
6b
7
rt
β
4
− 78
0
-
4
-
-
4
8
0
-
-
4
9
Cu(OTf)2 1.0
AgOTf 3.0
AgOTf 3.0
AgOTf 3.0
0
-
-
4
10
11
12
0
-
-
4
0
37
56
75/25
75/25
18
18
rt
284
a 2 eq. substrate; b THF used as solvent; c all reactions (except 10) were carried out with 3.0 eq. NIS
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
No formation of the glucoside occurred by switching to tetrahydrofuran (THF) as solvent
(entry 5) and increasing the amount of substrate (2.0 eq.) gave a slightly higher outcome
compared to 1.2 equivalents (48 %, entry 6). In a trial of different promoters, silver oxide
(Ag2O, entry 8), silver carbonate (Ag2CO3, entry 7) and also copper triflate (Cu(OTf)2, entry
9) all led to no conversion of the starting material at 0 °C. IBr as alternative additive resulted,
corresponding to the thiol experiments, in no PNG formation (entry 10). Switching from
acetate to benzyl protecting groups (18) expectedly increased the yield (56 %, entry 12), but
led in a similar manner as the benzylated thiol donors to an anomeric mixture (α/β = 75/25).
Lowering the temperature (0 °C) decreased the yield contrarily to the obtained results using
‘deactivating’ groups (37 %, entry 11).
Applications of a chloride leaving group in glucosylation reactions are seldom and often
considered less powerful in comparison to the other halogens. In order to compare them to
the ‘classic’ KOENIGS-KNORR leaving group (table 3), a few experiments were performed
within this study (table 4). Amongst the tested promoters, only AgOTf (37 %, 0 °C, entry 4)
in combination with NIS worked out leading to a reaction outcome in the same range as the
bromoglucoside (entry 2, table 3). Lowering the temperature (− 78 °C) resulted in nearly the
same yield (36 %, entry 5), while increasing the temperature (40 °C, entry 6) and substitution

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303
with IBr (1.1 eq., entry 7) led to no product formation. Tests with TfOH, BF3·OEt2 and
TMSOTf showed no conversion of the starting material (entries 1-3).
304
Table 4. Reaction conditions for the glucosylations with chlorine as leaving group.
entry substrate promoter [eq.]a T [°C] yield [%] α/β
1
2
3
4
5
6
7
TfOH 2.0
BF3·OEt2 2.0
TMSOTf 2.0
AgOTf 3.0
AgOTf 3.0
AgOTf 3.0
AgOTf 3.0
0
0
-
-
-
-
5
5
5
5
5
5
5
0
-
-
0
37
36
-
β
β
-
− 78
40
0
-
-
305
a all reactions (except 7) were carried out with 3.0 eq. NIS
306
307
308
Since the first introduction of fluorine as leaving groups in order to enhance stereoselectivity
during glycosylation reactions due to assumed lower reactivity compared to thioglycosides,
their application in the field of chemical glycosylations rose constantly.[96]
309
Table 5. Reaction conditions for the optimization of the fluoroglucosylation.
entry substrate promoter [eq.] T [°C] yield [%] α/β
1c
2a
3c
4
TMSOTf 2.0
SnCl2 2.0
0
0
-
-
-
9
9
-
AgOTf 3.0
0
-
-
9
TfOH 2.0
0
-
-
9
5
6c
BF3·OEt2 1.0
BF3·OEt2 1.0
BF3·OEt2 2.0
BF3·OEt2 6.0
BF3·OEt2 6.0
BF3·OEt2 2.0
BF3·OEt2 2.0
BF3·OEt2 2.0
BF3·OEt2 0.5
TMSOTf 0.5
TfOH 0.5
0
-
-
9
0
-
-
9
7
0
59
59
40
65
63
58
-
β
9
8
0
β
9
9
− 78
0
β
9
10
11
12b
13
14
15
71/29
17
17
17
17
17
17
− 78
0
75/25
46/54
0
-
-
-
0
-
0
-
SnCl2 2.0,
AgClO4
16
0
48
71/29
17
a
b
c
310
311
the reaction was also performed with NIS, but resulted in the same yield; ACN as solvent;
reactions were carried out with 3.0 eq. NIS.
312
313
314
315
The first reactions with the fluoroglucoside 9 were performed with acetate protecting groups
and a stoichiometric amount of various promoters. Among the latter were TMSOTf[97]
(2.0 eq., entry 1, table 5), SnCl2 (2.0 eq., entry 2), AgOTf (3.0 eq., entry 3) and TfOH (2.0
eq., entry 4), which all led to no formation of product. Also, first experiments with BF3·OEt2

316
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318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
(1.0 eq., entry 5), with and without (entry 6) the addition of NIS, bore no fruits. Only with the
further increase of the amount of promoter to two equivalents, the reaction with BF3·OEt2
resulted in the desired glucoside in good yield (59 %, entry 7). A further increase of
BF3·OEt2 (6.0 eq., entry 8) did not improve the amount of obtained product (59 %). Carrying
out the reaction at − 78 °C gave less PNG (40 %, entry 9). In analogy to the thiol and bromine
experiments, benzyl groups were tested in combination with fluorine as leaving group (17).
Likewise, the reaction outcome grew in comparison to acetate groups using two equivalents
of BF3·OEt2 at 0 °C and − 78 °C (65 resp. 63 %, entry 10 / 11), but resulted in an anomeric
mixture of approximately α/β = 3/1 due to the lack of the neighbouring effect and the
anomeric effect taking over. Utilizing acetonitrile as solvent shifted the reaction slightly
towards the β-anomer (58 %, α/β = 46/54, entry 12). Furthermore, low amounts of the
promoters TfOH, TMSOTf and BF3·OEt2 (0.5 eq., entries 13 – 15) were tested with
fluorobenzyl donors, but led to no conversion of the starting material. Lastly, stannous
chloride in combination with silver perchlorate was examined, but resulted in a lower yield
compared to the other experiments (48 %, entry 16).
After scoping various pathways towards the formation of the glyosidic bond, the last step of
this study revolved around the deprotection of the acetonide and acetate/benzyl groups.
Because of the stability of acetate groups in acidic medium and the stability of the acetonide
group under alkaline conditions, a two-step deprotection procedure had to be applied to the
acetate protected PNG (21). Benzyl groups (23) could be cleaved with the aid of palladium
and hydrogen (Scheme 10).
337
338
Scheme 10. The deprotection of PNG involved a two-step procedure.
339
340
341
342
343
344
345
Application of a mild procedure involving pH-control with aqueous solutions of potassium
and sodium hydroxide followed by cleaving the acetonide group in a slightly acidic media at
higher temperatures led to the deprotected PNG (1) in quantitative yield. Also, the
hydrogenation with palladium and hydrogen followed by the acid deprotection proceeded
with the same excellent yield. The validity of the anomeric outcome was verified by
NMR-spectroscopy and the transformation with β-glycosidase from almonds was followed
by HPLC-analysis.

346
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348
349
350
351
352
353
354
355
356
357
Closing the circle back to the requirements the proposed method should feature, the
arrangement with the literature regarding aspects like yield and working effort seems
adequately comparable, since biotechnological methods, e.g. utilizing Alfalfa seeds, result
also in yields ranging from 35 – 60 %.[29] Furthermore, biotechnological methods for the
preparation of β-PNG suffer from the detriment of arduous upscaling, limiting the methods to
microgram batches, whereas the proposed method can be scaled up quite simply, especially
since the starting materials are cheap and easy accessible, making it an interesting alternative
for the synthesis of isotopically labeled standards. Also, with this study, only a first glance of
the chemistry behind the glycosylation of pyridoxine is given, providing the opportunity to
increase the yield even further by testing other leaving groups or modifying the reactivity of
the substrates.[98] Additionally, this method can be used to further scout the influence of
pyridine-based derivatives in glycosylation reactions and their influence on the mechanism.
358
359
360
361
362
363
364
365
366
367
368
3. Conclusions
The catalog of procedures entitled ‘chemical glycosylations’ contains a manifold of various
methods and hereby, every known strategy also inherits numerous variables for the specific
adaptation towards the particularly investigated substrate. As part of this study, a small part
of well-known strategies was examined in order to develop an alternative preparation of
pyridoxine glycosides to the common biotechnological procedures and furthermore open
avenues for additional investigations regarding the glycosylation of vitamin B6. Hereby, best
conversions of the acetonide-protected pyridoxine were obtained using fluoroglucosides in
combination with acetate protection groups and BF3·OEt2 (2.0 eq.) as promoter generating
the twofold protected PNG in 59 % yield. Thereupon, the deprotection was accomplished
stepwise through change of basic and acid milieu to obtain the desired 5'-β-PNG.
369
4. Materials and Methods
370
371
372
373
374
375
376
377
378
4.1. Experimental procedures
Reactions sensitive to air or moisture were carried out in dried glassware under a positive
pressure of argon using standard Schlenk techniques. Solvents were distilled and stored over
molecular sieves prior to use. Chemicals received from commercial sources (Acros,
Sigma-Aldrich, Fluka, Fisher Scientific) were used without further purification unless stated
otherwise. β-Glucosidase from almonds was purchased from Sigma-Aldrich. Column
chromatography was performed on silica gel 60 (Merck, 230-240 mesh) with the eluent
mixtures given for the corresponding procedures. Thin-layer Chromatography (TLC) was
performed using silica-coated aluminium plates (silica gel 60). The substances were detected

379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
by UV (λ = 254 nm, 366 nm) or after visualization with CAM (cerium ammonium
molybdate)/potassium permanganate (KMnO4) solution. NMR spectra were recorded either
on a Bruker AV III system (400 MHz, Bruker, Rheinstetten, Germany) or on a Bruker AV III
system (500 MHz, Bruker, Rheinstetten, Germany). 1H- and 13C NMR spectra were recorded
1
13
at 400 or 500 MHz and at 101 or 126 MHz, respectively. H and C NMR spectroscopic
chemical shifts δ are reported in parts per million (ppm) relative to residual proton signal. All
coupling constants (J) are reported in Hertz (Hz). The following abbreviations were used to
explain multiplicities: s = singlet, d = doublet, dd = doublet of doublets, t = triplet, m =
multiplet. LC-MS/MS was carried out on a Shimadzu LC-30A Prominence system
(Shimadzu, Kyoto, Japan) with the mobile phase combinations water/acetonitrile or
water/methanol. The injection volume was 1 µL. The LC was interfaced with a triple
quadrupole ion trap mass spectrometer (LCMS-8050, Shimadzu, Kyoto, Japan). Data
acquisition was performed with LabSolutions software 5.80 (Shimadzu, Kyoto, Japan). The
optical rotation was measured on a P3000 polarimeter by Kruess. All preparations of the
sugar donors can be found in the supplementary information.
394
395
396
397
398
399
400
401
402
403
404
4.1.1. General procedure for glucosylation reactions (A1)
A mixture of α4,3-O-isopropylidene pyridoxine, the respective saccharide and molecular
sieves (4 Å) was stirred under argon atmosphere in dry solvent (5 mL) at rt for 1 h before it
was cooled to the respective temperature T. The promoter was added and the reaction
mixture allowed to reach rt overnight. The mixture was diluted with dichloromethane (10
mL) and filtered through a pad of celite. Afterwards, the filtrate was washed with Na2S2O3
(10 % in water, 30 mL) and the aqueous phase was extracted with dichloromethane (3 × 40
mL). The combined organic layers were washed with distilled water (1 × 50 mL), brine (1 ×
50 mL) and dried over Na2SO4. The solvent was evaporated under reduced pressure and the
crude product subjected to column chromatography using SiO2 (pentane/ethyl acetate 1/1 to
1/4, gradient elution) followed by C18 (methanol, isocratic) to afford the glucoside.
405
4.1.2. General procedure for deprotection reactions (A2)
406
407
408
409
410
411
A solution of potassium hydroxide (1 M) was added dropwise to a solution of protected
glucoside in acetonitrile/water (8 mL, v/v = 1/1) until the pH reached 11. After 1 h at pH = 11,
0.5 mL of a 2 M NaOH-solution were added and the mixture stirred at rt until completion of
the reaction (ESI-MS). The solvent was evaporated under reduced pressure, the residue
suspended in a solution of abs. EtOH / 1% HCOOH (5 mL, v/v = 0.6 mL/4.4 mL) and the
reaction heated to reflux for 1.5 h. The solvent was evaporated under reduced pressure and

412
413
the crude product purified via column chromatography using Sephadex (methanol, isocratic)
and preparative HPLC (C18, water/acetonitrile 90/10, isocratic) to obtain the glucoside.
414
4.1.3. 2,3,4,6-Tetra-O-acetyl-α-D-glucopyranosyl bromide (4)
415
416
417
418
419
420
421
422
423
424
425
426
427
HBr (33 % wt in acetic acid, 8.88 g, 6.25 mL, 109.7 mmol, 86 eq.) was added dropwise to a
cooled solution (0 °C) of 1,2,3,4,6-penta-O-acetyl-α/β- -glucopyranoside (3, 0.50 g,
D
1.28 mmol, 1.00 eq.) in dichloromethane (10 mL) and stirred for 3 h at rt. Ice water (50 mL)
was added to the mixture and the aqueous phase was extracted with dichloromethane (3 × 50
mL). The combined organic layers were washed with 0.5 % Na2S2O3 (1 × 75 mL), sat.
NaHCO3 (3 × 75 mL), brine (1 × 75 mL) and dried over Na2SO4. The solvent was evaporated
under reduced pressure and the crude product crystallized from diethylether/pentane to
afford the halogenated substrate (0.44 g, 1.12 mmol, 88 %). 1H-NMR (360 MHz, CDCl3, 292
K) α-Anomer δ (ppm) = 6.61 (d, J = 4.0 Hz, 1 H), 5.56 (t, J = 9.7 Hz, 1 H), 5.16 (t, J = 9.8 Hz,
1 H), 4.84 (dd, J = 10.0, 4.1 Hz, 1 H), 4.35-4.27 (m, 2 H), 4.15-4.10 (m, 1 H), 2.10 (s, 3 H),
2.10 (s, 3 H), 2.05 (s, 3 H), 2.03 (s, 3 H); 13C-NMR (101 MHz, CDCl3, 292 K) α-Anomer δ
(ppm) = 170.6, 170.0, 169.9, 169.6, 86.7, 72.3, 70.8, 70.3, 67.3, 61.1, 20.81, 20.8, 20.8, 20.7;
ESI-MS m/z 411.2 [M + H]+; Anomeric ratio α/β = 100/0.[99]
428
4.1.4. 2,3,4,6-Tetra-O-acetyl-α-D-glucopyranosyl chloride (5)
429
430
431
432
433
434
435
436
437
438
439
440
441
442
Thionyl chloride (1.22 g, 0.74 mL, 10.2 mmol, 2.00 eq.) and Tin(IV)chloride (1.33 g, 0.59
mL, 5.12 mmol, 1.00 eq.) were added dropwise to solution of
1,2,3,4,6-penta-O-acetyl-α/β- -glucopyranoside (3, 2.00 g, 5.12 mmol, 1.00 eq.) in
a
D
dichloromethane (30 mL) and stirred for 2 h at rt. The mixture was added to a cold solution of
sat. NaHCO3 and the aqueous phase was extracted with dichloromethane (3 × 50 mL). The
combined organic layers were washed with brine (1 × 75 mL) and dried over Na2SO4 The
solvent was evaporated under reduced pressure and the crude product purified via column
chromatography (hexane/ethyl acetate = 3/2) to obtain the desired product (1.83 g, 4.99
mmol, 97 %). 1H-NMR (360 MHz, CDCl3, 292 K) α-Anomer δ (ppm) = 6.29 (d, J = 4.0 Hz,
1 H), 5.55 (t, J = 9.7 Hz, 1 H), 5.13 (t, J = 9.7 Hz, 1 H), 5.01 (dd, J = 10.1, 4.0 Hz, 1 H), 4.31
(d, J = 11.8 Hz, 2 H), 4.13 (d, J = 10.5 Hz, 1 H), 2.10 (s, 3 H), 2.09 (s, 3 H), 2.04 (s, 3 H), 2.03
13
(s, 3 H); C-NMR (101 MHz, CDCl3, 292 K) α-Anomer δ (ppm) = 170.6, 170.0, 170.0,
169.6, 90.2, 70.8, 70.5, 69.5, 67.5, 61.2, 20.8, 20.7, 20.7, 20.6; ESI-MS m/z 388.8 [M + Na]+;
Anomeric ratio α/β = 100/0; Rf 0.43 (pentane/diethyl ether 1/1) [CAM].[32]
443
4.1.5. Benzoxazolyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranoside (6)

444
445
446
447
448
449
450
451
452
453
454
455
456
457
A solution of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (4, 1.00 g, 2.43 mmol, 1.00
eq.) in dry acetone (2.5 mL) was added to a suspension of 2-mercaptobenzoxazole (0.51 g,
3.40 mmol, 1.40 eq.) and potassium carbonate (0.47 g, 3.40 mmol, 1.40 eq.) in acetone (7.5
mL) at 40 °C. The reaction was stirred at the elevated temperature for 2.5 h and at rt
overnight. Dichloromethane (30 mL) was added, the mixture washed with 1 % NaOH (25
mL) and dist. water (2 × 25 mL), dried over Na2SO4 and the solvent removed under reduced
pressure yielding the product, which could be used without further purification (1.07 g, 2.22
1
mmol, 91 %). H-NMR (360 MHz, CDCl3, 292 K) δ (ppm) = 7.68 – 7.58 (m, 1 H), 7.50 –
7.44 (m, 1 H), 7.35 – 7.27 (m, 2 H), 5.70 (d, J = 10.4 Hz, 1 H), 5.36 (t, J = 9.3 Hz, 1 H), 5.31
– 5.13 (m, 2 H), 4.28 (dd, J = 12.5, 4.7 Hz, 1 H), 4.14 (dd, J = 12.5, 2.2 Hz, 1 H), 3.96 (ddd,
J = 10.1, 4.7, 2.3 Hz, 1 H), 2.05 (s, 3 H), 2.04 (s, 3 H), 2.03 (s, 3 H), 2.01 (s, 3 H); 13C-NMR
(101 MHz, CDCl3, 292 K) δ (ppm) = 170.7, 170.1, 169.5, 169.5, 161.0, 152.1, 141.6, 124.7,
124.7, 119.0, 110.3, 83.5, 76.5, 73.8, 69.7, 68.0, 61.8, 20.8, 20.7 (3x); ESI-MS m/z 504.10
[M + Na]+.[92]
458
4.1.6. 2,3,4,6-Tetra-O-acetyl-β-D-glucopyranosyl fluoride (9)
459
460
461
462
463
464
465
466
467
468
469
470
471
472
A cooled (0 °C) solution of 2,3,4,6-tetra-O-acetyl-α/β-
D
-glucopyranoside (7, 0.51 g, 1.46
mmol, 1.00 eq.) in dry dichloromethane (12 mL) was stirred for 20 min with molecular
sieves (4 Å) before diethylaminosulfur trifluoride (DAST) (0.27 g, 0.22 mL, 1.68 mmol,
1.15 eq.) was added and the solution was allowed to warm to rt over 2.5 h. After dilution with
dichloromethane (20 mL) and filtration through a pad of silica gel, the organic phase was
washed with sat. NaHCO3 (2 × 50 mL), dist. water (3 × 50 mL), brine (1 × 50 mL) and dried
over Na2SO4. The solvent was evaporated under reduced pressure and the crude product
crystallized from diethyl ether/pentane to afford the halogenated product (0.35 g, 0.99 mmol,
68 %). 1H-NMR (360 MHz, CDCl3, 292 K) β-Anomer δ (ppm) = 5.36 (dd, J = 52.0, 6.0 Hz, 1
H), 5.27 – 5.16 (m, 2 H), 5.16 – 5.05 (m, 1 H), 4.31 – 4.18 (m, 2 H), 3.90 (ddt, J = 7.6, 4.7, 2.3
Hz, 1 H), 2.10 (d, J = 2.7 Hz, 6 H), 2.04 (d, J = 2.8 Hz, 6 H); 13C-NMR (101 MHz, CDCl3,
292 K) β-Anomer δ (ppm) = 170.7, 170.1, 169.4, 169.2, 106.3 (d, J = 219.7 Hz), 72.2 (d, J =
3.9 Hz), 71.9 (d, J = 8.3 Hz), 71.3 (d, J = 28.7 Hz), 67.5, 61.9, 20.8, 20.7, 20.7, 20.7; ESI-MS
m/z 373.3 [M + Na]+.[35]
473
4.1.7. Phenyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranoside (10)
474
475
476
BF3·Et2O (16.6 mL, 130.7 mmol, 3.00 eq.) was added to a cooled (0 °C) solution of
peracetylated glucose (3, 17.0 g, 43.6 mmol, 1.00 eq.) in dichloromethane (150 mL) in one
portion. Thiophenol (PhSH, 6.67 mL, 65.3 mmol, 1.50 eq.) was added dropwise to the

477
478
479
480
481
482
483
484
485
486
487
reaction mixture at 0 °C, followed by stirring at rt until completion of the reaction (TLC).
The mixture was diluted with dichloromethane (50 ml) and successively washed with sat.
NaHCO3 (100 ml) and brine (100 ml). The organic layer was dried over Na2SO4 and the
solvent evaporated under reduced pressure. Purification via column chromatography
(pentane/ethyl acetate = 3/2) gave the desired product (13.7 g, 31.1 mmol, 71 %). 1H-NMR
(360 MHz, CDCl3, 292 K) δ (ppm) = 7.46 (m, 2 H), 7.29 (m, 3 H), 5.20 (t, J = 9.3 Hz, 1 H),
5.01 (t, J = 9.8 Hz, 1 H), 4.94 (t, J = 9.5 Hz, 1 H), 4.69 (d, J = 10.1 Hz, 1 H), 4.30 – 4.01 (m,
2 H), 3.70 (m, 1 H), 2.05 (s, 3 H), 2.05 (s, 3 H), 1.99 (s, 3 H), 1.96 (s, 3 H); 13C-NMR (101
MHz, CDCl3, 292 K) δ (ppm) = 170.5, 170.1, 169.4, 169.2, 133.1, 131.6, 128.9, 128.4, 85.7,
75.8, 73.9, 69.9, 68.2, 20.7, 20.7, 20.6, 20.6; Rf 0.30 (pentane/ethyl acetate 3/2)
[KMnO4].[100]
488
4.1.8. Ethyl 2,3,4,6-tetra-O-benzoyl-1-thio-α/β-D-glucopyranoside (13)
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
Benzoyl chloride (BzCl, 0.28 g, 0.23 mL, 1.96 mmol, 4.40 eq.) was added dropwise to a
solution of ethyl 1-thio-α/β- -glucopyranoside (12, 103 mg, 0.46 mmol, 1.00 eq.) in pyridine
D
(5 mL) over 15 min and the mixture was stirred at rt for 12 h. Distilled water (5 mL) was
added to the reaction at 0 °C and it was diluted with dichloromethane (10 mL). The aqueous
phase was extracted with dichloromethane (3 × 10 mL). The combined organic phases were
washed with sat. CuSO4 (3 × 50 mL), dist. water (2 × 50 mL), brine (1 × 50 mL) and dried
over Na2SO4. The solvent was evaporated and the crude product subjected to column
chromatography (pentane/ethyl acetate = 6/1) to obtain the desired product (285 mg, 0.41
1
mmol, 89 %) as colorless oil. H-NMR (360 MHz, CDCl3, 292 K) α-Anomer δ (ppm)
= 8.11-7.80, 7.62-7.27 (m, 20 H), 6.07 (t, J = 9.87 Hz, 1 H), 5.94 (d, J = 4.2 Hz, 1 H), 5.68 (t,
J = 8.00 Hz, 1 H), 5.50 (dd, J = 10.2, 5.78 Hz, 1 H), 4.89-4.88 (m, 1 H), 4.59 (d, J = 2.81 Hz,
1 H), 4.53 (d, J = 5.45 Hz, 1 H), 2.67-2.58 (m, 2 H), 1.25 (t, J = 6.00 Hz, 3 H); β-Anomer δ
(ppm) = 8.11-7.80, 7.62-7.27 (m, 20 H), 5.93 (t, J = 9.57 Hz, 1 H), 5.67 (t, J = 9.79 Hz, 1 H),
5.57 (t, J = 9.72 Hz, 1 H), 4.86 (d, J = 9.96 Hz, 1 H), 4.63 (dd, J = 12.2, 3.16 Hz, 1 H), 4.50
(dd, J = 12.2, 5.44 Hz, 1 H), 4.19-4.16 (m, 1 H), 2.83-2.70 (m, 2 H), 1.26 (t, J = 7.46 Hz, 3
13
H); C-NMR (101 MHz, CDCl3, 292 K) β-Anomer δ (ppm) = 166.3, 166.0, 165.4, 165.3,
130.3, 130.0, 130.0, 129.9, 129.9, 129.8, 129.3, 129.0, 128.9, 128.6, 128.6, 128.5, 128.5,
128.4, 84.1, 76.5, 74.3, 70.8, 69.8, 63.5, 24.6, 15.1; ESI-MS m/z 663.3 [M + Na]+; Rf 0.39
(α), 0.25 (β, dichloromethane/methanol 9/1) [CAM].[101]
508
4.1.9. Ethyl 2,3,4,6-tetra-O-pivaloyl-1-thio-β-D-glucopyranoside (14)

509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
Pivaloyl chloride (PivCl, 0.44 g, 0.45 mL, 3.65 mmol, 7.80 eq.) was added dropwise to a
solution of ethyl 1-thio-α/β- -glucopyranoside (12, 0.11 g, 0.47 mmol, 1.00 eq.) in pyridine
D
(0.50 mL). The reaction mixture was stirred at 75 °C for 48 h. Methanol (5 mL) was added
and the mixture was diluted with dichloromethane (10 mL). The mixture was washed with
sat. CuSO4 (4 × 50 mL), dist. water (2 × 50 mL), brine (1 × 50 mL) and dried over Na2SO4.
The solvent was evaporated under reduced pressure and the crude product objected to
column chromatography (pentane/ethyl acetate = 10/0.1 to 9/1) to obtain the desired product
(198 mg, 0.35 mmol, 75 %) as colorless oil. 1H-NMR (400 MHz, CDCl3) β-Anomer δ (ppm)
= 5.33 (t, J = 9.4 Hz, 1 H), 5.12 (t, J = 9.8 Hz, 1 H), 5.07 (t, J = 9.7 Hz, 1 H), 4.51 (d, J = 10.1
Hz, 1 H), 4.22 (dd, J = 12.3, 1.9 Hz, 1 H), 4.05 (dd, J = 12.4, 5.5 Hz, 1 H), 3.73 (ddd, J = 10.2,
5.5, 1.9 Hz, 1 H), 2.84 – 2.56 (m, 2 H), 1.26 (m, 3 H), 1.22 (s, 9 H), 1.17 (s, 9 H), 1.15 (s, 9 H),
1.11 (s, 9 H); 13C-NMR (101 MHz, CDCl3) β-anomer δ (ppm) = 178.2, 177.3, 176.7, 176.6,
83.6, 76.6, 73.4, 69.7, 68.0, 62.3, 39.0, 38.9, 38.9, 38.8, 27.3, 27.3, 27.2, 24.0, 15.1; ESI-MS
m/z 583.4 [M + Na]+, 599.4 [M + K]+; Rf 0.83 (α), 0.75 (β, pentane/ethyl acetate 9/1)
[CAM].[102]
524
4.1.10. Phenyl 1,2,3,4,6-tetra-O-benzyl-1-thio-β-D-glucopyranoside (15)
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
A solution of sodium methoxide (NaOMe, 30 % in MeOH, 0.78 mL) was added to a solution
of phenyl 2,3,4,6-tetra-O-acetyl-1-thio-β- -glucopyranoside (10, 5.00 g, 11.3 mmol, 1.00
D
eq.) in dry methanol at rt and stirred until complete conversion of starting material (TLC).
Afterwards the reaction mixture was neutralized using Dowex 5W (H+-Form), filtered and
the solvent evaporated under reduced pressure. The obtained glucopyranoside (3.06 g, 11.2
mmol, 1.00 eq.) was dissolved in dry DMF (150 mL) and the reaction mixture cooled to 0 °C.
Sodium hydride (NaH, 60 %, 4.49 g, 112 mmol, 10.0 eq.) was added portionwise and the
resulting slurry mixed for additional 30 min at low temperature while warming up. Benzyl
bromide (BnBr, 19.2 g, 13.3 mL, 112 mmol, 10 eq.) was added at room temperature and the
mixture stirred for 22 h. The solution was cooled to 0 °C and cold dist. water (100 mL) was
added slowly. The aqueous phase was extracted with dichloromethane (3 × 50 mL). The
collected organic phases were washed with dist. water (2 × 50 mL) and brine (1 × 50 mL),
dried over Na2SO4 and the solvent evaporated under reduced pressure. The crude product
was purified via column chromatography (pentane/ethyl acetate = 10/0.5) to obtain the
desired product as white solid (6.09 g, 9.62 mmol, 85 % over two steps). 1H-NMR (360 MHz,
CDCl3, 292 K) β-Anomer δ (ppm) = 7.60 (m, 2 H), 7.41 – 7.19 (m, 23 H), 4.92 – 4.81 (m, 4
H), 4.74 (d, J = 10.3 Hz, 2 H), 4.68 (d, J = 9.7 Hz, 1 H), 4.64 – 4.54 (m, 3 H), 3.80 (dd, J =

542
543
544
545
546
10.9, 2.1 Hz, 1 H), 3.76 – 3.63 (m, 3 H), 3.52 (m, 2 H); 13C-NMR (101 MHz, CDCl3, 292 K)
β-Anomer δ (ppm) = 138.5, 138.4, 138.1, 133.9, 132.0, 129.0, 128.6, 128.6, 128.5, 128.5,
128.4, 128.3, 128.0, 128.0, 127.9, 127.8, 127.7, 127.6, 87.5, 86.9, 80.9, 79.2, 77.9, 75.9, 75.5,
75.2, 73.5, 69.1; ESI-MS m/z 654.1 [M + Na]+; Rf 0.61 + 0.69 (pentane/diethyl ether 2/1)
[KMnO4].[100]
547
4.1.11. 2,3,4,6-Tetra-O-benzyl-α/β-D-glucopyranosyl fluoride (17)
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
Diethylaminosulfur trifluoride (0.28 g, 1.74 mmol, 1.20 eq.) was added to a cooled (0 °C)
solution of 2,3,4,6-tetra-O-benzyl-α/β- -glucopyranose (16, 0.78 g, 1.45 mmol, 1.00 eq.) in
D
dichloromethane (10 mL) and stirred for 1.5 h. The reaction mixture was diluted with
dichloromethane (10 mL) and filtrated through a pad of Celite. The filtrate was washed with
sat. NaHCO3 (2 × 20 mL), dist. water (3 × 20 mL) and brine (1 × 20 mL), dried over Na2SO4
and the solvent evaporated under reduced pressure. The crude product was purified via
column chromatography (pentane/ethyl acetate 9/1) to obtain the desired product as as white
solid containing both the α- and β-anomer (0.72 g, 1.33 mmol, 92 %) 1H-NMR (360 MHz,
CDCl3, 292 K) α+β-Anomer δ (ppm) = 7.38 – 7.25 (m, 18 H), 7.15 (dd, J = 6.7, 2.8 Hz, 2 H),
5.56 (dd, J = 53.2, 2.7 Hz, 1 H, α-anomer), 5.26 (dd, J = 52.8, 6.7 Hz, 1 H, β-anomer), 4.97 –
13
4.46 (m, 8 H), 4.01 – 3.53 (m, 6 H); C-NMR (101 MHz, CDCl3, 292 K) α+β-Anomer δ
(ppm) = 138.6, 138.4, 138.5, 138.0, 137.9, 137.8, 137.8, 137.8, 128.7, 127.8, 110.0 (d, J =
215.9 Hz), 105.7 (d, J = 227.1 Hz), 83.6, 83.5, 81.7, 81.5, 81.5, 79.5, 79.3, 77.3, 77.0, 76.7,
75.9, 75.6, 75.3, 75.1, 75.0, 74.9, 74.6, 74.5, 73.7, 73.6, 73.6, 72.8, 72.7, 68.5, 67.9; ESI-MS
m/z 560.1 [M + NH4]+, 565.1 [M + Na]+; Anomeric ratio α/β = 32/68; Rf 0.82 (pentane/ethyl
acetate 4/1) [CAM].[103]
564
4.1.12. 2,3,4,6-Tetra-O-benzyl-α-D-glucopyranosyl bromide (18)
565
566
567
568
569
570
571
572
573
574
Oxalyl bromide (0.71 g, 0.46 mL, 3.39 mmol, 2.00 eq.) was added dropwise to a cooled
(0 °C) solution of 2,3,4,6-tetra-O-benzyl-α/β- -glucopyranose (16, 0.91 g, 1.70 mmol, 1.00
D
eq.) in dichloromethane/dimethyl formamide (10 mL/0.15 mL) and was allowed to reach rt.
After complete conversion of the starting material (TLC), the reaction was cooled (0 °C) and
ice water (20 mL) was added dropwise. The layers were separated and the aqueous phase
extracted with dichloromethane (3 × 15 mL). The collected organic phases were washed with
brine, dried over Na2SO4 and the solvent evaporated under reduced pressure to obtain the
bromide (0.87 g, 1.44 mmol, 85 %) as yellow oil, which was used without further
1
purification; H-NMR (360 MHz, CDCl3, 292 K) δ (ppm) = 7.45 – 7.20 (m, 18 H), 7.20 –
7.09 (m, 2 H), 6.43 (d, J = 3.7 Hz, 1 H), 4.97 (d, J = 10.8 Hz, 1 H), 4.83 (dd, J = 10.8, 8.9

575
576
577
Hz, 2 H), 4.71 (s, 2 H), 4.44 – 4.60 (m, 3 H), 4.07 – 4.01 (m, 2 H), 3.77 (m, 2 H), 3.65 (dd, J
= 11.0, 2.0 Hz, 1 H), 3.53 (dd, J = 9.3, 3.8 Hz, 1 H); Rf 0.88 (pentane/ethyl acetate 4/1)
[CAM].[104]
578
4.1.13. α4,3-O-Isopropylidene pyridoxine (20)
579
580
581
582
583
584
585
586
587
588
589
590
Para-toluenesulfonic acid monohydrate (11.1 g, 58.3 mmol, 4.00 eq.) was added to a
solution of pyridoxine hydrochloride (19, 3.00 g, 14.6 mmol, 1.00 eq.) and
2,2-dimethoxypropane (25.5 g, 30.0 mL, 245 mmol, 16.8 eq.) in acetone (60 mL). The
mixture was stirred at rt for 23 h. After neutralization with sat. NaHCO3, the solvent was
evaporated under reduced pressure and the aqueous residue was extracted with
dichloromethane (3 × 50 mL). The combined organic layers were washed with dist. water (1
× 75 mL), brine (1 × 75 mL) and dried over Na2SO4. The solvent was evaporated under
reduced pressure and the crude product crystallized from diethyl ether/pentane to afford the
title compound (2.92 g, 13.9 mmol, 96 %) as a yellowish solid. 1H-NMR (CDCl3, 360 MHz)
13
δ (ppm) 7.83 (s, 1 H), 4.93 (s, 2 H), 4.55 (s, 2 H), 2.37 (s, 3 H), 1.54 (s, 6 H); C-NMR
(CDCl3, 101 MHz) δ 148.0, 146.2, 138.9, 129.4, 126.0, 99.9, 60.4, 58.7, 24.9, 18.5; ESI-MS
m/z 210.6 [M + H]+.[105]
591
4.1.14. Tetraacetyl-β-D-glucopyranosyl isopropylidene pyridoxine (21)
592
593
594
595
596
597
598
599
600
601
602
603
604
605
Prepared according to A1 with α4,3-O-isopropylidene pyridoxine (20, 50.0 mg, 0.24 mmol,
1.00 eq.), 2,3,4,6-tetra-O-acetyl-β- -glucopyranosyl fluoride (9, 1.2 eq.) and BF3·OEt2 (68.0
D
mg, 61.0 µL, 0.48 mmol, 2.00 eq.) in dichloromethane (5 mL) at 0 °C to obtain the product as
colorless oil (77.0 mg, 0.14 mmol, 59 %). 1H-NMR (CDCl3, 360 MHz, β-Anomer) δ 7.89 (s,
1 H, H6), 5.13 (t, 1 H, H12), 5.06 (t, 1H, H13), 4.99 (t, 1 H, H11), 4.80 (d, J = 1.7 Hz, 2 H,
H8), 4.64 (dd, J = 82.2, 12.1 Hz, 2 H, H7), 4.46 (d, J = 7.9 Hz, 1 H, Hβ10), 4.22 (dd, J = 12.3,
4.9 Hz, 1 H, H15), 4.13 (dd, J = 12.3, 2.4 Hz, 1 H, H15), 3.64 (ddd, J = 9.8, 4.9, 2.4 Hz, 1 H,
H14), 2.39 (s, 3 H, CH39), 2.09 (s, 3 H, H17), 2.00 (s, 3 H, H19), 1.98 (s, 3 H, H23), 1.97 (s,
3 H, H21), 1.53 (s, 3 H, CH325/CH326), 1.51 (s, 3 H, CH325/CH326); 13C-NMR (CDCl3, 101
MHz, β-Anomer) δ 170.7 (C16), 170.3 (C20), 169.4 (C22), 169.3 (C18), 149.0 (C2), 146.2
(C3), 139.9 (C6), 126.3 (C5), 124.6 (C4), 99.9 (C24), 98.7 (C10), 72.9 (C12), 72.0 (C14),
71.3 (C11), 68.3 (C13), 66.0 (C7), 61.9 (C15), 58.5 (C8), 25.0 (C25/C26), 24.6 (C25/C26),
20.8 (C17), 20.6 (C19, C21, C23), 18.6 (C9); TLC Rf 0.29 (pentane/ethyl acetate 1/4)
[CAM]; ESI-MS m/z 540.2 [M + H]+.
606
4.1.15. Tetrabenzyl-β-D-glucopyranosyl isopropylidene pyridoxine (23)

607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
Prepared according to A1 with α4,3-O-isopropylidene pyridoxine (20, 50.1 mg, 0.24 mmol,
1.00 eq.), 2,3,4,6-tetra-O-benzyl-α/β- -glucopyranosyl fluoride (17, 0.15 g, 0.29 mmol, 1.2
D
eq.) and BF3·OEt2 (68.0 mg, 61.0 µL, 0.48 mmol, 2.00 eq.) in dichloromethane (5 mL) at 0
°C to obtain the product as a colorless oil in a mixture of anomers (0.11 mg, 0.15 mmol, 65
%, α/β = 71/29). 1H-NMR (CDCl3, 360 MHz, β-Anomer) δ 8.00 (s, 1 H, H6), 7.39 – 7.22 (m,
18 H, Bn-H), 7.15 (m, 2 H, Bn-H), 4.95 - 4.86 (m, 3 H, H8, H19), 4.87 - 4.76 (m, 4 H, H19,
H7, H11, H17/H18), 4.69 (d, 1H, H17/H18), 4.62 (d, 1H, H16), 4.58 - 4.50 (m, 3 H, H7, H16,
H17/H18), 4.40 (d, J = 7.7 Hz, 1 H, Hβ10), 3.73 - 3.67 (m, 2 H, H15), 3.64 - 3.59 (m, 2 H,
H13, H12), 3.49 - 3.42 (m, 2 H, H11, H14), 2.41 (s, 3 H, CH39), 1.47 (s, 3 H, CH325/CH326),
1.44 (s, 3 H, CH325/CH326); 13C-NMR (CDCl3, 101 MHz, β-Anomer) δ 148.5 (C2), 146.1
(C3), 140.2 (C6), 138.7 - 138.0 (CBn), 126.2 (C5), 125.6 (C4), 128.5 - 127.7 (CBn), 102.1
(C10), 99.9 (C24), 84.9 (C12/C13), 82.2 (C11/C14), 77.9 (C12/C13), 75.8 (C19), 75.0 (3C:
C11/C14, C17, C18), 73.6 (C16), 68.9 (C15), 66.0 (C7), 58.7 (C8), 18.7 (C9), 25.0
(C25/C26), 24.6 (C25/C26); TLC Rf 0.36 (pentane/ethyl acetate 1.5/1) [CAM]; ESI-MS m/z
732.4 [M + H]+.
622
4.1.16. Tetrapivaloyl-β-D-glucopyranosyl isopropylidene pyridoxine (24)
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
Prepared according to A1 with α4,3-O-isopropylidene pyridoxine (20, 51.0 mg, 0.24 mmol,
1.00 eq.), ethyl 2,3,4,6-tetra-O-pivaloyl-1-thio-β- -glucopyranoside (14, 0.16 g, 0.29 mmol,
D
1.2 eq.) and TfOH (37.0 mg, 22.0 µL, 0.24 mmol, 1.00 eq.) in dichloromethane (5 mL) at 0
°C to obtain the product as colorless oil (27.8 mg, 39.2 µmol, 16 %). 1H-NMR (CDCl3, 360
MHz, β-Anomer) δ 7.87 (s, 1 H, H6), 5.30 (t, J = 9.5 Hz, 1 H, H12), 5.12 (t, J = 9.7 Hz, 1 H,
H13), 5.03 (dd, J = 9.6, 8.0 Hz, 1 H, H11), 4.92 – 4.77 (m, 2 H, H8), 4.72 (d, J = 11.5 Hz, 1 H,
H7), 4.56 (d, J = 8.0 Hz, 1 H, Hβ10), 4.44 (d, J = 11.5 Hz, 1 H, H7), 4.22 (dd, J = 12.3, 1.9 Hz,
1 H, H15), 4.04 (dd, J = 12.3, 5.4 Hz, 1 H, H15), 3.71 (ddd, J = 10.1, 5.4, 1.9 Hz, 1 H, H14),
2.39 (s, 3 H, CH39), 1.53 (s, 3 H, CH325, CH326), 1.52 (s, 3 H, CH325, CH326), 1.23 (s, 9 H,
13
CH3Piv), 1.14 (s, 9 H, CH3Piv), 1.09 (s, 9 H, CH3Piv), 1.07 (s, 9 H, CH3Piv); C-NMR
(CDCl3, 101 MHz, β-Anomer) δ 178.1 (C16), 177.2 (C20), 176.6 (C22), 176.5 (C18), 148.7
(C2), 146.2 (C3), 139.7 (C6), 126.3 (C5), 125.0 (C4), 99.9 (C10, C24), 72.5 (C14), 72.2
(C12, C13), 71.1 (C11), 68.0 (C12, C13), 66.1 (C7), 61.9 (C15), 58.6 (C8), 39.0 (C17), 38.8
(C19), 38.8 (C21), 38.8 (C23), 27.2 (CH3Piv x2), 27.1 (CH3Piv), 27.1 (CH3Piv), 24.9 (C25,
C26), 24.8 (C25, C26), 18.7 (C9); TLC Rf 0.64 (pentane/ethyl acetate 1/1) [CAM]; ESI-MS
m/z 708.1 [M + H]+.
639
4.1.17. Tetrabenzoyl-β-D-glucopyranosyl isopropylidene pyridoxine (25)

640
641
642
643
644
645
646
647
648
649
650
651
652
653
Prepared according to A1 with α4,3-O-isopropylidene pyridoxine (20, 49.4 mg, 0.24 mmol,
1.00 eq.), ethyl 2,3,4,6-tetra-O-benzoyl-1-thio-α/β -glucopyranoside (13, 0.18 g, 0.28
-
D
mmol, 1.2 eq.) and TfOH (35.0 mg, 21.0 µL, 0.24 mmol, 1.00 eq.) in dichloromethane (5
1
mL) at 0 °C to obtain the product as colorless oil (28.2 mg, 35.8 µmol, 15 %). H-NMR
(CDCl3, 360 MHz, β-Anomer) δ 8.10 – 7.22 (m, 21 H, HBz, H6), 5.87 (t, J = 9.7 Hz, 1 H,
H12), 5.68 (t, J = 9.7 Hz, 1 H, H13), 5.54 (dd, J = 9.7, 7.8 Hz, 1 H, H11), 4.85 (d, J = 7.9 Hz,
1 H, Hβ10), 4.80 (d, J = 12.0 Hz, 1 H, H7), 4.68 (d, J = 1.5 Hz, 2 H, H8), 4.67 – 4.63 (m, 1 H,
H15), 4.60 – 4.49 (m, 2 H, H7, H15), 4.15 (ddd, J = 10.0, 5.3, 3.2 Hz, 1 H, H14), 2.35 (s, 3 H,
13
CH39), 1.32 (s, 3 H, CH321/CH322), 1.29 (s, 3 H, CH321/CH322); C-NMR (CDCl3, 101
MHz, β-Anomer) δ 166.2 (C16), 165.8 (C18), 165.2 (C17), 165.1 (C19), 148.9 (C2), 146.2
(C3), 139.9 (C6), 134.0 – 133.3 (m, CBz), 130.5 – 128.3 (m, CBz), 126.4 (C5), 124.7 (C4),
99.8 (C20), 99.3 (C10), 72.9 (C12), 72.5 (C14), 71.8 (C11), 69.7 (C13), 66.2 (C7), 63.0
(C15), 58.5 (C8), 24.7 (C21, C22), 24.4 (C21,C22), 18.6 (C9); TLC Rf 0.61 (pentane/ethyl
acetate 1/2) [CAM]; ESI-MS m/z 788.1 [M + H]+.
654
4.1.18. Pyridoxine-5'-β-D-glucoside (5'-β-PNG, 1)
655
656
657
658
659
660
661
662
Prepared according to A2 with 23 (50.0 mg, 0.09 mmol, 1.00 eq.) to obtain the glucoside as
white solid in quantitative yield. 1H-NMR (D2O, 360 MHz, β-Anomer) δ 7.65 (s, 1 H, H6),
4.93 (d, J = 12.5 Hz, 1 H, H7), 4.78 – 4.70 (m, 3 H, H7, H8), 4.43 (d, J = 7.9 Hz, 1 H, Hβ10),
3.83 (d, J = 11.4 Hz, 1 H, H15), 3.65 (m, J = 6.0 Hz, 1 H, H15), 3.41 - 3.35 (m, 1 H, H12,
H14), 3.32 (m, 1 H, H13), 3.22 (t, J = 8.5 Hz, 1 H, H11), 2.38 (s, 3 H, CH39); 13C-NMR (D2O,
101 MHz, β-Anomer) δ 159.7 (C3), 145.0 (C2), 139.2 (C5), 131.8 (C4), 126.9 (C6), 101.3
(C10), 75.9 (C12/C14), 75.6 (C12/C14), 73.0 (C11), 69.5 (C13), 66.1 (C7), 60.6 (C15), 56.1
(C8), 15.6 (C9); ESI-MS m/z 331.8 [M + H]+, 353.9 [M + Na]+, 330.2 [M - H]-.
663
4.1.19. Pyridoxine-5'-β-D-glucoside (5'-β-PNG, 1)
664
665
666
667
668
669
670
671
672
Starting from 24. Palladium/Coal (5.30 mg, 15.0 µmol, 0.30 eq.) was added to a solution of
protected pyridoxine glucoside (24, 36.0 mg, 50.0 µmol, 1.00 eq.) in dry ethanol. A pressure
of 1 atm H2 was applied to the reaction vessel and uphold until complete conversion of the
starting material (ESI-MS). The mixture was filtered, the solvent evaporated under reduced
pressure, the residue suspended in a solution of abs. EtOH / 1% HCOOH (5 mL, v/v = 0.6
mL/4.4 mL) and the reaction heated to reflux for 1.5 h. The solvent was evaporated under
reduced pressure and the crude product purified via column chromatography using Sephadex
(methanol, isocratic) and preparative HPLC (C18, water/acetonitrile 90/10, isocratic) to
obtain the glucoside as white solid in quantitative yield.

673
674
Supplementary Materials: Experimental procedures and NMR-spectra of the new
substances are available online.
675
676
Author Contributions: T.B. and M.R. conceived and designed the experiments; T.B.
performed the experiments and analyzed the data; T.B. and M.R. wrote the paper.
677
678
Funding: The study was funded by a grant from the German Research Association DFG (RY
19/17-1).
679
680
681
Acknowledgments: The authors gratefully acknowledge the support by the Chair of Food
Chemistry and Molecular Science, Technical University Munich, Germany, for the NMR
measurements
682
Conflicts of Interest: The authors declare no competing financial interests
683
684
685
Abbreviations: Bn, benzyl; Bz, benzoyl; LG, leaving group; P, protecting group; Piv,
pivaloyl; PN, pyridoxine; PL, pyridoxal; PM, pyridoxamine; PLP, pyridoxal phosphate;
PMP, pyridoxamine phosphate; PNG, pyridoxine glucoside.
686
References
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
[1]
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[3]
[4]
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325-327. 10.1111/j.1432-1033.1973.tb03200.x.
L. Siegel, D. Melnick, B.L. Oser, Bound Pyridoxine (Vitamin B6) in Biological Materials, J. Biol.
Chem. 149 (1943) 361-367.
J.C. Rabinowitz, E.E. Snell, The Vitamin B6 Group, Distribution of Pyridoxal, Pyridoxamine, and
Pyridoxine in some natural Products, J. Biol. Chem. 176 (1948) 1157-1167.
K. Tadera, F. Yagi, A. Kobayashi, Specificity of a particulate glucosyltransferase in seedlings of
Pisum sativum L. which catalyzes the formation of 5'-O-(β-D-glucopyranosyl)pyridoxine, J. Nutr. Sci.
Vitaminol. 28 (1982) 359-366. 10.3177/jnsv.28.359.
[5]
K. Ogata, Y. Tani, Y. Uchida, T. Tochikura, Microbial formation of pyridoxine glucoside, a new
derivative of vitamin B6, Biochim. Biophys. Acta. 165 (1968) 578-579.
10.1016/0304-4165(68)90249-3.
[6]
[7]
[8]
F. Kawai, H. Yamada, K. Ogata, Studies on Transglycosidation to Vitamin B6 by Microorganisms,
Agric. Biol. Chem. 35 (1971) 1660-1667.
F. Kawai, H. Yamada, K. Ogata, Studies on Transglycosidation to Vitamin B6 by Microorganisms,
Agric. Biol. Chem. 35 (1971) 184-190. 10.1271/bbb1961.35.184.
K. Ogata, Y. Tani, Y. Uchida, T. Tochikura, Studies on transglycosidation to vitamin B6 by
microorganisms. I. Formation of a new vitamin B6 derivative, pyridoxine glucoside, by Sarcina lutea,
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