Synthesis and antitumor activity of novel pyridoxine-based structural analogs of saccharumoside-B

Article abstract of DOI:10.1007/s00044-021-02719-4

A series of 11 new pyridoxine-based structural analogs of saccharumoside-B were obtained using original synthetic approach. Antitumor activity of these compounds against nine human tumor cell lines (MCF-7, MDA-MB-231, A-498, SNB-19, M-14, NCI-H322M, HCT-115, HCT-116, and PC-3) was studied, and cytotoxic activity to three normal (HEK-293, Chang Liver, and MSC) cell lines was evaluated. Among the synthesized compounds, 12d, 12e, 13b, 13d, 13e, and 14 exhibited the highest antitumor activity, comparable to that of camptothecin and doxorubicin, but with significantly increased selectivity toward tumor cells. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s00044-021-02719-4

MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research (2021) 30:1139–1150
https://doi.org/10.1007/s00044-021-02719-4
ORIGINAL RESEARCH
Synthesis and antitumor activity of novel pyridoxine-based
structural analogs of saccharumoside-B
Mikhail V. Pugachev1 Maria N. Agafonova1 Oksana A. Bastrikova1 Oleg I. Gnezdilov2 Tatyana V. Nikishova1
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Konstantin V. Balakin1 Yurii G. Shtyrlin
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Received: 11 February 2021 / Accepted: 10 March 2021 / Published online: 25 March 2021
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021
Abstract
A series of 11 new pyridoxine-based structural analogs of saccharumoside-B were obtained using original synthetic
approach. Antitumor activity of these compounds against nine human tumor cell lines (MCF-7, MDA-MB-231, A-498,
SNB-19, M-14, NCI-H322M, HCT-115, HCT-116, and PC-3) was studied, and cytotoxic activity to three normal (HEK-
293, Chang Liver, and MSC) cell lines was evaluated. Among the synthesized compounds, 12d, 12e, 13b, 13d, 13e, and 14
exhibited the highest antitumor activity, comparable to that of camptothecin and doxorubicin, but with significantly
increased selectivity toward tumor cells.
Graphical Abstract
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Keywords Drug discovery Pyridoxine Vitamin B6 Saccharumoside-B Antitumor activity Cytotoxicity
Introduction
[4, 5], fungicidal [6], antiviral [7], etc. A wide number of
glycosides described in previous studies showed promising
antitumor activity [8–19]. Saccharumoside-B (Fig. 1A), a
phenolic glycoside isolated from Sugar Maple (Acer sac-
charum) bark, also demonstrated promising antitumor
effects [20]. In particular, saccharumoside-B and its deri-
vatives (Fig. 1B) showed high antiproliferative activity
against various tumor cell lines (MCF-7, HL-60, MIA
PaCa-2, DU145, HeLa, CaCo-2, and MCF10A) with IC50
values ranged from 4.43 0.35 to 49.63 3.59 μM,
and low cytotoxicity to normal cells (IC50 > 100 μM) [21].
Among the described compounds, a structural analog of
saccharumoside-B containing a p-fluorobenzoyl fragment
(Fig. 1B) exhibited the highest antiproliferative activity
against MCF-7 and HL-60 cells with IC50 6.13 0.64 and
4.43 0.35 μM, respectively, and showed comparable
activity with сamptothecin. The mechanistic studies
of the lead compound showed that it caused arrest of
the cell cycle at G0/G1 phase, apoptotic population
Natural glycosides provide viable starting points for med-
icinal chemistry modification due to their wide spectrum of
biological activities, such as anti-inflammatory and anti-
pyretic (e.g., salicin) [1, 2], antiseptic (e.g., arbutin) [3],
antidepressant and anxiolytic (e.g., salidroside, rosavin)
Supplementary information The online version contains
supplementary material available at https://doi.org/10.1007/s00044-
021-02719-4.
* Yurii G. Shtyrlin
yurii.shtyrlin@kpfu.ru
1
Kazan (Volga region) Federal University, Kremlyovskaya 18,
Kazan 420008, Russia
2
Zavoisky Physical-Technical Institute, FRC Kazan Scientific
Center, Russian Academy of Sciences, Kazan 420111, Russia

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Medicinal Chemistry Research (2021) 30:1139–1150
Fig. 1 A Structure of saccharumoside-B; B Structures of bioisosteric analogs of saccharumoside-B; C Structures of pyridoxine-based analogs of
saccharumoside-B obtained in this work
elevation, mitochondrial membrane potential loss, increase
of cytosolic cytochrome c and Bax levels, decrease of Bcl-2
levels, and increase of caspase-9 and caspase-3 activities in
MCF-7 and HL-60 cells. These results demonstrated antic-
ancer and apoptosis-inducing potentials of the structural
analogs of saccharumoside-B [21].
Materials and methods
Chromatographic purification of compounds was carried out
using column chromatography on Acros silica gel (60–200
mesh). Reaction progress and purity of compounds were
monitored by TLC on Sorbfil PTLC-AF-A-UF plates.
Melting points of the products were determined using a
Stanford Research Systems MPA-100 OptiMelt appliance.
1H, 13C, HSQC, COSY NMR spectra were recorded on a
Bruker Avance 400 spectrometer (400.17 and 100.62 MHz).
Signals of chloroform-d (δH 7.24, δC 77.23), dimethyl sulf-
oxide-d6 (δH 2.50, δC 39.51), and methanol-d4 (δH 3.31, 4.87
Several pyridoxine derivatives were described as
active antitumor agents [22]. In addition to its inherent
activity, pyridoxine scaffold provides rich opportunities
for the design of bioisosteric modifications of various
biologically active molecules. For example, in our recent
work, two series of pyridoxine-containing bioisosteric
analogs of a natural biologically active compound,
dehydrosingerone (DZG), were synthesized by replacing
the aromatic fragment of DZG with the pyridoxine ring
[23]. The most active compounds had pronounced cyto-
toxicity comparable to doxorubicin with improved
selectivity towards tumor cells. They also were much
more cytotoxic than DZG but, at the same time, demon-
strated clear similarities in the mechanisms of cytotoxic
action. In another work [24, 25], a series of novel
pyridoxine-based bioisosteric analogs of trans-stilbenes
were synthesized, which showed high specificity and
antiproliferative activity against estrogen-dependent
tumor cells MCF-7 (ER+) (IC50 < 5 μM), as well as a
higher therapeutic index compared to the reference
compound raloxifene (69 versus 1.4). These examples
demonstrate that the pyridoxine-based bioisosteric mod-
ification of various pharmacophores can significantly
improve their activity and safety profile.
δC 49.00) were used as references in the H and 13C NMR
1
spectra. Coupling constants (J) are reported in Hz (splitting
abbreviations: s, singlet; d, doublet; t, triplet; m, multiplet; br,
broad; and combinations thereof). HPLC/MS-experiment
was carried out using a TripleTOF 5600, AB Sciex superhigh
resolution mass spectrometer (Germany) from the solution in
methanol by turboionic spray (TIS) ionization method with
the collision energy with nitrogen molecules of 10 eV. The
compounds were analyzed by FTIR spectroscopy in atte-
nuated total internal reflection mode on a Frontier spectro-
meter (PerkinElmer) in the range of 400–4000 cm−1 (the
resolution was 1 cm−1, and the number of scans was 20). For
analyzing optically active substances, “ADP 440” (B + S)
polarimeter was used.
Synthesis
General method of synthesis of benzoyl chlorides (5a–5c)
To further explore biological activity potential of the
interesting natural pharmacophore represented by
saccharumoside-B and its analogs (Fig. 1A, B), in this
work, we synthesized a series of their new pyridoxine-based
structural modifications (Fig. 1C) and studied their anti-
tumor activity and cytotoxicity.
The aromatic carboxylic acid 4a–4c (3.00 g) was dis-
solved in 12 mL of SOCl2 and refluxed for 2 h. Excess of
SOCl2 was removed under vacuum, and the obtained
residue was used at the next step without further
purification.

Medicinal Chemistry Research (2021) 30:1139–1150
1141
1
(6-Formyl-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]
pyridin-9-yl)-2,3,4,6-tetra-O-acetyl-β-D-glucopyranoside
(10) (1) Phase-transfer catalyst Aliquat-336 (Starks’ cata-
lyst) (0.97 g, 2.41 mmol), compound 2 (2.97 g, 7.22 mmol),
and a solution of K2CO3 (1.00 g, 7.22 mmol) in 15 mL of
water were added sequentially to a solution of compound 9
(1.14 g, 4.81 mmol) in 15 mL of CHCl3. The reaction mix-
ture was stirred for 6 h at 45 °С. Then the organic part was
separated and dried in vacuo. The dry residue was dissolved
in methylene chloride and purified using column chromato-
graphy (eluent acetonitrile-methylene chloride 1:7, v/v).
White amorphous solid; yield 92% (0.76 g). H NMR
(DMSO-d6, 400 MHz) δ 1.43 (s, 6H, С(CH3)2), 2.57 (s, 3H,
CH3), 3.13 (m, 2H, 2CHO), 3.28 (m, 2H, 2CHO), 3.43 (m,
1H, CH2OH), 3.64 (dd, 1H, 2JHH = 11.4 Hz, 3JHH = 4.3 Hz,
CH2OH), 4.45 (t, 1H, 3JHH = 5.1 Hz, CH2OH), 4.58 (d, 1H,
3JHH = 7.3 Hz, OCHO), 4.94 (d, 1H, JHH = 16.8 Hz,
2
3
CH2O), 5.04 (d, 1H, JHH = 2.5 Hz, CHOH), 5.14 (d, 1H,
2JHH = 16.8 Hz, CH2O), 5.14 (d, 1H, JHH = 4.6 Hz,
3
2
CHOH), 5.15 (d, 1H, JHH = 18.5 Hz, CH2O), 5.19 (d,
2
3
1H, JHH = 18.5 Hz, CH2O), 5.63 (d, 1H, JHH = 4.7 Hz,
CHOH), 9.93 (s, 1Н, C(O)H). 13С NMR (DMSO-d6,
400 MHz) δ 19.6 (CH3), 23.5 (С(CH3)2), 23.6 (С(CH3)2),
58.9 (CH2O), 59.8 (CH2O), 61.1 (CH2O), 69.8 (CHO), 73.9
(CHO), 76.2 (CHO), 77.0 (CHO), 102.2 (С(CH3)2), 104.9
(OCHO), 136.6 (CPyr), 143.4 (CPyr), 143.9 (CPyr), 150.7
(CPyr), 151.6 (CPyr), 194.8 (C(O)H). HRMS (ESI+) m/z
calcd for C18H26NO9 400.1602, found 400.1610 (М + H+).
1
White crystals; yield 80% (2.19 g); mp 91 °C. H NMR
(CDCl3, 400 MHz) δ 1.46 (s, 3H, С(CH3)2), 1.49 (s, 3H, С
(CH3)2), 2.03 (s, 6H, 2CH3С(О)O), 2.04 (s, 3H, CH3С(О)
O), 2.15 (s, 3H, CH3С(О)O), 2.55 (s, 3H, CH3), 3.60 (ddd,
1H,
3JHH = 9.6 Hz,
3JHH = 5.5 Hz,
3JHH = 2.2 Hz,
2
3
CHCH2O), 4.08 (dd, 1H, JHH = 12.3 Hz, JHH = 2.2 Hz,
CHCH2O), 4.22 (dd, 1H, JHH = 12.3 Hz, JHH = 5.5 Hz,
CHCH2O), 4.78 (d, 1H, JHH = 7.8 Hz, OCHO), 4.89 (d,
1H, JHH = 16.5 Hz, CH2O), 4.99 (d, 1H, JHH = 16.5 Hz,
2
3
3
General method of synthesis of compounds 12a–12e
2
2
3
CH2O), 5.15, (t, 1H, JHH = 9.6 Hz, CHO), 5.24 (d, 1H,
Me2SnCl2 (0.044 g, 0.20 mmol) was added to a solution of
compound 11 (0.80 g, 2.01 mmol) in 20 mL of THF. The
reaction was stirred for 10 min at room temperature, then
DIPEA (0.70 mL, 4.02 mmol) and benzoyl chloride 5a–5e
(2.01 mmol) were sequentially added at 0 °C. After stirring
at 0 °C for 1 h and then at room temperature for 1 h, the
reaction was quenched with methanol, and then the result-
ing mixture was evaporated under reduced pressure. The
product was purified by column chromatography (eluent
methanol–methylene chloride 1:15, v/v).
2JHH = 17.8 Hz, CH2O), 5.27 (t, 1H, JHH = 9.6 Hz, CHO),
3
2
3
5.33 (d, 1H, JHH = 17.8 Hz, CH2O), 5.35 (dd, 1H, JHH
=
9.6 Hz, JHH = 7.8 Hz, CHO), 10.05 (s, 1Н, C(O)H). 13С
NMR (CDCl3, 400 MHz) δ 19.1 (CH3), 20.3 (CH3С(О)O),
20.4 (2CH3С(О)O), 20.5 (CH3С(О)O), 23.3 (С(CH3)2),
23.4 (С(CH3)2), 58.5 (CH2O), 59.9 (CH2O), 61.9 (CH2O),
68.1 (CHO), 70.7 (CHO), 71.0 (CHO), 71.8 (CHO), 100.4
(С(CH3)2), 102.2 (OCHO), 136.6 (CPyr), 143.6 (CPyr), 144.6
(CPyr), 149.3 (CPyr), 150.8 (CPyr), 169.1 (CH3С(О)O), 169.4
(CH3С(О)O), 169.7 (CH3С(О)O), 170.1 (CH3С(О)O),
194.8 (C(O)H). HRMS (ESI+) m/z calcd for C26H34NO13
568.2025, found 568.2030 (М + H+).
3
(6-Formyl-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]
pyridin-9-yl)-6-O-benzoyl-β-D-glucopyranoside (12a) This
compound was obtained using the general method with
benzoyl chloride (0.23 mL, 2.01 mmol).
(2) Tetra-n-butylammonium bromide (0.77 g, 2.41 mmol),
compound 2 (2.97 g, 7.22 mmol), and a solution of K2CO3
(1.00 g, 7.22 mmol) in 15 mL of water were added sequen-
tially to a solution of compound 9 (1.14 g, 4.81 mmol) in
15 mL of CHCl3. The reaction mixture was stirred for 6 h at
45 °С. Then the organic part was separated and dried in vacuo.
The dry residue was dissolved in methylene chloride and
purified using column chromatography (eluent acetonitrile-
methylene chloride 1:7, v/v). Yield 87% (2.38 g).
1
White amorphous solid; yield 81% (0.82 g). H NMR
(DMSO-d6, 400 MHz) δ 1.25 (s, 3H, С(CH3)2), 1.37 (s, 3H,
С(CH3)2), 2.52 (s, 3H, CH3), 3.32 (m, 3H, 3CHO), 3.52 (m,
1H, CHO), 4.26 (dd, 1H, JHH = 11.6 Hz, JHH = 6.6 Hz,
CHCH2O), 4.54 (d, 1H, JHH = 11.6 Hz, CHCH2O), 4.72
(d, 2H, JHH = 7.2 Hz, OCHO), 4.93 (d, 1H, JHH
2
3
2
3
2
=
2
16.6 Hz, CH2O), 5.03 (d, 1H, JHH = 16.6 Hz, CH2O),
5.11 (s, 2H, CH2O), 5.31 (d, 1H, JHH = 1.9 Hz, CHOH),
3
3
3
(6-Formyl-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]
pyridin-9-yl)-β-D-glucopyranoside (11) A solution of
K2CO3 (0.57 g, 4.12 mmol) in 2 mL of water was added to a
solution of compound 10 (1.17 g, 2.06 mmol) in 20 mL of
methanol. The reaction mixture was stirred at room tem-
perature for 1 h. Then the solvents were evaporated under
reduced pressure at 45 °C, and the product was purified by
column chromatography (eluent ethanol–methylene chlor-
ide 1:4, v/v).
5.43 (d, 1H, JHH = 2.9 Hz, CHOH), 5.75 (d, 1H, JHH
=
4.5 Hz, CHOH), 7.45 (t, 2H, 3JHH = 7.5 Hz, 2CHAr), 7.63 (t,
3
3
1H, JHH = 7.5 Hz, CHAr), 7.83 (d, 2H, JHH = 7.5 Hz,
2CHAr), 9.90 (s, 1H, C(O)H). 13С NMR (DMSO-d6,
400 MHz) δ 19.3 (CH3), 23.3 (С(CH3)2), 23.4 (С(CH3)2),
58.5 (CH2O), 59.9 (CH2O), 63.9 (CH2O), 69.9 (CHO), 73.7
(CHO), 73.8 (CHO), 75.9 (CHO), 102.0 (С(CH3)2), 104.4
(OCHO), 128.6, 129.2, 129.6, 133.3, 136.4, 143.2, 143.9,
150.3, 151.3 (5CPyr + 6CAr), 165.6 (C(O)O), 194.8 (C(O)

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Medicinal Chemistry Research (2021) 30:1139–1150
H). HRMS (ESI+) m/z calcd for C25H30NO10 504.1864,
found 504.1870 (М + H+).
(6-Formyl-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]
pyridin-9-yl)-6-O-(4-methylbenzoyl)-β-D-glucopyranoside
(12d) This compound was obtained using the general
method with 4-methylbenzoyl chloride (0.27 mL, 2.01 mmol).
(6-Formyl-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]
pyridin-9-yl)-6-O-(4-(benzyloxy)-3-methoxybenzoyl)-β-D-
glucopyranoside (12b) This compound was obtained using
the general method with 4-(benzyloxy)-3-methoxybenzoyl
chloride (0.56 g, 2.01 mmol).
1
White amorphous solid; yield 73% (0.76 g). H NMR
(CDCl3, 400 MHz) δ 1.46 (s, 3H, С(CH3)2), 1.49 (s, 3H, С
(CH3)2), 2.41 (s, 3H, CH3), 2.57 (s, 3H, CH3), 3.30–3.73
2
(m, 7H, CHO + 3CHOH), 4.38 (d, 1H, JHH = 12.3 Hz,
1
3
White amorphous solid; yield 73% (0.94 g). H NMR
CHCH2O), 4.64 (d, 1H, JHH = 7.3 Hz, OCHO), 4.76 (dd,
(DMSO-d6, 400 MHz) δ 1.26 (s, 3H, С(CH3)2), 1.37 (s, 3H,
1H, 2JHH = 12.3 Hz, 3JHH = 3.5 Hz, CHCH2O), 4.95 (d, 1H,
2
С(CH3)2), 2.52 (s, 3H, CH3), 3.32 (m, 3H, 3CHO), 3.52 (m,
2JHH = 16.5 Hz, CH2O), 5.12 (d, 1H, JHH = 16.5 Hz,
2
2
1H, CHO), 3.75 (s, 3H, CH3O), 4.29 (dd, 1H, JHH
=
=
CH2O), 5.23 (d, 1H, JHH = 17.6 Hz, CH2O), 5.31 (d, 1H,
3
2
3
11.7 Hz, JHH = 6.6 Hz, CHCH2O), 4.46 (d, 1H, JHH
2JHH = 17.6 Hz, CH2O), 7.21 (d, 2H, JHH = 8.0 Hz,
3
3
11.7 Hz, CHCH2O), 4.73 (d, 1H, JHH = 7.1 Hz, OCHO),
2CHAr), 7.87 (d, 2H, JHH = 8.0 Hz, 2CHAr), 10.02 (s, 1H,
2
2
4.93 (d, 1H, JHH = 16.7 Hz, CH2O), 4.99 (d, 1H, JHH
=
C(O)H). 13С NMR (CDCl3, 400 MHz) δ 19.6 (CH3), 21.9
(CH3), 23.7 (С(CH3)2), 23.9 (С(CH3)2), 59.3 (CH2O), 61.0
(CH2O), 62.9 (CH2O), 69.6 (CHO), 74.1 (CHO), 74.8
(CHO), 75.7 (CHO), 102.7 (С(CH3)2), 103.9 (OCHO),
126.4, 129.4, 130.1, 137.4, 144.7, 147.9, 150.0, 151.3
(5CPyr + 6CAr), 167.7 (C(O)O), 195.3 (C(O)H). HRMS
(ESI+) m/z calcd for C26H32NO10 518.2021, found
518.2026 (М + H+).
16.7 Hz, CH2O), 5.10 (s, 2H, CH2O), 5.15 (s, 2H, CH2O),
3
3
5.27 (d, 1H, JHH = 4.0 Hz, CHOH), 5.39 (d, 1H, JHH
=
3
4.8 Hz, CHOH), 5.72 (d, 1H, JHH = 4.5 Hz, CHOH), 7.06
(d, 1H, JHH = 8.5 Hz, CHAr), 7.35-7.48 (m, 7H, 7CHAr),
3
9.88 (s, 1H, C(O)H). 13С NMR (DMSO-d6, 400 MHz) δ
19.3 (CH3), 23.3 (С(CH3)2), 23.5 (С(CH3)2), 55.5 (CH3O),
58.4 (CH2O), 59.9 (CH2O), 63.6 (CH2O), 69.9 (CHO), 73.9
(CHO), 75.9 (CHO), 79.2 (CH2O), 102.0 (С(CH3)2), 104.4
(OCHO), 111.9, 112.3, 122.0, 123.0, 128.0, 128.1,
128.5, 136.4, 143.0, 143.8, 148.5, 150.3, 151.3, 151.9
(5CPyr + 12CAr), 165.3 (C(O)O), 194.8 (C(O)H). HRMS
(ESI+) m/z calcd for C33H38NO12 640.2389, found
640.2395 (М + H+).
(6-Formyl-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]
pyridin-9-yl)-6-O-(4-fluorobenzoyl)-β-D-glucopyranoside
(12e) This compound was obtained using the general
method with 4-fluorobenzoyl chloride (0.24 mL,
2.01 mmol).
1
White amorphous solid; yield 75% (0.78 g). H NMR
(6-Formyl-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxepino[5,6-c]
pyridin-9-yl)-6-O-(3,4-dimethoxybenzoyl)-β-D-glucopyrano-
side (12c) This compound was obtained using the general
method with 3,4-dimethoxybenzoyl chloride (0.40 g,
2.01 mmol).
(CDCl3, 400 MHz) δ 1.42 (s, 3H, С(CH3)2), 1.48 (s, 3H, С
(CH3)2), 2.55 (s, 3H, CH3), 3.43–3.73 (m, 7H, CHO +
3CHOH), 4.48 (d, 1H, JHH = 12.0 Hz, CHCH2O), 4.63 (d,
2
3
2
1H, JHH = 7.5 Hz, OCHO), 4.67 (dd, 1H, JHH = 12.0 Hz,
3JHH = 4.2 Hz, CHCH2O), 4.94 (d, 1H, JHH = 16.5 Hz,
2
1
2
White amorphous solid; yield 81% (0.92 g). H NMR
CH2O), 5.10 (d, 1H, JHH = 16.5 Hz, CH2O), 5.23 (d, 1H,
2
(CDCl3, 400 MHz) δ 1.46 (s, 3H, С(CH3)2), 1.50 (s, 3H, С
(CH3)2), 2.61 (s, 3H, CH3), 3.40–3.49 (m, 2H, 2CHO),
3.64–3.75 (m, 2H, 2CHO), 3.92 (s, 3H, CH3O), 3.96 (s, 3H,
2JHH = 17.6 Hz, CH2O), 5.30 (d, 1H, JHH = 17.6 Hz,
3
3
CH2O), 7.08 (t, 2H, JHH = 8.5 Hz, JHF = 8.5 Hz, 2CHAr),
3
4
7.98 (dd, 2H, JHH = 8.5 Hz, JHF = 5.5 Hz, 2CHAr), 10.02
(s, 1H, C(O)H). 13С NMR (CDCl3, 400 MHz) δ 19.6 (CH3),
23.7 (С(CH3)2), 23.9 (С(CH3)2), 59.3 (CH2O), 61.0
(CH2O), 63.4 (CH2O), 69.8 (CHO), 74.0 (CHO), 74.6
(CHO), 75.8 (CHO), 102.8 (С(CH3)2), 103.9 (OCHO),
2
CH3O), 4.32 (d, 1H, JHH = 12.4 Hz, CHCH2O), 4.66 (d,
3
2
1H, JHH = 7.3 Hz, OCHO), 4.83 (d, 1H, JHH = 12.4 Hz,
2
CHCH2O), 4.97 (d, 1H, JHH = 16.5 Hz, CH2O), 5.12 (d,
2
2
1H, JHH = 16.5 Hz, CH2O), 5.25 (d, 1H, JHH = 17.4 Hz,
2
2
4
CH2O), 5.32 (d, 1H, JHH = 17.4 Hz, CH2O), 7.86 (d, 1H,
115.9 (d, JFC = 22.0 Hz, 2CHAr), 125.5 (d, JFC = 2.7 Hz,
CAr), 132.6 (d, JFC = 9.4 Hz, 2CHAr), 137.4 (CPyr), 144.0
3JHH = 8.4 Hz, CHAr), 7.51 (br s, 1H, CHAr), 7.63 (d, 1H,
3JHH = 8.4 Hz, CHAr), 10.04 (s, 1H, C(O)H). 13С NMR
(DMSO-d6, 400 MHz) δ 19.3 (CH3), 23.3 (С(CH3)2), 23.5
(С(CH3)2), 55.4 (CH3O), 55.7 (CH3O), 58.4 (CH2O), 59.9
(CH2O), 63.6 (CH2O), 69.9 (CHO), 73.9 (CHO), 75.9
(CHO), 102.0 (С(CH3)2), 104.4 (OCHO), 110.8, 111.6,
121.7, 123.2, 136.5, 143.0, 143.8, 148.3, 150.3, 151.3,
152.9 (5CPyr + 6CAr), 165.3 (C(O)O), 194.8 (C(O)H).
HRMS (ESI+) m/z calcd for C27H34NO12 564.2076, found
564.2081 (М + H+).
3
(CPyr), 144.9 (CPyr), 150.0 (CPyr), 151.2 (CPyr), 166.3 (d,
1JFC = 255.5 Hz, CAr), 166.4 (C(O)O), 195.2 (C(O)H).
HRMS (ESI+) m/z calcd for C25H29FNO10 522.1770, found
522.1775 (М + H+).
General method of synthesis of compounds 13a–13e
NaBH4 (1 eq) was added portionwise to a solution of
compound 12a–12e (1 eq) in 20 mL of methanol at 0 °C.

Medicinal Chemistry Research (2021) 30:1139–1150
1143
After stirring at room temperature for 20 min, the solution
was neutralized with an aqueous solution of hydrochloric
acid to pH = 7. Then the solvent was removed in vacuo, and
the residue was purifed by column chromatography (eluent
ethanol–methylene chloride 1:8, v/v).
7H, 7CHAr). 13С NMR (DMSO-d6, 400 MHz) δ 19.2 (CH3),
23.4 (С(CH3)2), 23.5 (С(CH3)2), 55.5 (CH3O), 58.7
(CH2O), 59.9 (CH2O), 63.5 (CH2O), 63.6 (CH2O), 69.9
(CHO), 73.7 (CHO), 73.9 (CHO), 75.9 (CHO), 77.2
(CH2O), 101.7 (С(CH3)2), 104.5 (OCHO), 111.9, 112.5,
122.0, 123.1, 128.0, 128.1, 128.5, 131.3, 136.5, 141.9,
147.0, 148.5, 148.6, 151.3, 151.9 (5CPyr + 12CAr), 165.3 (C
(O)O). HRMS (ESI+) m/z calcd for C33H40NO12 642.2545,
found 642.2553 (М + H+).
(6-(Hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxe-
pino[5,6-c]pyridin-9-yl)-6-O-benzoyl-β-D-glucopyranoside
(13a) This compound was obtained using the general
method with compound 12a (0.80 g, 1.59 mmol) and
NaBH4 (0.060 g, 1.59 mmol).
(6-(Hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxe-
pino[5,6-c]pyridin-9-yl)-6-O-(3,4-dimethoxybenzoyl)-β-D-
glucopyranoside (13c) This compound was obtained using
the general method with compound 12c (0.60 g, 1.07 mmol)
and NaBH4 (0.041 g, 1.07 mmol).
White amorphous solid; yield 68% (0.55 g); ½αŠ25 − 7.9°
D
(c 0.047, methanol); IR (neat) νmax 3000, 2930, 1722, 1604,
1587, 1453, 1379, 1357, 1276, 1220, 1067, 1028, 834,
713 cm−1; 1H NMR (DMSO-d6, 400 MHz) δ 1.20 (s, 3H, С
(CH3)2), 1.34 (s, 3H, С(CH3)2), 2.41 (s, 3H, CH3), 3.31 (m,
White amorphous solid; yield 72% (0.43 g); ½αŠ25 − 18.3°
D
2
3H, 3CHO), 3.45 (m, 1H, CHO), 4.21 (dd, 1H, JHH
=
=
(c 0.033, methanol); IR (neat) νmax 3000, 2925, 1715, 1603,
1517, 1458, 1420, 1379, 1355, 1271, 1220, 1071, 1023,
835, 763, 627 cm−1; 1H NMR (DMSO-d6, 400 MHz) δ 1.23
(s, 3H, С(CH3)2), 1.35 (s, 3H, С(CH3)2), 2.41 (s, 3H, CH3),
3.30 (m, 3H, 3CHO), 3.44 (m, 1H, CHO), 3.76 (s, 3H,
3
3
11.6 Hz, JHH = 5.9 Hz, CHCH2O), 4.45 (d, 2H, JHH
4.8 Hz, CH2OH), 4.53–4.59 (br m, 2H, CHCH2O +
2
OCHO), 4.82 (d, 1H, JHH = 17.0 Hz, CH2O), 4.84 (d,
2
2
1H, JHH = 16.7 Hz, CH2O), 4.86 (d, 1H, JHH = 17.0 Hz,
2
2
CH2O), 5.00 (d, 1H, JHH = 16.7 Hz, CH2O), 5.11 (t, 1H,
CH3O), 3.83 (s, 3H, CH3O), 4.21 (dd, 1H, JHH = 11.8 Hz,
3JHH = 4.8 Hz, CH2OH), 5.26 (br s, 1H, CHOH), 5.39 (br s,
3JHH = 5.7 Hz, CHCH2O), 4.44 (d, 2H, JHH = 4.7 Hz,
3
3
2
1H, CHOH), 5.69 (br s, 1H, CHOH), 7.50 (t, 2H, JHH
=
CH2OH), 4.49 (d, 1H, JHH = 11.8 Hz, CHCH2O), 4.57
3
3
2
7.5 Hz, 2CHAr), 7.65 (t, 1H, JHH = 7.5 Hz, CHAr), 7.86 (d,
(d, 1H, JHH = 5.6 Hz, OCHO), 4.81 (d, 1H, JHH =
2H, JHH = 7.5 Hz, 2CHAr). 13С NMR (DMSO-d6,
18.6 Hz, CH2O), 4.85 (d, 1H, JHH = 18.6 Hz, CH2O),
4.86 (d, 1H, JHH = 16.6 Hz, CH2O), 4.98 (d, 1H, JHH =
16.6 Hz, CH2O), 5.13 (t, 1H, JHH = 4.7 Hz, CH2OH), 5.25
3
2
2
2
400 MHz) δ 19.1 (CH3), 23.4 (С(CH3)2), 23.5 (С(CH3)2),
58.8 (CH2O), 59.9 (CH2O), 63.6 (CH2O), 63.9 (CH2O),
69.9 (CHO), 73.6 (CHO), 73.9 (CHO), 75.9 (CHO), 101.8
(С(CH3)2), 104.5 (OCHO), 128.7, 129.2, 129.6, 131.4,
142.0, 147.0, 148.4, 151.5 (5CPyr + 6CAr), 165.7 (C(O)O).
HRMS (ESI+) m/z calcd for C25H32NO10 506.2021, found
506.2029 (М + H+).
3
(br s, 1H, CHOH), 5.37 (br s, 1H, CHOH), 5.68 (br s, 1H,
3
CHOH), 7.04 (d, 1H, JHH = 8.4 Hz, CHAr), 7.36 (br s, 1H,
3
CHAr), 7.47 (d, 1H, JHH = 8.4 Hz, CHAr). 13С NMR
(DMSO-d6, 400 MHz) δ 19.2 (CH3), 23.4 (С(CH3)2), 23.5
(С(CH3)2), 55.4 (CH3O), 55.7 (CH3O), 58.7 (CH2O), 59.9
(CH2O), 63.5 (CH2O), 63.6 (CH2O), 69.9 (CHO), 73.7
(CHO), 73.9 (CHO), 75.9 (CHO), 101.8 (С(CH3)2), 104.5
(OCHO), 111.0, 111.5, 121.8, 123.3, 131.4, 141.9, 147.0,
148.3, 148.5, 151.38, 152.9 (5CPyr + 6CAr), 165.4 (C(O)O).
HRMS (ESI+) m/z calcd for C27H36NO12 566.2232, found
566.2238 (М + H+).
(6-(Hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxe-
pino[5,6-c]pyridin-9-yl)-6-O-(4-(benzyloxy)-3-methoxyben-
zoyl)-β-D-glucopyranoside (13b) This compound was
obtained using the general method with compound 12b
(0.75 g, 1.17 mmol) and NaBH4 (0.045 g, 1.17 mmol).
White amorphous solid; yield 81% (0.61 g); ½αŠ25 − 22.9°
D
(c 0.016, methanol). 1H NMR (DMSO-d6, 400 MHz) δ 1.21
(s, 3H, С(CH3)2), 1.35 (s, 3H, С(CH3)2), 2.41 (s, 3H, CH3),
3.30 (m, 3H, 3CHO), 3.44 (m, 1H, CHO), 3.77 (s, 3H,
(6-(Hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxe-
pino[5,6-c]pyridin-9-yl)-6-O-(4-methylbenzoyl)-β-D-gluco-
pyranoside (13d) This compound was obtained using the
general method with compound 12d (0.40 g, 0.77 mmol)
and NaBH4 (0.029 g, 0.77 mmol).
2
3
CH3O), 4.21 (dd, 1H, JHH = 11.8 Hz, JHH = 5.9 Hz,
3
CHCH2O), 4.45 (d, 2H, JHH = 5.3 Hz, CH2OH), 4.49
(dd, 1H, JHH = 11.8 Hz, JHH = 1.0 Hz, CHCH2O), 4.57
White amorphous solid; yield 50% (0.20 g); ½αŠ25 − 22.8°
2
3
D
3
2
(d, 1H, JHH = 6.7 Hz, OCHO), 4.80 (d, 1H, JHH
17.1 Hz, CH2O), 4.85 (d, 1H, JHH = 17.1 Hz, CH2O),
4.85 (d, 1H, JHH = 16.6 Hz, CH2O), 4.98 (d, 1H, JHH
16.6 Hz, CH2O), 5.12 (t, 1H, JHH = 5.3 Hz, CH2OH), 5.18
=
(c 0.005, methanol); IR (neat) νmax 3000, 2933, 1720, 1614,
1449, 1379, 1376, 1276, 1220, 1070, 1042, 1000, 836,
754 cm−1; 1H NMR (DMSO-d6, 400 MHz) δ 1.23 (s, 3H, С
(CH3)2), 1.35 (s, 3H, С(CH3)2), 2.38 (s, 3H, CH3), 2.40 (s,
3H, CH3), 3.32 (m, 3H, 3CHO), 3.43 (m, 1H, CHO), 4.18
2
2
2
=
3
3
(s, 2H, CH2O), 5.23 (d, 1H, JHH = 1.4 Hz, CHOH), 5.35
(d, 1H, 3JHH = 3.8 Hz, CHOH), 5.66 (d, 1H, 3JHH = 4.0 Hz,
(dd, 1H, JHH = 11.8 Hz, JHH = 6.0 Hz, CHCH2O), 4.45
2
3
3
3
2
CHOH), 7.13 (d, 1H, JHH = 8.5 Hz, CHAr), 7.34–7.48 (m,
(d, 2H, JHH = 5.4 Hz, CH2OH), 4.54 (d, 1H, JHH =

1144
Medicinal Chemistry Research (2021) 30:1139–1150
3
11.8 Hz, CHCH2O), 4.55 (d, 1H, JHH = 6.0 Hz, OCHO),
atm pressure for 4 h. Then the precipitate was filtered off,
and the filtrate was evaporated under reduced pressure. The
crude was purified by using column chromatography (eluent
ethanol–methylene chloride 1:6, v/v).
2
2
4.82 (d, 1H, JHH = 16.4 Hz, CH2O), 4.84 (d, 1H, JHH
16.7 Hz, CH2O), 4.87 (d, 1H, JHH = 16.4 Hz, CH2O), 5.00
=
2
2
3
(d, 1H, JHH = 16.7 Hz, CH2O), 5.11 (t, 1H, JHH = 5.4 Hz,
CH2OH), 5.23 (d, 1H, 3JHH = 3.2 Hz, CHOH), 5.36 (d, 1H,
White amorphous solid; yield 86% (0.30 g); ½αŠ25 − 16.8°
D
3JHH = 3.9 Hz, CHOH), 5.66 (d, 1H, JHH = 4.3 Hz,
(c 0.005, methanol); IR (neat) νmax 3000, 2934, 1710, 1600,
1517, 1431, 1381, 1375, 1285, 1219, 1070, 1045, 833,
764 cm−1; 1H NMR (DMSO-d6, 400 MHz) δ 1.23 (s, 3H, С
(CH3)2), 1.35 (s, 3H, С(CH3)2), 2.41 (s, 3H, CH3), 3.30 (m,
3H, 3CHO), 3.43 (m, 1H, CHO), 3.77 (s, 3H, CH3O), 4.18
3
3
CHOH), 7.30 (d, 2H, JHH = 8.0 Hz, 2CHAr), 7.75 (d, 2H,
3JHH = 8.0 Hz, 2CHAr). 13С NMR (DMSO-d6, 400 MHz) δ
19.1 (CH3), 21.2 (CH3), 23.4 (С(CH3)2), 23.5 (С(CH3)2),
58.8 (CH2O), 59.9 (CH2O), 63.5 (CH2O), 63.7 (CH2O),
69.8 (CHO), 73.6 (CHO), 73.8 (CHO), 75.9 (CHO), 101.8
(С(CH3)2), 104.5 (OCHO), 126.9, 129.2, 131.4, 141.9,
143.6, 147.0, 148.4, 151.4 (5CPyr + 6CAr), 165.6 (C(O)O).
HRMS (ESI+) m/z calcd for C26H34NO10 520.2177, found
520.2184 (М + H+).
2
3
(dd, 1H, JHH = 11.8 Hz, JHH = 5.9 Hz, CHCH2O), 4.45
3
2
(d, 2H, JHH = 5.4 Hz, CH2OH), 4.48 (dd, 1H, JHH
=
=
3
3
11.8 Hz, JHH = 1.4 Hz, CHCH2O), 4.56 (d, 1H, JHH
2
6.9 Hz, OCHO), 4.80 (d, 1H, JHH = 16.2 Hz, CH2O), 4.86
2
2
(d, 1H, JHH = 16.2 Hz, CH2O), 4.86 (d, 1H, JHH
=
2
16.7 Hz, CH2O), 4.98 (d, 1H, JHH = 16.7 Hz, CH2O),
5.10 (t, 1H, JHH = 5.4 Hz, CH2OH), 5.22 (d, 1H, JHH =
3
3
(6-(Hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxe-
pino[5,6-c]pyridin-9-yl)-6-O-(4-fluorobenzoyl)-β-D-glucopyr-
anoside (13e) This compound was obtained using the
general method with compound 12e (0.40 g, 0.76 mmol)
and NaBH4 (0.029 g, 0.76 mmol).
3
2.3 Hz, CHOH), 5.34 (d, 1H, JHH = 4.2 Hz, CHOH), 5.66
(d, 1H, 3JHH = 4.2 Hz, CHOH), 6.83 (d, 1H, 3JHH = 8.8 Hz,
4
CHAr), 7.36 (d, 1H, JHH = 1.5 Hz, CHAr), 7.37 (dd, 1H,
3JHH = 8.8 Hz, 4JHH = 1.5 Hz, CHAr), 9.97 (s, 1Н, OH). 13С
NMR (DMSO-d6, 400 MHz) δ 19.2 (CH3), 23.4 (С(CH3)2),
23.5 (С(CH3)2), 55.5 (CH3O), 58.8 (CH2O), 59.9 (CH2O),
63.4 (CH2O), 63.5 (CH2O), 69.8 (CHO), 73.7 (CHO), 73.9
(CHO), 75.9 (CHO), 101.8 (С(CH3)2), 104.5 (OCHO),
112.5, 115.1, 120.5, 123.6, 131.4, 141.9, 147.0, 147.3,
148.5, 151.4, 151.5 (5CPyr + 6CAr), 165.5 (C(O)O). HRMS
(ESI+) m/z calcd for C26H34NO12 552.2076, found
552.2084 (М + H+).
White amorphous solid; yield 37% (0.15 g); ½αŠ25 − 4.2°
D
(c 0.005, methanol); IR (neat) νmax 3000, 2931, 1725, 1605,
1510, 1415, 1384, 1358, 1278, 1221, 1070, 1000, 836, 768,
609 cm−1; 1H NMR (DMSO-d6, 400 MHz) δ 1.20 (s, 3H, С
(CH3)2), 1.34 (s, 3H, С(CH3)2), 2.40 (s, 3H, CH3), 3.31 (m,
3H, 3CHO), 3.45 (m, 1H, CHO), 4.21 (dd, 1H, JHH
11.8 Hz, JHH = 6.4 Hz, CHCH2O), 4.45 (d, 2H, JHH
5.3 Hz, CH2OH), 4.51–4.58 (br m, 2H, CHCH2O +
OCHO), 4.82 (d, 1H, JHH = 16.4 Hz, CH2O), 4.84 (d,
1H, JHH = 16.7 Hz, CH2O), 4.87 (d, 1H, JHH = 16.4 Hz,
2
=
=
3
3
2
2
2
Cytotoxicity evaluation
2
CH2O), 4.98 (d, 1H, JHH = 16.7 Hz, CH2O), 5.13 (t, 1H,
3JHH = 5.3 Hz, CH2OH), 5.24 (d, 1H, JHH = 3.1 Hz,
The cytotoxicity was evaluated on MCF-7 (human breast
cancer cells), MDA-MB-231 (human breast cancer cells),
A-498 (human kidney cancer cell), SNB-19 (human glio-
blastoma cell), M-14 (melanoma cell), NCI-H322M (lung
cancer cell), HCT-15 (colon cancer cell), HCT-116 (colon
cancer cell), PC-3 (prostate cancer), HEK-293 (human
embryonic kidney), Chang Liver (human liver), and MSC
(human mesenchymal stem cells) by using MTT assay.
Cells were cultured in a-MEM (minimum essential medium
Eagle)/DMEM (Dulbecco’s modified Eagle’s medium)
supplemented with 10% FBS, 2 mM L-glutamine, 100 μg/
mL penicillin and 100 μg/mL streptomycin. Cells were
seeded in 96-well plates at the density of 10,000 cells per
well and grown overnight at 37 °C and 5% CO2 in humi-
dified atmosphere. Then the medium was changed to the
fresh one containing compounds to be tested in concentra-
tion of 0.1–100 μg/mL. After 72 h of cultivation, the cul-
tural fluid was discarded and MTT solution (in DPBS) was
added to the fresh media until final concentration of 0.5 mg/
mL. After 2 h the liquid was replaced with dimethyl sulf-
oxide (Sigma-Aldrich, St. Louis, MO) to dissolve formazan
3
3
CHOH), 5.37 (d, 1H, JHH = 4.2 Hz, CHOH), 5.67 (d, 1H,
3JHH = 4.4 Hz, CHOH), 7.33 (t, 2H, JHH = 8.5 Hz, JHF
=
3
3
8.5 Hz, 2CHAr), 7.91 (dd, 2H, 3JHH = 8.5 Hz, 4JHF = 5.7 Hz,
2CHAr). 13С NMR (DMSO-d6, 400 MHz) δ 19.1 (CH3),
23.3 (С(CH3)2), 23.5 (С(CH3)2), 58.8 (CH2O), 59.9
(CH2O), 63.5 (CH2O), 64.1 (CH2O), 69.9 (CHO), 73.5
(CHO), 73.8 (CHO), 75.9 (CHO), 101.8 (С(CH3)2), 104.5
2
4
(OCHO), 115.8 (d, JFC = 22.1 Hz, 2CHAr), 126.2 (d, JFC
= 2.5 Hz, CAr), 131.3 (CPyr), 131.3 (d, JFC = 9.6 Hz,
2CHAr), 142.0 (CPyr), 147.0 (CPyr), 148.4 (CPyr), 151.4
3
1
(CPyr), 164.7 (C(O)O), 165.1 (d, JFC = 251.1 Hz, CAr).
HRMS (ESI+) m/z calcd for C25H31FNO10 524.1927, found
524.1936 (М + H+).
(6-(Hydroxymethyl)-3,3,8-trimethyl-1,5-dihydro-[1,3]dioxe-
pino[5,6-c]pyridin-9-yl)-6-O-(4-hydroxy-3-methoxybenzoyl)-
β-D-glucopyranoside (14) Pd/CaCO3 catalyst (5%, 0.04 g)
was added to a solution of compound 13b (0.40 g,
0.62 mmol) in 30 mL of methanol, and the reaction mixture
was stirred at room temperature under H2 atmosphere at 2.2

Medicinal Chemistry Research (2021) 30:1139–1150
1145
Scheme 1 Synthesis of α-D-
acetobromoglucose 2.
Scheme 2 Synthesis of benzoyl
chlorides 5a-5c.
crystals, and absorption was measured on Tecan Infinite
200Pro at 557 nm with reference 700 nm. Based on data
obtained, the CC50 values (concentrations decreasing the
metabolic activity by twofold) were calculated. Experiments
were carried out in biological triplicates (i.e., newly pre-
pared cultures and medium) with independent repeats in
each one. The IC50 and CC50 were calculated by plotting the
log doses vs. inhibition (expressed as a percentage relative
to the control)—variable slope in Prism 6 (GraphPad
Software Inc.).
chloride precursors were obtained using the reported
methods (Schemes 1, 2). In particular, α-D-aceto-
bromoglucose 2 was synthesized by the reaction of pen-
taacetyl-α-D-glucose 1 with HBr in glacial acetic acid
(Scheme 1) [26].
Benzoyl chlorides 5a–5c were obtained from commercial
reagents 3, 3c, and 4a according to Scheme 2. In the first stage,
the hydroxyl group in vanillin 3 was protected with benzyl
chloride to give O-benzyl vanillin 3b [27]. Then the aldehyde
groups of 3b and 3c were oxidized with potassium perman-
ganate in an aqueous solution of acetone to give the corre-
sponding acids 4b and 4c [28, 29]. In the final stage, the
benzoic acids 4a–4c were quantitatively converted to the
corresponding benzoyl chlorides 5a–5c by refluxing in SOCl2.
The synthesis of the target pyridoxine-based structural
analogs of saccharumoside-B is shown in Scheme 3. The key
aldehyde intermediate 9 was obtained in three synthetic steps
from pyridoxine hydrochloride 6 using our reported methods.
Results and discussions
Сhemistry
The synthetic approach to the title compounds is depicted in
Schemes 1–3. The key glucosyl bromide and benzoyl

1146
Medicinal Chemistry Research (2021) 30:1139–1150
Scheme 3 Synthesis of the
target pyridoxine-based
structural analogs of
saccharumoside-B.
Specifically, the cyclic ketal 7 was obtained by the treatment
of 6 with acetone in the presence of hydrochloric acid, and the
6-hydroxymethyl substituted derivative 8 was then obtained
by reaction of 7 with formaldehyde under mild alkaline con-
ditions [30]. The treatment of alcohol 8 with MnO2 in acet-
onitrile led to the corresponding aldehyde 9 [31].
Pyridoxine-containing O-glycoside 10 could be prepared in
80% yield by the phase-transfer reaction of α-D-aceto-
bromoglucose 2 with aldehyde 9 in the presence of K2CO3 and
aliquat-336 in CHCl3:H2O (1:1, v/v). The use of TBAB
instead of aliquat-336 allowed to increase the yield of com-
pound 10 to 87%. The removal of the acetyl groups with a
methanol-water solution (10:1, v/v) of potassium carbonate led
to tetraol 11 in 92% yield. Regioselective O-6 benzoylation of
pyridoxine β-D-glucopyranoside 11 using benzoyl chlorides
5a–5e and Me2SnCl2 as catalyst according to literature
methods with minor modifications [32–34] gave compounds
12a–12e in 73–81% yields. The aldehyde groups of
compounds 12a–12e were reduced by the treatment with
NaBH4 in MeOH to give compounds 13a–13e in 37–81%
yields.
Finally, compound 13b was debenzylated by the treat-
ment with Pd/CaCO3 catalyst under H2 atmosphere
(Scheme 3) to obtain the final product 14 in 86% yield. The
reaction was carried out in methanol at room temperature
and a pressure of 2.2 atm for 4 h.
The structures of the synthesized compounds were con-
1
firmed by IR, HSQC, COSY, H, and 13C NMR spectro-
scopy and mass spectrometry.
For solutions of compounds 10, 11, and 12a–12e in
methanol, we observed gradual changes in the angles of
rotation of the plane of polarization. For example, for com-
pound 12d, the value of this parameter changed from [α]25
=
1
+3.4o to [α]25 = −14.1° 40 min after dissolving. The H
NMR spectrum of 12d recorded in CD3OD showed the
disappearance of signal from the carbonyl group, the

Medicinal Chemistry Research (2021) 30:1139–1150
1147
Scheme 4 Formation of
hemiacetal 15 in a methanolic
solution of aldehyde 12.
appearance of two characteristic singlets at 5.45–5.55 ppm,
and the triplication of all other signals. The 13C NMR
spectrum of 12d in CD3OD showed two singlets at 97 ppm,
and two septet signals at 53 ppm. These observations suggest
the formation of hemiacetal 15 as two diastereomers (Scheme
4). According to spectral data, the ratio of the starting com-
pound 12d and the hemiacetal 15 5 min after dissolution was
4:3, while the final equilibrium at a ratio of 3:5 was achieved
in 19 h. The mass spectral measurements also showed a
molecular peak corresponding to hemiacetal 15.
tumor cell lines, our compounds were slightly less active
than the reference drugs. At the same time, all our com-
pounds were much less toxic to normal cells than camp-
tothecin and doxorubicin, and this effect was most
pronounced for liver cells (CC50 > 100–200 μM). As a
result, all compounds demonstrated significantly higher
values of the therapeutic index compared to reference
drugs (Table 2).
The following structure–activity relationship (SAR)
patterns have been observed. The derivatives of
saccharumozide-B 12 containing a carbonyl group in the
sixth position of pyridoxine show activity comparable to
their reduced forms 13. The H-bond acceptor groups, such
as methoxy, hydroxy or benzyloxy, in the third and the
fourth positions of the benzoyl moiety can be found in the
most active compounds, while compounds with unsub-
stituted benzoyl fragment, such as 12a and 13a, show the
lowest potency against the studied cancer cell lines. How-
ever, the small number of the synthesized compounds
makes it problematic to establish the more reliable SARs.
Further SAR exploration studies of this promising structural
chemotype can be based on biological evaluation of an
extended series of compounds which can be obtained by
varying the cyclic acetal and ketal protecting groups at the
pyridoxine fragment.
Cytotoxicity evaluation
The synthesized pyridoxine-based structural analogs of
saccharumoside-B were evaluated for in vitro cytotoxi-
city against a panel of human tumor and normal cell lines
using MTT assay. Doxorubicin and camptothecin were
used as reference drugs. The screening results are shown
in Table 1.
According to Table 1, most of the new compounds
exhibited moderate to good in vitro cytotoxic activity
against the studied tumor cell lines, with IC50 values ran-
ging from 1.5 to 52 μM. Compounds 12d, 12e, 13b, 13d,
13e, and 14 demonstrated the highest potency with IC50
values ranging from 4.24 to 27.51 μM (12d), 2.17 to
13.82 μM (12e), 1.88 to 16.70 μM (13b), 2.14 to 14.36 μM
(13d), 2.69 to 13.43 μM (13e), and 1.58 to 12.94 μM (14).
Based on direct comparison with camptothecin, all these
compounds were more active than saccharumoside-B for
which IC50 values ranged from 24.90 to 44.67 μM for the
studied tumor cell lines.21 In particular, saccharumoside-B
was five times less active against MCF-7 tumor cells in
comparison with сamptothecin, while сompound 14
showed comparable activity to the reference drug.21
Compounds 12a, 12c and 13a, 13c showed the lowest
activity in the series (IC50 8.86–52.34 μM). Compound
12b was not tested due to solubility and stability issues. It
is noteworthy that all the synthesized pyridoxine-based
structural analogs of saccharumoside-B showed higher
activity against human glioblastoma cell line SNB-19
compared to camptothecin and doxorubicin. For other
Conclusions
An efficient method of synthesis of 11 novel pyridoxine-
based structural analogs of saccharumoside-B was
developed. The obtained compounds were evaluated
in vitro for antitumor activity against a panel of nine
human cancer cell lines. Cytotoxicity of all compounds
against three normal human cell lines was also studied.
Among the synthesized compounds, 12d, 12e, 13b, 13d,
13e, and 14 exhibited the highest antitumor activity,
comparable to that of camptothecin and doxorubicin, but
with the significantly increased selectivity towards tumor
cells. Based on direct comparison with camptothecin, it
can be concluded that the reported compounds represent

1148
Medicinal Chemistry Research (2021) 30:1139–1150

Medicinal Chemistry Research (2021) 30:1139–1150
Table 2 Therapeutic index SI
1149
SI (CC50, HEK-293/IC50)
(CC50/IC50)
Compound
PC-3MDA-MB-231MCF-7M-14SNB-19HCT-116HCT-115A498NCI-H322M
12a
12c
12d
12e
13a
13b
13c
13d
13e
14
3
1
2
2
3
3
2
1
3
3
2
2
1
3
4
3
0
0
1
1
1
1
1
1
3
1
1
1
12 17
19
15
4
12
7
16
9
12
6
15 10
5
2
9
2
8
8
17
2
9
8
2
1
1
2
1
20
1
16
3
6
9
8
7
6
1
1
1
1
1
22
21
16
11
16
0.8
0.9
9
12
12
9
14
8
6
6
9
12
4
9
11 22
8
9
11
Camptothecin0.7 0.6
1.7
1.1
0.9
1.2
0.3
0.6
1.8 0.8
0.4 0.6
Doxorubicin 1
0.4
SI (CC50, MSC/IC50)
Compound
PC-3MDA-MB-231MCF-7M-14SNB-19HCT-116HCT-115A498NCI-H322M
12a
12c
12d
12e
13a
13b
13c
13d
13e
14
3
5
3
6
3
3
2
3
3
4
2
3
3
5
4
4
0
0
1
2
2
3
2
3
9
4
2
4
13 19
21
23
11
24
7
13
11
4
18
14
3
13
10
2
16 11
14 12
8
5
26
6
4
3
12 28
9
14
2
12
2
10
3
9
4
4
3
2
11 31
20
15 31
22
11
23
2
12
9
16
12
13
2.2
1.4
19
8
9
9
8
12
6
8
11
4.2
1.2
13
0.7
0.7
16
Camptothecin1.6 1.6
Doxorubicin 1.2 0.5
4.3 1.9
0.4 0.7
1
Compliance with ethical standards
the improved modifications of saccharumoside-B with the
increased antitumor activity. The mechanistic studies of
the previously described saccharumoside-B analog
showed that it caused arrest of the cell cycle at G0/G1
phase which ultimately led to apoptosis via intrinsic
pathway.21 Considering clear structural similarity of our
active compounds with that agent, we can suggest that
they act via the similar mechanisms, but this hypothesis
requires further investigation that is currently in progress.
In general, the leading compounds described in this work
provide a promising starting point for the design of novel
anticancer drug candidates with the improved efficacy and
safety profiles.
Conflict of interest The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
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