Nitroalkene ring closure route to carbon-linked scaffolds for mimicking α-d-mannopyranosyl natural linkage

Article abstract of DOI:10.1007/s00706-020-02614-5

Abstract: Controlled treatment of 3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-nitro-d-manno-hept-1-enitol with sodium methoxide in methanol was stopped by decationization at a point providing about equimolar mixture of α-d-mannopyranosyl and β-d-mannopyranosyl nitromethanes, from which the target α-anomer was isolated by chemisorption chromatography on a cation exchange resin in the Ba²⁺ form in a 36% yield. Direct reduction of the above mixture with ferrous hydroxide in situ to the corresponding amines, followed by the selective N-acetylation and the analogical chromatographic separation of both pertinent isomers with their stable ring structures gave N-acetyl-C-α-d-mannopyranosyl-methylamine. Alternative stopping of the initial ring forming reaction with acidified methanol at the above given product ratio initiated a subsequent Nef reaction and α-d-mannopyranosyl methanal dimethyl acetal was then chromatographically separated from its β-isomer on an anion exchange resin in the OH^? form. Activations of two latter C-α-d-mannopyranosyl scaffolds by acid hydrolysis into respective reactive free amine or aldehyde forms were developed as well. Detailed reinvestigation of the classical method of preparation of d-mannosyl nitromethanes by thermal dehydration of a 1-deoxy-1-nitroalditol derived from d-mannose showed a maximum occurrence of only 18% of the required α-d-mannopyranosyl anomer. Graphic abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s00706-020-02614-5

Monatshefte für Chemie - Chemical Monthly
https://doi.org/10.1007/s00706-020-02614-5
ORIGINAL PAPER
Nitroalkene ring closure route to carbon‑linked scafolds
for mimicking α‑d‑mannopyranosyl natural linkage
Božena Pribulová1 · Hana Kováčová1 · Jana Jakubčinová1 · Marek Baráth1 · Alexandra Blahušiaková1 ·
Mária Petrušová1 · Ladislav Petruš1
Received: 17 January 2020 / Accepted: 5 May 2020
© Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract
Controlled treatment of 3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-nitro-d-manno-hept-1-enitol with sodium methoxide in
methanol was stopped by decationization at a point providing about equimolar mixture of α-d-mannopyranosyl and β-d-
mannopyranosyl nitromethanes, from which the target α-anomer was isolated by chemisorption chromatography on a cation
exchange resin in the Ba2+ form in a 36% yield. Direct reduction of the above mixture with ferrous hydroxide in situ to the
corresponding amines, followed by the selective N-acetylation and the analogical chromatographic separation of both per-
tinent isomers with their stable ring structures gave N-acetyl-C-α-d-mannopyranosyl-methylamine. Alternative stopping of
the initial ring forming reaction with acidifed methanol at the above given product ratio initiated a subsequent Nef reaction
and α-d-mannopyranosyl methanal dimethyl acetal was then chromatographically separated from its β-isomer on an anion
exchange resin in the OH− form. Activations of two latter C-α-d-mannopyranosyl scafolds by acid hydrolysis into respective
reactive free amine or aldehyde forms were developed as well. Detailed reinvestigation of the classical method of prepara-
tion of d-mannosyl nitromethanes by thermal dehydration of a 1-deoxy-1-nitroalditol derived from d-mannose showed a
maximum occurrence of only 18% of the required α-d-mannopyranosyl anomer.
Graphic abstract
FeSO4
NH4OH
NaOMe
2%
1%
46%
51%
33%
HCl
MeOH
MeOH
30%
A kinetic stage
Overall isolated yields
Keywords C-glycosyl compounds · Cyclizations · d-Mannosyl nitromethanes · Tautomerism · Thermodynamics
Introduction
aldoses and=CHNO2 for glycosyl nitromethanes [1]. Con-
comitant endeavour to generate this acyclic precursor of
d-galactosyl nitromethanes from other starting compounds
than unsubstituted 1-deoxy-1-nitroalditol has led to the dis-
closure of an alternative method of their preparation from a
1-deoxy-1-nitroalditol peracetate by treatment with sodium
methoxide in methanol [1]. Prior to a complete deacetyla-
tion and cyclization of thus formed intermediate nitroalkene,
there temporarily occurs a parallel, 2-O-methoxide addi-
tion–elimination reaction detour. Then, kinetically controlled
intramolecular ring closure of the intermediate nitroalkene
amasses up to 70% of both anomeric d-galactofuranosyl
A recent close reinvestigation of the classical method of
preparation of d-galactosyl nitromethanes by thermal dehy-
dration of a 1-deoxy-1-nitroalditol derived from d-galactose
has revealed that glycosyl nitromethanes undergo a similar
mutarotation like aldoses, namely via the acyclic species
HOCH2-(CHOH)n–CH=X, where the moiety=X is=O for
* Ladislav Petruš
ladislav.petrus@savba.sk
1
Institute of Chemistry, Centre for Glycomics, Slovak
Academy of Sciences, 84538 Bratislava, Slovakia
Vol.:(0123456789)
1 3

B. Pribulová et al.
nitromethanes and fnally the entire mutarotational proce-
dure ends in a thermodynamically equilibrated mixture of all
four anomeric glycosyl nitromethanes with highly prevail-
ing pyrano-equatorial anomer [1]. Previously, the classical
procedure has never been studied in details and was almost
solely used for preparation of the thermodynamically sta-
ble pyrano-equatorial anomers of glycosyl nitromethanes
derived from naturally common hexoses and pentoses [2–5].
These compounds have been used in mimicking the natu-
rally occurring β-d-pyranosyl linkage either directly [6] or
after their conversion into more appropriate building blocks
[7–13].
to d-Mannosyl nitromethanes 4–7 (Scheme 1). So far
only two of the four possible d-Mannosyl nitromethanes
have been isolated from more or less thermodynamically
equilibrated reaction mixtures of their preparation by the
classical method; the highly prevailing and fully character-
ized β-pyrano anomer 7 [5, 18] and, in comparison with
it, “in a very small amount present” α-pyrano anomer 6,
characterized as per-O-acetyl derivative by X-ray crystal-
lography only [19]. Therefore, for the reinvestigation of the
classical method, frstly, three d-Mannosyl nitromethanes
4–6, complementary to the completely known anomer 7,
were prepared by boiling an aqueous solution of starting
nitroalditol 1, isolated by preparative paper chromatography
and identifed. Compound 1 as a major component of an
epimeric 1-deoxy-1-nitroheptitol mixture obtained by the
nitromethane synthesis from d-mannose is easily available
by crystallization from an aqueous solution [20].
In nature, glycosylation frequently occurs also in other
than the pyrano-equatorial confguration of the glycosyl
moiety, and the pyrano-axial as well as both furano anomeric
arrangements are quite common. The furano anomeric struc-
tures are being found mainly for both d- and l-arabinose,
d-ribose, d-galactose, and d-fructose, while the pyrano-axial
architecture is very frequent for d-mannose, d-glucose, and
d-galactose. The most frequent natural occurrence of d-man-
nose in the form of the α-d-mannopyranosyl moiety also
evokes a continuous demand for such non-naturally linked
scafolds [14–16]. The present contribution investigates for
the frst time in details both the methods whether and how
they can be used for preparation of α-d-mannopyranosyl
nitromethane and also shows its simple conversions into two
other, not mutarotating and more versatile building blocks
with the pyrano-axial anomeric arrangement convenient for
mimicking the naturally occurring α-d-mannopyranosyl
linkages in the search for specifc or essentially selective
inhibitors of the pertinent pathophysiological carbohydrate
recognitions [17].
Monitoring the entire time dependence of the reaction
mixture composition revealed that already from the very
early stages of the conversion of the starting compound 1
up to its remaining about 20% amount what happened after
about three hours, the content of the furano anomers 4 and
5 was practicaly stationary and did not exceed the respec-
tive 13% and 6% proportions (Table 1). This points to their
substantially shorter kinetic persistence, apparently due to
the repulsion of their cis-arranged C-3 and C-4 substitu-
ents, in comparison to that of the C-3,C-4 trans-arranged
d-galactofuranosyl nitromethanes, the proportions of which
under the comparable conditions have been more accumu-
lated and culminated at more than double the values [1].
Starting nitroalditol 1 completely disappearded after about
10 h and the raction mixture reached its thermodynamic
equilibrium of d-Mannosyl nitromethanes 4:5:6:7=2:1:4:93
after additional 5 h. The content of the target pyrano-axial
anomer 6 was gradually increasing from the beginning up to
three hours when reached its maximum of 18%.
Results and discussion
For monitoring the entire time dependence of composition
changes in the reaction mixture for the reinvestigation of
the classical method by 13C NMR analysis, 1-deoxy-1-d-
glycero-d-galacto-heptitol (1), which in aqueous solution is
partly tautomerized to its aci-nitro form 2, was used for gen-
eration of the intermediate nitroalkene 3 and its cyclization
A much better conversion of the nitroalkene intermediate
3 to the requested α-pyrano anomer 6 was achieved when this
intermediate was generated from its per-O-acetyl precursor 8
by treatment with sodium methoxide at 30 °C (Scheme 2). In
the initial stages of the treatment, however, both mannofura-
nosyl nitromethanes 4 and 5 and both temporarily appearing
1 3

Nitroalkene ring closure route to carbon‑linked scafolds for mimicking α‑d‑mannopyranosyl n…
Table 1 Compositiona of the
reaction mixture obtained by
refuxing 1-deoxy-1-nitro-d-
glycero-d-galacto-heptitol (1) in
a 5% aqueous solution
mixture on a column of strongly acidic cation exchange resin
in the Ba2+ form, which is the most efciently complexing
common cation for separation of cyclic polyols [21], enabled
isolation of the requested compound 6 in an interesting yield
of 36%. The observed kinetic stereoselectivity in the conver-
sion of intermediate 3 to the respective α-anomers 4 and 6 at
the reaction temperature used is the result of the preferential
intramolecular addition of the C-5–OH group in the sickle
conformation 3a or the C-6–OH group in the triple-sickle
conformation 3b on the double bond from the less hindered
Si faces (Scheme 2). The same fnal thermodynamic mixture
of d-Mannosyl nitromethanes 4:5:6:7=2:1:4:93 as that for
the classical thermal method was confrmed after 7 weeks
of the treatment also for this methoxide addition–elimina-
tion method.
Reaction Compound /%
time /h
1
4
5
6
7
1/4
1/2
1
2
3
75
6
3
5
6
5
5
1
1
1
1
8
9
8
56 12
29 13
24 13
19 12
8
–
–
–
18
15 37
16 42
18 46
15 72
5
4
3
3
2
10
15
42
7
5
4
89
91
93
aDetermined from the 13C NMR
spectra on the basis of the peak
height measurements and their
corelation with those of artif-
cial mixtures of known compo-
sition
A remarkable striking diference within this novel method
of preparation of glycosyl nitromethanes is a signifcantly
decreased addition ability of d-manno nitroalkenitol 8
towards methoxide nucleophile when compared to that of
d-galacto nitroalkenitol [1]. While the latter compound in
its frst stages of the treatment is completely amenable to the
2-O-methoxide addition–elimination reaction detour and the
pertinent intermediate 2-O-methyl adduct could have been
isolated after a 5 min treatment as a single epimer in an
almost quantitative yield [1], the occurrence of the meth-
oxylated species 13 and 14 among the reaction products in
the present study did not exceed their summary 40% propor-
tion and actually the frst slightly prevailing products were
rather mannofuranosyl nitromethanes 4 and 5 (Table 2). The
apparent reason here is that the C-3–C-4 rotational fip from
the zig-zag conformation 3 to the sickle conformation 3a
(Scheme 2), necessary for the primary cyclization to the
fve-member ring products, does not require to encounter
epimeric 2-O-methyl-1-deoxy-1-nitroalditols 13 and 14 were
dominating kinetic products until about half an hour, when
d-mannopyranosyl nitromethanes 6 and 7 were beginning to
preponderate in the reaction mixture (Table 2). The accrual
of the target α-pyranosyl anomer 6 reached its maximum
at around 46% between 8 and 16 h. Since at the latter time
point both temporarily appearing methoxy derivatives 13
and 14 (characteristic by the respective 13C NMR chemical
shifts of their C-2–OMe groups at 57.5 and 60.0 ppm) have
already disappeared and both mannofuranosyl nitromethanes
4 and 5 were present at their respective lowermost amounts
(2% and 1%) only, the sodium methoxide treatment was
stopped by decationization with a cation exchange resin.
Following chemisorption chromatography of thus obtained
1 3

B. Pribulová et al.
Table 2 Compositiona of the reaction mixture obtained upon treat-
ment of 2% solution of 1,2-dideoxy-1-nitro-d-manno-hept-1-enitol
peracetate (8) in MeOH with 1.3 equiv. of NaOMe at 30 °C
converted by electron-transfer reduction with ferrous
hydroxide in situ [23] to the mixture of the corresponding
amines 15 and 16 with their stable ring structures. Further-
more, both the amines were transformed according to the
procedure [24] to the respective N-acetamido derivatives 17
and 18 and subjected to the same chromatographic separa-
tion as their nitro precursors 6 and 7 exploiting the retention
of derivative 17 caused by its stronger complexation with
immobilized Ba2+ cations than that of 18. Regeneration of
free amine 15 from its N-acetyl derivative 17 was accom-
plished by hydrolysis with 2 M trifuoroacetic acid [25]. The
procedure is advantageous also for analytical characteriza-
tion of the fnal product as trifuoroacetate salt 19, which did
not contain any traces of 20; the acid is easily volatile for
its removal and the salt retains just an equimolar amount of
the counteranion visible in the 13C NMR spectrum as two
quartets at around 163.0 and 116.4 ppm. Free amine 15 can
be then regenerated for use by deanionization of its salt 19
with strongly basic anion exchange resin in the OH− form in
decarbonized water and evaporation of the aqueous fltrate.
Finally, another useful and not mutarotating α-d-
mannopyranosyl scafold 23, together with its β-anomer
24, was obtained when the reaction mixture of starting
compound 8 with sodium methoxide after 16 h of the treat-
ment was treated with diluted methanolic HCl (Scheme 4).
The thus initiated reaction enabled to transform glycosyl
nitromethanes 6 and 7, present in this reaction mixture as
their respective sodium nitronate forms 21 and 22, at narrow
concentration ranges of around 0.1 N strong acid directly to
the dimethyl acetal protected aldehydes 23 and 24; at higher
acid concentrations a competitive conversion to the corre-
sponding methyl carboxylates starts to occur signifcantly
[26]. The resulting dimethyl acetals 23 and 24 were chroma-
tographically separated on a column of strongly basic anion
exchange resin in the OH−form, similarly as structurally
Reaction time /h
Compound /%
4
5
6
7
13+14
1/12
1/6
1/2
2
8
16
24
48
1176
36
34
27
16
6
2
2
16
12
9
5
2
1
1
1
1
7
4
37 (21+14)
32 (19+13)
27 (16+11)
17 (11+6)
11
18
32
46
46
41
27
4
11
19
30
42
51
56
70
93
4 (3+1)
–
–
–
–
2
2
aDetermined from the 13C NMR spectra similarly, as for the data in
Table 1
an intermediary HO–C-3–C-4–OH eclipsed conformation
which, however, had to be overcome in the case of the ana-
logical rotational fip of d-galacto nitroalkenitol [1]. As the
consequence of that obstacle, the intermolecular addition of
methoxide on that nitroalkenitol has more signifcantly com-
peted with obviously highly preferred intramolecular reac-
tion even after its complete deacetylation [1]. Previously, the
metoxide addition to sugar nitroalkene peracetates has been
used for synthesis 2-O-methylaldoses only and the metox-
ide elimination from intermediary 1-deoxy-2-O-methyl-1-
nitroalditols has not been reported [22].
For obtention of a much more versatile and not mutaro-
tating C-α-d-mannopyranosyl-methylamine (15, Scheme 3),
the above mixture from the 16 h treatment of compound 8
with sodium methoxide containing 97% of both d-manno-
pyranosyl nitromethanes 6 and 7 (Table 2) was promptly
Scheme 3
1 3

Nitroalkene ring closure route to carbon‑linked scafolds for mimicking α‑d‑mannopyranosyl n…
Scheme 4
and functionally relative glycosides [27], and the demanded
α-acetal 23 was eluted second and collected in a 30% yield.
Its potential for retaining the anomeric confguration in
synthetic products was demonstrated by hydrolysis with
3 N H2SO4 to α-d-mannopyranosyl-methanal (25), and its
reduction with NaBH4 in the presence of a small excess of
NaHCO3, necessary for neutralization of the acid, provided
2,6-anhydro-d-glycero-d-manno-heptitol (27) as practi-
chemisorption chromatography aforded a 36% yield of α-d-
mannopyranosyl nitromethane. When such a decationized
product mixture was immediately subjected to the reduction
with ferrous hydroxide in situ and then selectively derivat-
ized, N-acetyl-C-α-d-mannopyranosyl-methylamine was
similarly isolated in a 33% yield. Alternative interruption
of the equilibration of the initial ring forming reaction at
the appropriate time point with diluted methanolic HCl and
following chromatographic separation gave a 30% yield of
α-d-mannopyranosyl methanal dimethyl acetal. Acid hydro-
lytic activations of two latter derivatives into respective reac-
tive free amine or free aldehyde forms were elaborated as
well. Moreover, the accessibility of α-d-mannopyranosyl
nitromethane and other such non-thermodynamic derivatives
may initiate further developments of organic nitro chemis-
try [30] and other useful applications of non-aromatic nitro
compounds for stereoselective synthesis of pharmaceutically
relevant molecules [31]. Last but not least, the parent ring
closure reaction also outlines behavioral pattern of d-man-
nose in kinetic stages of its complete (but not yet studied)
mutarotation, which encompasses all the steps of its cycliza-
tion and interconversions of its tautomers before reaching its
thermodynamic equilibrium, which is then obviously difer-
ent from that of d-Mannosyl nitromethanes because of the
anomeric efects.
1
cally the only product; H NMR analysis detected only a
3% admixture of 2,6-anhydro-d-glycero-d-galacto-heptitol
(28), which was determined by the integration of its H-6
signal at 3.23 ppm [28]. This admixture apparently origi-
nated from the reduction of β-d-mannopyranosyl-methanal
(26), the side product of previously reported base-catalyzed
epimerization of 2,6-anhydroheptose 25 [29], concurrently
appearing during the reduction.
Conclusion
The contribution describes the case when for the frst time
ever there was observed during an equilibration of a revers-
ible ring closure reaction a non-thermodynamic pyrano-
axial glycosyl nitromethane as the predominating prod-
uct, which then could have been converted into two other,
thermodynamically stable C-glycosyl scafolds possess-
ing the same stereochemistry of the glycosyl moiety and
applicable for synthesis of non-hydrolyzable analogues of
natural oligosaccharides or glycoconjugates containing α-d-
mannopyranosyl linkage. Thus, the discontinuation of this
equilibration starting from d-manno confgured terminal
pentahydroxynitroalkene, generated from sodium methox-
ide-catalyzed deacetylation of its peracetate, at the most
appropriate product composition with a cation exchange
resin in the H+ form and further isolation procedure by
Experimental
Melting points were measured on a Kofer stage. Optical
rotations were obtained with a Jasco P2000 polarimeter at
20 °C. Elemental analyses (C, H, N) were performed using
a Fisons EA-1108 instrument, their results were found to be
in good agreement ( 0.3%) with the calculated values. High
resolution mass determination was achieved by ESI–MS on
1 3

B. Pribulová et al.
a Thermo Scientifc Orbitrap Exactive instrument operating
in positive mode. 1H and 13C NMR spectra were recorded
at 295 K on VNMRS 400 MHz or 600 MHz Varian spec-
trometers. Full spectral assignment was accomplished using
the COSY, NOESY, and HSQC techniques. Descent paper
chromatography (PC) was performed on Whatman No. 1
and 3 sheets with the upper layer of the S1 solvent mixture
butan-1-ol–ethanol–water 5:1:4 (v/v). Compounds were vis-
ualized under the 254 nm UV light or irreversibly by devel-
oping the paper with alkaline silver nitrate. TLC was run
on Merck 60 F254 silica gel precoated aluminium plates in
the solvent system S2 butan-1-ol–methanol–water 9:7:3 (v/v)
or S3 butan-1-ol–methanol–water–25% aqueous ammonia
9:7:2:1 (v/v); visualisation was efected by briefy immers-
ing the plates into 10% ethanolic sulfuric acid and charring
them with a hot air gun, or alternatively, with alkaline silver
nitrate. Relative chromatographic mobilities of compounds,
Rman, are related to that of d-mannose (Rman = 1.00). Pre-
parative chemisorption chromatography was performed on
column C1 (90 cm×2 cm) of Dowex 50WX8 (38–75 μm) in
the Ba2+ form or column C2 (90 cm×2 cm) of Dowex 1X8
(38–75 μm) in the OH− form using elution with water at fow
rate of 10 cm3 h−1.
1 H, H-5), 3.99 (dd, J=8.8, 2.8 Hz, 1 H, H-3), 3.91 (ddd,
J=8.8, 5.9, 2.8 Hz, 1 H, H-2), 3.74 (dd, J=12.1, 2.6 Hz, 1
H, H-1a), 3.57 (dd, J =12.0, 5.8 Hz, 1 H, H-1b) ppm; 13C
NMR (D2O): δ = 79.8 (C-3), 77.7 (C-6), 77.3 (C-7), 73.4
(C-5), 71.1 (C-4), 69.1 (C-2), 62.9 (C-1) ppm.
2,5‑Anhydro‑1‑deoxy‑1‑nitro‑d‑glycero‑d‑galacto‑heptitol
(β‑d‑mannofuranosyl nitromethane, 5, C7H13NO7) Yield
20 mg (4%); PC Rman = 2.36 (S1); glassy foam; m.p.:
45–46 °C; [α]D20= − 79.4 (c=1.0, water); 1H NMR (D2O):
δ=4.70–4.85 (m, 3 H, H-1a, H-1b, H-2), 4.59 (dd, J=6.9,
4.6 Hz, 1 H, H-3), 4.38 (dd, J = 4.6, 3.9 Hz, 1 H, H-4),
3.95 (ddd, J=8.6, 5.9, 2,8 Hz, 1 H, H-6), 3.90 (dd, J=8.5,
3.7 Hz, 1 H, H-5), 3.75 (dd, J = 12.0, 2.8 Hz, 1 H, H-7a),
3.60 (dd, J=12.0, 5.9 Hz, 1 H, H-7b) ppm; NOE contacts:
H-3,2; H-3,4; H-3,5; H-4,2; H-4,3; H-4,5; 13C NMR (D2O):
δ = 79.6 (C-5), 76.9 (C-1), 76.1 (C-2), 71.7 (C-3), 71.0
(C-4), 69.7 (C-6), 63.0 (C-7) ppm.
2,6‑Anhydro‑7‑deoxy‑7‑nitro‑d‑glycero‑d‑manno‑heptitol
(α‑d‑mannopyranosyl nitromethane, 6, C7H13NO7) Yield
35 mg (7%); PC Rman =1.74 (S1); m.p.: 125–126 °C (EtOH);
[α]D20 = + 36.0 (c = 1.0, water); H NMR (D2O): δ = 5.03
1
(dd, J=13.3, 10.6 Hz, 1 H, H-7a), 4.82 (dd, J=13.3, 3.5 Hz,
1 H, H-7b), 4.68 (dt, J = 10.4, 3.3 Hz, 1 H, H-6), 3.98 (t,
J=3.0 Hz, 1 H, H-5), 3.65–3.82 (m, 5 H, H-1a, H-1b, H-2–
4) ppm; 13C NMR (D2O): δ=75.6 (C-2), 74.4 (C-6), 73.8
(C-7), 70.6 (C-3), 68.3 (C-5), 67.2 (C-4), 60.6 (C-1) ppm.
d‑Mannosyl nitromethanes 4–7 via thermal dehydration
of 1‑deoxy‑1‑nitro‑d‑glycero‑d‑galacto‑heptitol (1) and
monitoring the reaction course The starting compound 1
(0.5 g, 2.07 mmol) [20] was dissolved in 5 cm3 deionized
and distilled water. The solution was stirred and heated at an
internal temperature of 100 °C for 30 min, then evaporated
under vacuum, and the residue crystallized from methanol
recovered compound 1 (0.1 g). The non-crystallizing resid-
ual syrup was diluted with 1 cm3 methanol, soaked by means
of a capillary onto starting lines of three standard sheets of
the Whatman No. 3 paper, simultaneously blown from below
with warm air, and descendingly chromatographed with the
S1 solvent mixture along the entire length of the sheets. The
elution zones of the individual components of the reaction
mixture, containing the nitro group, on the developed and
air-dried chromatographic sheets were visualized under the
254 nm UV light in dark and demarked with a pencil, cut of,
extracted with water, evaporated under vacuum at tempera-
ture below 35 °C and identifed. In addition to d-Mannosyl
nitromethanes 4–7, another amount of recovered 1 (0.11 g;
overall 42%); PC Rman =1.39 (S1), was isolated.
2,6‑Anhydro‑1‑deoxy‑1‑nitro‑d‑glycero‑d‑galacto‑hepti‑
tol (β‑d‑mannopyranosyl nitromethane, 7) Yield 67 mg
(13%); PC Rman = 1.85 (S1); m.p.: 149–150 °C (MeOH);
[α]D20 =−25.0 (c=1.0, water); Ref [5]. m.p.: 150–151 °C;
[α]D20 =−25.6 (c=4.8, water); Ref [18]. m.p.: 151–152 °C;
[α]D20 = −26.1 (c = 2.5, water); H and 13C NMR spectra
1
were found to be identical with the ones described in Ref.[5].
Monitoring of formation and interconversion
of d‑mannosyl nitromethanes 4–7 introduced
by thermal treatment
Compound 1 (1 g) dissolved in 10 cm3 deionized and distilled
water was stirred and heated at 100 °C. At selected time inter-
vals (Table 1), 0.4-cm3 samples were taken, concentrated in a
rotary evaporator under vacuum at temperature below 35 °C
and subjected to the 13C NMR spectroscopy analysis.
3,6‑Anhydro‑7‑deoxy‑7‑nitro‑d‑glycero‑d‑manno‑heptitol
(α‑d‑mannofuranosyl nitromethane, 4, C7H13NO7) Yield
48 mg (9%); PC Rman = 2.03 (S1); glassy foam; m.p.:
48–49 °C; [α]D20 = +77.9 (c=1.0, water); 1H NMR (D2O):
δ=4.82 (dd, J=13.7, 2.7 Hz, 1 H, H-7a), 4.70 (dd, J=13.8,
8.8 Hz, 1 H, H-7b), 4.46 (td, J=8.6, 2.8 Hz, 1 H, H-6), 4.29
(dd, J = 4.3, 2.8 Hz, 1 H, H-4), 4.23 (dd, J = 8.6, 4.2 Hz,
Sodium methoxide‑catalyzed methanolysis
of 1,2‑dideoxy‑1‑nitro‑d‑manno‑hept‑1‑enitol
peracetate (8)
Compound 8 (0.5 g, 1.15 mmol, [32] was stirred in a mixture
of 25 cm3 anhydrous MeOH and 1.5 cm3 of 1 M NaOMe in
1 3

Nitroalkene ring closure route to carbon‑linked scafolds for mimicking α‑d‑mannopyranosyl n…
MeOH at 30 °C. After the given time (Table 2), 2-cm3 sam-
ples were taken, mixed with Amberlite IR120 (300–850 μm),
H+ form (0.5 cm3 of its suspension in MeOH) and fltered.
The neutral fltrate was evaporated under vacuum at tem-
perature below 35 °C and the composition of the reaction
mixture in the pertinent time was determined by 13C NMR
analysis of the destilation residue.
evaporated under vacuum. The obtained syrup (0.64 g, 87%)
was partitioned in two portions on the column C1. Eluted
frst was compound 18 (0.41 g, 40%) followed by 17 (0.37 g,
36%).
Compound 17 PC Rman =1.30 (S1); TLC Rman =0.86 (S2);
syrup; [α]D20 = +37.2 (c=1, MeOH); 1H NMR (CD3OD):
δ=3.89 (dt, J=8.7, 4.4 Hz, 1 H, H-6), 3.81 (dd, J=11.7,
6.8 Hz, 1 H, H-1a), 3.75 (dd, J=4.4, 3.4 Hz, 1 H, H-5), 3.74
(dd, J=11.7, 2.8 Hz, 1 H, H-1b), 3.70 (dd, J=7.4, 3.3 Hz,
1 H, H-4), 3.64 (dd, J = 7.3, 7.1 Hz, 1 H, H-3), 3.57 (td,
J=6.9, 2.9 Hz, 1 H, H-2), 3.48 (dd, J=14.1, 4.6 Hz, 1 H,
H-7a), 3.40 (dd, J=14.1, 8.7 Hz, 1 H, H-7b), 1.97 (s, 3 H,
CH3) ppm; 13C NMR (CD3OD): δ=173.5 (CO), 77.6 (C-2),
75.9 (C-6), 72.6 (C-4), 70.0 (C-5), 69.7 (C-3), 62.6 (C-1),
39.8 (C-7), 22.5 (CH3) ppm; HRMS (ESI): m/z calcd for
C9H17NO6H+ ([M+H]+) 236.1129, found 236.1131.
α‑d‑Mannopyranosyl nitromethane (6) from nitroalkene 8 A
solution of 2 g compound 8 (4.62 mmol) in a mixture of
100 cm3 anhydrous methanol and 6 cm3 of 1 M NaOMe/
MeOH was stirred in a closed round-bottom fask at 30 °C
for 16 h. Then Amberlite IR120, H+ form (20 cm3, vide
supra) was added and the procedure continued as above.
The vacuum evaporated residual syrup (0.93 g, 90%) was
chromatographed in three portions on the column C1. Eluted
frst was compound 7 (0.41 g, 40%) followed by compound
6 (0.37 g, 36%).
Compound 18 PC Rman =1.47 (S1); TLC Rman =0.93 (S2);
1
7‑Acetamido‑2,6‑anhydro‑7‑deoxy‑d‑glycero‑d‑manno‑hep‑
titol (N‑acetyl‑C‑α‑d‑mannopyranosyl methylamine, 17,
C9H17NO6) and 1‑acetamido‑2,6‑anhydro‑1‑deoxy‑d‑glyc‑
ero‑d‑galacto‑heptitol (N‑acetyl‑C‑β‑d‑mannopyranosyl
methylamine, 18, C9H17NO6) The syrup obtained pre-
cisely according to the procedure described in the forego-
ing paragraph and containing 97% of compounds 6 and
7 was dissolved in 10 cm3 of pre-boiled water and mixed
with a solution of 8.75 g FeSO4·7H2O (31.5 mmol) in 10
cm3 of similarly deaerated water and, after addition of 15
cm3 of a 25% aqueous ammonia, the mixture was stirred
under argon at room temperature for 15 min. The resulting
mixture was boiled because of a better flterability, cooled,
and the precipitate was paper-fltered of and washed with
5% aqueous ammonia (5 × 10 cm3). The collected fltrate
and washing solutions were mixed with 13 g of powdery
BaCO3 (66 mmol), concentrated at 40 °C on a rotary evapo-
rator under vacuum to a thick suspension and then, always
after addition of 50 cm3 of water, the evaporation procedure
was repeated thrice. Finally, the combined fltrates obtained
after fltrating and washing the precipitate with water (4×10
cm3) were in decreasing concentration order passed through
a column (1.5 cm×50 cm) of Dowex 1X8 (38–75 μm) in the
OH− form at fow rate 1 cm3 min−1, and fnaly the column
was washed with 50 cm3 of water. The combined eluates
were concentrated on a rotary evaporator under vacuum and
resulting syrup containing compounds 15 and 16 (0.71 g,
91%) was obtained. A part of the syrup (0.6 g) was dissolved
in 20 cm3 of water and 2 cm3 of methanol and Amberlite
syrup; [α]D20 =−42.8 (c=1, MeOH); H NMR (CD3OD):
δ=3.90 (dd, J=11.7, 2.3 Hz, 1 H, H-7a), 3.77 (dd, J=3.2,
1.1 Hz, 1 H, H-3), 3.65 (dd, J= 11.7, 7.0 Hz, 1 H, H-7b),
3.55 (dd, J=13.6, 4.4 Hz, 1 H, H-1a), 3.49 (t, J=9.4 Hz,
1 H, H-5), 3.48 (ddd, J =8.3, 4.2, 1.1 Hz, 1 H, H-2), 3.45
(dd, J=9.3, 3.2 Hz, 1 H, H-4), 3.24 (dd, J=13.5, 8.3 Hz, 1
H, H-1b), 3.21 (ddd, J=9.2, 6.9, 2.3 Hz, 1 H, H-6), 1.96 (s,
3 H, CH3) ppm; 13C NMR (CD3OD): δ=173.6 (CO), 82.2
(C-6), 78.1 (C-2), 76.2 (C-4), 71.4 (C-3), 69.0 (C-5), 63.4
(C-7), 41.8 (C-1), 22.5 (CH3) ppm; HRMS (ESI): m/z calcd
for C9H17NO6H+ ([M+H]+) 236.1129, found 236.1130.
7 ‑ A m m o n i u m ‑ 2 , 6 ‑ a n h y d r o ‑ 7 ‑ d e o x y ‑ d ‑ g l y c ‑
ero‑d‑manno‑heptitol trifuoroacetate (C‑α‑d‑mannopyran‑
osyl methylammonium trifuoroacetate, 19, C7H15NO5) A
solution of 0.1 g of 17 in 2 M trifuoroacetic acid in water (5
cm3) was heated under refux for 8 h and then concentrated
on a rotary evaporator under vacuum. A residual excess
of the acid was removed by three times repeated evapora-
tion of the destilation residue dissolved in 2 cm3 of metha-
nol. Yield 0.13 g (100%); white solid; m.p.: 139–140 °C;
[α]D20 = +32.1 (c=1, water); 1H NMR (D2O): δ=4.03 (ddd,
J=11.0, 3.5, 3.3 Hz, 1 H, H-6), 3.80 (dd, J=3.4, 3.2 Hz, 1
H, H-5), 3.74 (dd, J = 13.3, 6.7 Hz, 1 H, H-1a), 3.70 (dd,
J = 13.3, 2.8 Hz, 1 H, H-1b), 3.64 (dd, J = 7.9, 3.1 Hz, 1
H, H-4), 3.61 (dd, J = 7.9, 7.0 Hz, 1 H, H-3), 3.55 (ddd,
J=7.0, 6.6, 2.8 Hz, 1 H, H-2), 3.26 (dd, J=13.7, 10.9 Hz,
1 H, H-7a), 3.10 (dd, J = 13.7, 2.9 Hz, 1 H, H-7b) ppm;
13C NMR (D2O): δ=163.1 (q, J=35.6 Hz, COO−), 116.6
(q, J=291.8 Hz, CF3), 75.5 (C-2), 73.0 (C-6), 70.2 (C-4),
68.4 (C-5), 67.3 (C-3), 60.5 (C-1), 37.9 (C-7) ppm; HRMS
(ESI): m/z calcd for C7H15NO5H+ ([M + H]+) 194.1023,
found 194.1027.
−
IRA400 (300–850 μm) in the HCO3 form (30 cm3) was
added. The mixture was stirred and cooled to 0 °C, 0.6
cm3 of acetic anhydride was added and the mixture was
stirred then without cooling for 3 h. Finally, the mixture
was fltered, the resin washed with water (3×10 cm3) and
1 3

B. Pribulová et al.
1‑Ammonium‑2,6‑anhydro‑1‑deoxy‑d‑glycero‑d‑ga‑
lacto‑heptitol trifluoroacetate (C‑β‑d‑mannopyranosyl
methylammonium trifluoroacetate, 20, C7H15NO5) Com-
pound 18 (0.1 g) was treated and worked up precisely
as for the preparation of compound 19 from compound
17. Yield 0.13 g (100%); white solid; m.p.: 160–161 °C;
[α]D20 =−42.4 (c=1, water); 1H NMR (D2O): δ=3.83 (dd,
J=3.5, 1.2 Hz, 1 H, H-3), 3.81 (dd, J=12.2, 2.2 Hz, 1 H,
H-7a), 3.71 (ddd, J=8.9, 3.7, 1.1 Hz, 1 H, H-2), 3,57 (dd,
J=12.2, 7.2 Hz, 1 H, H-7b), 3.52 (dd, J=9.5, 3.4 Hz, 1 H,
H-4), 3.42 (t, J=9.6 Hz, 1 H, H-5), 3.27 (ddd, J=9.5, 7.2,
2.3 Hz, 1 H, H-6), 3.12 (dd, J = 13.4, 8.8 Hz, 1 H, H-1a),
3.12 (dd, J=13.5, 3.8 Hz, 1 H, H-1b) ppm; 13C NMR (D2O):
δ = 162.9 (q, J = 35.6 Hz, COO−), 116.3 (q, J= 291.8 Hz,
CF3), 79.9 (C-6), 73.8 (C-2), 73.6 (C-4), 69.4 (C-3), 67.0
(C-5), 61.4 (C-7), 40.6 (C-1) ppm; HRMS (ESI): m/z calcd
for C7H15NO5H+ ([M+H]+) 194.1023, found 194.1029.
H, H-2), 3.81 (dd, J = 11.8, 2.6 Hz, 1 H, H-7a), 3.73 (dd,
J=9.0, 3.4 Hz, 1 H, H-4), 3.72 (dd, J=11.7, 5.5 Hz, 1 H,
H-7b), 3.67 (t, J=8.9 Hz, 1 H, H-5), 3.57 (ddd, J=8.8, 5.5,
2.6 Hz, 1 H, H-6), 3.48 (s, 3 H, OMe), 3.46 (s, 3 H, OMe)
ppm; NOE contacts: H-1,4; H-1,6; H-1,3; H-1,5; H-3,4;
H-3,2; H-3,1; H-3,5; H-3,OMe-a; H-3,OMe-b; 13C NMR
(D2O): δ=101.2 (C-1), 77.5 (C-2), 76.2 (C-6), 70.9 (C-4),
68.2 (C-3), 66.6 (C-5), 61.1 (C-7), 55.5, 54.7 (2 OMe) ppm;
13C NMR (CD3OD): δ=103.5 (C-1), 79.0 (C-2), 78.1 (C-6),
73.1 (C-4), 70.0 (C-3), 68.7 (C-5), 63.2 (C-7), 55.8, 54.4
(2 OMe) ppm; HRMS (ESI): m/z calcd for C9H18NO7Na+
([M+H]+) 261.0945, found 261.0944.
Compound 24 PC Rman = 2.22 (S1); TLC Rman = 2.23
(S3); syrup; [α]D20 = + 6.8 (c = 1, MeOH), Ref [26]. gives
[α]D20 = +5.0 (c=2, MeOH); 13C NMR (CD3OD) and 1H
NMR (CD3OD) spectra with overlapped H-2, H-4, and
OCH3 signals; 1H NMR (D2O): δ=4.49 (d, J=7.6 Hz, 1 H,
H-1), 3.89 (dd, J=3.0, 1.0 Hz, 1 H, H-3), 3.77 (dd, J=12.4,
2.2 Hz, 1 H, H-7a), 3.58 (dd, J=12.4, 6.2 Hz, 1 H, H-7b),
3.49 (dd, J=9.5, 3.3 Hz, 1 H, H-4), 3.45 (dd, J=9.6, 8.9 Hz,
1 H. H-5), 3.44 (dd, J=7.5, 1.0 Hz, 1 H, H-2), 3.37 (s, 3 H,
OMe), 3.32 (s, 3 H, OMe), 3.22 (ddd, J=8.7, 6.2, 2.0 Hz, 1
H, H-6) ppm; 13C NMR (D2O): δ=102.3 (C-1), 80.2 (C-6),
76.7 (C-2), 73.9 (C-4), 68.5 (C-3), 66.9 (C-5), 61.1 (C-7),
55.6, 53.6 (2 OMe) ppm.
2,6‑Anhydro‑d‑glycero‑d‑talo‑heptose dimethyl acetal (α‑d‑
mannopyranosyl methanal dimethyl acetal, 23, C9H18NO7)
and 2,6‑anhydro‑d‑glycero‑d‑galacto‑heptose dimethyl
acetal (β‑d‑mannopyranosyl methanal dimethyl acetal, 24)
A solution of 0.6 g of compound 8 (1.39 mmol) in a mixture
of 30 cm3 anhydrous methanol and 1.8 cm3 of 1 M NaOMe/
MeOH was stirred in a closed round-bottom fask at 30 °C
for 16 h. The reaction mixture was cooled at 5 °C, poured
at once under stirring into 24.9 cm3 of equally cold 0.3 M
HCl/MeOH and left under stirring to warm up to room tem-
perature within 2 h. Amberlite IR120 (300–850 μm) in H+
form (5 cm3) and Amberlite IRA400 (300–850 μm) in OH−
form (30 cm3) were added and the resulting mixture was
stirred for 30 min, then fltered through a frit funnel and the
resins were washed with water (5×15 cm3). The collected
fltrate and washing solutions were in decreasing concen-
tration order passed through a burette flled with Dowex
1X8 (38–75 μm) in the OH− form (50 cm3) at a fow rate 1
cm3 min−1 and fnaly the burette content was washed with
30 cm3 of water. The combined eluates were concentrated
on a rotary evaporator under vacuum and resulting syrup
containing compounds 23 and 24 (0.26 g, 79%) was chro-
matographed on the column C2. Eluted frst was compound
24 (0.11 g, 33%) followed by 23 (0.10 g, 30%).
2 , 6 ‑ A n hyd ro ‑ d ‑ g l yce ro ‑ d ‑ m a n n o ‑ h e p t i t o l ( 2 7 ,
C7H14NO6) Compound 23 (0.06 g) was dissolved in 2 cm3
of 1.5 M H2SO4 and left to stand at room temperature for
48 h. Then gradually under stirring 0.55 g of NaHCO3 and
0.18 g of NaBH4 were added at a rate to prevent violent
foaming and the resulting solution was kept at room tem-
perature for 16 h. Aqueous suspensions of Amberlite IR120
(300–850 μm) in H+ form (13 cm3) and Amberlite IRA400
(300–850 μm) in OH− form (25 cm3) were added, the mix-
ture was mixed up for 5 min, fltered on a frit funnel and
washed with water (3×15 cm3). The fltrate and washings
were evaporated to dryness and the residue was further
repeatedly 3 times evaporated after its dissolution in 1 cm3
of methanol. Yield 0.04 g (80%); TLC Rman =0.95 (S2); TLC
Rman = 3.46 (S3); syrup; [α]D20 = + 23.5 (c = 1, water); H
1
NMR (D2O): δ=3.93 (ddd, J=8.8, 4.2, 2.5 Hz, 1 H, H-6),
3.89 (t, J=2.8 Hz, 1 H, H-5), 3.83 (dd, J=12.2, 8.8 Hz, 1
H, H-7a), 3.77 (dd, J=12.1, 2.6 Hz, 1 H, H-1a), 3.72 (dd,
J=12.2, 5.8 Hz, 1 H, H-1b), 3.65 (dd, J=8.7, 3.2 Hz, 1 H,
H-4), 3.62 (dd, J=8.6, 8.3 Hz, 1 H, H-3), 3.61 (dd, J=12.2,
4.2 Hz, 1 H, H-7b) ppm; 13C NMR (D2O): δ=79.4 (C-6),
75.6 (C-2), 71.9 (C-4), 69.4 (C-5), 68.2 (C-3), 62.0 (C-1),
59.2 (C-7) ppm; HRMS (ESI): m/z calcd for C7H14NO6Na+
([M+Na]+) 217.0683, found 217.0684.
Compound 23 PC Rman =2.14 (S1); TLC Rman =2.12 (S3);
syrup; [α]D20 = −9.0 (c = 1, MeOH); H NMR (D2O):
1
δ=4.69 (d, J=7.4 Hz, 1 H, H-1), 3.95 (dd, J=3.5, 2.1 Hz,
1 H, H-3), 3.73 (dd, J = 7.3, 2.1 Hz, 1 H, H-2), 3.71 (dd,
J = 12.4, 2.3 Hz, 1 H, H-7a), 3.69 (dd, J = 9.2, 3.5 Hz, 1
H, H-4), 3.61 (dd, J = 12.3, 5.6 Hz, 1 H, H-7b), 3.57 (t,
J = 9.3 Hz, 1 H, H-5), 3.47 (ddd, J = 9.4, 5.6, 2.4 Hz, 1
H, H-6), 3.38 (s, 3 H, OMe), 3.37 (s, 3 H, OMe) ppm; 1H
NMR (CD3OD): δ = 4.66 (d, J = 6.6 Hz, 1 H, H-1), 4.02
(dd, J=3.3, 2.1 Hz, 1 H, H-3), 3.86 (dd, J=6.6, 2.2 Hz, 1
1 3

Nitroalkene ring closure route to carbon‑linked scafolds for mimicking α‑d‑mannopyranosyl n…
16. Bertolotti B, Sutkeviciute I, Ambrosini M, Ribeiro-Viana R, Rojo
Acknowledgements This work was supported by the Slovak Grant
Agency for Science VEGA under the Project No. 2/0024/16 and the
Research & Development Operational Programmes funded by the
ERDF (‘‘Centre of Excellence on Green Chemistry Methods and Pro-
cesses”, CEGreenI, Contract No. 26240120001 as well as ‘‘Amplif-
cation of the Centre of Excellence on Green Chemistry Methods and
Processes”, CEGreenII, Contract No. 26240120025).
J, Fieschi F, Dvořáková H, Kašáková M, Parkan K, Hlaváčková
M, Nováková K, Moravcová J (2017) Org Biomol Chem 15:3995
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(1990) Carbohydr Res 208:1
20. Köll P, Stenns C, Seelhorst W, Brandenburg H (1991) Liebigs Ann
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