The Staudinger/aza-Wittig/Grignard reaction as key step for the concise synthesis of 1-C-Alkyl-iminoalditol glycomimetics

Article abstract of DOI:10.1016/j.carres.2016.04.006

The scope of a one-pot tandem approach for the synthesis of C-1 alkyl iminoalditol derivatives with a Staudinger/aza-Wittig/Grignard cascade has been evaluated. The reaction conditions have been optimized for two azidodeoxy aldose substrates and a range o

Full text of DOI:10.1016/j.carres.2016.04.006

Accepted Manuscript
Title: The staudinger/aza-wittig/grignard reaction as key step for the concise
synthesis of 1-c-alkyl-iminoalditol glycomimetics
Author: Manuel Zoidl, Andres Gonzalez Santana, Ana Torvisco, Christina
Tysoe, Aloysius Siriwardena, Stephen G. Withers, Tanja M. Wrodnigg
PII:
S0008-6215(16)30102-1
DOI:
Reference:
http://dx.doi.org/doi: 10.1016/j.carres.2016.04.006
CAR 7169
To appear in:
Carbohydrate Research
Received date: 8-2-2016
Revised date: 6-4-2016
Accepted date: 7-4-2016
Please cite this article as: Manuel Zoidl, Andres Gonzalez Santana, Ana Torvisco, Christina
Tysoe, Aloysius Siriwardena, Stephen G. Withers, Tanja M. Wrodnigg, The staudinger/aza-
wittig/grignard reaction as key step for the concise synthesis of 1-c-alkyl-iminoalditol
glycomimetics, Carbohydrate Research (2016), http://dx.doi.org/doi:
10.1016/j.carres.2016.04.006.
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The Staudinger/aza-Wittig/Grignard Reaction as Key Step for the
Concise Synthesis of 1-C-Alkyl-Iminoalditol Glycomimetics
Manuel Zoidl,a Andres Gonzalez Santana,b Ana Torvisco,c Christina Tysoe,b Aloysius
Siriwardena,d Stephen G. Withers,b Tanja M. Wrodnigga,*
aGlycogroup, Institute of Organic Chemistry, Graz University of Technology,
Stremayrgasse 9, A-8010 Graz, Austria
bDepartment of Chemistry, University of British Columbia,
2036 Main Mall, Vancouver, BC, Canada V6T 1Z1
cInstitute of Inorganic Chemistry Graz University of Technology,
Stremayrgasse 9, A-8010 Graz, Austria
dLaboratoire des Glycochimie, des Antimicrobiens et des Agroressources (UMR 7378 CNRS),
Université de Picardie Jules Verne, 33 Rue St Leu, 80039 Amiens, France
Correspondence to
Tanja M. Wrodnigg
Glycogroup, Institute of Organic Chemistry
Graz University of Technology
Stremayrgasse 9
A-8010 Graz
Austria
Phone 0043 316 873 32433
Fax: 0043 316 873 10 32433
email:t.wrodnigg@tugraz.at
Page 1 of 31

Highlights

The Staudinger/aza-Wittig Grignard reaction cascade
 Concise synthetic approach to 1-C-alkyl iminoalditol glycomimetics


Stereoselective control of C-1 alkyl substitution
Compounds exhibit selective b-glucosidase inhibition
Graphical Abstract
 ABSTRACT
The scope of an one-pot tandem approach for the synthesis of C-1 alkyl iminoalditol derivatives
with a Staudinger/aza-Wittig/Grignard cascade has been evaluated. The reaction conditions have
been optimized for two azidodeoxy aldose substrates and a range of Grignard reagents. The
nature of both, substrate as well as nucleophile, was found to control the stereoselectivity of the
alkyl addition to the cyclic iminium intermediate at position C-1. This approach enabled the
synthesis of a collection of C-alkyl iminoalditols, which were biologically evaluated as inhibitors
against a set of standard glycoside hydrolases. All compounds were found to exhibit highly
selective inhibition of -glucosidase activity.
Keywords:
C-Glycoside Iminosugars, Staudinger/aza Wittig/Grignard Reaction Cascade, -
Glucosidase Inhibitors, Glycomimetics
Page 2 of 31

1. Introduction
Iminoalditols are glycomimetics wherein the sugar-ring oxygen is replaced by a nitrogen atom.
Paradigmatic monocyclic examples include 1-deoxynojirimycin (1) and 1,5-dideoxy-1,5-imino-
D-xylitol (4). Regarding their properties as inhibitors of carbohydrate processing enzymes (CPE),
this substance class has attracted continued interest since their first reported synthesis and
subsequent isolation in the 1960s. As such they have found promise in the treatment of diseases
where CPEs have been shown to play key roles, such as Type II diabetes, cancer and viral as
well as bacterial infections.1,2,3,4,5,6,7,8,9,10,11,12,13 Furthermore, iminoalditols have gained
considerable interest as pharmacological chaperones for mutant lysosomal enzymes in the
management of neuropathological forms of lysosomal storage disorders.14,15,16,17 In particular, N-
substituted derivatives of iminosugar glycomimetics (Figure 1) such as compounds 2, 3 and 518,19
as well as C-glycoside iminoalditol analogs such as compound 6,20,21,22,23 have been shown to
exhibit promising chaperone activities due to their ability to interact with CPEs24,25,26 in general
and with lysosomal proteins27,28,29,23 in particular.
Whereas N-substituted iminoalditol derivatives are relatively easily accessible by conventional
reductive amination or substitution reactions at the nitrogen, the corresponding C-glycosidic
iminosugar-based glycomimetics are much more challenging synthetic targets, as stereoselective
C-C-bond formation adjacent to the ring-nitrogen is far more difficult to control. Reported
synthetic strategies30,31,32,33,34 include those taking advantage of intramolecular cyclisation
approaches as well as others, exploiting electrophilic iminosugar donor strategies. An excellent
review provides an overview of these and other synthetic routes.35 In particular, cyclic species,
36,37,38,39,40,41,42,43
such as acyl iminium salts, nitrones or iminium ions, have become versatile
intermediates for the C-C-bond formation of the iminoalditol skeleton because of their utility for
functionalization reactions.
We became interested in the Staudinger/aza-Wittig (SAW) reaction sequence as a concise
method for the preparation of iminoalditol glycomimetics via carbohydrate-derived cyclic
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iminium intermediates.44,45,46,47,48 In our first studies, we demonstrated that iminium
intermediates from a SAW reaction of 5-azidodeoxy aldoses could be effectively trapped by
cyanide as nucleophile, allowing the stereoselective introduction of a C-synthon at the pseudo
anomeric position.49 This strategy facilitated the efficient synthesis of C-cyano iminosugar
scaffolds such as compounds 7 and 9, which served as building blocks for the construction of
imino-C-glycosides 8 and 10, respectively. In all cases studied, attack of cyanide ion occurs
stereoselectively from the -face of the in situ-generated iminium species (cis-orientation with
respect to the adjacent substituent on the iminoalditol skeleton).
Several of these compounds exhibit selective inhibition of -glucosidases, Ki values against the
human lysosomal -glucosidase were found to be in the low micromolar range, suggesting their
potential as pharmacological chaperones for the treatment of Gaucher disease. As an extension to
this work we describe herein the SAW reaction cascade wherein we explore various
commercially available Grignard reagents as nucleophiles for trapping the in-situ generated
iminium ion for the synthesis of iminoalditol-based 1-C-alkyl glycomimetics and their biological
evaluation with a set of glycosidases (Scheme 1).
2. Results and discussion
2.1. Synthesis
5-Azidodeoxy-2,3-di-O-benzyl-,-D-xylose 1150 was selected as starting material to optimize
the reaction conditions for the proposed Staudinger/aza-Wittig/Grignard synthetic approach. We
presumed that both the SAW sequence and the Grignard reaction would be compatible with the
choice of THF as reaction solvent (Scheme 2, a). Thus, compound 11, when dissolved in THF
and treated with PMe3 was smoothly converted into the corresponding cyclic iminium ion
intermediate followed by addition of commercially available benzylmagnesium bromide to give
the corresponding 1-C-benzyl-2,3-O-tribenzyl-iminoxylitol 12 in a yield of 40%. Likewise, when
5-azidodeoxy-2,3-O-isopropylidene-D-ribose 1351 was submitted to the same reaction conditions
(Scheme 2, c) employing commercially available vinylmagnesium bromide as nucleophilic
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reactant, the corresponding isopropylidene-protected 1-C-vinyl-iminoribitol 14 could be isolated
in 20% yield.
Disappointed by the moderate yields obtained in these initial attempts we were curious to see if
the solvent exchange strategy introduced by Overkleeft and co-workers might offer a solution.46
In an adaptation of the latter protocol, the Staudinger/aza Wittig transformation was conducted in
methanol employing PMe3. Upon consumption of the azidodeoxy aldose, methanol was
evaporated in vacuo, and the crude iminium ion species dissolved in THF. The Grignard reagent
was thereupon added to the reaction mixture which was stirred at 0 °C until complete
consumption of the iminium ion intermediate had occurred (as indicated by TLC) (Scheme 2, b).
Gratifyingly, this solvent exchange method gave significantly improved yields. Compound 12
(1-C-benzyl-D-xylo-iminoalditol) was obtained in 85% and compound 14 (1-C-vinyl-D-ribo-
iminoalditol) in 80% yield, both isolated as single stereoisomers.
The configuration of the newly formed stereocenter at position C-1 has been assigned by NMR
spectroscopy. For compound 12, the coupling constant of vicinal protons H-1 and H-2 was found
to be JH1,H2 = 9.6 Hz, consistent with a trans orientation of the 1-C-alkyl substituent to the O-
benzyl group at position C-2 ((S)-configuration of C-1) (Scheme 3). However, this configuration
was surprising in the light of the stereochemical outcome observed in our previous work,49 where
attack of cyanide on the unprotected iminium ion intermediates proceeded to give exclusively the
alternate cis-orientated products, following Woerpel’s rule.52,53 A closer examination of the
presumed 2,3-O-benzyl protected iminium ion intermediate 11a argued that the approach of the
benzylmagnesium bromide from its bottom face would be sterically hindered by the benzyl
group at position O-3. Thus, the introduction of the Grignard nucleophile in this particular case
would be expected to occur preferentially from the top face of the cyclic intermediate,
consequently leading to the product with (S)-configuration as in compound 12. The absolute
configuration of the latter was confirmed from its single crystal x-ray structure54 (Figure 2).
Page 5 of 31

Likewise, analysis of the NMR spectral data of compound 14 revealed the (S)-configuration at
the newly formed chiral center (evident from a coupling constant of JH1,H2 = 8.8 Hz, Scheme 4).
In this particular case it is the 2,3-O-isopropylidene group which hinders the approach of the
Grignard reagent from the bottom face of the sugar-derived cyclic iminium ion intermediate 13a.
The exclusive top-face attack consequently leads to product 14 with trans-orientation between
substituents at positions C-1 and C-2.
With the optimised reaction conditions in hand, the scope of the SAW-Grignard one-pot tandem
reaction sequence was explored for a variety of alternative commercially available Grignard
reagents, such as propylmagnesium bromide and isopropylmagnesium bromide (Scheme 3): the
results are summarized in Table 1. In all cases examined for the Grignard reaction, the solvent
exchange from methanol to THF upon iminium ion formation gave far better yields of the target
products than use of THF alone. The stereochemical outcome influenced by steric vs
stereoelectronic control observed in these studies is in accordance with previous findings by
Davis and co-workers.42
The configurations at position C-1 in compounds 16, 18 and 20 were assigned as (R) in each case
based upon an analysis of coupling constant data (see experimental section). The attack of the
smaller aliphatic Grignard reagents such as vinyl, propyl, as well as isopropyl, on the iminium
ion intermediate 11a is seen to occur from its bottom face consistent with Woerpel’s model,
leading to a cis-orientation of the substituents at positions C-1 and C-2 in products 16, 18 as well
as 20. The x-ray structure of compound 1955 confirmed this configuration unequivocally (Figure
2). Compounds 16, 18, and 20, as well as their respective unprotected C-alkyl-iminoxylitols 17,
1
19 and 21, are all seen to adopt a C4 conformational preference, which has been observed
previously by us and others, for similar alkyl-iminoxylitols.27,49,23
The reaction of 2,3-O-isopropylidene protected azidodeoxyribose 13 in the SAW/Grignard
sequence employing benzylmagnesium bromide as nucleophile furnished the corresponding 1-C-
Page 6 of 31

benzyl iminoribitol derivative 23 with (S)-configuration at position C-1 in accordance to the
stereochemical outcome observed for iminoribitol 14.
Deprotection of the benzyl groups in compounds 12, 16, 18 and 20 by hydrogenolysis under
catalytic conditions or acidic removal of the isopropylidene protected C-glycosyl iminosugars 14
and 23 gave the free 1-C-alkyl iminosugar glycomimetics 15, 17, 19, 21, 22 and 24, respectively,
in good yields.
For evaluation of follow up transformations that are possible for customized functionalisation of
these building blocks, compound 16 was converted to 1-C-hydroxyethyl iminosugar derivative
27 (Scheme 4). Protection of the ring nitrogen of compound 16 with a Cbz group followed by
benzylation of the free hydroxyl group at position O-4 under standard conditions, gave
compound 25. Subsequent hydroboration of the terminal alkene function was performed
employing sodium borohydride and dimethyl sulfate to give primary alcohol 26. Deprotection
under catalytic hydrogenolysis conditions using Pd/C, led to the target 1-C-hydroxyethyl-
iminoxylitol 27 in good yields. Compound 27 itself represents a versatile precursor: Elaboration
of its terminal hydroxyl group would afford a variety of useful analogs for different applications.
2.2. Biological evaluation
Deprotected 1-C-alkyl iminoxylitol glycomimetics 15, 17, 19, 21, as well as 27 were subjected to
evaluation as inhibitors of selected glycoside hydrolases (Table 2). All compounds were highly
selective inhibitors of -glucosidases with Ki values in the micromolar range. None were found
to inhibit either the -glucosidase from S. cerevisae, the E. coli -galactosidase, or the human
lysosomal -galactosidase (Fabrazyme). All compounds proved to be far more active against the
human -glucosidase (Gaucher-disease-related enzyme, GCase) compared to the bacterial -
glucosidase from Agrobacterium sp. (ABG). This tendency has also been reported by Martin and
co-workers for other 1-C-alkyl iminoxylitols and can be explained by the lipophilic character of
the alkyl substituent at position C-1 which fits well into the lipophilic entrance of the active site
Page 7 of 31

of this enzyme.23 Compound 15 with -configuration at the pseudo-anomeric position shows
weaker inhibitory activity against GCase (Ki = 5.9 µM) than do the corresponding C-1--
configured compounds 17, 19, 21 as well as 27. Compound 19 featuring a 1-C-propyl substituent
shows better inhibitory activity (Ki = 1.3 µM) than the 1-C-ethyl substituted iminoxylitol 17 (Ki
= 2.3 µM), consistent with the observation that enhanced lipophilicity of substituents at position
C-1 leads to increased inhibition of the human enzyme. Compound 27, featuring a rather
hydrophilic terminal hydroxyl group and expected thus to have a weaker interaction with the
human GCase, gives a Ki = 26.7 µM, confirming this tendency. No inhibition or only weak
inhibition (Ki values higher than 1 mM) was observed for E. coli -galactosidase, human
lysosomal -galactosidase as well as yeast -glucosidase respectively, establishing that this new
compound class displays a notably high selectivity for the Gaucher enzyme.
3. Conclusions
In conclusion, we have developed a short and efficient one-pot tandem strategy for the synthesis
of 1-C-alkyl iminosugar glycomimetics. The key step is a Staudinger/aza Wittig/Grignard
reaction cascade employing azidodeoxy aldoses as starting materials. The addition of Grignard
reagents to the iminium ion intermediate allows C-functionalisation at the pseudo-anomeric
position C-1 and is found to proceed with complete stereoselectivity dictated by both the
protecting groups of the sugar substrates as well as the nature of the nucleophilic Grignard
reagent. Compounds 15, 17, 19, 21 as well as 27 featuring the D-xylo configuration showed
excellent inhibitory activity as well as selectivity for -glucosidases. In particular, their Ki values
against the human -glucosidase (GCase, Gaucher-disease-related enzyme) were found to be in
the low micromolar range, clearly underlining the potential of this compound class as
pharmacological chaperones for the treatment of Gaucher disease. By this approach, 1-C-alkyl-
Page 8 of 31

iminoalditol building blocks that can undergo further functionalisation for customised
applications are easily available.
Page 9 of 31

4. Experimental
4.1. General methods
General: NMR spectra were recorded on a Varian INOVA 500 operating at 599.82 MHz (1H),
and at 125.894 MHz (13C) or on a Bruker Ultrashield spectrometer at 300.36 (1H) and 75.53
(13C) MHz, respectively. CDCl3 was employed for protected compounds and methanol-d4 or
D2O for unprotected inhibitors as indicated. Chemical shifts are listed in ppm employing
residual, non-deuterated solvent as the internal standard. The signals of the protecting groups as
well as of the N-substituents were found in the expected regions and are only listed explicitly
when overlapping with important spectral features of the iminoalditol. Structures of crucial
intermediates were unambiguously assigned by 1D-TOCSY and HSQC experiments. Optical
rotations were measured on a Perkin Elmer 341 polarimeter at the wavelength of 589 nm and a
path length of 10 cm at 20° C. MALDI-TOF Mass Spectrometry was performed on a Micromass
TofSpec 2E Time-of-Flight Mass Spectrometer. Analytical TLC was performed on precoated
aluminum plates Silica Gel 60 F254 (E. Merck 5554), detected with UV light (254 nm). For
staining, a solution of vanillin (9 g) in a mixture of H2O (950 mL)/ EtOH (750 mL)/ H2SO4 (120
mL) or ceric ammonium molybdate (100 g ammonium molybdate/8 g ceric sulphate in 1 L 10%
H2SO4) were employed followed by heating on a hotplate. For column chromatography, silica
gel 60 (230-400 mesh, E. Merck 9385) or silica gel 60 (Acros Organics, AC 24036) were used.
Unless otherwise specified, all starting materials, reagents and solvents are commercially
available and were used without further purification.
4.2. Kinetic Studies
Kinetic studies were performed at 37C in an appropriate buffer using a known concentration of
enzyme (specific conditions depicted below). Ki determinations were performed using the
corresponding 4-nitrophenyl - or -D-glycopyranoside as substrate. In a typical assay, the
Page 10 of 31

enzyme was incubated with different inhibitor concentrations for up to 5 minutes before
initiating the reaction by the addition of substrate. The initial reaction rate was measured by
monitoring the increase in absorbance at 400 nm for up to ten minutes. Ki determinations were
performed using at least two different substrate concentrations. For each inhibitor, a range of
four to six inhibitor concentrations bracketing the Ki value ultimately determined was used for
each substrate concentration. Dixon plots (1/v vs [I]) were constructed to validate the use of the
competitive inhibition model. The data were then fitted using non-linear regression analysis with
Grafit 7.0.
Specific assay conditions for each enzyme:
Agrobacterium sp. -glucosidase:56,57 50 mM sodium phosphate buffer (pH 7) using 1.85x10-4
mg/mL of enzyme (Km = 4.1 mM).
E.coli lac z -galactosidase: 50 mM sodium phosphate, 1.0 mM MgCl2 (pH 7) using 6.4x10-4
mg/mL of enzyme (Km = 60 M).
Fabrazyme (Acid -galactosidase): 20 mM sodium citrate, 50 mM sodium phosphate, 1.0 mM
tetrasodium EDTA, 0.25% v/v Triton X-100® and 0.25% w/v taurocholic acid buffer (pH5.5)
using 5x10-5 mg/mL of enzyme (Km = 0.65 mM).
S. cerevisae -glucosidase: 50 mM sodium phosphate buffer (pH 7) using 5x10-3 mg/mL of
enzyme (PNP -Glc, Km = 0.75 mM).
-Glucocerebrosidase: 20 mM citric acid, 50 mM sodium phosphate, 1 mM tetrasodium EDTA,
0.25% v/v Triton X-100, and 0.25% w/v taurocholic acid (pH 7.0) (Km = 1.1 mM).
4.3. General procedures
Page 11 of 31

General Procedure A for the SAW – Grignard reaction in THF: PMe3 (1M in toluene, 2 eq)
was added to a solution of the respective azidodeoxyaldose in anhydrous THF under nitrogen
atmosphere. Upon consumption of the starting material (detected on TLC, eluent:
cyclohexane/EtOAc = 1/1, v/v) and formation of the imine intermediate (detected on TLC,
eluent: EtOAc/MeOH = 10/1, v/v) the Grignard reagent (5 eq) was added at 0°C. Upon
consumption of the imine intermediate the reaction was quenched with NH4Cl satd. The aqueous
layer was extracted with EtOAc three times, the combined organic phases were dried over
Na2SO4, filtered and concentrated in vacuo followed by purification on silica gel
chromatography employing eluents as indicated.
General Procedure B for the SAW – Grignard reaction with solvent exchange: PMe3 (1M in
toluene, 2 eq) was added to a solution of the respective azidodeoxyaldose in MeOH under
nitrogen atmosphere. Upon consumption of the starting material (detected by TLC, eluent:
CH/EtOAc = 1/1, v/v) and formation of the imine intermediate (detected by TLC, eluent:
EtOAc/MeOH = 10/1, v/v) the reaction mixture was concentrated under reduced pressure and the
residue was coevaporated twice with toluene. The product was collected in anhydrous THF and
the respective Grignard reagent (5 eq) was added at 0°C under nitrogen atmosphere. The reaction
mixture was then treated as described in general procedure A.
General Procedure C for the deprotection of benzylated products: The protected sugar
compound was dissolved in MeOH/H2O (v/v = 1/1), Pd(OH)2/C added and the reaction mixture
stirred under hydrogen atmosphere at ambient pressure. Upon consumption of the starting
material (detected by TLC, eluent: EtOAc/MeOH = 10/1, v/v) the reaction mixture was filtered,
concentrated under reduced pressure and the desired compound purified by silica gel
chromatography employing eluents as indicated.
Page 12 of 31

General Procedure D for the deprotection of isopropylidene protected products: The
protected sugar compound was dissolved in H2O to give a 10% solution. HCl conc. was added
until pH 2 was reached and the reaction mixture was stirred until the starting material was
consumed (detected by TLC, eluent: EtOAc/MeOH = 10/1, v/v). The reaction mixture was
concentrated under reduced pressure and purified by silica gel chromatography employing
eluents as indicated.
4.4
1(S)-1-C-Benzyl-2,3-di-O-benzyl-1,5-dideoxy-1,5-imino-xylitol
(3,4-di-O-benzyl-1,2,6-
trideoxy-1,5-imino-6-C-phenyl-L-glucitol, 12)
Following general procedure B, 5-azidodeoxy-D-xylose 11 (100 mg, 0.28 mmol) was dissolved
in MeOH (5 mL) and treated with PMe3 (1M in toluene, 560 µL, 0.56 mmol). After removal of
MeOH in vacuo the cyclic iminium ion intermediate was dissolved in THF (5 mL) and
benzylmagnesium bromide (2M in THF, 700 µL, 1.40 mmol) was added. Silica gel
chromatography (EtOAc/MeOH = 10/1, v/v) gave compound 12 (97 mg) in a yield of 85 % as
colourless oil. Recrystallization with MeOH/EtOAc (v/v 1/1) afforded compound 12 as white
1
crystals. 12: = - 39.0 (c 1.00, CHCl3); Rf = 0.63 (EtOAc/MeOH = 10/1, v/v); H NMR (300
MHz, MeOH-d4) δ = 7.44-7.18 (m, 15H, Ph), 5.03 (d, 1H, CH2Ph), 4.94 (d, 1H, CH2Ph), 4.82
(d, 1H, CH2Ph), 4.70 (d, 1H, CH2Ph), 3.69 (ddd, 1H, J4,5a 9.8 Hz, H-4), 3.44 (dd, 1H, J3,4 8.3 Hz,
J2,3 8.8 Hz, H-3) 3.25 (d, 1H, H-1’), 3.21 (d, 1H, H-2), 3.02 (dd, 1H, J5a,5e 11.9 Hz, J4,5e 5.1 Hz,
H-5e), 2.80 (ddd, 1H, J1,2 9.7 Hz, H-1), 2.44 (d, 1H, H-1’), 2.38 (dd, 1H, J4,5a 10.6 Hz, H-5a); 13C
NMR (75.5 MHz, MeOH-d4) δ = 140.4, 139.8, 139.7 (3C, Ph), 130.3–127.7 (Ph), 89.1 (C-3),
84.0 (C-2), 76.4-76.2 (2C, CH2Ph), 73.0 (C-4), 62.7 (C-1), 51.5 (C-5), 39.3 (C-1’); MS: Calcd.
for [C26H29NO3Na]: m/z 426.2045 [M + Na]+; Found [M + Na]+ 426.2044.
Page 13 of 31

4.10 (1S)-1-C-Benzyl-1,5-dideoxy-1,5-imino-xylitol (1,2,6-trideoxy-1,5-imino-6-C-phenyl-L-
glucitol, 15):
Following general procedure C, Pd(OH)2/C was added to a 10% solution of compound 12 (76
mg, 0.19 mmol) in MeOH/H2O and stirred under a hydrogen atmosphere at ambient pressure.
Purification by silica gel chromatography (CHCl3/MeOH/concd NH4OH = 6/1/0.01, v/v/v) gave
compound 15 (40 mg) in a yield of 95 % as colourless oil. 15: = - 37.3 (c 1.00, MeOH); Rf
1
= 0.44 (CHCl3/MeOH/concd NH4OH = 3/1/0.01, v/v/v); H NMR (300 MHz, D2O) δ = 7.39-
7.24 (m, 5H, Ph) 3.70–3.61 (m, 1H, J4, 5e 5.0 Hz, J4,4 9.6 Hz, H-4), 3.48-3.37 (m, 3H, J1,2 7.4 Hz,
J2,3 9.0 Hz, H-2, H-3, H-1’), 3.16 (dd, 1H, J4,5e 4.9 Hz, J5a,5e 12.5 Hz, H-5e), 3.10-3.07 (m, 1H, H-
1), 2.66 (dd, 1H, H-1’), 2.57 (dd, 1H, J4,5a 11.8 Hz, H-5a); 13C NMR (75.5 MHz, D2O) δ = 134.6,
129.6, 129.3, 127.9 (6C, Ph), 76.1 (C-3), 71.3 (C-2), 66.9 (C-4), 60.3 (C-1), 46.3 (C-5), 35.2 (C-
1’); MS: Calcd. for [C12H17NO3Na]: m/z 246,1106 [M + Na]+; Found [M + Na]+ 246.1106.
4.5
1(S)-1-C-Vinyl-2,3-di-O-benzyl-1,5-dideoxy-1,5-imino-xylitol
(3,4-di-O-benzyl-1,2,6-
trideoxy-1,5-imino-6-C-vinyl-D-iditol, 16)
Following general procedure B, 5-azidodeoxy-D-xylose 11 (200 mg, 0.70 mmol) was dissolved
in MeOH (10 mL) and treated with PMe3 (1M in toluene, 1.40 mL, 1.40 mmol). After removal
of MeOH in vacuo the cyclic iminium ion intermediate was dissolved in THF (10 mL) and
vinylmagnesium bromide (1M in THF, 3.50 mL, 3.50 mmol) was added. Silica gel
chromatography (EtOAc/MeOH = 30/1, v/v) gave compound 16 (115 mg) in a yield of 60 % as
1
colourless oil. 16: = - 36.9 (c 1.00, MeOH); Rf = 0.2 (EtOAc/MeOH = 10/1, v/v); H NMR
(300 MHz, MeOH-d4) (pH = 1) δ = 7.42-7.23 (m, 10H, Ph), 6.03 (ddd, 1H, H-1’), 5.59-5.30 (m,
2H, H-7), 4.72 (d, 1H, CH2Ph), 4.68 (d, 1H, CH2Ph), 4.62 (d, 1H, CH2Ph), 4.52 (d, 1H CH2Ph),
4.10 (bs, 1H, H-4), 4.04 (d, 1H, J1,2 6.7 Hz, H-1, 3.95 (dd, 1H, J3,4 4.0 Hz, J2,3 3.8 Hz, H-3), 3.77
13
(bs, 1H, H-2), 3.43 (dd, 1H, J5a,5e 13.6 Hz, H-5e), 3.29 (dd, 1H, H-5a); C NMR (75.5 MHz,
MeOH-d4) δ = 139.1, 138.5 (2C, Ph), 131.9 (C-1’), 129.7-129.27 (Ph), 122.7 (C-2’), 759 (C-2),
Page 14 of 31

73.9 (2C, CH2Ph), 72.9 (C-3), 65.3 (C-4), 58.8 (C-1), 47.6 (C-5); MS: Calcd. for
[C21H25NO3Na]: m/z 362.1732 [M + Na]+; Found [M + Na]+ 362.1767.
4.11 1(R)-1-C-Ethyl-1,5-dideoxy-1,5-imino-xylitol (1,2,6-trideoxy-1,5-imino-6-C-ethyl-D-iditol,
17):
Following general procedure C, Pd(OH)2/C was added to a 10% solution of compound 16 (50
mg, 0.15 mmol) in MeOH/H2O and stirred under a hydrogen atmosphere. Purification by silica
gel chromatography (CHCl3/MeOH/concd NH4OH = 2/1/0.25, v/v/v) gave compound 17 (20
mg) in a yield of 84 % as colourless oil. 17: = - 5.2 (c 0.66, H2O); Rf = 0.25
1
(CHCl3/MeOH/concd NH4OH = 1/1/0.25, v/v/v); H NMR (300 MHz, D2O) δ = 3.67-3.56 (m,
3H, H-2, H-3, H-4), 3.00 (dd, 1H, J4,5e 2.6 Hz, H-5a), 2.94 (dd, 1H, J1,2 2.3 Hz, H-1), 2.83 (dd,
1H, J4,5a 3.5 Hz, J5a,5e 13.5 Hz, H-5a), 1.50-1.29 (m, 2H, H-1’), 0.67 (t, 3H, H-2’); 13C NMR
(75.5 MHz, D2O) δ = 68.3, 67.1 (3C, C-2, C-3, C-4), 56.5 (C-1), 44.9 (C-5) 20.4 (C-1’), 9.0 (C-
2’); MS: Calcd. for [C7H15NO3Na]: m/z 184.0950 [M + Na]+; Found [M + Na]+ 184.0949.
4.6
1(R)-1-C-Propyl-2,3-di-O-benzyl-1,5,dideoxy-1,5-imino-xylitol
(3,4-di-O-benzyl-1,2,6-
trideoxy-1,5-imino-6-C-propyl-D-iditol, 18):
Following general procedure B, 5-azidodeoxy-D-xylose 11 (100 mg, 0.28 mmol) was dissolved
in MeOH (5 mL) and treated with PMe3 (1M in toluene, 560 µL, 0.56 mmol). After removal of
MeOH in vacuo the cyclic iminium ion intermediate was dissolved in THF (5 mL) and
propylmagnesium bromide (2M in THF, 700 µL, 1.40 mmol) was added. Silica gel
chromatography (EtOAc/MeOH = 15/1, v/v) gave compound 18 (48 mg) in a yield of 48 % as
1
colourless oil. 18: = + 4.1 (c 1.00, MeOH); Rf = 0.15 (EtOAc/MeOH = 10/1, v/v); H
NMR (300 MHz, MeOH-d4): δ = 7.39-7.29 (m, 10H, Ph), 4.71 (d, 2H, CH2Ph), 4.66 (d, 2H,
CH2Ph), 4.62 (d, 2H, CH2Ph), 4.46 (d, 2H, CH2Ph), 3.76 (dd, 1H, J2,3 4.3 Hz, J3,4 4.5 Hz, H-3)
3.67 (m, 1H, H-4), 3.45 (dd, 1H, J1,2 3.1 Hz, H-2), 3.02 (dd, 1H, J4,5e 3.1 Hz, J5a,5e 13.6 Hz, H-
Page 15 of 31

5e), 2.94 (ddd, 1H, H-1), 2.82 (dd, 1H, J4,5a 4.0 Hz, H-5a) 1.60-1.40 (m, 2H, H-1’), 1.37-1.11 (m,
2H, H-2’), 0.90 (t, 3H, H-3’); 13C NMR (75.5 MHz, MeOH-d4): δ = 140.0, 139.3 (2C, Ph),
129.6-128.9 (Ph), 77.4 (C-2), 76.4 (C-3), 74.1, 73.5 (2C, CH2Ph), 69.1 (C-4), 55.2 (C-1), 48.0
(C-5), 32.9 (C-1’), 20.2 (C-2’), 14.6 (C-3’); MS: Calcd. for [C22H29NO3Na]: m/z 378.2045 [M +
Na]+; Found [M + Na]+ 378.2044.
4.12 1(R)1-C-Propyl-1,5,dideoxy-1,5-imino-xylitol (1,2,6-trideoxy-1,5-imino-6-C-propyl-D-
iditol, 19):
Following general procedure C, Pd(OH)2/C was added to a 10% solution of compound 18 (60
mg, 1.70 mmol) in MeOH/H2O and stirred under a hydrogen atmosphere. Purification by silica
gel chromatography (CHCl3/MeOH/concd NH4OH = 3/1/0.25, v/v/v) gave compound 19 (24
mg) in a yield of 81 % as colourless oil. Recrystallization with HCl in MeOH/EtOAc (v/v 1/1)
.
afforded the corresponding hydrochloride (19 HCl) as white crystals. Free base 19: = +
1
12.4 (c 0.40, H2O); Rf = 0.5 (CHCl3/MeOH/concd NH4OH = 1/1/0.25, v/v/v); H NMR (300
MHz, D2O) δ = 3.67-3.30 (m, 3H, H-2, H-3, H-4), 2.85-2.77 (ddd, 1H, J1,1’ 7.0 Hz, J1,2 3.3 Hz,
H-1) 2.75 (dd, 1H, J4,5e 3.78 Hz, J5a,5e 13.3 Hz, H-5e) 2.50 (dd, 1H, J4,5a 7.1 Hz, H-5a), 1.29-1.18
(m, 2H, H-1’), 1.18-0.97 (m, 2H, H-2’) 0.64 (t, 3H, H-3‘); 13C NMR (75.5 MHz, D2O) δ = 71.5,
71.4 (2C, C-2, C-3), 69.7 (C-4), 54.6 (C-1), 44.1 (C-5), 28.0 (C-1’), 18.7 (C-2’), 13.1 (C-3’);
MS: Calcd. for [C8H17NO3Na]: m/z 198.1106 [M + Na]+; Found [M + Na]+ 198.1102.
4.7 1(R)-1-C-Isopropyl-2,3-di-O-benzyl-1,5-dideoxy-1,5-imino-xylitol (3,4-di-O-benzyl-1,2,6-
trideoxy-1,5-imino-6-C-isopropyl-L-iditol, 20)
Following general procedure B, 5-azidodeoxy-D-xylose 11 (100 mg, 0.28 mmol) was dissolved
in MeOH (5 mL) and treated with PMe3 (1M in toluene, 560 µL, 0.56 mmol). After removal of
MeOH in vacuo the cyclic iminium ion intermediate was dissolved in THF (5 mL) and
isopropylmagnesium bromide (2M in THF, 700 µL, 1.40 mmol) was added. Silica gel
Page 16 of 31

chromatography (EtOAc/MeOH = 30/1, v/v) gave compound 20 (57 mg) in a yield of 57 % as
1
colourless oil. 20: = + 3.5 (c 0.80, MeOH); Rf = 0.32 (EtOAc/MeOH = 10/1, v/v); H NMR
(300 MHz, MeOH-d4) δ = 7.38-7.33 (m, 10H, Ph), 4.69 (d, 2H, CH2Ph), 4.59 (d, 1H, CH2Ph),
4.41 (d, 1H, CH2Ph), 3.90 (bs, 1H, H-3), 3.70 (bs, 1H, H-4), 3.60 (bs, 1H, H-2), 3.07 (dd, 1H,
J4,5e 3.07 Hz, J5a,5e 13.7 Hz, H-5e), 2.93 (dd, 1H, H-5a), 2.50 (bd, 1H, H-1), 1.87-1.76 (m, 1H, H-
13
1’), 1.00, 0.79 (2xd, 6H, 3xH-2’); C NMR (75.5 MHz, MeOH-d4) δ = 139.8, 139.1 (2C, Ph),
129.7-128.8 (Ph) 75.5 (C-2), 73.9 (C-3), 73.4, 73.2 (2C, CH2Ph), 67.7 (C-4), 61.4 (C-1), 49.2 (C-
5), 29.9 (C-1’), 20.5, 19.9 (2C, C-2’); MS Calcd. for [C22H29NO3Na]: m/z 378.2045 [M + Na]+;
Found [M + Na]+ 378.2042.
4.13 1(R)-1-C-Isopropyl-1,5-dideoxy-1,5-imino-xylitol (1,2,6-trideoxy-1,5-imino-6-C-isopropyl-
L-iditol, 21):
Following general procedure C, Pd(OH)2/C was added to a 10% solution of compound 20 (61
mg, 1.70 mmol) in MeOH/H2O and stirred under a hydrogen atmosphere. Purification by silica
gel chromatography (CHCl3/MeOH/concd NH4OH = 5/1/0.25, v/v/v) gave compound 21 (30
mg) in a yield of 99 % as colourless oil. 21: = - 9.3 (c 0.40, H2O); Rf = 0.4
1
(CHCl3/MeOH/concd NH4OH = 1/1/0.25, v/v/v); H NMR (300 MHz, D2O) δ = 3.66 (bs, 1H,
J2,3 1.8 Hz, J3,4 3.3 Hz, H-3), 3.67 (bs, 1H, H-2) 3.44 (bs, 1H, H-4) 2.75 (dd, 1H, J5a,5e 14.0 Hz,
J4,5a 2.3 Hz, H-5a), 2.64 (dd, 1H, J4,5e 1.9 Hz, H-5e), 2.49 (dd, 1H, J1,6 9.4 Hz, H-1) 1.87-1.75 (m,
1H, H-6), 1.00 (d, 3H, J6,7 6.7 Hz, H-7), 0.94 (d, 3H, J6,7’ 6.7 Hz, H-7’); 13C NMR (75.5 MHz,
D2O) δ = 68.9, 68.6 (2C, C-2 C-3), 67.6 (C-4), 59.7 (C-1), 46.1 (C-5), 27.7 (C-6), 19.4, 18.8 (2C,
2xC-2’); MS: Calcd. for [C8H17NO3Na]: m/z 198.1106 [M + Na]+; Found [M + Na]+ 198.1105.
4.8 1(S)-1-C-Vinyl-2,3-isopropylidene-1,5-dideoxy-1,5-imino-ribitol (1,2,6-trideoxy-1,5-imino-
3,4-O-isopropylidene-6-C-vinyl-L-allitol, 14)
Page 17 of 31

Following general procedure B, 5-azidodeoxy-D-ribose 13 (95 mg, 0.44 mmol) was dissolved in
MeOH (5 mL) and treated with PMe3 (1M in toluene, 880 µL, 0.88 mmol). After removal of
MeOH in vacuo the cyclic iminium ion intermediate was dissolved in THF (5 mL) and
vinylmagnesium bromide (1M in THF, 2.20 mL, 2.2 mmol) was added. Silica gel
chromatography (EtOAc/MeOH = 5/1, v/v) gave compound 14 (70 mg) in a yield of 80 % as
1
colourless oil. 14: = - 32.6 (c 1.00, MeOH); Rf = 0.16 (EtOAc/MeOH = 10/1, v/v); H
NMR (300 MHz, MeOH-d4) δ = 5.79 (ddd, 1H, H-1’), 5.08 (dd, 2H, H-2’), 4.25 (dd, 1H, J2,3=3,4
4.2 Hz, H-3), 3.70 (ddd, 1H, H-4), 3.61 (dd, 1H, J1,2 9.1 Hz, H-2), 2.93 (ddd, 1H, H-1), 2.78 (dd,
1H, J5a,5e 11.7 Hz, J4,5e 5.4 Hz, H-5e), 2.59 (dd, 1H, J4,5a 11.4 Hz, H-5a), 1.38, 1.22 (2C, 2xCH3);
13C NMR (75.5 MHz, MeOH-d4) δ = 138.5 (C-1’), 117.0 (C-2’), 110.8 (C-6), 79.1, 77.1 (2C, C-
2, C-3), 67.9 (C-4), 61.4 (C-1), 47.8 (C-5), 28.7, 26.6 (2C, 2xCH3).
4.9
1(S)-1-C-Benzyl-2,3-isopropylidene-1,5-dideoxy-1,5-imino-ribitol
(6-C-benyzl-1,2,6-
trideoxy-1,5-imino-3,4-O-isopropylidene-L-allitol, 23)
Following general procedure B, 5-azidodeoxy-D-xylose 13 (43 mg, 0.20 mmol) was dissolved in
MeOH (2 mL) and treated with PMe3 (1M in toluene, 400 µL, 0.40 mmol). After removal of
MeOH in vacuo the cyclic iminium ion intermediate was dissolved in THF (2 mL) and
benzylmagnesium bromide (2M in THF, 500 µL, 1.00 mmol) was added. Silica gel
chromatography (EtOAc/MeOH = 20/1, v/v) gave compound 23 (27 mg) in a yield of 51 % as
1
colourless oil. 23: = - 44.9 (c 1.00, MeOH); Rf = 0.46 (EtOAc/MeOH = 10/1, v/v); H
NMR (300 MHz, MeOH-d4) δ = 7.32-7.18 (m, Ph), 4.40 (dd, 1H, J3,4=2,3 3.9 Hz, H-3), 3.86 (ddd,
1H, H-4), 3.78 (dd, 1H, J1,2 9.1 Hz, H-2), 3.10 (dd, 1H, H-1’), 2.85 (dd, 1H, J5a,5e 11,5 Hz, J4,5e
5.4 Hz, H-5e), 2.75 (ddd, 1H, H-1), 2.59 (dd, 1H, J4,5a 11.2 Hz, H-5a), 2.42 (dd, 1H, H-1’), 1.55
(s, 3H, H-8), 1.39 (s, 3H, H-8’); 13C NMR (75.5 MHz, MeOH-d4) δ = 139.4, 130.3, 129.8, 129.7,
127.7 (Ph), 110.8 (C-6), 79.0, 77.1 (2C, C-2, C-3), 67.8 (C-4), 60.6 (C-1), 48.1 (C-5), 39.7 (C-
1’), 28.7, 26.7 (2C, 2xCH3).
Page 18 of 31

4.14 1(S)-1-C-Vinyl-1,5-dideoxy-1,5-imino-ribitol (6-C-vinyl-1,5,6-trideoxy-1,5-imino-L-allitol,
22):
Following general procedure D, compound 14 (18 mg, 0.10 mmol) gave after purification by
silica gel chromatography (CHCl3/MeOH/concd NH4OH = 5/1/0.25, v/v/v) compound 22 (15
mg) in a yield of 96 % as colourless oil. 22: = - 8.4 (c 1.05, H2O); Rf = 0.56
1
(CHCl3/MeOH/concd NH4OH = 1/1/0.25, v/v/v); H NMR (300 MHz, D2O) δ = 5.82-5.70 (m,
1H, H-1’), 5.05 (dd, 2H, H-2’), 4.11 (bs, 1H, H-3), 3.04 (ddd, 1H, H-4), 3.73-3.70 (m, 2H, H-1,
13
H-2), 3.20 (dd, 1H, J5a,5e 12.3 Hz, J4,5e 4.1 Hz, H-5e), 3.06 (dd, 1H, J4,5a 11.8 Hz, H-5a); C
NMR (75.5 MHz, D2O) δ = 129.6 (C-1’), 124.8 (C-2’), 69.7 (C-3), 68.3 (C-2), 64.7 (C-4), 56.2
(C-1), 41.5 (C-5); MS: Calcd. for [C7H13NO3H]: m/z 160.0974 [M + H]+; Found [M + H]+
160.0975.
4.15 1(S)-1-C-Benzyl-1,5-dideoxy-1,5-imino-ribitol (6-C-benzyl-1,5,6-trideoxy-1,5-imino-L-
allitol, 24):
Following general procedure D, compound 23 (30 mg, 0.10 mmol) gave after purification by
silica gel chromatography (CHCl3/MeOH/concd NH4OH = 10/1/0.25, v/v/v) compound 24 (24
mg) in a yield of 94 % as colourless oil. 24: = - 18.0 (c 1.00, H2O); Rf = 0.70
1
(CHCl3/MeOH/concd NH4OH = 1/1/0.25, v/v/v); H NMR (300 MHz, D2O) δ = 7.20-7.10 (m,
Ph), 4.02 (bs, 1H, H-3), 3.81 (ddd, 1H, J4,3 2.6 Hz, H-4), 3.61 (dd, 1H, J2,3 2.4 Hz, J1,2 10.4 Hz,
H-2), 3.38 (ddd, 1H, H-1), 3.27 (dd, 1H, H-1’), 3.00 (dd, 1H, J5e,5a 12.2 Hz, J4,5e 4.9 Hz, H-5e),
13
2.85 (dd, 1H, J4,5a 11.8 Hz, H-5a), 2.67 (dd, 1H, H-1’); C NMR (75.5 MHz, D2O) δ = 134.6,
129.7, 129.4, 129.3, 127.9 (Ph), 69.8 (C-3), 68.6 (C-2), 64.5 (C-4), 55.3 (C-1), 42.1 (C-5), 34.7
(C-1’); MS: Calcd. for [C12H17NO3H]: m/z 224.1287 [M + H]+; Found [M + H]+ 224.1668.
Page 19 of 31

4.16 1(R)-1-C-Vinyl-2,3,4-tri-O-benzyl-6-N-Cbz-1,5-dideoxy-1,5-imino-xylitol (3,4-di-O-benzyl-
N-benzylcarboyl-1,2,6-trideoxy-1,5-imino-6-C-vinyl-D-iditol, 25):
Compound 12 (180 mg, 0.59 mmol, 1 eq) was dissolved in MeOH (10 ml) and cooled to 0°C.
Et3N (166 µl, 1.17 mmol, 2 eq) and Cbz chloride (91 µl, 0.65 mmol, 1.1 eq) were added and the
reaction was allowed to warm to room temperature. Upon consumption of the starting material
(detected on TLC, solvent: EtOAc/MeOH = 10/1, v/v) the reaction mixture was concentrated
under reduced pressure, diluted in CH2Cl2 and extracted with 2N HCl and satd NaHCO3. The
organic phase was dried over Na2SO4 and concentrated under reduced pressure. The obtained
colourless oil (330 mg, 0.70 mmol) was dissolved in DMF (10 ml) and cooled to 0°C, sodium
hydride (51 mg, 52 mmol, 2.2 eq) was added and the reaction mixture was stirred for 30 minutes
at 0°C. Benzyl bromide (130 µl, 0.84 mmol, 1.2 eq) was added and the reaction mixture was
stirred until room temperature was reached. Upon consumption of the starting material (detected
on TLC, solvent: CH/EtOAc = 3/1, v/v) the reaction mixture was quenched with MeOH and
concentrated under reduced pressure. The obtained syrup was diluted in CH2Cl2 and extracted
with 2N HCl and satd NaHCO3 solution. The combined organic phases were dried over Na2SO4,
filtered and concentrated under reduced pressure. The crude material was purified using silica
gel chromatography with CH/EtOAc = 10/1, (v/v) as eluent to give compound 25 (300 mg) as
colourless oil in a yield of 90%. 25: = + 25.6 (c = 1.12, CHCl3); Rf = 0.66 (CH/EtOAc =
3/1, v/v); 1H NMR (300 MHz, CDCl3) δ = 7.47-7.30 (m, Ph), 6.17 (m, 1H, H-1’), 5.45–5.16 (m,
4 ½ H, H-1, H-2’, CH2Ph), 5.05 (bs, ½ H, H-1), 54.9 (dd, 2H, CH2Ph), 4.77 (dd, 4H, CH2Ph),
4.44, 4.22 (2xdd, 1H, J5e,5a 13.4 Hz, J5a,4 5.4 Hz, H-5a) 3.72–3.54 (m, 3H, H-2, H-3, H-4) 3.03-
2.93 (m, 1H, H-5e). Due to two pronounced rotameric populations (25) of the N-Cbz group,
signal splitting in the respective NMR spectra has been observed leading to somewhat poor
1
13
resolution of the H-NMR spectrum. C NMR (75.5 MHz, CDCl3) δ = 155.7, (d, C=O), 138.9,
138.2, 138.1, 136.5 (4C, Ph), 131.0 (d, C-1’), 130.9–127.6 (Ph), 118.2 (d, C-2’), 82.6 (d, C-2),
79.6 (d, C-3), 78.3 (C-4), 75.8 (2C, CH2Ph), 73.3, 73.1, 72.6 (2C, CH2Ph), 67.7 (CH2Ph), 55.0
Page 20 of 31

(d, C-1), 42.1 (d, C-5). Due to two pronounced rotameric populations (25) of the N-Cbz group,
13
signal splitting in the respective NMR spectra has been observed in C-NMR spectrum. MS:
Calcd. for [C36H37NO5Na]: m/z 586.2570 [M + Na]+; Found [M + Na]+ 586.2901.
6.17 1(R)-1-C-Hydroxyethyl-2,3,4-tri-O-benzyl-6-N-Cbz-1,5-dideoxy-1,5-imino-xylitol (3,4-di-
O-benzyl-N-benzylcarboyl-1,2,6-trideoxy-6-C-hydroxyehtyl-1,5-imino-D-iditol, 26):
Compound 25 (125 mg, 0.22 mmol) was added to a solution of powdered NaBH4 (50 mg, 1.33
mmol, 6 eq) in anhydrous THF (10 mL). Dimethylsulfate (DMS, 126 µl, 1.33 mmol, 6 eq) was
added and the reaction mixture was stirred at room temperature until complete consumption of
the starting material was detected by TLC (cyclohexane/EtOAc = 3/1, v/v). Subsequently H2O (2
ml), 3M NaOH (4 ml) and H2O2 (30% solution, 4 ml) were added. The aqueous layer was
separated and extracted with CH2Cl2. The combined organic layers were dried over Na2SO4,
filtered and concentrated under reduced pressure. The crude material was purified employing
silica gel chromatography (CH/EtOAc = 10/1, v/v) to give compound 26 (77 mg) as colourless
1
oil in a yield of 60 %. 26: = + 12.5 (c 1.00, CHCl3); Rf = 0.30 (CH/EtOAc = 3/1, v/v); H
NMR (300 MHz, CDCl3) δ = 7.12-6.95 (m, Ph), 5.12-4.96 (m, 2H, CH2Ph), 4.77 (dd, 2H,
CH2Ph), 4.68-4.53 (m, 5H, 2xCH2Ph, H-1), 4.34, 4.10 (2xdd, 1H, J5e,5a 13.4 Hz, J5a,4 5.4 Hz, H-
5a) 3.64–3.46 (m, 3H, H-2, H-3, H-2’) 3.46–3.28 (m, 2H, H-4, H-2‘), 2.63 (dd, 1H, H-5e), 2.08–
1.96, 1.66–1.46 (2xm, 2H, H-1’). Due to two pronounced rotameric populations (26) of the N-
Cbz group, signal splitting in the respective NMR spectra has been observed leading to
1
13
somewhat poor resolution of the H-NMR spectrum. C NMR (75.5 MHz, CDCl3) δ = 156.54
(d, C=O), 138.8, 138.1, 137,9, 136.2 (Ph), 128.7-127.7 (Ph), 82.0 (C-2), 79.2 (d, C-3), 77.9 (d,
C-4), 75.7 (CH2Ph), 73.6, 73.2, 72.8 (3C, CH2Ph), 68.0 (d, CH2Cbz), 58.3 (d, C-2’), 49.7 (d, C-
1), 41.5 (d, C-5), 27.2 (d, C-6). Due to two pronounced rotameric populations (26) of the N-Cbz
13
group, signal splitting in the respective NMR spectra has been observed in C-NMR spectrum.
MS: Calcd. for [C36H39NO6Na]: m/z 604.2675 [M + Na]+; Found [M + Na]+ 604.2679.
Page 21 of 31

4.17 1(R)-1-C-Hydroxyethyl-1,5-dideoxy-1,5-imino-xylitol (1,2,6-trideoxy-6-C-hydroxyehtyl-1,5-
imino-D-iditol, 27):
Following general procedure C, Pd(OH)2/C was added to a 10% solution of compound 26 (60
mg, 0.10 mmol) in MeOH/H2O and stirred under a hydrogen atmosphere. Purification by silica
gel chromatography (CHCl3/MeOH/concd NH4OH = 3/1/0.25, v/v/v) gave compound 27 (15
mg) in a yield of 82 % as colourless oil. 27: = - 6.9 (c 1.00, H2O); Rf = 0.55
1
(CHCl3/MeOH/concd NH4OH = 1/1/0.25, v/v/v); H NMR (300 MHz, D2O) δ = 4.01-3.92 (m,
2H, H-3, H-4), 3.91–3.85 (dd, 1H, J2,1 2.4 Hz, J2,3 4.9 Hz, H-2) 3.70 (dd, 1H, H-1’), 3.61 (dd, 1H,
H-1) 3.42-3.35 (m, 1H, H-5a), 3.29–3.23 (m, 1H, H-5e), 1.95-1.85(m, 2H, H-2’); 13C NMR (75.5
MHz, D2O) δ = 68.1, 67.2, 66.0 (3C, C-2, C-3, C-4), 57.8 (C-2’), 53.5 (C-1), 45.3 (C-5), 29.8 (C-
1’); MS: Calcd. for [C7H15NO4Na]: m/z 200.0899 [M + Na]+; Found [M + Na]+ 200.0892.
Acknowledgment
Financial support by the Austrian Academy of Sciences (ÖAW) is gratefully acknowledged
(DOC-fellowship for M.Z.). Support from NAWI Graz is gratefully acknowledged (M.Z.,
T.M.W). A.G.S. thanks the European Molecular Biology Organization (EMBO) for a long-term
postdoctoral fellowship.
Figure 1. Structures of iminoalditols 1-10.
Page 22 of 31

Figure 2: X-Ray structures of compounds 12 (left) and 19 (right).
Scheme 1: SAW/Grignard reaction sequence: Staudinger reaction of azidodeoxy aldose I with
phosphine reagents to the corresponding phosphazene II followed by intramolecular aza-Wittig
reaction leads to cyclic imine intermediate III, which can be trapped by Grignard reagents
affording the target 1-C-alkyl iminoalditols IV.
Scheme 2. a) PMe3, THF then BnMgBr, 40%; b) PMe3, MeOH then THF, BnMgBr, 85%; c)
PMe3, THF then vinylMgBr, 20%; d) PMe3, MeOH then THF, vinylMgBr, 80%.
Page 23 of 31

Scheme 3: Steric control driving the addition of benzylmagnesium bromide to give exclusive
formation of 1,2-trans product 12.
Scheme 4: Steric control driving the addition of vinylmagnesium bromide to give exclusive
formation of 1,2-trans product 14.
Scheme 5: a) PMe3, MeOH, then THF, RMgBr b) Pd/C, H2, MeOH, 15: 95%, 17: 84%, 19:
81%, 21: 99% c) HCl, H2O, pH = 2, 22: 96%, 24: 94%.
Page 24 of 31

Scheme 6: a) CbzCl, pyr, then BnBr, NaH, DMF, 90 % b) NaBH4, DMS, 60% c) Pd/C, H2,
MeOH, 82%.
Table 1: Yields of the SAW Grignard reaction sequence using two alternative methods: A: THF
as single solvent; B: MeOH for the SAW reaction, THF for the Grignard reaction.
Sugar
Grignard
product
yield %
configuration conformation
substrate reagent
11
11
11
11
13
13
BnMgBr
12
16
18
A: 40
B: 85
(S), 1,2-trans 4C1
vinylMgBr
C3H7MgBr
A: 38
B: 60
(R), 1,2-cis
(R), 1,2-cis
(R), 1,2-cis
1C4
1C4
1C4
A: 35
B: 48
(CH3)2CHMgBr 20
A: n.p.
B: 57
vinylMgBr
BnMgBr
14
23
A: 20
B: 80
(S), 1,2-trans 4C1
(S), 1,2-trans 4C1
A: 22
B: 51
Page 25 of 31

Table 2. Ki-values [M] of compounds with ABG = -glucosidase/-galactosidase from Agrobacterium sp.; E. coli = lac Z -galactosidase from E.
coli; Fabrazyme = commercial recombinant human lysosomal -galactosidase; -glucosidase S. cerevisae; human -glucocerebrosidase Gaucher;
N.I. = no inhibition or weak inhibition with estimated Ki values higher than 1 mM.
Compounds
Enzyme
15
46.6
N.I.
N.I.
N.I.
5.9
17
27.2
N.I.
N.I.
N.I.
2.3
19
10.9
N.I.
N.I.
N.I.
1.3
21
131.3
N.I.
27
30.2
N.I.
N.I.
N.I.
26.7
-Glu, ABG
-Gal, E. coli
N.I.
Fabryzyme, -Gal
-Glc, S. cerv.
-Glc, Gaucher
N.I.
12.4
Page 26 of 31

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