Synthesis of C(2)-Substituted manno-Configured Tetrahydroimidazopyridines and Their Evaluation as Inhibitors of Snail β-Mannosidase

Article abstract of DOI:10.1002/hlca.200390293

It was shown that retaining β-glucosidases and galactosidases of families 1-3 feature a strong interaction between C(2)OH of the substrate and the catalytic nucleophile. An analogous interaction can hardly take place for retaining β-mannosidases. A structure-activity comparison between the inhibition of the β-glucosidase from Caldocellum saccharolyticum (family 1) and β-glucosidase from sweet almonds by the gluco-imidazoles 1-6, and the inhibition of snail β-mannosidase by the corresponding manno-imidazoles 8-13 does not show any significant difference, suggesting that also the mechanisms of action of these glycosidases do not differ significantly. For this comparison, we synthesized and tested the manno-imidazoles 9-13, 28, 29, 32, 35, 40, 41, 43, 46, 47, and 50. Among these, the alkene 29 is the strongest known inhibitor of snail β-mannosidase (K_i= 6 nM, non-competitive); the aniline 35 is the strongest competitive inhibitor (Ki=8 nM).

Full text of DOI:10.1002/hlca.200390293

3482
Helvetica Chimica Acta Vol. 86 (2003)
Synthesis of C(2)-Substituted manno-Configured Tetrahydroimidazopyridines
and Their Evaluation as Inhibitors of Snail b-Mannosidase
by Miroslav Terinek and Andrea Vasella*
Laboratorium f¸r Organische Chemie, ETH-Hˆnggerberg, Wolfgang Pauli-Strasse 10, CH-8093 Z¸rich
It was shown that retaining b-glucosidases and galactosidases of families 1 3 feature a strong interaction
between C(2)OH of the substrate and the catalytic nucleophile. An analogous interaction can hardly take place
for retaining b-mannosidases. A structureÀactivity comparison between the inhibition of the b-glucosidase from
Caldocellum saccharolyticum (family 1) and b-glucosidase from sweet almonds by the gluco-imidazoles 1 6,
and the inhibition of snail b-mannosidase by the corresponding manno-imidazoles 8 13 does not show any
significant difference, suggesting that also the mechanisms of action of these glycosidases do not differ
significantly. For this comparison, we synthesized and tested the manno-imidazoles 9 13, 28, 29, 32, 35, 40, 41,
43, 46, 47, and 50. Among these, the alkene 29 is the strongest known inhibitor of snail b-mannosidase (Ki ˆ
6 nm, non-competitive); the aniline 35 is the strongest competitive inhibitor (Ki ˆ 8 nm).
Introduction. The strong inhibition of b-glucosidases by imidazoles of type 1 [1
3] has been rationalized by the similarity of shape of the inhibitor and of the putative
reactive intermediate, an oxycarbenium cation, and by the cooperative interaction of
the imidazole with the catalytic nucleophile and acid [4]. A correlation between the
inhibition constant and the pK value of the C(2)- and C(3)-acetamido imidazoles 7 and
14 16, and by related azoles has established that substituents at C(3) lower the
inhibitory activity [5]. The structureÀactivity relation (SAR) resulting from varying
the C(2)-substituents has been studied in detail [6]. It was shown that the HOCH2
group at C(2) in 2, and particularly the flexible hydrophobic PhCH2CH2 group in 3 lead
to an improved inhibition, with Ki values as low as 0.1n m (against Caldocellum
saccharolyticum b-glucosidase)1). The C(2)-substituents affect both the strength and
the type of the inhibition (competitive or mixed, with a varying between 2.5 and 15).
Legler and Withers evidenced that the C(2)OH group of b-glucosides and b-
galactosides interacts with the catalytic nucleophile of the retaining b-glucosidases and
b-galactosidases of families 1 [8], 2 [9], and 3 [10][11]. 2-Deoxy- and 2-deoxy-2-fluoro-
b-d-glucosides and -galactosides are cleaved much less readily than the parent
substrates, the rate-determining step being deglycosylation of the enzyme. The
transition state for this reaction is considered very similar to that of the enzyme
glycosylation [9], and the most important interaction in the transition state was
considered with the C(2)OH2). That 2-deoxyglucosides are cleaved less readily than
the parent substrates is surprising, as the OH group at C(2) is known to destabilize an
1
)
)
Similar effects of these substituents on the inhibition of Escherichia coli b-galactosidase and almonds b-
glucosidase have recently been reported for l-arabinose-derived imidazoles [7].
However, a crystal structure of the retaining b-glucosidase from maize (ZMGlu1) in complex with 4-
nitrophenyl-b-d-thioglucoside showed only interactions of C(3)-, C(4)- and C(6)OH of the glucoside with
the enzyme [12].
2

Helvetica Chimica Acta Vol. 86 (2003)
3483
oxycarbenium cation [13]. It appears improbable that the catalytic nucleophile of
retaining b-mannosidases will similarly interact with C(2)OH located on the opposite
side of the b-mannopyranoside ring. This prompts the question to which extent the
mechanism of action of retaining b-glucosidases and b-mannosidases differ from each
other. We wondered if a comparison of the SAR for the inhibition of retaining b-
glucosidases with the SAR for the inhibition of retaining b-mannosidases by C(2)-
substituted gluco- and manno-configured imidazoles, respectively, would suggest such a
difference, or not.
So far, the inhibitory activity of the 2- and 3-acetamido-d-manno-imidazopyridines
14 and 16 has been compared to that of the unsubstituted imidazopyridine 8, and to the
inhibition of b-glucosidases from Caldocellum saccharolyticum (family 1) and from
sweet almonds by the corresponding gluco-imidazopyridines 7, 15, and 1, respectively
[5]. A similar effect of the substituent at C(3) was observed. We decided to further
explore the inhibition of snail b-mannosidase by manno-imidazopyridines possessing
further substituents at C(2), differing in polarity and flexibility, and to compare the
inhibition of the relevant mannosidases and glucosidases by the manno- and gluco-
imidazopyridines 9 13 and 2 6, respectively.
We planned to prepare the manno-imidazopyridines by first iodinating the known
imidazopyridine 17 (Scheme 1). The resulting C(2)-iodinated intermediate 20 should
allow the straightforward synthesis of the desired manno-imidazopyridines
(Schemes 1 3).
Synthesis. The manno-imidazopyridine 17 is available from 5-amino-2,3,4,6-tetra-
O-benzyl-5-deoxy-d-gluconolactam in three steps [2], leading to mixtures of 17 and its
gluco-analogue in ratios of up to 3 :1. We obtained 17 in an overall yield of 35 37% on
a scale of 15 30 g3). The 2-iodoimidazopyridine 20 (Scheme 1) was prepared similarly
as described for the corresponding 2-halo-gluco- and -galacto-imidazoles [6][15].
Treatment of 17 with excess NIS led to the 2,3-diiodo derivative 18 (80%), while milder
conditions resulted in the formation of the 3-iodo derivative 19 (55%) besides 18
(22%). Mono-deiodination of 18 by sequential treatment with EtMgBr and H2O
3
)
Similar results were obtained, on a scale of 100 mg, by starting from 5-amino-2,3,4,6-tetra-O-benzyl-5-
deoxy-d-mannonolactam [14].

3484
Helvetica Chimica Acta Vol. 86 (2003)
Scheme 1
a) N-Iodosuccinimide (NIS), DMF, 808; 80% of 18. b) NIS, DMF, 508; 56% of 19, 23% of 18. c) EtMgBr, THF;
88%. d) BCl3, CH2Cl2, À 788 ! 108; 97% of 9, 64% of 13, 56% of 21, 85% of 28. e) 1. EtMgBr, THF, 2. DMF,
À 358 ! 238; 85%. f) NaBH4, EtOH; 89%. g) Methyl acrylate, Pd(OAc)2[P(2-tolyl)3]2, K2CO3, DMF, 908; 94%
of 24. h) Styrene, Pd(OAc)2[P(2-tolyl)3]2, K2CO3, DMF, 808; 45% of 25. i) H2, Pd/C, AcOEt/MeOH/AcOH;
88% of 11. j) H2, Pd(OH)2/C, AcOEt/MeOH/H2O/AcOH; 46% of 10. k) H2, Pd/C, AcOEt/MeOH/AcOH;
48%. l) 1m aq. HCl, 608; 85%. m) Phenylacetylene, [Pd(PPh3)4], CuI, Et3N, DMF, 808; 83%. n) H2, Pd(OH)2/C,
AcOEt/MeOH/H2O/AcOH; 80%. o) Diethyl benzylphosphonate, t-BuOK, THF, 08; 87%. p) N,N-Dimethy-
laniline, AlCl3; 42%.
yielded 88% of the 2-iodo derivative 20. The unprotected iodoimidazopyridines 214)
and 13 were obtained by BCl3-promoted debenzylation [16] of 19 (56%) and 20 (64%),
respectively.
The 2-(hydroxymethyl)imidazopyridine 9 was synthesized similarly to the gluco-
analogue 2 [6] by sequential formylation of 20 to the carbaldehyde 22 (85%), reduction
of 22 to the alcohol 23 (89%), and debenzylation (BCl3, 97%).
4
)
Similarly to the C(3)-substituted gluco- and manno-imidazopyridines 15 and 16 [5], 21 possesses a
distorted conformation (see below) and proved a poor inhibitor of the snail b-mannosidase (Ki ˆ 73 mm).

Helvetica Chimica Acta Vol. 86 (2003)
3485
To prepare the [2-(methoxycarbonyl)ethyl]-, the 2-(carboxyethyl)-, and the (2-
phenylethyl)imidazopyridines 11, 12, and 10, respectively, we again followed the
synthesis of their gluco-analogues 4, 5, and 3 [6]. The reaction of 20 with methyl
acrylate or styrene under standard Heck conditions (Pd(OAc)2, Ph3P, Et 3N or K2CO3,
DMF, 80 908) gave the coupling products 24 (54%) and 25 (25%), respectively,
besides variable amounts of 17 and 20. The yield of 24 and 25 was increased to 94 and
45%, respectively, by replacing Pd(OAc)2/PPh3 by Herrmann×s catalyst [17]. In contrast
to the gluco-series [6], addition of H2O (14% (v/v)) lowered the yield of 25 to 18 24%.
Treating the benzylated acrylate 24 with H2 in the presence of Pd/C (AcOH, 6 bar)
afforded the unprotected methyl propanoate 11 (88%) that was hydrolyzed to the acid
12. Hydrogenation of the 2-phenylethenyl derivative 25 under conditions that led to
smooth debenzylation of 24 proceeded slowly and yielded mostly the benzylated 2-
phenylethyl derivative 26, while treatment with H2 in the presence of Pd(OH)2/C gave
the desired debenzylated 10 (46%). The overall yield of 10 from the iodoimidazopyr-
idine 20 was significantly increased by proceeding via the alkyne 27. It was obtained in
83% yield by Sonogashira coupling [18 20] of 20 with phenylacetylene, followed by
hydrogenation (proceeding more rapidly than the one of 25) to the imidazopyridine 10
(80%).
In addition to the manno-imidazopyridines 9 13 corresponding to known gluco-
isomers, we prepared the unprotected phenylethynyl and phenylethenyl derivatives 28
and 29, respectively, to learn about the influence of flexibility of the substituent at C(2).
BCl3-Promoted debenzylation of 27 yielded 85% of 28, while the analogous
debenzylation of 25 to 29 proceeded in only 34%. This yield was increased to 42%
by using AlCl3/N,N-dimethylaniline [21], providing 29 in an overall yield of 19% from
20. The overall yield of 29 was increased to 31% by alkenylating 22 with diethyl
benzylphosphonate [22][23], to provide 87% of 255).
Further analogues of the 2-phenylethyl derivative 10, which were considered of
interest, are the phenoxymethyl and anilinomethyl derivatives 32 and 35, respectively
(Scheme 2). We had observed [6] that the introduction of the HOCH2 substituent of 2
led to a fourfold increase of the inhibition of the C. saccharolyticum b-glucosidase,
while the introduction of the H2NCH2 group lowered the inhibition from Ki ˆ 20 nm to
IC50 ˆ 150 nm. This was rationalized by postulating a binding interaction between the
catalytic acid, and both the imidazole N(1) and the HOCH2ÀC(2) group, and by the
‡
competing interaction of the H3N CHÀC(2) group and the catalytic acid with N(1). A
combination of the hydrophobic Ph group with the H-bond accepting ether O-atom in
32, or with the (weakly basic) NH in 35 should then lead to strong inhibition.
To prepare the phenoxymethyl derivative 32, we treated the alcohol 23 with SOCl2.
The chloride 30 was obtained in 86% yield after chromatographic purification. Treating
this chloride with phenol and t-BuOK in DMF [25] yielded 74% of 31; other conditions
[26 29] (cf. Exper. Part) resulted in lower yields. The overall yield of 31 from 23 was
increased from 64 to 70% when 30 was not purified. Debenzylation of 31 (Pd(OH)2/C,
1atm.) yielded the [(phenoxy)methyl]imidazopyridine 32 (63%) and the cyclohex-
yloxymethyl analogue 33 (9%)6).
5
)
No reaction was observed when the aldehyde 22 was subjected to a Zn-promoted olefination with a,a-
dichlorotoluene in the presence of Me3SiCl [24].

3486
Helvetica Chimica Acta Vol. 86 (2003)
Scheme 2
a) SOCl2, CH2Cl2; 86%. b) PhOH, t-BuOK, DMF, 808; 74%. c) H2, Pd(OH)2/C, AcOEt/MeOH/H2O/AcOH;
63% of 32 and 9% of 33. d) 1. Aniline, MgSO4, CH2Cl2, 2. NaBH4, EtOH; 75%. e) BCl3, CH2Cl2, À 788 ! 158;
77%. f) 1-Fluoro-2-nitrobenzene, NaH, DMF, 808; 94%. g) 1-Fluoro-4-nitrobenzene, NaH, DMF, 808; 89%. h)
1-Fluoro-2,4-dinitrobenzene, NaH, DMF; 63%. i) 1-Fluoro-3-nitrobenzene, NaH, DMF, 1408; 56%. j) Anisole,
AlCl3, CH2Cl2; 75% of 40, 72% of 41, 75% of 42, 54% of 43.
To study the influence of substituents of the Ph ring of 32, we prepared the mono-
and dinitrophenyl-substituted imidazoles 40 43. For this, the alcohol 23 was O-
arylated with either 1-fluoro-2-nitro- and 1-fluoro-4-nitrobenzene (NaH, DMF, 808) to
give the imidazopyridines 36 (94%) and 37 (89%), respectively. Similarly, treatment of
23 with NaH and 1-fluoro-3-nitrobenzene at elevated temperature (1408) gave the (3-
nitrophenyloxy)methyl derivative 39 (56%). The reaction of 23 with 1-fluoro-2,4-
dinitrobenzene (DNP; NaH, DMF, 808) did not lead to the (2,4-dinitrophenyloxy)-
methyl derivative 38, which was, however, obtained in 63% yield by performing the
reaction at 238. The imidazopyridines 36 39 were debenzylated with AlCl3 in the
presence of anisole [21] to provide 40 (75%), 41 (72%), 42 (75%), and 43 (54%)7).
The compound 42 was not stable enough to be tested.
Reductive amination of the carbaldehyde 22 with aniline yielded 75% of the
(phenylamino)methyl derivative 34. Debenzylation with BCl3 provided 35 (77%).
6
)
)
For examples of a Pd-catalyzed hydrogenation of phenols, cf. [30 34].
7
The 4-nitrophenyl ether 41 was also obtained (70%) by BCl3-promoted debenzylation. Cleavage of the
C(2)CH2ÀOC6H4NO2 bond was not observed, while the BCl3-promoted debenzylation of 31 to 32 was
accompanied by substantial cleavage of the C(2)CH2ÀOPh bond (cf. Exper. Part).

Helvetica Chimica Acta Vol. 86 (2003)
3487
Considering the strong effects of the short HOCH2 and H2NCH2 substituents, we
also prepared the ester 46, the corresponding acid 47, and the tetrazolylimidazo-
pyridine 50 (Scheme 3). The tetrazolyl group is an established mimic of the carboxy
group [35][36]. The acid 47 and the tetrazolyl derivative 50 should, however, differ by
their pK values.
Scheme 3
a) MnO2, NaCN, AcOH/MeOH; 78% of 44 or 65% of 44 and 21% of 45 (cf. Exper. Part). b) 1. BuLi, THF, 2.
ClCOOMe, À 788 ! 238; 43%. c) H2, Pd/C, AcOEt/MeOH/AcOH; 88%. d) KOH, EtOH/H2O, 508; 83%. e) 1 .
EtMgBr, THF, 2. TsCN; 73%. f) Me3Al, Me3SiN3, toluene, 808; 76%. g) BCl3, CH2Cl2, À 788 ! 108; 85% of 50.
The methyl ester 44 was obtained by two routes. Oxidation of the carbaldehyde 22
(MnO2, NaCN, MeOH) [37][38] provided 44 in a yield of 78%8). A shorter, but
lower-yielding route, viz. lithiation of the iodoimidazopyridine 20 followed by
methoxycarbonylation [40][41] also provided 44 (35 48%), besides the deiodonation
product 17 (42 58%). Debenzylation of 44 (H2, Pd/C, AcOH) yielded 88% of the
ester 46 that was saponified to afford 83% of the desired acid 47. The ester 46 was
hydrolysed by treatment with 1m HCl at 50 908.
To synthesize the tetrazolyl derivative 50, we prepared the 2-carbonitrile 48,
similarly as described for its gluco-analogue [6], by treatment of the organomagnesium
derivative of the 2-iodoimidazopyridine 20 with TsCN. Attempts to improve the yield
of 48 (73%) by Pd-catalyzed coupling of 20 with various metal cyanides were not
successful. Thus, treatment of 20 with Zn(CN)2 in DMF at 1508 in the presence of
[Pd(PPh3)4] [42 44] afforded 48 in only 40% yield, while almost no reaction was
observed when 20 was heated with either NaCN, CuI, and [Pd(PPh3)4] in DMF or
MeCN [45], or with Zn(CN)2 in DMF in the presence of Pd(OAc)2 [46]. To form the
tetrazole ring, the 2-carbonitrile 48 was subjected to a 1,3-dipolar cycloaddition with in
situ prepared Al(N3)3 [47]. This yielded 76% of the tetrazolyl derivative 499), which
was debenzylated (BCl3) to afford the tetrazolylimidazopyridine 50 (85%).
8
)
The methyl ester 44 was isolated by aqueous workup, followed by chromatography. If aqueous workup was
omitted, chromatography (SiO2; hexane/AcOEt) led to isolation of 44 (65%) and the corresponding ethyl
ester 45 (21%); transesterification was presumably catalysed by residual AcOH (cf. [39]).
Similar results were obtained when 48 was treated with Me3SiN3 in toluene at 1108 in the presence of
Bu2SnO [48], while no reaction was observed upon treating 48 with either NaN3 and NH4Cl in DMF [49
51], or with NaN3 in DMSO [52].
9
)

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Helvetica Chimica Acta Vol. 86 (2003)
The structure of the diiodoimidazopyridine 18 was established by X-ray analysis10
)
(Fig.). Similarly to its gluco-analogue [6], it adopts a conformation between 6H711) and
a sofa conformation with C(7) below the ring plane, as expected from the 1,5-
interaction between the I-substituent at C(3) and the C(5)ÀCH2OBn group (cf.
[5][6]). This conformation is also observed in solution, as evidenced by the vicinal
coupling constants (cf. Table 4 in Exper. Part). As expected, a similar conformation is
also adopted by the 3-iodoimidazopyridine 19, while the 2-iodoimidazopyridine 20,
6
similarly to the parent 17 [2], is a 2 :1mixture of the 7H6 and H7 conformers.
Figure. ORTEP Representation of the crystal structure of the diiodoimidazole 18
With the exception of the additional signals of the substituents at C(2) and their
1
influence on the chemical shifts of HÀC(3), C(2), and C(3), the H- and 13C-NMR
spectra of the protected and unprotected C(2)-functionalized imidazopyridines 9 12,
22 48, and 50 closely resemble those of the 2,3-unsubstituted imidazopyridines 17 and
8 [2]. The 13C signals of C(5) C(8) of the protected imidazoles 27, 31, and 34 (cf.
Table 5 in Exper. Part) were assigned on the basis of HSQC.GRASP spectra; those of
the other imidazopyridines were assigned by analogy. The signals of C(5) C(8) of the
unprotected imidazopyridines (cf. Table 6 in Exper. Part) differ from those of the O-Bn-
10
)
The crystallographic data have been deposited with the Cambridge Crystallographic Data Centre as
deposition No. CCDC-213714. Copies of the data can be obtained, free of charge, on application to the
CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax: ‡44(1223)336033; e-mail: deposit@ccdc.cam.-
ac.uk).
Since the direction of the atom numbering of imidazopyridines (cf. 17 in Scheme 1) is opposite to that of
pyranosides, the sides above and below the plane of the imidazopyridines, as defined by the clockwise and
counterclockwise numbering, are interchanged with those defined according to carbohydrate numbering.
11
)

Helvetica Chimica Acta Vol. 86 (2003)
3489
protected analogues by upfield shifts of ca. 5 9 ppm. A strong deshielding effect for
HÀC(5), HÀC(7), and HÀC(8) with Dd values of 0.14, 0.20, and 0.64 ppm (as
compared to 17), respectively, is observed for the tetrazolyl derivative 49 (cf. Table 7 in
Exper. Part), while the coupling constants did not change significantly.
Enzymatic Tests and Discussion. The C(2)-substituted imidazopyridines 9 13, 28,
29, 32, 35, 40, 41, 43, 46, 47, and 50, and the 2,3-unsubstituted imidazopyridine 8 were
tested as inhibitors of b-mannosidase from snail (acetate buffer, 258, pH 4.5) and a-
mannosidase from Jack beans (acetate buffer‡ ZnCl2, 378, pH 4.5), with the
corresponding 4-nitrophenyl mannosides as substrates. The inhibition data for the b-
mannosidase Ki (in some cases IC50) and Ki/KM and the pK values for those manno-
and gluco-imidazopyridines that possess the same substituents at C(2) are compiled in
Table 1, while the data for the inhibition of this b-mannosidase by the other manno-
imidazopyridines are listed in Table 2. Table 3 shows the inhibition data for the a-
mannosidase from Jack beans, and the selectivity of the inhibition of the two
mannosidases.
A comparison of the inhibition data in Table 1 shows qualitatively the same
dependence of the Ki and Ki/KM values on the nature of the substituent at C(2) in the
gluco- and manno-series. The difference between the inhibition of the two glucosidases
is somewhat smaller than the difference between the inhibition of the glucosidases and
the mannosidase. That the manno-imidazopyridines, overall, are weaker inhibitors than
the gluco-imidazopyridines may reflect the different pH optima of the glycosidases, and
the different extent to which the imidazopyridines are protonated at the pH of the
assay. Considering this, the quantitative differences between the relative Ki values for
imidazopyridines of the gluco- and manno-series are small. This may reflect, in part, the
strong interaction of a protonated imidazopyridine with the catalytic nucleophile [4],
meaning that only the interaction with the catalytic acid is impaired for the more
strongly basic imidazopyridines. This comparison of the SAR in the gluco- and manno-
series evidences that the mechanisms of action for b-glucosidases of family 1and snail
b-mannosidase do not differ significantly. A recent rationalization of the interaction of
the catalytic nucleophile with HOÀC(2) in b-glucosidases, but not in b-mannosidases
[54], suggests that this factor should decrease rather than increase the mechanistic
differences. It is, however, not clear how far this finding can be generalised to include
retaining b-glucosidases and -mannosidases of other families.
A comparison of the inhibition by the 2-phenylethyl derivative 10 and its analogues
32, 35, 40, 41, and 43 shows that the aniline 35 is the best inhibitor, in keeping with the
rationalization of the effect of the C(2)CH2OH and C(2)CH2NH2 substituents in the
gluco-imidazopyridines. The phenoxy derivative 32 is only a slightly weaker (mixed-
type) inhibitor, and the introduction of a NO2 group weakens the inhibition, with the
exception of the 3-nitro derivative 43, where the effects of lowering the basic properties
of the phenoxy group and of the modified interaction with the b-mannosidase appear to
cancel out. Unexpectedly, the restriction of the flexibility of the 2-phenylethyl-
imidazopyridine, and the concomitant lowering of the pK value, as realized in the
phenylethynyl and 2-phenylethenyl derivatives 28 and 29, respectively, resulted in very
strong, albeit no longer competitive inhibition. The carboxylic acid 47 (essentially
dissociated at the pH of the assay) is a weak, mixed-type inhibitor (Ki ˆ 1.21 mm). The

Table 1. The C(2)-Substituted manno- and gluco-Imidazoles 8 13 and 1 6: pKHA Values and a Comparison of the Inhibition of the b-Mannosidase from Snail, and of the b-
Glucosidases from Caldocellum saccharolyticum and from Sweet Almonds
manno-
Inhibition of
gluco-Imidazolesb) Inhibition of b-glucosidasesb)
Comparison of Ki values
Imidazoles b-mannosidasea)
from Caldocellum from sweet
Ki (rel)
b-Mannosidase b-Glucosidase
(snail)
Ki (rel)
Ki (rel)
b-Glucosidase
saccharolyticum
almonds
(C. saccharolyticum) (almonds)
c
d
e
R
No. pKHA Ki [nm] Ki/KM
)
No.
pKHA
Ki [nm] Ki/KM
170
)
Ki [nm] Ki/KM )
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a) At 258 and pH 4.5. b) Data taken from [6]. c) KM ˆ 0.61m m (mean value of all measurements; cf. Exper. Part). d) KM ˆ 0.51m m [53]. e) KM ˆ 3.0 mm. ) No inflection of
i
j
the titration curve was observed between pH values of 1.7 and 4.9. g) IC50/2. h) Taken from [5]. ) IC50 ˆ 115 nm [3]. ) Mixed-type inhibition (a ˆ 3.2). k) No second pK
l
value was observed between pH 2.2 and 5.5. ) Mixed-type inhibition (a ˆ 5.3). m) Mixed-type inhibition (a ˆ 2.5). n) Non-competitive inhibition. o) Mixed-type inhibition
(a ˆ 15).

Helvetica Chimica Acta Vol. 86 (2003)
3491
Table 2. The C(2)-Substituted manno-Imidazoles 8, 28, 29, 32, 35, 40, 41, 43, 46, 47, and 50: pKHA Values and a
Comparison of the Inhibition of the b-Mannosidase from Snail: Ki, Ki/KM, and Ki (rel)
manno-Imidazoles
Inhibition of b-mannosidasea)
b
R
No.
pKHA
Ki [nm]
Ki/KM
)
Ki (rel)
COOH
COOMe
CHN4
H
CH2OC6H4(2-NO2)
CH2OC6H4(4-NO2)
CH2OC6H4(3-NO2)
CH2OPh
47
46
50
8
40
41
43
32
35
28
29
4.70/2.2 5.3c)
2.2 5.3d)
1
a ˆ214.8)
0 (
1.98 ¥ 10À3
2.33 ¥ 10À4
1.97 ¥ 10À4
1.89 ¥ 10À4
7.05 ¥ 10À5
10.522
1.235
1.043
ꢀ1
142 (a ˆ 4.3)
20 (4.54/6.411
a ˆ 6.1)
5.7e)
1
)
1
5
f
4.25
4.15
4.36
43
0.374
0.191
0.104
0.104
0.070
0.061
0.052
À5
22 (a ˆ 3.8)
3.61¥ 10
12
1.97 ¥ 10À5
1.97 ¥ 10À5
1.31 ¥ 10À5
4.39
12 (a ˆ 2.0)
CH2NHPh
CꢀCPh
5.09/2.3 7.4c)
8
2.1 5.4 d
4.77
)
7 (a ˆ 1.8)
1.15 ¥ 10
À5
CHˆCHPh
6g)
9.84 ¥ 10À6
a) At 258 and pH 4.5. b) KM ˆ 0.61m m (mean value of all measurements; cf. Exper. Part). c) No second pK value
was observed in the indicated pH range. d) No inflection of the titration curve was observed between indicated
pH values. e) Taken from [5]. f) IC50 ˆ 115 nm [3]. g) Non-competitive inhibition.
Table 3. The C(2)-Substituted Imidazoles 8 13, 28, 29, 32, 35, 40, 41, 43, 46, 47, and 50: pKHA Values and a
Comparison of the Inhibition of the a-Mannosidase from Jack Beans and of the b-Mannosidase from Snail: Ki,
Ki/KM, and Ki (rel)
manno-
Imidazoles
Inhibition of
Inhibition of
Comparison of
a-mannosidasea) b-mannosidaseb) Ki values
c
R
No. pKHA
Ki [mm] Ki/KM
)
Ki [nm]
Ki (rel)
Ki (rel)
a-mannosidase (a-mannosidase/
(Jack beans) b-mannosidase)
COOMe
CH2OH
I
CꢀCPh
COOH
CHN4
CH2CH2COOH
H
CH2CH2COOMe 11 5.52
46 2.2 5.3d)
12.5
5.43 ¥ 10À3 142
16.667
5.04
4.667
3.213
1.773
1.04
88.0
56.4
15.4
344.3
1.1
9
5.08
3.78 1.64 ¥ 10À3 67
13 1.7 4.9d)
3.50 1.52 ¥ 10À3 227
2..401501¥ 1
28 2.1 5.4 d
)
7
À3
47 4.70/2.2 5.3e) 1.33
50 4.54/6.410.78 03.39 ¥ 1
5.78 ¥ 10À4 1210
À4
120
6.5
7.8
12 4.15/2.2 5.5e) 0.78 3.39 ¥ 10À4 100
1.04
8
5.7f)
0.75g) 3.26 ¥ 10À4 115
ꢀ16.5
À4
0.60 2.61¥ 10
28
0.8
21.4
22.8
11.5
25
10.4
2.2
CH2OPh
32 4.39
10 6.04
29 4.77
0.273 1.19 ¥ 10À4 12
0.364
0.307
0.2
0.167
0.125
CH2CH2Ph
CHˆCHPh
0.23 1.00 ¥ 10À4 20
0.15 6.52 ¥ 10À5
6
CH2OC6H4(3-NO2) 43 4.36
CH2OC6H4(2-NO2) 40 4.25
0.125 5.43 ¥ 10À5 12
0.094 4.09 ¥ 10À5 43
CH2NHPh
CH2OC6H4(4-NO2) 41 4.15
35 5.09/2.3 7.4e) 0.068 2.96 ¥ 10À5
8
0.0918.5
0.055
0.041 1.78 ¥ 10À5 22
1.9
a) At 378 and pH 4.5. b) Only Ki values shown (for the inhibition type see Tables 1 and 2). c) KM ˆ 2.3 mm (mean
value of all measurements; cf. Exper. Part). d) No inflection of the titration curve was observed between
indicated pH values. e) No second pK value was observed in the indicated pH range. f) Taken from [5].
g) IC50 ˆ 0.60 mm [3].

3492
Helvetica Chimica Acta Vol. 86 (2003)
corresponding methyl ester 46 proved a better inhibitor by ca. one order of magnitude.
Also the tetrazolyl derivative 50 (essentially undissociated at the pH of the assay) is a
better inhibitor than the acid, about equipotent to the ester, suggesting a disrupting
influence of the negative charge of the carboxylate, perhaps diverting the protonation
of the −glycosidic heteroatom× by the catalytic acid.
To the best of our knowledge, the aniline 35 is the strongest competitive inhibitor of
the b-mannosidase from snail, and the 2-phenylethenyl derivative 29 the most potent,
albeit non-competitive, inhibitor of this enzyme.
Table 3 shows the data for the inhibition of the a-mannosidase from Jack beans. All
imidazopyridines proved competitive inhibitors. The selectivity for the inhibition of the
b- vs. a-mannosidase range from 1.1 for the carboxylate 47 to 344 for the 2-
phenylethynyl derivative 28. There is no clear correlation of the selectivity with the
strength of the inhibition of the b-mannosidase; weaker inhibitors tend to be more
selective. For the imidazoles 9, 32, 40, 41, and 43, possessing an oxymethylene
substituent at C(2), one finds a correlation between the selectivity and the pK value
(R ˆ 0.96), the more strongly basic imidazopyridines being more highly selective12).
This correlation still holds (R ˆ 0.90), when the 2-phenylethenyl derivative 29 is
included in the comparison, but not when the aniline 35 is included (R ˆ 0.40). The best
inhibitor of the a-mannosidase is the (4-nitrophenoxy)methyl derivative 41 (Ki ˆ
41n m).
We thank Dr. B. Schweizer for the determination of the X-ray structure of 18, M. Schneider and D. Manser
for the pKHA determinations, Dr. B. Bernet for checking the experimental part, and the Swiss National Science
Foundation and Oxford Glycosciences Ltd., Abingdon (UK), for generous support.
Experimental Part
General. Solvents were distilled before use: THF and toluene from Na, benzophenone and CH2Cl2 from
P2O5, and DMF from CaH2. Reactions were carried out under Ar, unless stated otherwise. Qual. TLC:
precoated silica-gel plates (Merck silica gel 60 F254); detection by heating with −mostain× (400 ml of 10% H2SO4
soln., 20 g of (NH4)6Mo7O24 ¥ 6 H2O, 0.4 g of Ce(SO4)2). Flash chromatography (FC): silica gel Fluka 60 (0.04
0.063 mm). M.p.: uncorrected. Optical rotations: 1-dm cell at 258, 589 nm. UV Spectra (ca. 0.2 mm solns.): in 1-
cm cell at 258 in the range of 190 to 500 nm (log e values in parenthesis). FT-IR spectra: KBr or ca. 2% soln. in
CHCl3, absorption in cmÀ1. 1H- and 13C-NMR spectra: chemical shifts d in ppm rel. to TMS as external standard,
and coupling constants J in Hz. FAB-MS: in 3-nitrobenzyl alcohol (NOBA) matrix. MALDI- and HR-MALDI-
MS: in gentisic acid (ˆ2,5-dihydroxybenzoic acid, DHB) matrix. The pKHA values were determined in H2O by
potentiometric titration with HCl at 258. [Pd(OAc)2(P(2-tolyl)3)2] was prepared according to [17]. The b-
mannosidase from snail acetone powder (EC 3.2.1.25, as a suspension in 3.0m (NH4)2SO4 containing 10 mm
AcONa, pH ca. 4.0, Sigma M-9400), a-mannosidase from Jack beans (EC 3.2.1.24, as a suspension in 3.0m
(NH4)2SO4 and 0.1m m zinc acetate, pH ca. 7.5, Sigma M-7257), 4-nitrophenyl b-d-mannopyranoside (Sigma N-
1268), and 4-nitrophenyl a-d-mannopyranoside (Sigma N-2127) were used without further purification.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2,3-diiodoimidazo[1,2-
a]pyridine (18) and (5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-3-iodoimi-
dazo[1,2-a]pyridine (19). a) A soln. of 17 (5.34 g, 9.52 mmol) in DMF (60 ml) was treated with N-
iodosuccinimide (NIS; 21.6 g, 96.0 mmol, 10 equiv.) and stirred under Ar at 808 for 14 h. The brown mixture was
cooled, diluted with Et2O (250 ml), and washed with Na2S2O3 (10% aq. soln., 3 Â 150 ml). The combined H2O
layers were extracted with Et2O (2 Â 100 ml). The combined org. layers were washed with H2O (150 ml) and
12
)
Among the lactone and lactame oxime-derived inhibitors, the more strongly basic ones proved less
selective [55].

Helvetica Chimica Acta Vol. 86 (2003)
3493
brine (150 ml), dried (MgSO4), filtered, and concentrated i.v. FC (cyclohexane/AcOEt 1:0 ! 5 :1 ! 1:3) gave
18 (6.17 g, 80%) as an oil, which crystallized i.v. Recrystallisation from AcOEt/hexane gave 18 as white crystals.
b) A soln. of 17 (100 mg, 0.178 mmol) in DMF (1.5 ml) was treated with NIS (136 mg, 0.604 mmol,
3.4 equiv.) and stirred under Ar at 508 for 8 h. After workup and FC (similarly as described in a), 19 (68 mg,
56%) and 18 (33 mg, 23%) were obtained.
25
D
Data of 18: Rf (hexane/AcOEt 5 :1) 0.32. M.p. 134.6 135.58. ‰aŠ ˆ À99.9 (c ˆ 1.08, CHCl3). UV (CHCl3):
268 (2.98). IR (CHCl3): 3065w, 2870m, 1953w, 1878w, 1812w, 1603w, 1497w, 1451m, 1358m, 1178w, 1098s, 1026m,
1
978w, 91 1w. H-NMR (CDCl3, 300 MHz): see Table 4; additionally, 4.44 (d, J ˆ 11.8, PhCH); 4.51( d, J ˆ 12.1,
PhCH); 4.55 (d, J ˆ 11.5, PhCH); 4.60 (br. s, PhCH2); 4.62 (d, J ˆ 12.1, PhCH); 4.74 (d, J ˆ 11.8, PhCH); 4.78
(d, J ˆ 12.5, PhCH); 7.23 7.39 (m, 20 arom. H). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 70.66,
70.91(2 t, CH2ÀC(5), PhCH2); 72.04 (t, PhCH2); 73.33 (t, 2 PhCH2); 127.78 128.52 (several d); 137.39, 137.52,
‡
‡
‡
137.64, 138.08 (4s). FAB-MS: 1625 (5, [2M ‡ H] ), 813 (100, [M ‡ H] ), 721(6, [ M À Bn] ), 705 (18, [M À
‡
‡
‡
BnO] ), 685 (5, [M À I] ), 579 (9), 493 (6), 91(83). HR-MALDI-MS: 851.0275 (7, C 36H34I2KN2O4, [M ‡ K] ;
‡
calc. 851.0249), 835.0490 (100, C36H34I2N2NaO4, [M ‡ Na] ; calc. 835.0509), 813.0681 (37, C36H35I2N2O4, [M ‡
‡
‡
H] ; calc. 813.0690), 709.1560 (30), 705.0119 (92, C29H27I2N2O3, [M À BnO] ; calc. 705.0115), 687.1698 (44),
579.1132 (60), 561.2747 (9), 451.2002 (21). Anal. calc. for C36H34I2N2O4 (812.48): C 53.22, H 4.22, N 3.45; found:
C 53.45, H 4.37, N 3.63.
Table 4. Selected 1H-NMR Chemical Shifts [ppm] and Coupling Constants [Hz] of the Protected Imidazoles 18
20, 22 27, and 30 in CDCl3
1
8
1
9
20
22
23
24
25
26
27
30
a
a
HÀC(3)
HÀC(5)
HÀC(6)
HÀC(7)
HÀC(8)
CHÀC(5)
CH'ÀC(5)
J(5,6)
)
7.86
4.18
4.29
3.88
4.814.79
3.60
3.73
6.8
7.11
4.09
4.24
3.86
)
7.20
4.13
6.82
4.06
97.417.1
4.12
4.26
4.36
4.47
3.75
4.75
3.62
3.72
2.5
4.41
4.11
4.12
4.09
4.514.26
3.79
4.79
3.68
3.75
2.2
4.25
4.30
4.87
4.314.26
3.88
3.84
4.77
3.57
3.72
7.2
3.86
3.90
3.86
3.88
4.80
4.80
4.7614.79
3.60
3.60
3.75
7.5
3.59
3.73
7.2
3.63
3.77
7.2
3.59
3.73
7.2
3.58
3.73
7.2
3.73
7.2
J(6,7)
7.8
7.8
9.3
8.7
9.3
9.3
9.3
9.3
9.3
9.3
J(7,8)
3.13.13.13.13.13.12.8
3.13.1 2.8
7.2
J(5,CH)
J(5,CH')
J(CH,CH')
5.0
8.7
9.3
5.0
9.0
9.3
7.2
3.12.8
10.3
6.9
7.2
7.2
6.9
7.2
7.2
2.8
3.13.13.13.0
10.0
2.8
10.0
10.0
10.0
10.0
10.1
10.0
a) Hidden by signals of the Ph groups at 7.24 7.42 ppm.
X-Ray Analysis of 18. Orthorhombic P212121; a ˆ 11.9793(2), b ˆ 14.8025(3), c ˆ 19.5612(5); V ˆ
3468.66(13) ä3, Dcalc ˆ 1.556 Mg/m3, Z ˆ 4. The reflexions were measured on a Bruker Nonius-KappaCCD
difractometer (graphite monochromator, MoKa radiation, l ˆ 0.71073) at 298 K. R ˆ 0.0535, Rw ˆ 0.1541. All
calculations were performed using maXus [56]. The non-H-atoms were refined anisotropically with SHELXL-
97 [57]. The H-atoms were calculated at idealized positions and included in the structure-factor calculation with
fixed isotropic displacement parameters.
25
D
Data of 19: Rf (hexane/Et2O 5 :1) 0.38. ‰aŠ ˆ À90.2 (c ˆ 1.00, CHCl3). UV (CHCl3): 285 (2.74), 258 (3.11),
242 (3.80). IR (CHCl3): 3065w, 2936m, 2870m, 1953w, 1878w, 1812w, 1744w, 1638w, 1603w, 1497m, 1450s, 1357m,
1096s, 1026s, 91 1m, 833m. 1H-NMR (CDCl3, 300 MHz): see Table 4; additionally, 4.49 (d, J ˆ 11.8, PhCH); 4.53
(d, J ˆ 12.1, PhCH); 4.55 (d, J ˆ 11.8, PhCH); 4.57 (d, J ˆ 11.2, PhCH); 4.61( d, J ˆ 11.2, PhCH); 4.65 (d, J ˆ
12.1, PhCH); 4.78 (d, J ˆ 12.1, PhCH); 4.82 (d, J ˆ 12.1, PhCH); 7.15 (s, HÀC(2)); 7.26 7.43 (m, 20 arom. H).
13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 70.73, 71.16 (2t, CH2ÀC(5), PhCH2); 72.07, 73.40, 73.46
(3t, 3 PhCH2); 127.94 128.65 (several d); 137.77, 137.92, 138.03, 138.45 (4s). HR-MALDI-MS: 725.1251 (4,
‡
‡
C36H35IKN2O4, [M ‡ K] ; calc. 725.1280), 709.1534 (83, C36H35IN2NaO4, [M ‡ Na] ; calc. 709.1541), 687.1715
‡
‡
(62, C36H36IN2O4, [M ‡ H] ; calc. 687.1721), 579.1141 (87, C29H28IN2O3, [M À BnO] ; calc. 579.1146), 561.2756

3494
Helvetica Chimica Acta Vol. 86 (2003)
Table 5. Selected 13C-NMR Chemical Shifts [ppm] of the Protected Imidazoles 18 20, 22 27, 30, 31, 34, 36 39,
44, 45, 48, and 49 in CDCl3
Compound
C(2)
C(3)
C(5)
CH2ÀC(5)
C(6)
C(7)
C(8)
C(8a)
a
18
19
20
22
23
24
25
96.30
136.98
82.17
142.00
82.5162.60
69.93
125.04
125.95
116.65
)
)
)
)
77.6180.39
68.69 48.171
68.74
a
60.99
60.10
60.47
59.80
60.14
59.89
59.68
60.09
59.99
59.84
59.81
59.92
60.10
59.89
59.92
60.42
60.34
60.48
60.78
77.99
73.75
73.67
73.92
74.03
74.03
74.14
73.82
74.00
73.93
74.04
73.89
73.99
73.68
73.84
73.76
73.79
80.92
146.80
145.08
145.04
143.05
144.72
143.34
a
79.79
79.47
80.06
79.83
80.03
80.29
79.87
80.18
80.06
80.13
68.22
68.55
68.63
68.19
68.46
68.79
68.33
68.76
a
142.11
70.80
a
127.95 128.93
140.48
122.33
)
)
)
b
a
)
b
a
b
26
)
115.38
123.48
118.54
118.33
116.39
118.43
119.23
119.48
118.71
125.78
125.71
127.72 128.52
121.31
)
27c)
30
124.30
137.67 138.80
138.17
140.29
137.01
136.86
135.61
136.78
133.35
70.78
143.20
143.57
142.99
142.78
a
)
31c)
34c)
36
70.74
70.77
68.63
68.79
a
)
79.9168.43 42.176
37
38
39
44
45
48
49
70.99
80.05
79.58
79.89
79.97
79.99
68.83
68.39
68.56
68.45
68.75
143.61
143.23
143.26
143.99
144.05
a
)
)
)
)
)
)
a
a
a
133.77
114.11 114.76
126.85
a
73.4178.95
73.20 78.86
67.4841.165
67.50
a
145.63
a) Two t for CH2ÀC(5) and a PhCH2 at 70.07 71.45 ppm. b) Not assigned. c) Assignments based on HSQC-
GRASP spectrum.
(100), 453.2174 (57). Anal. calc. for C36H35IN2O4 (686.58): C 62.98, H 5.14, N 4.08; found: C 63.04, H 5.25, N
4.09.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-iodoimidazo[1,2-a]pyri-
dine (20). EtMgBr soln. in THF (1m, 7.5 ml, 7.50 mmol) was added dropwise to a stirred soln. of 18 (5.11 g,
6.29 mmol) in freshly distilled THF (60 ml) at 238 for 10 min. After 25 min, the mixture was treated with sat.
NH4Cl soln. (50 ml) and diluted with Et2O (100 ml). The layers were separated, and the org. layer was washed
with sat. NH4Cl soln. (2 Â 50 ml). The combined H2O layers were extracted with Et2O (2 Â 40 ml). The
combined org. layers were washed with H2O (70 ml) and brine (70 ml), dried (MgSO4), filtered, and
evaporated. FC (hexane/AcOEt 1:0 ! 8 :1 ! 5 :1 ! 1:1) gave 20 (3.82 g, 88%) and 17 (0.36 g, 10%) as oils.
25
Data of 20: Rf (hexane/AcOEt 1:1) 0.62. ‰aŠ ˆ À37.5 (c ˆ 0.98, CHCl3). IR (CHCl3): 3065w, 2869m,
D
1
1954w, 1879w, 1813w, 1728w, 1602w, 1495m, 1454m, 1427w, 1363m, 1256w, 1112s, 1026s, 946w, 91 4w. H-NMR
(CDCl3, 300 MHz): see Table 4; additionally, 4.46 (br. s, PhCH2); 4.60 (d, J ˆ 12.1, PhCH); 4.61( d, J ˆ 11.2,
PhCH); 4.66 (d, J ˆ 12.1, PhCH); 4.67 (d, J ˆ 11.8, PhCH); 4.75 (d, J ꢁ 12.8, PhCH); 4.99 (d, J ˆ 11.2, PhCH);
7.24 7.42 (m, 20 arom. H, HÀC(3)). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 70.63, 70.79, (2t,
CH2ÀC(5), PhCH2); 71.86, 73.23 (2t, 2 PhCH2); 75.00 (t, PhCH2); 127.61 128.58 (several d); 137.33, 137.69,
‡
‡
137.87, 137.98 (4s). FAB-MS: 1373 (5, [2M ‡ 1] ), 687 (100, [M ‡ 1] ), 579 (14), 473 (6), 367 (5), 91 (51). HR-
‡
‡
MALDI-MS: 709.1563 (48, C36H35IN2NaO4, [M ‡ Na] ; calc. 709.1541), 687.1705 (100, C36H36IN2O4, [M ‡ H] ;
‡
calc. 687.1721), 579.1149 (73, C29H28IN2O3, [M À BnO] ; calc. 579.1146), 561.2750 (27), 453.2167 (16). Anal.
calc. for C36H35IN2O4 (686.58): C 62.98, H 5.14, N 4.08; found: C 62.89, H 5.27, N 3.97.
(5R,6R,7S,8R)-5-(Hydroxymethyl)-5,6,7,8-tetrahydro-3-iodoimidazo[1,2-a]pyridine-6,7,8-triol (21). A soln.
of 19 (35 mg, 51.0 mmol) in CH2Cl2 (1.5 ml) was treated at À 788 with 1m BCl3 soln. in CH2Cl2 (0.9 ml,
0.90 mmol), stirred until the mixture had reached a temp. of 158 (ca. 5 h), cooled to À 788, and treated with H2O
(2 ml). After evaporation, FC (AcOEt/MeOH 10 :1 ! 5 :1) and lyophilisation gave 21 (9.3 mg, 56%) as a
25
D
colourless hygroscopic resin. Rf (AcOEt/MeOH 5 :1) 0.11. ‰aŠ ˆ À39.0 (c ˆ 0.70, MeOH). UV (MeOH): 223
(3.63). IR (KBr): 3600 2400s (br.), 2921m, 1632w, 1523w, 1443m, 1340w, 1273w, 1177m, 1130w, 1077s, 979w,
937w, 899w. 1H-NMR (CD3OD, 300 MHz): 3.90 (dd, J ˆ 6.5, 14.3, CHÀC(5)); 3.91( dd, J ˆ 4.1, 6.2, irrad. at

Helvetica Chimica Acta Vol. 86 (2003)
3495
Table 6. Selected 13C-NMR Chemical Shifts [ppm] of the Deprotected Imidazoles 9 13, 21, 28, 29, 32, 35, 40, 41,
43, 46, 47, and 50 in CD3OD
Compound
C(2)
C(3)
C(5)
CH2ÀC(5)
C(6)
C(7)
C(8)
C(8a)
9a)
10
143.65
118.80
115.62
115.96
115.72
125.38
69.86
63.63
63.44
63.61
61.83b)
64.07
64.83
64.04
63.80
63.76
60.77
63.22b)
63.86
63.82
64.25
61.55
61.14
62.11
62.95
62.94
59.32
62.90
63.26
62.95
62.94
63.00
59.22
62.15
63.07
63.05
62.98
59.56
59.30
67.34
67.06
67.15
65.08
67.31
70.43
67.09
67.08
73.63
73.15
73.17
69.29
72.66
72.79
72.81
73.00
73.01
70.8163.71
70.13b)
73.01
72.98
72.70
70.79
70.76
66.55
65.69
65.71
62.26b)
66.35
66.05
65.55
65.75
65.68
147.91
145.79
146.32
142.71
149.18
150.51
147.23
147.20
146.83
147.31
147.47
147.37
147.13
148.42
145.42
145.92
c
)
11
141.78
136.30
81.61
12a)
13
21
28
29
136.95
c
)
123.61
c
141.09
138.71
139.70
141.75
137.68
137.72
133.49
137.70
131.48
)
32
118.62
115.36
67.10
35a)
40
64.48b)
69.11b)
67.16
)
b
c
)
64.04b)
65.72
65.69
41
43
119.47
119.17
126.01
121.84
116.70
67.12
46
67.05
65.62
47a)
50a)
64.74b)
64.51b)
63.90b)
63.81b)
a) Measured in D2O. b) Assignment may be interchanged. c) Not assigned.
4.45 ! d, J ˆ 4.1, irrad. at 4.80! d, J ˆ 6.2, HÀC(7)); 4.14 (dd, J ˆ 7.2, 14.3, CH'ÀC(5)); 4.11 4.17 (m, irrad. at
4.45 ! change, HÀC(5)); 4.45 (dd, J ˆ 2.2, 6.2, HÀC(6)); 4.80 (d, J ˆ 3.7, HÀC(8)); 7.10 (s, HÀC(2)). 13C-NMR
‡
(CD3OD, 75 MHz): see Table 6. HR-MALDI-MS: 326.9830 (100, C8H12IN2O4, [M ‡ H] ; calc. 326.9844).
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-iodoimidazo[1,2-a]pyridine-6,7,8-triol (13). A soln.
of 20 (100 mg, 0.146 mmol) in CH2Cl2 (4 ml) was treated at À 788 with 1m BCl3 soln. in CH2Cl2 (2.5 ml,
2.50 mmol), stirred until the mixture had reached a temp. of 158 (ca. 5 h), cooled to À 788, and treated with H2O
‡
(3 ml). After evaporation, FC (AcOEt/MeOH 10 :1), ion-exchange chromatography (Amberlite CG-120, H
form, elution with 0.1m aq. NH3), and lyophilisation gave 13 (30.6 mg, 64%). Colourless hygroscopic resin. Rf
25
D
(AcOEt/MeOH 5 :1) 0.20. ‰aŠ ˆ À16.5 (c ˆ 0.47, MeOH). UV (MeOH): 226 (3.56), 206 (3.76). IR (KBr):
3600 2400s (br.), 2925m, 2852w, 1695w, 1632m, 1485w, 1432m, 1382m, 1337m, 1259w, 1223m, 1176w, 1098m,
1004w, 957w, 903w, 635w. 1H-NMR (CD3OD, 300 MHz): 3.80 (dd, J ˆ 3.7, 9.0, irrad. at 4.09 ! br. d, J ꢁ 3.4, irrad.
at 4.79 ! d, J ˆ 9.0, HÀC(7)); 3.87 (dd, J ˆ 5.6, 13.4, CHÀC(5)); 3.85 3.92 (m, irrad. at 4.09 ! change,
HÀC(5)); 4.09 (dd, J ˆ 7.2, 9.3, irrad. at 3.80 ! br. d, J ꢁ 6.2, HÀC(6)); 4.13 (dd, J ˆ 5.3, 13.4, CH'ÀC(5)); 4.79
(d, J ˆ 3.7, irrad. at 3.80 ! s, HÀC(8)); 7.44 (s, HÀC(3)). 13C-NMR (CD3OD, 75 MHz): see Table 6. HR-
‡
MALDI-MS: 326.9838 (100, C8H12IN2O4, [M ‡ H] ; calc. 326.9844).
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyridine-2-
carbaldehyde (22). A soln. of 20 (320 mg, 0.466 mmol, dried for 1week i.v. over P2O513) in THF (6.5 ml) was
treated at À 358 with 1m EtMgBr soln. in THF (940 ml, 0.940 mmol), stirred under Ar at À 358 for 10 min and at
238 for 10 min. The mixture was cooled to À 358, treated with DMF (600 ml, 7.80 mmol), and stirred at À 358 to
238 for 3 h. The mixture was treated with H2O (10 ml), diluted with Et2O (60 ml), and washed with sat. NH4Cl
soln. (3 Â 30 ml). The combined aq. layers were extracted with Et2O (2 Â 30 ml). The combined org. layers were
washed with H2O (40 ml) and brine (40 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt
2 :1 ! 1:1) gave 22 (234 mg, 85%) as an oil, which crystallized i.v., and 17 (18 mg, 7%) as an oil.
Data of 22: Rf (hexane/AcOEt 1:1) 0.29. [ a]2D5 ˆ À48.6 (c ˆ 1.17, CHCl3). UV (CHCl3): 278 (3.34). IR
(CHCl3): 3150w, 3065w, 3008m, 2868m, 1954w, 1878w, 1812w, 1689s, 1604w, 1537m, 1497w, 1454m, 1364m, 1257w,
1106s, 1025m, 91 4w. 1H-NMR (CDCl3, 300 MHz): see Table 4; additionally, 4.44 (d, J ˆ 12.1, PhCH); 4.48
(d, J ˆ 12.1, PhCH); 4.61( d, J ˆ 11.8, PhCH); 4.62 (d, J ˆ 11.2, PhCH); 4.68 (d, J ˆ 12.5, 2 PhCH); 4.78 (d, J ˆ
12.5, PhCH); 4.96 (d, J ˆ 11.5, PhCH); 7.23 7.28 (m, 4 arom. H); 7.29 7.38 (m, 14 arom. H); 7.39 7.43
(m, 2 arom. H); 9.88 (s, CHO). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 70.48, 71.03 (2t, PhCH2,
13
)
Required to secure reproducible yields of 22 (80 90%).

3496
Helvetica Chimica Acta Vol. 86 (2003)
CH2ÀC(5)); 72.06 (t, PhCH2); 73.33 (t, PhCH2); 74.83 (t, PhCH2); 127.76 128.60 (several d); 137.10, 137.55,
‡
137.66, 137.68 (4s); 185.79 (d, CHO). HR-MALDI-MS: 611.2509 (65, C37H36N2NaO5, [M ‡ Na] ; calc.
‡
‡
611.2522), 589.2688 (100, C37H37N2O5, [M ‡ H] ; calc. 589.2702), 481.2132 (53, C30H29N2O4, [M À BnO] ; calc.
‡
481.2127), 453.2179 (17, C29H29N2O3, [M À BnO À CO] ; calc. 453.2178). Anal. calc. for C37H36N2O5 (588.70): C
75.49, H 6.16, N 4.76; found: C 75.53, H 6.35, N 4.68.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyridine-2-
methanol (23). a) A soln. of 22 (100 mg, 0.170 mmol) in THF (6 ml) was treated at 238 with LiAlH4 (65 mg,
1.71 mmol) and stirred for 30 min. The mixture was treated with MeOH/H2O (4 :1, 5 ml). The suspension was
filtered through Celite, and the residue was washed with Et2O (80 ml). The filtrate was washed with sat. NH4Cl
soln. (3 Â 30 ml), and the combined aq. layers were extracted with Et2O (2 Â 20 ml). The combined org. layers
were washed with H2O (60 ml) and brine (60 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt
1:1 ! 0 :1) gave 23 (85 mg, 85%). Colourless oil.
b) At 238, a soln. of 22 (95 mg, 0.161 mmol) in EtOH (6 ml) was treated with NaBH4 (12 mg, 0.317 mmol),
stirred for 30 min, and evaporated. Workup and FC (as described in a) gave 23 (85 mg, 89%).
25
D
Data of 23: Rf (AcOEt) 0.15. ‰aŠ ˆ À33.7 (c ˆ 0.96, CHCl3). UV (CHCl3): 266 (3.21). IR (CHCl3): 3400w,
3160w, 3066w, 3008m, 2929m, 2870m, 1954w, 1878w, 1812w, 1729w, 1603w, 1498m, 1454m, 1364m, 1258m, 1101s,
1
1025s, 91 3w. H-NMR (CDCl3, 300 MHz): see Table 4; additionally, 3.30 3.47 (br. s, exchange with CD3OD,
OH); 4.45 (br. s, PhCH2); 4.58 4.62 (m, irrad. at 3.38 ! change, CH2OH); 4.59 (d, J ˆ 11.8, PhCH); 4.60 (d, J ˆ
11.2, PhCH); 4.67 (d, J ˆ 11.8, PhCH); 4.68 (d, J ˆ 12.1, PhCH); 4.75 (d, J ˆ 12.1, PhCH); 5.00 (d, J ˆ 11.2,
PhCH); 7.23 7.35 (m, 18 arom. H); 7.36 7.41 (m, 2 arom. H). 13C-NMR (CDCl3, 75 MHz): see Table 5;
additionally, 58.49 (t, CH2ÀC(2)); 70.80 (2t, PhCH2, CH2ÀC(5)); 71.76 (t, PhCH2); 73.18 (t, PhCH2); 74.94
(t, PhCH2); 127.49 128.51 (several d); 137.48, 137.81, 137.97, 138.21 (4s). HR-MALDI-MS: 613.2673 (37,
‡
‡
C37H38N2NaO5, [M ‡ Na] ; calc. 613.2678), 591.2848 (100, C37H39N2O5, [M ‡ H] ; calc. 591.2859), 483.2296 (32,
‡
‡
C30H31N2O2, [M À BnO] ; calc. 483.2284), 453.2183 (14, C29H29N2O3, [M À BnO À CH2O] ; calc. 453.2178),
375.1714 (11), 359.1761 (11). Anal. calc. for C37H38N2O5 (590.72): C 75.23, H 6.48, N 4.74; found: C 75.16, H 6.58,
N 4.70.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-2,5-bis(hydroxymethyl)imidazo[1,2-a]pyridine-6,7,8-triol (9). A soln. of
23 (70 mg, 0.119 mmol) in CH2Cl2 (3 ml) was treated at À 788 with 1m BCl3 in CH2Cl2 (1.5 ml, 1.5 mmol), stirred
until the mixture had reached a temp. of 108 (ca. 4 h), cooled to À 788, treated with H2O (3 ml), neutralised with
sat. NaHCO3 soln. (10 ml), and evaporated. The residue was taken up in H2O (3 ml) and applied to ion-
‡
exchange column (Amberlite CG-120, H form, elution with 0.1m aq. NH3). Lyophilisation gave 9 (26.5 mg,
25
D
97%). Colourless hygroscopic resin. Rf (AcOEt/MeOH 2 :1) 0.13. ‰aŠ ˆ À41.1 (c ˆ 1.00, H2O). UV (MeOH):
220 (3.74). IR (KBr): 3600 2400s (br.), 2926m, 2879m, 1642m, 1572w, 1512m, 1456m, 1412m, 1381m, 1320m,
1213m, 1178m, 1095s, 1062s, 1029m, 995s, 901m. 1H-NMR (D2O, 300 MHz): 3.91( dt, J ˆ 3.1, 7.8, irrad. at 4.00!
change, HÀC(5)); 3.93 (dd, J ˆ 4.0, 10.0, irrad. at 4.87 ! d, J ˆ 10.3, HÀC(7)); 4.00 (dd, J ˆ 3.1, 12.8,
CHÀC(5)); 4.18 (dd, J ˆ 8.1, 10.3, irrad. at 3.93! change, HÀC(6)); 4.19 (dd, J ꢁ 3.1, 13.4, irrad. at 4.00!
br. d, J ꢁ 4.4, CH'ÀC(5)); 4.48 (br. s, CH2ÀC(2)); 4.87 (d, J ˆ 3.7, irrad. at 3.93 ! s, HÀC(8)); 7.24 (s, HÀC(3)).
13C-NMR (D2O, 75 MHz): see Table 6; additionally, 59.59 (t, CH2ÀC(2)). HR-MALDI-MS: 253.0802 (56,
‡
‡
C9H14N2NaO5, [M ‡ Na] ; calc. 253.0802), 231.0979 (100, C9H15N2O5, [M ‡ H] ; calc. 231.0981), 213.0876 (59,
‡
C9H13N2O4, [M À OH] ; calc. 213.0876).
Methyl (E)-3-{(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydroimidazo[1,2-
a]pyridin-2-yl}-prop-2-enoate (24). a) At 238, a suspension of 20 (50.9 mg, 74.1 mmol), Pd(OAc)2 (5.9 mg,
26.3 mmol), PPh3 (7.5 mg, 28.6 mmol), and Et3N (1 6ml, 0.115 mmol) in freshly distilled and degassed DMF (1 ml)
was treated with methyl acrylate (10 ml, 0.111 mmol) and heated to 908 for 15 h. The mixture was diluted with
Et2O (10 ml) and washed with sat. NaHCO3 soln. (3 Â 10 ml). The combined aq. layers were extracted with
Et2O (2 Â 10 ml). The combined org. layers were washed with H2O (15 ml) and brine (15 ml), dried (MgSO4),
filtered, and evaporated. FC (hexane/AcOEt 1:0 ! 9 :1 ! 7:3 ! 1:1) gave 24 (25.8 mg, 54%) and 17 (4.5 mg,
11%). Oils.
b) A suspension of 20 (115 mg, 0.168 mmol), [Pd(OAc)2(P(2-tolyl)3)2] (11.6 mg, 11.9 mmol) and K2CO3
(65 mg, 0.656 mmol) in freshly distilled and degassed DMF (2 ml) was treated with methyl acrylate (0.2 ml,
2.22 mmol) and heated to 908 for 165 min. Workup and FC, as described in a, gave 24 (101.6 mg, 94%).
25
D
Data of 24: Rf (hexane/AcOEt 3 :1) 0.16. ‰aŠ ˆ À42.2 (c ˆ 0.90, CHCl3). UV (CHCl3): 328 (2.73). IR
(CHCl3): 3148w, 3065w, 2950m, 2869m, 1953w, 1878w, 1812w, 1705s, 1643s, 1497w, 1447m, 1364m, 1301m, 1271s,
1168s, 1109s, 1025s, 981m, 91 4w. 1H-NMR (CDCl3, 300 MHz): see Table 4; additionally, 3.79 (s, MeO); 4.46 (br.
s, PhCH2); 4.57 (d, J ˆ 12.1, PhCH); 4.62 (d, J ˆ 12.1, PhCH); 4.66 (d, J ˆ 12.1, PhCH); 4.69 (d, J ˆ 12.1, PhCH);
4.77 (d, J ˆ 11.2, PhCH); 4.99 (d, J ˆ 11.2, PhCH); 6.60 (d, J ˆ 15.6, CHˆCHÀC(2)); 7.25 7.38 (m, 18 arom. H,

Helvetica Chimica Acta Vol. 86 (2003)
3497
HÀC(3)); 7.42 7.45 (m, 2 arom. H); 7.56 (d, J ˆ 15.6, CHˆCHÀC(2)). 13C-NMR (CDCl3, 75 MHz): see
Table 5; additionally, 51.61 (q, MeO); 70.77, 70.98 (2t, PhCH2, CH2ÀC(5)); 71.92 (t, PhCH2); 73.42 (t, PhCH2);
75.02 (t, PhCH2); 115.94 (d, CHˆCHÀC(2)); 127.95 128.83 (several d, including C(2)); 136.72
‡
(d, CHˆCHÀC(2)); 137.56, 137.90, 138.08, 138.37 (4s); 168.43 (s, CˆO). FAB-MS: 1289 (3, [2M ‡ 1] ), 645
‡
(100, [M ‡ 1] ), 537 (11), 431 (9), 220 (7), 91 (77). Anal. calc. for C40H40N2O6 (644.77): C 74.51, H 6.25, N 4.34;
found: C 74.69, H 6.30, N 4.28.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-[(E)-2-phenylethenyl]-
imidazo[1,2-a]pyridine (25). a) A suspension of 20 (31mg, 45.2 mmol), Pd(OAc)2 (1.5 mg, 6.68 mmol), PPh3
(3.0 mg, 11.4 mmol), and K2CO3 (9.5 mg, 68.7 mmol) in degassed DMF (0.7 ml) was treated with styrene (0.1ml,
0.87 mmol), and stirred at 808 for 16 h, cooled to r.t., diluted with Et2O (15 ml), and washed with sat. NH4Cl
soln. (3 Â 10 ml). The combined aq. layers were extracted with Et2O (2 Â 5 ml). The combined org. layers were
washed with H2O (10 ml) and brine (10 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt
1:0 ! 7:1 ! 1:1 ! 1:2) gave 17 (5.0 mg, 20%) as an oil, and 25/20 (17 mg, ca. 3 :2). HPLC (hexane/Et2O 3 :1 )
of this mixture gave 25 (7.6 mg, 25%) and 20 (5.6 mg, 18%) as yellowish oils.
b) As described in a, but with [Pd(OAc)2(P(2-tolyl)3)2] instead of Pd(OAc)2 and PPh3. Compounds 17
(2%), 25 (45%), and 20 (23%) were isolated as oils.
c) As described in a, but in DMF/H2O 6 :1instead of DMF. After workup, FC and HPLC gave 17 (5%), 25
(24%), and 20 (25%).
d) As described in c, but with [Pd(OAc)2(P(2-tolyl)3)2] instead of Pd(OAc)2 and PPh3: workup gave 17
(13%), 25 (18%), and 20 (30%).
e) A soln. of 22 (40 mg, 67.947 mmol) and diethyl benzylphosphonate (43 ml, 0.2063 mmol) in THF (1.3 ml)
was treated at 08 with 1m soln. of t-BuOK in THF (0.20 ml, 0.20 mmol) and stirred at 08 for 5 min. The mixture
was treated with sat. NH4Cl soln. (3 ml). The mixture was diluted with CH2Cl2 (25 ml) and washed with sat.
NH4Cl soln. (25 ml). The aq. layer was extracted with CH2Cl2 (2 Â 25 ml). The combined org. extracts were
washed with brine (40 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt 5 :1) gave 25 (39.3 mg,
87%). Colourless oil.
25
D
Data of 25: Rf (hexane/AcOEt 4 :1) 0.26. ‰aŠ ˆ À32.8 (c ˆ 1.00, CHCl3). UV (CHCl3): 311 (4.37), 302
(4.37), 239 (3.99). IR (CHCl3): 3150w, 3067w, 3033m, 3013m, 2929m, 2869m, 1950w, 1877w, 1812w, 1644w,
1599w, 1535w, 1497m, 1455m, 1364m, 1343m, 1266w, 1113s, 1028m, 963m, 91 0m. 1H-NMR (CDCl3, 300 MHz):
see Table 4; additionally, 4.48 (br. s, PhCH2); 4.62 (d, J ˆ 12.1, PhCH); 4.63 (d, J ˆ 11.2, PhCH); 4.71( d, J ˆ 12.1,
PhCH); 4.74 (d, J ˆ 11.8, PhCH); 4.81( d, J ˆ 12.1, PhCH); 5.02 (d, J ˆ 11.2, PhCH); 6.99 (d, J ˆ 16.2,
C(2)ÀCHˆCH); 7.22 7.38 (m, 21arom. H, C(2) ÀCHˆCH); 7.41 7.45 ( m, 2 arom. H); 7.49 7.52 (m, 2 arom.
H). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 70.62, 70.92 (2t, CH2ÀC(5), PhCH2); 71.67
(t, PhCH2); 73.18 (t, PhCH2); 74.89 (t, PhCH2); 117.61 (d); 120.23 (d); 126.21 (2d); 127.06 (2d); 127.51 (d);
‡
127.73 128.55 (several d); 137.45, 137.66, 137.74, 137.96, 138.10 (5s). MALDI-MS: 1327 ([2M ‡ H] ), 663
‡
‡
([M ‡ H] ). HR-MALDI-MS: 685.3043 (14, C44H42N2NaO4, [M ‡ Na] ; calc. 685.3042), 663.3209 (100,
‡
‡
C44H43N2O4, [M ‡ H] ; calc. 663.3223), 555.2633 (40, C37H35N2O3, [M À BnO] ; calc. 555.2647). Anal. calc. for
C44H42N2O4 (662.83): C 79.73, H 6.39, N 4.23; found: C 79.85, H 6.55, N 4.29.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-(2-phenylethyl)imida-
zo[1,2-a]pyridine (26). a) A soln. of 25 (25 mg, 37.7 mmol) in AcOEt/MeOH/AcOH 1:1:1(1.5 ml) was treated
with 10% Pd/C (12 mg) and hydrogenated for 96 h at 6 bar. Filtration over Celite, evaporation and FC (hexane/
AcOEt 2 :1) gave 26 (12 mg, 48%). Colourless oil.
b) A soln. of 25 (22 mg, 33.2 mmol) in AcOEt (1 ml) was treated with 10% Pd/C (10 mg) and hydrogenated
25
D
for 6 h at 6 bar. Workup and FC as described in a gave 26 (16.5 mg, 75%). Rf (hexane/AcOEt 2 :1) 0.18. ‰aŠ
ˆ
À32.3 (c ˆ 1.03, CHCl3). UV (CHCl3): 241(3.69). IR (CHCl 3): 3088w, 3066w, 3031m, 3012m, 2928m, 2865m,
1951w, 1875w, 1810w, 1726w, 1603w, 1585w, 1559w, 1497m, 1454s, 1363m, 1315w, 1267w, 1207w, 1171w, 1099s,
1027s, 91 3m. 1H-NMR (CDCl3, 300 MHz): see Table 4; additionally, 2.83 2.99 (m, CH2CH2); 4.41( d, J ˆ 12.1,
PhCH); 4.46 (d, J ˆ 12.1, PhCH); 4.62 (d, J ˆ 11.2, PhCH); 4.64 (d, J ˆ 11.8, PhCH); 4.68 (d, J ˆ 11.5, PhCH);
4.71( d, J ˆ 11.8, PhCH); 4.76 (d, J ˆ 12.1, PhCH); 5.01( d, J ˆ 11.2, PhCH); 7.13 7.21 (m, 2 arom. H); 7.22 7.40
(m, 23 arom. H). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 30.46, 35.90 (2t, CH2CH2); 70.53, 70.83
(2t, CH2ÀC(5), PhCH2); 71.65 (t, PhCH2); 73.12 (t, PhCH2); 74.92 (t, PhCH2); 125.67 (d, C(4) of Ph); 127.26
(d); 127.58 128.32 (several d); 137.45, 137.76, 137.94, 138.23 (4s); 141.90, 141.93, 142.18 (3s, C(2), C(8a), C(1) of
‡
Ph). HR-MALDI-MS: 687.3209 (13, C44H44N2NaO4, [M ‡ Na] ; calc. 687.3199), 665.3381 (100, C44H45N2O4,
‡
‡
[M ‡ H] ; calc. 665.3379), 557.2803 (24, C37H37N2O3, [M À BnO] ; calc. 557.2804), 537.2750 (76).
Methyl 3-[(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-6,7,8-trihydroxy-5-(hydroxymethyl)imidazo[1,2-a]pyridin-2-
yl]-propanoate (11). A soln. of 24 (117 mg, 0.181 mmol) in AcOEt/MeOH/AcOH 1 :1:1 (2.4 ml) was treated

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Helvetica Chimica Acta Vol. 86 (2003)
with 10% Pd/C (100 mg), hydrogenated for 41 h at 6 bar, and filtered over Celite (washing with 25 ml of MeOH/
H2O 9 :1). Evaporation, FC (AcOEt/MeOH/H2O 1 5 :1 :1! 7 :1:1), and drying gave 11 (45.7 mg, ca. 88%) as a
colourless solid containing substantial amounts of H2O. The sample for microanalysis was dried for 4 d at
25
10À4 Torr. Rf (AcOEt/MeOH/H2O 7:1:1) 0.11. ‰aŠ ˆ À22.1( c ˆ 1.01, MeOH). UV (MeOH): 224 (3.71). IR
D
(KBr): 3600 2400s (br.), 2946m, 2926m, 2851m, 1738s, 1717s, 1635w, 1565w, 1505w, 1442s, 1370m, 1330m,
1260m, 1202m, 1176s, 1098s, 1059s, 1008m, 904m, 837w, 792m. 1H-NMR (CD3OD, 300 MHz): 2.61 2.68
(m, 2 H), 2.79 2.86 (m, 2 H) (CH2CH2); 3.65 (s, MeO); 3.77 (dd, J ˆ 3.7, 9.3, irrad. at 4.79 ! d, J ˆ 9.3,
HÀC(7)); 3.80 (ddd, J ˆ 2.8, 5.3, 7.8, irrad. at 4.15 ! change, HÀC(5)); 3.88 (dd, J ˆ 5.3, 11.8, irrad. at 4.15 ! br.
d, J ꢁ 4.7, CHÀC(5)); 4.09 (dd, J ˆ 7.8, 9.3, irrad. at 3.77 ! br. d, J ꢁ 6.9, HÀC(6)); 4.15 (dd, J ˆ 2.8, 11.8, irrad.
at 3.88 ! br. d, J ꢁ 3.7, CH'ÀC(5)); 4.79 (d, J ˆ 3.7, irrad. at 3.77 ! s, HÀC(8)); 7.09 (s, HÀC(3)). 13C-NMR
(CD3OD, 75 MHz): see Table 6; additionally, 24.43, 34.65 (2t, CH2CH2); 52.14 (q, MeO); 175.17 (s, CˆO). HR-
‡
‡
MALDI-MS: 325.0795 (2, C12H18KN2O6, [M ‡ K] ; calc. 325.0802), 309.1052 (77, C12H18N2NaO6, [M ‡ Na] ;
‡
‡
calc. 309.1062), 287.1233 (100, C12H19N2O6, [M ‡ H] ; calc. 287.1243), 269.1133 (14, C12H17N2O5, [M À OH] ;
‡
calc. 269.1137), 255.0973 (3, C11H15N2O5, [M À MeO] ; calc. 255.0981), 237.0868 (11, C11H13N2O4, [M À OH À
‡
MeOH] ; calc. 237.0875). Anal. calc. for C12H18N2O6 ¥ 0.6 H2O (297.09): C 48.51, H 6.51, N 9.43; found: C 48.40,
H 6.22, N 9.12.
3-[(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-6,7,8-trihydroxy-5-(hydroxymethyl)imidazo[1,2-a]pyridin-2-yl]pro-
panoic Acid (12). A soln. of 11 (15 mg, 52.4 mmol) in 1m aq. HCl (1ml) was stirred at 60 8 for 1h and applied to
‡
ion-exchange chromatography (Amberlite CG-120, H form, elution with 0.1m aq. NH3). Evaporation,
dissolving in H2O (3 ml), and lyophilisation yielded 12 (12.2 mg, 85%) as a colourless hygroscopic resin. Rf
25
D
(AcOEt/MeOH/H2O 3 :1:1) 0.14. ‰aŠ ˆ À11.5 (c ˆ 0.26, MeOH). UV (MeOH): 225 (3.63). IR (KBr): 3600
2400s (br.), 2925s, 1944w, 1633m, 1568s, 1405s, 1309m, 1211m, 1166m, 1099s, 1071s, 1019m, 904m, 828m.
1H-NMR (D2O, 300 MHz): 2.51( t, J ˆ 7.2, 2 H), 2.88 (t, J ˆ 7.2, 2 H) (CH2CH2); 4.03 (dd, J ˆ 3.7, 12.5,
CHÀC(5)); 4.05 (dd, J ˆ 4.1, 9.0, HÀC(7)); 4.10 (td, J ꢁ 3.1, 6.5, HÀC(5)); 4.18 (dd, J ˆ 2.8, 12.5, CH'ÀC(5));
4.27 (dd,J ˆ 6.5, 9.0, HÀC(6)); 5.07 (d, J ˆ 4.1, HÀC(8)); 7.28 (s, HÀC(3)). 13C-NMR (D2O, 75 MHz): see
Table 6 ; additionally, 21.80, 35.78 (2t, CH2CH2); 180.57 (s, CˆO). HR-MALDI-MS: 295.0896 (98,
‡
‡
C11H16N2NaO6, [M ‡ Na] ; calc. 295.0906), 273.1075 (100, C11H17N2O6, [M ‡ H] ; calc. 273.1086).
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-(2-phenylethyl)imidazo[1,2-a]pyridine-6,7,8-triol
(10). A soln. of 25 (50 mg, 75.4 mmol) in AcOEt/MeOH/H2O 1:1:1 (1.5 ml) was treated with AcOH (1.5 ml)
and 20% Pd(OH)2/C (50 mg), hydrogenated at 6 bar for 120 h, and filtered through Celite (washing with
MeOH/H2O (9 :1, 25 ml)). Evaporation of the combined filtrates, co-evaporation with toluene (3Â 5 ml), FC
(AcOEt/MeOH/H2O 15 :1:1), FC (RP-C18 SiO2; MeOH/H2O 7:3), and drying gave 10 (10.6 mg, ca. 46%) as a
white solid containing substantial amounts of H2O. The sample for microanalysis was dried for 4 d at 10À4 Torr.
25
D
Rf (AcOEt/MeOH/H2O 10 :1:1) 0.17. ‰aŠ ˆ À19.4 (c ˆ 0.98, MeOH). UV (MeOH): 211 (3.98). IR (KBr):
3600 2400s (br.), 3026m, 2925m, 2858m, 1938w, 1869w, 1801w, 1633w, 1604w, 1560w, 1497m, 1454m, 1401w,
1365w, 1331m, 1309m, 1263w, 1206w, 1182w, 1107s, 1060m, 1005m, 903m. 1H-NMR (CD3OD, 300 MHz): 2.77
2.82 (m, 2 H); 2.88 2.93 (m, 2 H) (CH2CH2); 3.77 (dd, J ˆ 3.7, 9.3, HÀC(7)); 3.78 (ddd, J ˆ 2.5, 5.6, 7.5,
HÀC(5)); 3.87 (dd, J ˆ 5.3, 11.8, CHÀC(5)); 4.09 (dd, J ˆ 7.8, 9.3, HÀC(6)); 4.13 (dd, J ˆ 2.5, 11.8, CH'ÀC(5));
4.80 (d, J ˆ 3.7, HÀC(8)); 7.02 (s, HÀC(3)); 7.10 7.27 (m, 5 arom. H). 13C-NMR (CD3OD, 75 MHz): see
Table 6; additionally, 31.29, 36.88 (2t); 126.73 (d, C(4) of Ph); 129.16 (2d); 129.24 (2d); 142.70, 142.98 (2s, C(1) of
‡
Ph, C(2)). HR-MALDI-MS: 327.1315 (13, C16H20N2NaO4 , [M ‡ Na] ; calc. 327.1321), 305.1491 (100,
‡
‡
C16H21N2O4, [M ‡ H] ; calc. 305.1501), 287.1387 (11, C16H19N2O3, [M À OH] ; calc. 287.1396). Anal. calc. for
C16H20N2O4 ¥ 0.5 H2O (313.36): C 61.33, H 6.75, N 8.94; found: C 61.55, H 6.78, N 8.75.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-6,7,8-tris(benzyloxy)-5-[(benzyloxy)methyl]-2-(2-phenylethynyl)imida-
zo[1,2-a]pyridine (27). At 238, a suspension of 20 (305 mg, 0.444 mmol), Pd(PPh3)4 (25 mg, 21.6 mmol), CuI
(9 mg, 47.3 mmol), and Et3N (300 ml, 2.15 mmol) in degassed DMF (7.5 ml) was treated with phenylacetylene
(150 ml, 1.37 mmol), stirred at 808 for 3 h, cooled to r.t., diluted with Et2O (50 ml), and washed with sat. NH4Cl
soln. (3 Â 20 ml). The combined aq. layers were extracted with Et2O (3 Â 15 ml). The combined org. layers were
washed with H2O (25 ml) and brine (25 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt
1:0 ! 7:1 ! 4 :1 ! 1:2) gave 27 (245 mg, 83%) and 17 (24 mg, 10%). Oils.
25
D
Data of 27: Rf (hexane/AcOEt 4 :1) 0.27. ‰aŠ ˆ À27.8 (c ˆ 0.99, CHCl3). UV (CHCl3): 299 (4.2), 283 (4.2),
252 (4.0), 241(4.0). IR (CHCl 3): 3157w, 3089w, 3066w, 2941m, 2868m, 2100w, 1952w, 1876w, 1811w, 1731w, 1599s,
1586m, 1496s, 1454s, 1364m, 1301m, 1174m, 1112s, 1050s, 1028s, 91 3w. 1H-NMR (CDCl3, 400 MHz): see Table 4;
additionally, 4.46 (br. s, PhCH2); 4.59 (d, J ˆ 12.0, PhCH); 4.61( d, J ˆ 11.2, PhCH); 4.659 (d, J ˆ 12.0, PhCH);
4.664 (d, J ˆ 12.2, PhCH); 4.760 (d, J ˆ 12.1, PhCH); 4.99 (d, J ˆ 11.2, PhCH); 7.23 7.36 (m, 21arom. H); 7.40
7.42 (m, 2 arom. H); 7.52 7.54 (m, HÀC(2) and HÀC(6) of Ph). 13C-NMR (CDCl3, 100 MHz): see Table 5;

Helvetica Chimica Acta Vol. 86 (2003)
3499
additionally, 70.68 (t, PhCH2); 71.77 (t, PhCH2); 73.20 (t, PhCH2); 74.90 (t, PhCH2); 82.98 (s, CꢀCÀC(2));
89.31( s, CꢀCÀC(2)); 123.23 (s, C(1) of Ph); 127.53 128.49 (several d); 131.48 (2d, C(2) and C(6) of Ph);
‡
137.32, 137.66, 137.86, 137.93 (4s). HR-MALDI-MS: 683.2916 (26, C44H40N2NaO4, [M ‡ Na] ; calc. 683.2886),
‡
‡
661.3069 (100, C44H41N2O4, [M ‡ H] ; calc. 661.3066), 553.2499 (63, C37H33N2O3, [M À BnO] ; calc. 553.2491).
Anal. calc. for C44H40N2O4 (660.81): C 79.98, H 6.10, N 4.24; found: C 79.91, H 6.11, N 4.09.
Hydrogenation of 27. A soln. of 27 (91mg, 0.1377 mmol) in AcOEt/MeOH/H 2O 3 :1:1(2.5 ml) was treated
with AcOH (2.5 ml), 20% Pd(OH)2/C (90 mg), hydrogenated at 6 bar for 41h, and filtered through Celite
(washing with MeOH/H2O (9 :1, 25 ml)). Evaporation of combined filtrates, co-evaporation with toluene (3Â
5 ml), FC (AcOEt/MeOH/H2O 15 :1:1), and FC (RP-C18 SiO2; MeOH/H2O 7:3) afforded 10 (33.4 mg, 80%).
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-(phenylethynyl)imidazo[1,2-a]pyridine-6,7,8-triol
(28). A soln. of 27 (90 mg, 0.136 mmol) in CH2Cl2 (3.6 ml) was treated at À 788 with 1m BCl3 in CH2Cl2 (2.25 ml,
2.25 mmol), stirred until the mixture had reached a temp. of 108 (ca. 5 h), cooled to À 788, treated with H2O
(3 ml), neutralised with aq. NH3 (1ml), and evaporated. FC (AcOEt/MeOH/H 2O 1:0 :0 ! 20 :1:1),
lyophilisation, and drying afforded 28 (34.7 mg, ca. 85%) as a yellowish hygroscopic resin containing substantial
amounts of H2O. The sample for microanalysis was dried for 4 d at 10À4 Torr. Rf (AcOEt/MeOH/H2O 1 0 :1 :1 )
25
D
0.16. ‰aŠ ˆ À16.0 (c ˆ 0.80, MeOH). UV (MeOH): 265 (4.02), 249 (4.02), 238 (4.05), 220 (4.12). IR (KBr):
3600 2400s (br.), 2925m, 2851m, 2219w, 2072w, 1958w, 1893w, 1721w, 1656m, 1630m, 1598m, 1550m, 1513w,
1487m, 1442m, 1406m, 1384m, 1314m, 1261m, 1210m, 1181m, 1094s, 1068s, 1008m, 902m, 841w, 805w. 1H-NMR
(CD3OD, 300 MHz): 3.84 (dd, J ˆ 3.7, 9.0, irrad. at 4.13 ! d, J ˆ 3.7, irrad. at 4.82 ! d, J ꢁ 8.7, HÀC(7)); 3.87
3.93 (m, HÀC(5)); 3.91( dd, J ˆ 5.9, 13.7, CHÀC(5)); 4.13 (dd,J ꢁ 6.9, 9.3, irrad. at 3.84 ! d,J ꢁ 5.0, HÀC(6));
4.17 (dd, J ˆ 5.0, 14.0, CH'ÀC(5)); 4.82 (d, J ˆ 3.7, irrad. at 3.84 ! s, HÀC(8)); 7.31 7.38 ( m, HÀC(3),
HÀC(4), and HÀC(5) of Ph); 7.43 7.49 (m, HÀC(2) and HÀC(6) of Ph); 7.60 (s, HÀC(3)). 13C-NMR
(CD3OD, 75 MHz): see Table 6; additionally, 83.54 (s, CꢀCÀC(2)); 90.07 (s, CꢀCÀC(2)); 124.30, 124.70
(2s, C(1) of Ph, C(2)); 129.20 (d, C(4) of Ph); 129.37 (2d, C(3) and C(5) of Ph); 132.11 (2d, C(2) and C(6) of
‡
Ph). HR-MALDI-MS: 323.0995 (5, C16H16N2NaO4, [M ‡ Na] ; calc. 323.1008); 301.1178 (100, C16H17N2O4,
‡
‡
[M ‡ H] ; calc. 301.1188); 283.1070 (8, C16H15N2O3, [M À OH] ; calc. 283.1083). Anal. calc. for C16H16N2O4 ¥
0.6 H2O (311.12): C 61.77, H 5.57, N 9.00; found: C 61.73, H 5.54, N 8.90.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-[(E)-phenylethenyl]imidazo[1,2-a]pyridine-6,7,8-
triol (29). a) A soln. of 25 (40 mg, 60.3 mmol) in CH2Cl2 (1.5 ml) was treated at À 788 with 1m BCl3 in CH2Cl2
(1.05 ml, 1.05 mmol), stirred until the mixture had reached a temp. of 158 (ca. 5 h), cooled to À 788, treated with
H2O (3 ml), neutralised with aq. NH3 (1ml), and evaporated. FC (AcOEt/MeOH/H 2O 1:0 :0 ! 1 5 :1 :1 ),
lyophilisation, and drying yielded 29 (6.2 mg, ca. 34%) as a yellowish hygroscopic resin containing substantial
amounts of AcOEt and H2O. The sample for microanalysis was dried for 4 d at 10À4 Torr.
b) A soln. of 25 (30 mg, 45.3 mmol) in CH2Cl2 (1ml) was treated with AlCl 3 (97 mg, 0.727 mmol) and N,N-
dimethylaniline (70 ml, 0.552 mmol), stirred for 18 h at 228, and treated with H2O (15 ml). The mixture was
diluted with AcOEt (15 ml) and extracted with H2O. Evaporation of the aq. layer, FC (as described in a),
lyophilisation, and drying yielded 29 (5.7 mg, ca. 42%) containing substantial amounts of AcOEt and H2O.
25
D
Data of 29: Rf (AcOEt/MeOH/H2O 10 :1:1) 0.13. ‰aŠ ˆ ‡2.5 (c ˆ 0.25, MeOH). UV (MeOH): 295
(4.19), 226 (4.04), 203 (4.22). IR (KBr): 3600 2400s (br.), 2925m, 2851w, 1633w, 1597w, 1535w, 1513w, 1490w,
1443w, 1381w, 1323w, 1261w, 1208w, 1180w, 1152w, 1095m, 1068m, 963w, 902w, 833w, 762w, 693m. 1H-NMR
(CD3OD, 300 MHz): 3.83 (dd, J ˆ 3.7, 9.3, HÀC(7)); 3.85 3.91( m, HÀC(5)); 3.93 (dd, J ˆ 5.6, 11.5,
CHÀC(5)); 4.13 (dd, J ˆ 7.2, 9.3, HÀC(6)); 4.19 (dd,J ˆ 2.5, 11.5, CH'ÀC(5)); 4.86 (d, J ˆ 3.7, HÀC(8)); 7.01
(d, J ˆ 16.2, C(2)ÀCHˆCH); 7.15 (d, J ˆ 16.5, C(2)ÀCHˆCH); 7.16 7.23 (m, HÀC(4) of Ph); 7.27 7.34
(m, HÀC(3) and HÀC(5) of Ph); 7.44 (s, HÀC(3)); 7.45 7.50 (m, HÀC(2) and HÀC(6) of Ph). 13C-NMR
(CD3OD, 75 MHz): see Table 6; additionally, 117.85 (d); 120.68 (d); 127.03 (d, C(2) and C(6) of Ph); 128.11 (d);
128.22 (d); 129.49 (d, C(3) and C(5) of Ph); 138.78 (s, C(1) of Ph). HR-MALDI-MS: 325.1160 (16,
‡
‡
C16H18N2NaO4, [M ‡ Na] ; calc. 325.1164); 303.1342 (100, C16H19N2O4, [M ‡ H] ; calc. 303.1345); 285.1230 (16,
‡
C16H17N2O3, [M À OH] , calc. 285.1239). Anal. calc. for C16H18N2O4 ¥ 0.5 AcOEt ¥ 0.5 H2O (355.39): C 60.83, H
6.52, N 7.88; found: C 60.67, H 6.28, N 7.88.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-2-(chloromethyl)-5,6,7 ,8-tetrahydroimida-
zo[1,2-a]pyridine (30). A soln. of 23 (85 mg, 0.144 mmol) in CH2Cl2 (3 ml) was treated with SOCl2 (20 ml,
0.275 mmol), stirred at 238 for 40 min, and treated with sat. NaHCO3 soln. (10 ml). The mixture was diluted
with Et2O (15 ml) and washed with sat. NaHCO3 soln. (2 Â 10 ml). The combined aq. layers were extracted with
Et2O (2 Â 10 ml). The org. layers were combined, washed with H2O (15 ml) and brine (15 ml), dried (MgSO4),
filtered, and evaporated. FC (hexane/AcOEt 3 :1) gave 30 (76 mg, 86%). Colourless oil. Rf (hexane/AcOEt
25
D
3 :1) 0.12. ‰aŠ ˆ À17.7 ( c ˆ 1.02, CHCl3). UV (CHCl3): 258 (3.04), 240 (3.57). IR (CHCl3): 3067w, 3007m,

3500
Helvetica Chimica Acta Vol. 86 (2003)
2868w, 1959w, 1879w, 1813w, 1497m, 1454m, 1363m, 1260m, 1097s, 1028s, 91 4w. 1H-NMR (CDCl3, 300 MHz): see
Table 4; additionally, 4.44 (d, J ˆ 12.5, PhCH); 4.48 (d, J ˆ 12.5, PhCH); 4.55 (d, J ˆ 12.1, PhCH); 4.58
(s, CH2Cl); 4.61( d, J ꢁ 10.9, PhCH); 4.66 (d, J ˆ 12.1, PhCH); 4.69 (d, J ˆ 12.1, PhCH); 4.74 (d, J ˆ 12.1,
PhCH); 5.00 (d, J ˆ 11.2, PhCH); 7.24 7.34 (m, 18 arom. H); 7.37 7.40 (m, 2 arom. H). 13C-NMR (CDCl3,
75 MHz): see Table 5; additionally, 39.91( t, CH2ÀC(2)); 70.83, 70.86 (2t, PhCH2, CH2ÀC(5)); 71.91 (t, PhCH2);
73.29 (t, PhCH2); 75.05 (t, PhCH2); 127.73 128.75 (several d); 137.67, 138.02, 138.18, 138.36, 138.80 (5s). HR-
‡
MALDI-MS: 1145.5028 (43), 631.2339 (18, C37H37ClN2NaO4, [M ‡ Na] ; calc. 631.2339), 609.2519 (91,
‡
‡
C37H38ClN2O4, [M ‡ H] ; calc. 609.2520), 573.2754 (59, C37H37N2O4, [M À Cl] ; calc. 573.2753), 501.1963 (100,
‡
C30H30ClN2O3, [M À BnO] ; calc. 501.1945), 467.2372 (50). Anal. calc. for C37H37ClN4 (609.16): C 72.95, H 6.12,
N 4.60; found: C 73.04, H 6.42, N 4.33.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-(phenoxymethyl)imida
zo[1,2-a]pyridine (31). a) A suspension of 30 (14.5 mg, 23.8 mmol), phenol (3.4 mg, 36.1 mmol), and K2CO3
(4.9 mg, 35.5 mmol) in THF (1ml) was stirred for 13 h at 55 60 8, diluted with Et2O (15 ml), and washed with
sat. NH4Cl soln. (3 Â 8 ml). The combined aq. layers were extracted with Et2O (2 Â 8 ml). The combined org.
layers were washed with H2O (10 ml) and brine (10 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/
AcOEt 3 :1) gave 31 (7.9 mg, 50%). Colourless oil.
b) A suspension of 30 (24 mg, 39.4 mmol), phenol (8 mg, 85.0 mmol), and t-BuOK (7.5 mg, 66.8 mmol) in
DMF (1ml) was stirred for 4 h at 80 8. Workup and FC as described in a gave 31 (16.2 mg, 74%).
c) As described in b, but with K2CO3 instead of t-BuOK, yielding 60% of 31.
d) A soln. of 30 (16 mg, 26.3 mmol) in DMF (1ml) was treated with 0.26 m soln. of NaOPh (141 ml,
36.7 mmol, prepared by the addition of Na (18 mg, 0.783 mmol) to a soln. of PhOH (76 mg, 0.808 mmol) in DMF
(3 ml) at 238) and stirred for 4 h at 808. Workup and FC as described in a gave 31 (6.6 mg, 38%).
e) A soln. of 23 (100 mg, 0.169 mmol) in CH2Cl2 (4 ml) was treated with SOCl2 (25 ml, 0.344 mmol), stirred
at 238 for 3 h, and treated with sat. NaHCO3 soln. (5 ml). The mixture was diluted with Et2O (25 ml) and washed
with sat. NaHCO3 soln. (3 Â 15 ml). The combined aq. layers were extracted with Et2O (2 Â 15 ml). The
combined org. layers were washed with H2O (25 ml) and brine (25 ml), dried (MgSO4), and filtered. After
evaporation, crude 30 (96 mg of a yellowish oil) was dissolved in DMF (4 ml), treated with t-BuOK (27 mg,
0.241mmol) and PhOH (29 mg, 0.308 mmol), and stirred for 3.5 h at 80 8. Workup and FC as described in a gave
31 (79.1mg, 70% from 23).
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D
Data of 31: Rf (hexane/AcOEt 2 :1) 0.28. ‰aŠ ˆ À22.5 (c ˆ 1.00, CHCl3). UV (CHCl3): 271(3.3), 265
(3.2), 240 (3.4). IR (CHCl3): 3157w, 3089w, 3066m, 2941m, 2868m, 1952w, 1876w, 1811w, 1731w, 1599m, 1586m,
1496s, 1454s, 1364m, 1301m, 1174m, 1112s, 1050s, 1028s, 91 3w. 1H-NMR (CDCl3, 400 MHz): see Table 7;
additionally, 4.43 (br. s, PhCH2); 4.60 (d, J ˆ 11.2, PhCH); 4.61( d, J ˆ 12.1, PhCH); 4.67 (d, J ˆ 12.0, 2 PhCH);
4.76 (d, J ˆ 12.2, PhCH); 4.98 (d, J ˆ 11.5, CHÀC(2)); 4.99 (d, J ˆ 11.1, PhCH); 5.02 (d, J ˆ 11.7, CH'ÀC(2));
6.94 (tt, J ˆ 1.0, 7.3, HÀC(4) of Ph); 6.99 7.02 (m, HÀC(2) and HÀC(6) of Ph); 7.23 7.34 (m, 18 arom. H,
HÀC(3) and HÀC(5) of Ph, HÀC(3)); 7.38 7.41( m, 2 arom. H). 13C-NMR (CDCl3, 100 MHz): see Table 5;
additionally, 64.32 (t, CH2ÀC(2)); 70.65 (t, PhCH2); 71.77 (t, PhCH2); 73.16 (t, PhCH2); 74.92 (t, PhCH2);
114.83 (d, C(2) and C(6) of Ph); 120.78 (d, C(4) of Ph); 127.46 128.48 (several d); 129.35 (d, C(3) and C(5) of
Ph); 137.45, 137.79, 137.97 (3s), 138.17 (2s, including C(2)); 158.76 (s, C(1) of Ph). HR-MALDI-MS: 689.2968
‡
‡
(26, C43H42N2O5, [M ‡ Na] ; calc. 689.2991), 667.3172 (100, C43H43N2O5, [M ‡ H] ; calc. 667.3171), 573.2733
‡
‡
(18, C37H37N2O4, [M À PhO] ; calc. 573.2753), 559.2594 (21, C36H35N2O4, [M À BnO] ; calc. 559.2597), 465.2172
‡
(11, C30H29N2O3, [M À BnO À PhOH] ; calc. 465.2178), 375.1705 (24), 359.1751 (14). Anal. calc. for C43H42N2O5
(666.82): C 77.45, H 6.35, N 4.20; found: C 77.39, H 6.50, N 4.18.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-(phenoxymethyl)imidazo[1,2-a]pyridine-6,7,8-triol
(32) and (5R,6R,7S,8R)-2-[(Cyclohexyloxy)methyl)]-5,6,7,8-tetrahydro-5-(hydroxymethyl)imidazo[1,2-a]pyr-
idine-6,7,8-triol (33). A soln. of 31 (39 mg, 58.5 mmol) in AcOEt/MeOH/H2O 3 :1:1 (2 ml) was treated with
AcOH (2 ml) and 20% Pd(OH)2/C (40 mg), and hydrogenated at atmospheric pressure for 44 h. The suspension
was filtered through Celite, and the residue was washed with MeOH/H2O 9 :1(30 ml). Evaporation of the
combined filtrates, co-evaporation with toluene (3 Â 5 ml), FC (AcOEt/MeOH/H2O 1 :0 :0! 1 5 :1 :1!
10 :1:1), and drying afforded 32 (11.3 mg, ca. 63%) containing substantial amounts of H2O, and 33 (1.7 mg,
9%). Colourless oils. The sample of 32 for microanalysis was dried for 4 d at 10À4 Torr.
25
D
Data of 32: Rf (AcOEt/MeOH/H2O 10 :1:1) 0.20. ‰aŠ ˆ À18.8 (c ˆ 0.64, MeOH). UV (MeOH): 277
(3.10), 271 (3.19), 219 (4.12). IR (KBr): 3600 2400s (br.), 2925m, 2857m, 1631w, 1599s, 1586m, 1496s, 1461m,
1
1384m, 1300m, 1239s, 1176m, 1094s, 1080s, 1030m, 1006m, 989m, 902m, 859m. H-NMR (CD3OD, 300 MHz):
3.81( dd, J ˆ 3.7, 9.3, irrad. at 4.83 ! d, J ˆ 9.3, HÀC(7)); 3.83 3.94 (m, HÀC(5), CHÀC(5)); 4.07 4.21
(m, HÀC(6), CH'ÀC(5)); 4.83 (d, J ˆ 3.7, irrad. at 3.81 ! s, HÀC(8)); 4.95 (br. s, CH2ÀC(2)); 6.91( tt, J ˆ 0.9,

Helvetica Chimica Acta Vol. 86 (2003)
3501
Table 7. Selected 1H-NMR Chemical Shifts [ppm] and Coupling Constants [Hz] of the Protected Imidazoles 31,
34, 36 39, 44, 45, 48, and 49 in CDCl3
3134
36
37
38
39
44
45
48
49
a
a
a
a
a
HÀC(3)
HÀC(5)
HÀC(6)
HÀC(7)
HÀC(8)
CHÀC(5)
CH'ÀC(5)
J(5,6)
)
7.04
4.07
4.28
3.87
4.77
3.59
3.73
7.2
)
)
)
)
7.85
4.16
4.28
3.86
7.80
4.12
4.25
3.82
71.718.1
4.14
4.18
4.10
4.28
3.88
4.80
3.60
3.74
7.4
4.12
4.30
3.88
4.77
3.62
3.76
7.2
4.13
4.28
3.90
4.80
3.62
4.10
4.24
3.87
4.75
3.59
3.73
7.2
4.14
4.28
3.90
4.814.82
3.62
3.76
7.2
4.29
4.34
4.07
3.84
4.80
4.74
5.45
3.57
3.72
7.2
3.54
3.69
7.2
3.56
3.69
6.9
3.71
3.79
6.5
3.76
7.2
J(6,7)
9.4
9.3
9.3
9.3
9.0
9.3
9.3
9.3
8.4
8.4
J(7,8)
3.13.0
7.0
3.0
3.13.13.4
3.12.8
7.2
3.13.13.13.12.5
2.8
7.2
3.12.8
7.2
3.4
10.0
J(5,CH)
J(5,CH')
J(CH,CH')
6.8
6.8
7.2
7.2
7.5
6.5
3.13.12.8
10.1
10.1
10.0
10.0
10.0
10.0
10.0
10.3
10.0
a) Hidden by signals of the Ph groups at 7.21 7.41ppm.
7.2, HÀC(4) of Ph); 6.94 6.99 (m, HÀC(2) and HÀC(6) of Ph); 7.21 7.28 ( m, HÀC(3) and HÀC(5) of Ph);
7.43 (s, HÀC(3)). 13C-NMR (CD3OD, 75 MHz): see Table 6; additionally, 64.55 (t, CH2ÀC(2)); 115.61 (d, C(2)
and C(6) of Ph); 121.71 (d, C(4) of Ph); 130.27 (d, C(3) and C(5) of Ph); 159.90 (s, C(1) of Ph). HR-MALDI-
‡
‡
MS: 329.1109 (62, C15H18N2NaO5, [M ‡ Na] ; calc. 329.1113); 307.1290 (82, C15H19N2O5, [M ‡ H] ; calc.
‡
307.1294); 213.0867 (100, C9H13N2O4, [M À PhO] ; calc. 213.0875). Anal. calc. for C15H18N2O5 ¥ 0.5 H2O
(315.33): C 57.14, H 6.07, N 8.88; found: C 57.14, H 5.98, N 8.64.
1
Data of 33: Rf (AcOEt/MeOH/H2O 10 :1:1) 0.11. H-NMR (CD3OD, 300 MHz): 1.20 1.38 (m, 3 CH2 of
C6H11); 1.70 1.80 (m, CH2 of C6H11); 1.89 2.00 (m, CH2 of C6H11); 3.36 3.48 (m, HÀC(1) of C6H11); 3.79
(dd, J ˆ 3.7, 9.3, HÀC(7)); 3.85 (ddd, J ꢁ 2.5, 5.6, 8.1, HÀC(5)); 3.89 (dd, J ˆ 5.6, 11.5, CHÀC(5)); 4.10 (dd, J ˆ
7.5, 9.3, HÀC(6)); 4.16 (dd, J ˆ 2.5, 11.5, CH'ÀC(5)); 4.44 (br. s, CH2ÀC(2)); 4.80 (d, J ˆ 3.7, HÀC(8)); 7.30
‡
(s, HÀC(3)). HR-MALDI-MS: 335.1576 (61, C15H24N2NaO5, [M ‡ Na] ; calc. 335.1583); 313.1754 (41,
‡
‡
C15H25N2O5, [M ‡ H] ; calc. 313.1763); 213.0870 (100, C9H13N2O4, [M À c-C6H11O] ; calc. 213.0875).
BCl3-Promoted Debenzylation of 31. a) A soln. of 31 (10 mg, 15.0 mmol) in CH2Cl2 (0.4 ml) was treated at
À 788 with 1m BCl3 in CH2Cl2 (0.25 ml, 0.25 mmol), stirred until the mixture had reached a temp. of 158 (ca.
4.5 h), cooled to À 788, treated with H2O (1ml), and evaporated. The residue was taken up in H 2O (2 ml) and
‡
applied to ion-exchange chromatography (Amberlite CG-120, H form, elution with 0.1m aq. NH3). Evaporation
and lyophilisation gave a 1:5 mixture of 35 and a product missing the PhO group (2.7 mg).
b) As described in a, but the mixture was neutralised with Amberlite IRA-68 after the addition of H2O.
‡
Filtration, evaporation, and ion-exchange chromatography (Amberlite CG-120, H form, elution with 0.1m aq.
NH3) gave a 1:1 mixture of 35 and a product missing the PhO group (3.1mg).
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-[(phenylamino)methyl]-
imidazo[1,2-a]pyridine (34). A suspension of 22 (50.0 mg, 84.9 mmol) and MgSO4 (12 mg, 99.7 mmol) in CH2Cl2
(1ml) was treated with freshly distilled PhNH 2 (9 ml, 98.7 mmol) and stirred for 4 h at 238. The mixture was
diluted with Et2O (15 ml) and washed with sat. NaHCO3 soln. (3 Â 10 ml). The combined aq. layers were
extracted with Et2O (2 Â 10 ml). The combined org. layers were washed with H2O (15 ml) and brine (15 ml),
dried (MgSO4), filtered, and evaporated. The 1H-NMR spectrum of the crude product (57 mg) showed a
mixture of the corresponding imine and starting material in a ratio ca. 91:9. This mixture was diluted with EtOH
(2 ml), treated with NaBH4 (10 mg, 0.264 mmol), stirred for 3 h at 238, treated with H2O (0.3 ml), evaporated,
diluted with Et2O (20 ml), and washed with sat. NH4Cl soln. (3 Â 15 ml). The combined aq. layers were
extracted with Et2O (2 Â 15 ml). The combined org. layers were washed with H2O (25 ml) and brine (25 ml),
dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt 2 :1 ! 1:1 ! 1:2) gave 34 (42.6 mg, 75%) and 23
(1.8 mg, 4%). Oils.
25
D
Data of 34: Rf (hexane/AcOEt 1:1) 0.19. ‰aŠ ˆ À27.1( c ˆ 1.00, CHCl3). UV (CHCl3): 295 (3.3), 244 (4.1).
IR (CHCl3): 3416w, 3089w, 3065w, 3032w, 2938m, 2868m, 1952w, 1876w, 1812w, 1731w, 1603s, 1504s, 1454s,

3502
Helvetica Chimica Acta Vol. 86 (2003)
1430w, 1364m, 1311m, 1260m, 1180w, 1099s, 1028s, 91 3w. 1H-NMR (CDCl3, 400 MHz): see Table 7; additionally,
4.11 4.19 (br. s, NH); 4.23 (br. s, CH2ÀC(2)); 4.42 (br. s, PhCH2); 4.60 (d, J ˆ 11.2, PhCH); 4.62 (d, J ˆ 12.0,
PhCH); 4.68 (br. d, J ꢁ 10.9, 2 PhCH); 4.76 (d, J ˆ 11.3, PhCH); 4.98 (d, J ˆ 11.2, PhCH); 6.65 6.72
(m, HÀC(2), HÀC(4), and HÀC(6 ) of Ph ) ; 7.14 7.19 ( m, HÀC(3) and HÀC(5) of Ph); 7.21 7.34
(m, 18 arom. H); 7.36 7.39 (m, 2 arom. H). 13C-NMR (CDCl3, 100 MHz): see Table 5; additionally, 42.29
(t, CH2ÀC(2)); 70.77 (t, PhCH2, CH2ÀC(5)); 71.80 (t, PhCH2); 73.21( t, PhCH2); 74.88 (t, PhCH2); 113.15
(d, C(2) and C(6) of Ph); 117.50 (d, C(4) of Ph); 127.46 128.48 (several d); 129.13 (d, C(3) and C(5) of Ph);
137.52, 137.85, 138.03, 138.28 (4s); 148.26 (s, C(1) of Ph). HR-MALDI-MS: 704.2906 (1, C43H43KN3O4, [M ‡
‡
‡
K] ; calc. 704.2890), 688.3140 (24, C43H43N3NaO4, [M ‡ Na] ; calc. 688.3151), 666.3329 (24, C43H44N3O4, [M ‡
‡
‡
H] ; calc. 666.3332), 573.2739 (100, C37H37N2O4, [M À PhNH] ; calc. 573.2753), 558.2759 (2, C36H36N3O3, [M À
‡
BnO] ; calc. 558.2756), 467.2322 (16). Anal. calc. for C43H43N3O4 (665.83): C 77.57, H 6.51, N 6.31; found: C
77.69, H 6.47, N 6.19.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-[(phenylamino)methyl]imidazo[1,2-a]pyridine-
6,7,8-triol (35). A soln. of 34 (64 mg, 96.1 mmol) in CH2Cl2 (4.9 ml) was treated at À 788 with 1m BCl3 in CH2Cl2
(1.2 ml, 1.20 mmol), stirred until the mixture had reached a temp. of 158 (ca. 4.5 h), cooled to À 788, treated with
H2O (2 ml), and evaporated. The residue was taken up in H2O (2 ml) and applied to ion-exchange
‡
chromatography (Amberlite CG-120, H form, elution with 0.1m aq. NH3). Evaporation, lyophilisation, and
drying gave 35 (22.6 mg, ca. 77%) as a colourless hygroscopic resin containing substantial amounts of H2O. The
25
sample for microanalysis was dried for 4 d at 10À4 Torr. Rf (AcOEt/MeOH/H2O 10 :1:1) 0.18. ‰aŠ ˆ À23.3 (c ˆ
D
0.96, MeOH). UV (MeOH): 294 (3.28), 242 (4.02), 210 (4.02). IR (KBr): 3600 2400s (br.), 3053m, 2925m,
2852m, 1603s, 1506s, 1463m, 1432m, 1382w, 1312m, 1253m, 1180m, 1096s, 1066m, 1007w, 902w, 752m, 694m.
1H-NMR (D2O, 300 MHz): 3.80 (br. td, J ꢁ 2.8, 8.7, irrad. at 3.96 ! change, irrad. at 4.15 ! change, HÀC(5));
3.84 (dd, J ˆ 3.7, 10.0, irrad. at 4.15 ! change, irrad. at 4.83 ! d, J ˆ 10.3, HÀC(7)); 3.96 (dd, J ˆ 3.4, 12.8,
CHÀC(5)); 4.12 (dd, J ꢁ 2.5, 13.1, irrad. at 3.96 ! change, CH'ÀC(5)); 4.15 (dd, J ˆ 8.7, 10.3, irrad. at 3.84 !
change, HÀC(6)); 4.17 (d, J ˆ 15.9, CHÀC(2)); 4.23 (d, J ˆ 15.9, CH'ÀC(2)); 4.83 (d, J ˆ 3.7, irrad. at 3.84 ! s,
HÀC(8)); 6.77 6.82 (m, HÀC(2), HÀC(4), and HÀC(6) of Ph); 7.12 (s, HÀC(3)); 7.18 7.23 (m, HÀC(3) and
HÀC(5) of Ph). 13C-NMR (D2O, 75 MHz): see Table 6; additionally, 41.22 (t, CH2ÀC(2)); 114.80 (d, C(2) and
C(6) of Ph); 119.03 (d, C(4) of Ph); 129.23 (d, C(3) and C(5) of Ph); 144.62 (s, C(1) of Ph). HR-MALDI-MS:
‡
‡
328.1271 (56, C15H19N3NaO4, [M ‡ Na] ; calc. 328.1273), 306.1449 (100, C15H20N3O4, [M ‡ H] ; calc. 306.1454),
‡
213.0866 (49, C9H13N2O4, [M À PhNH] ; calc. 213.0875). Anal. calc. for C15H19N3O4 ¥ 0.5 H2O (314.34): C 57.32,
H 6.41, N 13.37; found: C 57.10, H 6.31, N 13.03.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-[(2-nitrophenoxy)meth-
yl]imidazo[1,2-a]pyridine (36). A suspension of 23 (42 mg, 71.1 mmol) and NaH (8 mg, 0.183 mmol) in
degassed DMF (1 ml) was treated with 1-fluoro-2-nitrobenzene (16 ml, 0.151 mmol), stirred for 1 h at 808,
cooled to r.t., diluted with Et2O (20 ml), and washed with sat. NH4Cl soln. (3 Â 10 ml). The combined aq. layers
were extracted with Et2O (2 Â 15 ml). The combined org. layers were washed with H2O (30 ml) and brine
(30 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt 1:0 ! 2 :1 ! 1:1) gave 36 (47.7 mg,
25
D
94%). Yellow oil. Rf (hexane/AcOEt 1:1) 0.26. ‰aŠ ˆ À33.1( c ˆ 1.00, CHCl3). UV (CHCl3): 326 (3.4), 259
(3.7), 240 (3.8). IR (CHCl3): 3089w, 3067w, 2960m, 2869m, 1952w, 1890w, 1811w, 1731m, 1608s, 1584m, 1526s,
1
1496m, 1454s, 1356s, 1309m, 1276s, 1254s, 1166m, 1093s, 1047s, 1028s, 91 3w. H-NMR (CDCl3, 300 MHz): see
Table 7; additionally, 4.45 (br. s, PhCH2); 4.608 (d, J ˆ 11.2, PhCH); 4.614 (d, J ˆ 11.8, PhCH); 4.65 (d, J ˆ 11.8,
PhCH); 4.69 (d, J ˆ 11.8, PhCH); 4.75 (d, J ˆ 12.5, PhCH); 4.99 (d, J ˆ 11.2, PhCH); 5.19 (br. s, CH2ÀC(2));
7.01( ddd, J ˆ 1.2, 7.5, 8.1, irrad. at 7.50! br. dd, J ꢁ 1.9, 7.8, irrad. at 7.83! br. dd, J ꢁ 0.9, 7.8, HÀC(4) of
C6H4NO2); 7.22 7.41( m, 20 arom. H, HÀC(3), HÀC(6) of C6H4NO2); 7.50 (ddd, J ˆ 1.9, 7.5, 9.3, irrad. at
7.01 ! br. dd, J ꢁ 2.8, 8.7, irrad. at 7.83 ! br. dd, J ꢁ 6.9, 8.4, HÀC(5) of C6H4NO2); 7.83 (dd, J ˆ 1.9, 8.1, irrad. at
7.01 ! br. d, J ꢁ 2.5, irrad. at 7.50 ! br. d, J ꢁ 7.5, HÀC(3) of C6H4NO2). 13C-NMR (CDCl3, 75 MHz): see
Table 5; additionally, 66.42 (t, CH2ÀC(2)); 70.53, 70.59 (2t, PhCH2, CH2ÀC(5)); 71.81 (t, PhCH2); 73.21
(t, PhCH2); 74.86 (t, PhCH2); 115.65 (d, C(6) of C6H4NO2); 120.42 (d, C(4) of C6H4NO2); 125.46 (d, C(3) of
C6H4NO2); 127.43 128.38 (several d); 133.87 (d, C(5) of C6H4NO2); 137.01, 137.30, 137.65, 137.81, 137.93 (5s
including C(2)); 140.10 (s, C(2) of C6H4NO2); 142.76 (s, C(8a)); 152.01 (s, C(1) of C6H4NO2). HR-MALDI-MS:
‡
‡
734.2771(18, C 43H41N3NaO7, [M ‡ Na] ; calc. 734.2842), 718.2896 (17, C43H41N3NaO6, [M ‡ Na À O] ; calc.
‡
‡
718.2893), 712.3025 (43, C43H42N3O7, [M ‡ H] ; calc. 712.3023), 702.2916 (10, C43H41N3NaO5, [M ‡ Na À O2] ;
‡
calc. 702.2944), 604.2491(10, C 36H34N3O6, [M À BnO] ; calc. 604.2447), 573.2767 (100, C37H37N2O4, [M À
‡
‡
C6H4NO3] ; calc. 573.2753), 467.2384 (42), 465.2240 (10, C30H29N2O3, [M À C6H4NO3 À BnOH] ; calc.
465.2178), 359.1824 (16). Anal. calc. for C43H41N3O7 (711.81): C 72.56, H 5.81, N 5.90; found: C 72.29, H
6.00, N 5.98.

Helvetica Chimica Acta Vol. 86 (2003)
3503
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-[(4-nitrophenoxy)meth-
yl]imidazo[1,2-a]pyridine (37). A susp. of 23 (92 mg, 0.156 mmol) and NaH (15 mg, 0.344 mmol) in degassed
DMF (3 ml) was treated with 1-fluoro-4-nitrobenzene (35 ml, 0.330 mmol), stirred for 1h at 80 8, cooled to r.t.,
diluted with Et2O (20 ml), and washed with sat. NH4Cl soln. (3 Â 10 ml). The combined aq. layers were
extracted with Et2O (2 Â 15 ml). The combined org. layers were washed with H2O (30 ml) and brine (30 ml),
dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt 1:0 ! 2 :1 ! 1:1) gave 37 (99 mg, 89%). Yellow
25
D
oil. Rf (hexane/AcOEt 1:1) 0.30. ‰aŠ ˆ À13.8 (c ˆ 1.00, CHCl3). UV (CHCl3): 312 (4.1), 240 (3.7). IR (CHCl3):
3089w, 3066w, 2938w, 2870w, 1953w, 1890w, 1812w, 1731m, 1608m, 1593s, 1515s, 1497s, 1454m, 1374m, 1343s,
1298m, 1254s, 1174m, 1112s, 1046m, 1028m, 990m, 91 4w. 1H-NMR (CDCl3, 300 MHz): see Table 7; additionally,
4.44 (d, J ˆ 12.1, PhCH); 4.48 (d, J ˆ 12.8, PhCH); 4.62 (d, J ˆ 11.2, PhCH); 4.63 (d, J ˆ 11.8, PhCH); 4.68
(d, J ˆ 12.1, PhCH); 4.70 (d, J ˆ 12.1, PhCH); 4.78 (d, J ˆ 12.8, PhCH); 5.01( d, J ˆ 11.2, PhCH); 5.07 (d, J ˆ
11.5, CHÀC(2)); 5.07 (d, J ˆ 11.5, CH'ÀC(2)); 7.05 7.12 (m, Jvic ˆ 9.3, irrad. at 8.19 ! s, HÀC(2) and HÀC(6)
of C6H4NO2); 7.24 7.40 (m, 20 arom. H, HÀC(3)); 8.16 8.22 (m, Jvic ˆ 9.3, irrad. at 7.09 ! s, HÀC(3) and
HÀC(5) of C6H4NO2). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 65.18 (t, CH2ÀC(2)); 70.99
(t, PhCH2, CH2ÀC(5)); 72.05 (t, PhCH2); 73.37 (t, PhCH2); 75.13 (t, PhCH2); 115.06 (d, C(2) and C(6) of
C6H4NO2); 126.02 (d, C(3) and C(5) of C6H4NO2); 127.77 128.70 (several d); 137.58, 137.91, 138.04, 138.21 (4s);
141.72 (s, C(4) of C6H4NO2); 163.96 (s, C(1) of C6H4NO2). HR-MALDI-MS: 734.2789 (50, C43H41N3NaO7,
‡
‡
[M ‡ Na] ; calc. 734.2842), 718.2898 (66, C43H41N3NaO6, [M ‡ Na À O] ; calc. 718.2893), 712.3026 (52,
‡
‡
C43H42N3O7, [M ‡ H] ; calc. 712.3023), 698.3189 (55, C43H44N3O6, [M ‡ H À O2 ‡ H2O] ; calc. 698.3230),
‡
‡
696.3040 (55, C43H42N3O6, [M ‡ H À O] ; calc. 696.3073), 604.2490 (57, C36H34N3O6, [M À BnO] ; calc.
‡
604.2447), 596.2674 (30), 588.2529 (31, C36H34N3O5, [M À O À BnO] ; calc. 588.2498), 574.2835 (100,
‡
‡
C37H38N2O4 , [M ‡ H À C6H4NO3] ; calc. 574.2831), 573.2774 (78, C37H37N2O4 , [M À C6H4NO3] ; calc.
‡
573.2753), 467.2386 (48), 465.2244 (41, C30H29N2O3, [M À C6H4NO3 À BnOH] ; calc. 465.2178), 375.1776
(74), 359.1827 (43). Anal. calc. for C43H41N3O7 (711.80): C 72.56, H 5.81, N 5.90; found: C 72.43, H 5.63, N 5.83.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-2-[(2,4-dinitrophenoxy)methyl]-5,6,7,8-tetra-
hydroimidazo[1,2-a]pyridine (38). A suspension of 23 (50 mg, 84.6 mmol) and NaH (8 mg, 0.183 mmol) in
degassed DMF (2 ml) was treated with 1-fluoro-2,4-dinitrobenzene (22 ml, 0.180 mmol) and stirred for 5 h at
808. No reaction was observed at this moment (TLC). The mixture was left to stand at 238 for 3 weeks, diluted
with Et2O (20 ml), and washed with sat. NH4Cl soln. (3 Â 10 ml). The combined aq. layers were extracted with
Et2O (2 Â 15 ml). The combined org. layers were washed with H2O (30 ml) and brine (30 ml), dried (MgSO4),
filtered, and evaporated. FC (hexane/AcOEt 1:0 ! 2 :1 ! 1:1) gave 38 (40.0 mg, 63%) and 23 (2.8 mg, 6%) as
yellow oils.
25
D
Data of 38: Rf (hexane/AcOEt 1:1) 0.23. ‰aŠ ˆ À19.0 (c ˆ 1.00, CHCl3). UV (CHCl3): 296 (4.0), 258 (3.9),
240 (3.9). IR (CHCl3): 3090w, 3067w, 2961w, 2870m, 1952w, 1872w, 1810w, 1731s, 1608s, 1538s, 1496m, 1454m,
1
1420w, 1345s, 1314m, 1274s, 1152m, 1098s, 1071s, 1046s, 1028m, 970m, 91 4w. H-NMR (CDCl3, 300 MHz): see
Table 7; additionally, 4.43 (br. s, PhCH2); 4.59 (d, J ˆ 11.2, PhCH); 4.60 (d, J ˆ 12.1, PhCH); 4.65 (d, J ˆ 12.5,
PhCH); 4.67 (d, J ˆ 11.8, PhCH); 4.74 (d, J ˆ 12.1, PhCH); 4.96 (d, J ˆ 11.2, PhCH); 5.29 (br. s, CH2ÀC(2));
7.21 7.36 ( m, 20 arom. H, HÀC(3)); 7.62 (d, J ˆ 9.3, irrad. at 8.33 ! s, HÀC(6) of C6H3N2O4); 8.33 (dd, J ˆ 2.8,
9.3, irrad. at 7.62 ! br. d, J ꢁ 2.5, irrad. at 8.68 ! d, J ˆ 9.3, HÀC(5) of C6H3N2O4); 8.68 (d, J ˆ 2.8, irrad. at
8.33 ! s, HÀC(3) of C6H3N2O4). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 66.86 (t, CH2ÀC(2));
70.54, 70.73 (2t, CH2ÀC(5), PhCH2); 71.88 (t, PhCH2); 73.18 (t, PhCH2); 74.80 (t, PhCH2); 115.81 (d, C(6) of
C6H3N2O4); 121.69 (d, C(3) of C6H3N2O4); 127.65 128.48 (several d); 128.71 (d, C(5) of C6H3N2O4); 137.26,
137.64, 137.73, 137.84 (4s); 139.06, 139.97 (2s, C(2) and C(4) of C6H3N2O4); 156.58 (s, C(1) of C6H3N2O4). HR-
‡
‡
MALDI-MS: 779.2660 (1, C43H40N4NaO9, [M ‡ Na] ; calc. 779.2693), 757.2862 (12, C43H41N4O9, [M ‡ H] ; calc.
‡
757.2873), 743.3071 (17), 741.2910 (13, C43H41N4O8, [M ‡ H À O] ; calc. 741.2924), 649.2294 (8, C36H33N4O8,
‡
‡
[M À BnO] ; calc. 649.2298), 573.2732 (100, C37H37N2O4, [M À C6H3N2O5] ; calc. 573.2732), 467.232 (28),
‡
465.2167 (9, C30H29N2O3, [M À C6H3N2O5 À BnOH] ; calc. 465.2167), 359.1751 (12). Anal. calc. for C43H40N4O9
(756.81): C 68.24, H 5.33, N 7.40; found: C 68.25, H 5.45, N 7.27.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-[(3-nitrophenoxy)meth-
yl]imidazo[1,2-a]pyridine (39). A suspension of 23 (33 mg, 55.9 mmol) and NaH (7 mg, 0.160 mmol) in
degassed DMF (1 ml) was treated with 1-fluoro-3-nitrobenzene (12 ml, 0.112 mmol), stirred for 1 h at 808 (no
reaction) and then for 20 h at 1408, cooled to r.t., diluted with Et2O (20 ml), and washed with sat. NH4Cl soln.
(3 Â 10 ml). The combined aq. layers were extracted with Et2O (2 Â 15 ml). The combined org. layers were
washed with H2O (30 ml) and brine (30 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt
1:0 ! 2 :1 ! 1:1 ! 0 :1) gave 39 (22.2 mg, 56%) and 23 (8.8 mg, 27%). Yellow oils.

3504
Helvetica Chimica Acta Vol. 86 (2003)
25
D
Data of 39: Rf (hexane/AcOEt 1:1) 0.43. ‰aŠ ˆ À16.6 (c ˆ 0.89, CHCl3). UV (CHCl3): 328 (3.3), 269
(3.8), 240 (3.9). IR (CHCl3): 3089w, 3067w, 2932w, 2869w, 1951w, 1870w, 1811w, 1731w, 1619w, 1582w, 1530s,
1497m, 1482w, 1454m, 1352s, 1319m, 1284m, 1097s, 1027m, 990w, 91 2w. 1H-NMR (CDCl3, 300 MHz): see
Table 7; additionally, 4.47 (br. s, PhCH2); 4.62 (d, J ˆ 11.5, 2 PhCH); 4.688 (d, J ˆ 12.1, PhCH); 4.693 (d, J ˆ
11.8, PhCH); 4.77 (d, J ˆ 12.1, PhCH); 5.01( d, J ˆ 11.2, PhCH); 5.05 (d, J ˆ 11.8, CHÀC(2)); 5.10 (d, J ˆ 11.8,
CH'ÀC(2)); 7.25 7.36 (m, 18 arom. H, HÀC(3), HÀC(6) of C6H4NO2); 7.37 7.42 (m, 2 arom. H); 7.42 (t, J ˆ
8.1, HÀC(5) of C6H4NO2); 7.83 (ddd, J ˆ 0.9, 2.2, 8.1, HÀC(4) of C6H4NO2); 7.91( t, J ˆ 2.2, HÀC(2) of
C6H4NO2). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 64.89 (t, CH2ÀC(2)); 70.73, 70.81(2 t, PhCH2,
CH2ÀC(5)); 71.81 (t, PhCH2); 73.18 (t, PhCH2); 74.94 (t, PhCH2); 109.23 (d, C(2) of C6H4NO2); 115.76 (d, C(4)
of C6H4NO2); 121.92 (d, C(6) of C6H4NO2); 127.43 128.40 (several d); 129.71 (d, C(5) of C6H4NO2); 137.27,
137.60, 137.75, 137.93 (4s); 148.97 (s, C(3) of C6H4NO2); 159.07 (s, C(1) of C6H4NO2). HR-MALDI-MS:
‡
‡
734.2799 (73, C43H41N3NaO7, [M ‡ Na] ; calc. 734.2842), 718.290 (92, C43H41N3NaO6, [M ‡ Na À O] ; calc.
‡
718.2893), 712.3022 (71, C43H42N3O7, [M ‡ H] ; calc. 712.3023), 698.3188 (100, C43H44N3O6, [M ‡ H À O2 ‡
‡
‡
H2O] ; calc. 698.3230), 696.3047 (87, C43H42N3O6, [M ‡ H À O] ; calc. 696.3073), 604.2490 (98, C36H34N3O6,
‡
‡
[M À BnO] ; calc. 604.2447), 588.2529 (89, C36H34N3O5, [M À O À BnO] ; calc. 588.2498), 573.2782 (81,
‡
‡
C37H37N2O4, [M À C6H4NO3] ; calc. 573.2753), 465.2247 (63, C30H29N2O3, [M À C6H4NO3 À BnOH] ; calc.
465.2178), 375.1777 (70), 359.1828 (61). Anal. calc. for C43H41N3O7 (711.81): C 72.56, H 5.81, N 5.90; found: C
72.59, H 5.90, N 5.83.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-[(2-nitrophenoxy)methyl]imidazo[1,2-a]pyridine-
6,7,8-triol (40). A soln. of 36 (16.5 mg, 23.2 mmol) in CH2Cl2 (1ml) was treated with AlCl 3 (38 mg, 0.285 mmol)
and anisole (41 ml, 0.375 mmol), stirred for 13 h at 228, and treated with H2O (15 ml). The mixture was diluted
with AcOEt (15 ml). After extraction with H2O, the aq. layer was evaporated. FC (AcOEt/MeOH/H2O
1:0 :0 ! 1 5 :1 :1! 10 :1:1) yielded 40 (6.1mg, 75%). White solid. Rf (AcOEt/MeOH/H2O 15 :1:1) 0.10.
25
D
‰aŠ ˆ À17.8 ( c ˆ 0.30, MeOH). UV (MeOH): 320 (3.22), 254 (3.27), 214 (4.23). IR (KBr): 3600 2400s (br.),
2924w, 2857w, 1630m, 1608s, 1584m, 1525s, 1487w, 1459m, 1446m, 1398w, 1381w, 1352m, 1286m, 1260m, 1177w,
1165m, 1149w, 1121m, 1087m, 1040m, 91 w0, 861w. 1H-NMR (CD3OD, 300 MHz): 3.81( dd, J ˆ 3.7, 9.3,
HÀC(7)); 3.84 3.94 (m, HÀC(5), CHÀC(5)); 4.06 4.20 (m, HÀC(6), CH'ÀC(5)); 4.82 (d, J ˆ 3.7, HÀC(8));
5.12 (br. s, CH2ÀC(2)); 7.06 (ddd, J ˆ 1.2, 7.5, 8.1, HÀC(4) of C6H4NO2); 7.41( dd, J ˆ 1.2, 8.4, HÀC(6) of
C6H4NO2); 7.48 (s, HÀC(3)); 7.57 (ddd, J ˆ 1.9, 7.5, 8.4, HÀC(5) of C6H4NO2); 7.75 (dd, J ˆ 1.9, 8.1, HÀC(3) of
C6H4NO2). 1H-NMR (CD3OD/D2O 4 :1, 300 MHz): 3.87 (dd, J ˆ 3.7, 10.0, HÀC(7)); 3.89 (ddd, J ˆ 2.5, 4.7, 7.8,
HÀC(5)); 3.96 (dd, J ˆ 4.7, 11.8, CHÀC(5)); 4.17 (dd, J ˆ 7.8, 9.7, HÀC(6)); 4.19 (dd, J ˆ 2.5, 12.1, CH'ÀC(5));
4.87 (d, J ˆ 3.7, HÀC(8)); 5.16 (br. s, CH2ÀC(2)); 7.12 (ddd, J ˆ 1.2, 7.2, 8.4, HÀC(4) of C6H4NO2); 7.42 (dd, J ˆ
0.9, 8.7, HÀC(6) of C6H4NO2); 7.44 (s, HÀC(3)); 7.65 (ddd, J ˆ 1.6, 7.5, 8.7, HÀC(5) of C6H4NO2); 7.83 (dd, J ˆ
1.6, 8.1, HÀC(3) of C6H4NO2). 13C-NMR (CD3OD, 75 MHz): see Table 6; additionally, 66.57 (t, CH2ÀC(2));
116.52 (d, C(6) of C6H4NO2); 122.32, 122.69 (2d, C(4) of C6H4NO2, C(3)); 126.21 (d, C(3) of C6H4NO2); 135.27
(d, C(5) of C6H4NO2); 141.75 (s, C(2) of C6H4NO2); 151.66 (s, C(1) of C6H4NO2). HR-MALDI-MS: 374.0959
‡
‡
(100, C15H17N3NaO7, [M ‡ Na] ; calc. 374.0964), 360.1166 (54, C15H19N3NaO6, [M ‡ Na À O2 ‡ H2O] ; calc.
‡
‡
360.1171), 358.1012 (85, C15H17N3NaO6, [M ‡ Na À O] ; calc. 358.1015), 352.1137 (46, C15H18N3O7, [M ‡ H] ;
‡
calc. 352.1145), 342.1061 (31, C15H17N3NaO5, [M ‡ Na À O2] ; calc. 342.1066), 336.1186 (30, C15H18N3O6, [M ‡
‡
‡
H À O] ; calc. 336.1195), 320.1238 (83, C15H18N3O5, [M ‡ H À O2] ; calc. 320.1246), 213.0868 (88, C9H13N2O4,
‡
[M À C6H4NO3] ; calc. 213.0875).
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-[(4-nitrophenoxy)methyl]-imidazo[1,2-a]pyridine-
6,7,8-triol (41). a) A soln. of 37 (16.7 mg, 23.5 mmol) in CH2Cl2 (1ml) was treated with AlCl 3 (38 mg,
0.285 mmol) and anisole (41 ml, 0.375 mmol), stirred for 17 h at 228, and treated with H2O (15 ml). The mixture
was diluted with AcOEt (15 ml). After extraction with H2O, the aq. layer was evaporated. FC (AcOEt/MeOH/
H2O 1:0 :0 ! 20 :1:1) and drying yielded 41 (5.9 mg, ca. 72%) as a white foam containing substantial amounts
of MeOH and H2O. The sample for microanalysis was dried for 4 d at 10À4 Torr.
b) A soln. of 37 (30.7 mg, 43.1 mmol) in CH2Cl2 (1.1 ml) was treated at À 788 with 1m BCl3 in CH2Cl2
(0.8 ml, 0.80 mmol), stirred until the mixture had reached a temp. of 208 (ca. 5.5 h), cooled to À 788, treated
with H2O (2 ml), and evaporated. FC (AcOEt/MeOH/H2O 1:0 :0 ! 20 :1:1) gave 41 (10.7 mg, ca. 70%)
containing substantial amounts of MeOH and H2O.
25
D
Data of 41: Rf (AcOEt/MeOH/H2O 10 :1:1) 0.17. ‰aŠ À 24.3 (c ˆ 0.48, MeOH). UV (MeOH): 307 (3.99),
219 (4.09), 204 (4.15). IR (KBr): 3600 2400s (br.), 2928m, 1631w, 1606m, 1593s, 1510s, 1459m, 1383m, 1344s,
1299m, 1259s, 1177m, 1112s, 986m, 902w, 870m, 846m. 1H-NMR (CD3OD, 300 MHz): 3.82 (dd, J ˆ 3.7, 9.0,
HÀC(7)); 3.84 3.94 (m, HÀC(5), CHÀC(5)); 4.06 4.22 (m, HÀC(6), CH'ÀC(5)); 4.83 (d, J ˆ 3.7, HÀC(8));
5.10 (br. s, CH2ÀC(2)); 7.11 7.18 (m, Jvic ˆ 9.3, HÀC(2) and HÀC(6) of C6H4NO2); 7.50 (s, HÀC(3)); 8.16

Helvetica Chimica Acta Vol. 86 (2003)
3505
8.23 (m, Jvic ˆ 9.3, HÀC(3) and HÀC(5) of C6H4NO2). 13C-NMR (CD3OD, 75 MHz): see Table 6; additionally,
65.41( t, CH2ÀC(2)); 116.06 (d, C(2) and C(6) of C6H4NO2); 126.78 (d, C(3) and C(5) of C6H4NO2); 142.83
‡
(s, C(4) of C6H4NO2); 165.26 (s, C(1) of C6H4NO2). HR-MALDI-MS: 374.0957 (5, C15H17N3NaO7, [M ‡ Na] ;
‡
calc. 374.0964), 360.1163 (6, C15H19N3NaO6 , [M ‡ Na À O2 ‡ H2O] ; calc. 360.1171), 358.0997 (7,
‡
‡
C15H17N3NaO6 , [M ‡ Na À O] ; calc. 358.1015), 352.1138 (27, C15H18N3O7, [M ‡ H] ; calc. 352.1145),
‡
‡
338.1350 (38, C15H20N3O6, [M ‡ H À O2 ‡ H2O] ; calc. 338.1350), 336.1191 (28, C15H18N3O6, [M ‡ H À O] ;
‡
calc. 336.1195), 320.1237 (16, C15H18N3O5, [M ‡ H À O2] ; calc. 320.1246), 302.1130 (5, C15H16N3O4, [M À O2 À
‡
‡
OH] ; calc. 302.1141), 235.0681 (10, C9H12N2NaO4, [M ‡ Na À C6H5NO3] ; calc. 235.0695), 213.0866 (100,
‡
C9H13N2O4, [M À C6H4NO3] ; calc. 213.0875). Anal. calc. for C15H17N3O7 ¥ 0.5 MeOH ¥ 0.5 H2O (376.34): C
49.47, H 5.36, N 11.17; found: C 49.57, H 5.25, N 10.95.
(5R,6R,7S,8R)-2-[(2,4-Dinitrophenoxy)methyl]-5,6,7,8-tetrahydro-5-(hydroxymethyl)imidazo[1,2-a]pyri-
dine-6,7,8-triol (42). A soln. of 38 (27 mg, 35.7 mmol) in CH2Cl2 (1.6 ml) was treated with AlCl3 (60 mg,
0.450 mmol) and anisole (63 ml, 0.577 mmol), stirred for 17 h at 228, and treated with H2O (20 ml). The mixture
was diluted with AcOEt (25 ml). After extraction with H2O, the aq. layer was evaporated. FC (AcOEt/MeOH/
H2O 1 :0 :0! 15 :1:1) yielded pure 42 (7.6 mg, 75%; colourless solid) which partially decomposed before the
NMR measurement. Rf (AcOEt/MeOH/H2O 15 :1:1) 0.13. IR (KBr): 3600 2400s (br.), 2930m, 1955w, 1837w,
1603s, 1564s, 1525s, 1478m, 1432m, 1373m, 1330s, 1265s, 1169m, 1133s, 1096m, 1060m, 998m, 925m, 834m, 751m,
714m. 1H-NMR (CD3OD, 300 MHz, 3 :1mixture of 42 and a product missing the dinitrophenoxy group): 3.83
(dd, J ˆ 3.7, 9.0, HÀC(7)); 3.86 3.95 (m, HÀC(5), CHÀC(5)); 4.07 4.20 (m, HÀC(6), CH'ÀC(5)); 4.83
(d, J ˆ 3.7, HÀC(8)); 5.29 (br. s, CH2ÀC(2)); 7.56 (s, HÀC(3)); 7.67 (d, J ˆ 9.3, HÀC(6) of C6H3N2O4); 8.47
(dd, J ˆ 2.8, 9.3, HÀC(5) of C6H3N2O4); 8.69 (d, J ˆ 2.8, HÀC(3) of C6H3N2O4). HR-MALDI-MS: 396.9894
‡
‡
(24, C15H17N4O9, [M ‡ H] ; calc. 397.0995), 213.0865 (100, C9H13N2O4, [M À C6H3N2O5] ; calc. 213.0875).
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-[(3-nitrophenoxy)methyl]imidazo[1,2-a]pyridine-
6,7,8-triol (43). A soln. of 39 (9.7 mg, 13.6 mmol) in CH2Cl2 (0.6 ml) was treated with AlCl3 (22 mg, 0.165 mmol)
and anisole (24 ml, 0.220 mmol), stirred for 13 h at 228, and treated with H2O (10 ml). The mixture was diluted
with AcOEt (10 ml). After extraction with H2O, the aq. layer was evaporated. FC (AcOEt/MeOH/H2O
1:0 :0 ! 20 :1:1 ! 15 :1:1) yielded 43 (2.6 mg, ca. 54%) as a white solid containing substantial amounts of
MeOH. The sample for microanalysis was dried for 4 d at 10À4 Torr. Rf (AcOEt/MeOH/H2O 10 :1:1) 0.23.
‰aŠ ˆ À14.2 (c ˆ 0.29, MeOH). UV (MeOH): 267 (3.68), 214 (4.25). IR (KBr): 3600 2400s (br.), 2925m,
25
D
2851m, 1616m, 1528s, 1482m, 1460m, 1384m, 1351s, 1323m, 1285m, 1244m, 1181w, 1095m, 1029w, 1007m, 903w,
843w, 825w, 796w, 737m. 1H-NMR (CD3OD, 300 MHz): 3.81( dd, J ˆ 3.7, 9.3, irrad. at 4.11 ! d, J ꢁ 4.0, irrad. at
4.83 ! d, J ˆ 9.3, HÀC(7)); 3.84 3.90 (m, HÀC(5)); 3.90 (dd, J ˆ 5.6, 10.9, CHÀC(5)); 4.06 4.22
(m, HÀC(6), CH'ÀC(5)); 4.83 (d, J ˆ 3.7, irrad. at 3.81 ! s, HÀC(8)); 5.08 (br. s, CH2ÀC(2)); 7.39 (ddd, J ˆ
0.9, 2.5, 8.4, HÀC(6) of C6H4NO2); 7.49 (s, HÀC(3)); 7.50 (t, J ˆ 8.4, HÀC(5) of C6H4NO2); 7.81( ddd, J ˆ 0.9,
2.2, 8.7, HÀC(4) of C6H4NO2); 7.82 (t, J ꢁ 1.9, HÀC(2) of C6H4NO2). 13C-NMR (CD3OD, 75 MHz): see Table 6;
additionally, 65.30 (t, CH2ÀC(2)); 110.27 (d, C(2) of C6H4NO2); 116.48 (d, C(4) of C6H4NO2); 122.56 (d, C(6) of
C6H4NO2); 131.19 (d, C(5) of C6H4NO2); 150.39 (s, C(3) of C6H4NO2); 160.47 (s, C(1) of C6H4NO2). HR-
‡
MALDI-MS: 374.0952 (39, C15H17N3NaO7, [M ‡ Na] ; calc. 374.0964), 360.1168 (65, C15H19N3NaO6, [M ‡
‡
‡
Na À O2 ‡ H2O] ; calc. 360.1171), 358.1018 (67, C15H17N3NaO6, [M ‡ Na À O] ; calc. 358.1015), 352.1143 (70,
‡
‡
C15H18N3O7, [M ‡ H] ; calc. 352.1145), 338.1347 (100, C15H20N3O6, [M ‡ H À O2 ‡ H2O] ; calc. 338.1352),
‡
‡
336.1191 (96, C15H18N3O6, [M ‡ H À O] ; calc. 336.1195), 320.1234 (82, C15H18N3O5, [M ‡ H À O2] ; calc.
‡
320.1246), 213.0868 (90, C9H13N2O4 , [M À C6H4NO3] ; calc. 213.0875), 195.0758 (61, C9H11N2O3 , [M À
‡
C6H4NO3 À H2O] ; calc. 195.0770). Anal. calc. for C15H17N3O7 ¥ MeOH (383.36): C 50.13, H 5.52, N 10.96;
found: C 50.34, H 5.36, N 10.94.
Methyl and Ethyl (5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydroimida-
zo[1,2-a]pyridine-2-carboxylate (44 and 45, resp.). a) A soln. of 20 (210 mg, 0.306 mmol) in THF (10 ml) was
cooled to À 788, treated with a 1.44m soln. of BuLi14) in hexane (0.48 ml, 0.691mmol), stirred for 1h, treated
with ClCOOMe (0.20 ml, 2.60 mmol), stirred for 1h at À 788, and for another 17 h at 228. The mixture was
treated with sat. NH4Cl soln. (10 ml) and diluted with Et2O (40 ml). The layers were separated, and the Et2O
layer was washed with sat. NH4Cl soln. (2 Â 20 ml). The combined aq. layers were extracted with Et2O (2 Â
15 ml). The combined org. layers were washed with H2O (40 ml), brine (40 ml), and dried (MgSO4).
Evaporation and FC (hexane/AcOEt 1:0 ! 7:3 ! 1:1) yielded 44 (82 mg, 43%) and 17 (41mg, 24%). Oils.
14
)
The molar concentration of BuLi was determined by titration of Ph2CHCOOH as described by Kofron
and Baclawski [58].

3506
Helvetica Chimica Acta Vol. 86 (2003)
b) A suspension of 22 (75 mg, 0.127 mmol), MnO2 (285 mg, 3.28 mmol, Aldrich 21,764-6) and NaCN
(35 mg, 0.714 mmol) in MeOH (4 ml) was treated with AcOH (20 ml, 0.350 mmol), stirred at 228 for 12 h,
filtered through Celite (washing with 20 ml of MeOH and 20 ml of AcOEt). Evaporation of the filtrate and FC
(hexane/AcOEt 1:0 ! 2 :1 ! 1:1) gave 45 (17.1 mg, 21%) and 44 (51.6 mg, 65%). Colourless oils.
c) As described in b. After evaporation of the filtrate, the crude product was diluted with AcOEt (60 ml)
and washed with sat. NaHCO3 soln. (3 Â 30 ml). The combined aq. layers were extracted with AcOEt (2 Â
40 ml). The combined org. layers were washed with H2O (70 ml) and brine (70 ml), dried (MgSO4), filtered,
and evaporated. FC (cyclohexane/AcOEt 1:0 ! 1:1) afforded 44 (78%) as a single product.
25
D
Data of 44: Rf (hexane/AcOEt 1:1) 0.35. ‰aŠ ˆ À37.1( c ˆ 1.00, CHCl3). UV (CHCl3): 243 (3.98). IR
(CHCl3): 3090w, 3068w, 3024m, 3018m, 2953m, 2928w, 2869w, 1952w, 1876w, 1811w, 1718s, 1603w, 1552m, 1497m,
1455m, 1428w, 1363m, 1343m, 1327m, 1262m, 1217s, 1146m, 1097s, 1028s, 1010s, 943w, 91 3w. 1H-NMR (CDCl3,
300 MHz): see Table 7; additionally, 3.91( s, MeO); 4.45 (br. s, PhCH2); 4.62 (d, J ˆ 11.2, PhCH); 4.64 (d, J ˆ
12.1, PhCH); 4.66 (d, J ˆ 11.5, PhCH); 4.70 (d, J ˆ 12.1, PhCH); 4.74 (d, J ˆ 11.8, PhCH); 4.99 (d, J ˆ 11.2,
PhCH); 7.23 7.38 (m, 20 arom. H). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 51.80 (q, MeO);
70.45, 70.93 (2t, PhCH2, CH2ÀC(5)); 71.95 (t, PhCH2); 73.23 (t, PhCH2); 74.92 (t, PhCH2); 127.44 128.44
(several d); 137.07, 137.49, 137.65, 137.80 (4s); 163.12 (s, CˆO). HR-MALDI-MS: 657.2380 (4, C38H38KN2O6,
‡
‡
[M ‡ K] ; calc. 657.2367), 641.2586 (77, C38H38N2NaO6, [M ‡ Na] ; calc. 641.2627), 619.2809 (100, C38H39N2O6,
‡
‡
[M ‡ H] ; calc. 619.2808), 587.2574 (3, C37H35N2O5, [M À MeO] ; calc. 587.2546), 511.2265 (31, C31H31N2O5,
‡
‡
[M À BnO] ; calc. 511.2232), 479.2002 (15, C30H27N2O4, [M À BnO À MeOH] ; calc. 479.1970). Anal. calc. for
C38H38N2O6 (618.73): C 73.77, H 6.19, N 4.53; found: C 73.79, H 6.33, N 4.64.
25
D
Data of 45: Rf (hexane/AcOEt 1:1) 0.53. ‰aŠ ˆ À35.6 (c ˆ 0.58, CHCl3). UV (CHCl3): 242 (4.01). IR
(CHCl3): 3159w, 3090w, 3068w, 3019m, 2963m, 2929w, 2870w, 1953w, 1878w, 1811w, 1717m, 1603w, 1550w, 1497w,
1455m, 1393w, 1367m, 1338w, 1323m, 1262m, 1217s, 1146m, 1096s, 1027s, 930w, 91 w3. 1H-NMR (CDCl3,
300 MHz): see Table 7; additionally, 1.36 (t, J ˆ 7.2, MeCH2); 4.34 (q, J ˆ 7.2, MeCH2); 4.42 (br. s, PhCH2); 4.58
(d, J ˆ 11.2, PhCH); 4.60 (d, J ˆ 12.1, PhCH); 4.62 (d, J ˆ 11.5, PhCH); 4.66 (d, J ˆ 11.2, PhCH); 4.70 (d, J ˆ
12.1, PhCH); 4.95 (d, J ˆ 11.2, PhCH); 7.20 7.35 (m, 20 arom. H). 13C-NMR (CDCl3, 75 MHz): see Table 5;
additionally, 14.46 (q, MeCH2); 60.53 (t, MeCH2); 70.48, 70.86 (2t, PhCH2, CH2ÀC(5)); 71.89 (t, PhCH2); 73.22
(t, PhCH2); 74.90 (t, PhCH2); 127.51 128.50 (several d); 137.19, 137.58, 137.77, 137.93 (4s); 162.87 (s, CˆO).
‡
‡
‡
MALDI-MS: 655 ([M ‡ Na] ), 633 ([M ‡ H] ). HR-MALDI-MS: 671.2537 (9, C39H40KN2O6, [M ‡ K] ; calc.
‡
‡
671.2523), 655.2787 (100, C39H40N2NaO6, [M ‡ Na] ; calc. 655.2784), 633.2966 (54, C39H41N2O6, [M ‡ H] ; calc.
‡
‡
633.2964), 587.2550 (7, C37H35N2O5, [M À EtO] ; calc. 587.2546), 525.2393 (26, C32H33N2O5, [M À BnO] ; calc.
‡
525.2389), 479.1981 (19, C30H27N2O4, [M À BnO À EtOH] ; calc. 479.1971). Anal. calc. for C39H40N2O6 (632.75):
C 74.03, H 6.37, N 4.43; found: C 74.18, H 6.50, N 4.23.
Methyl (5R,6R,7S,8R)-5,6,7,8-Te trahydro-6,7,8-trihydroxy-5-(hydroxymethyl)imidazo[1,2-a]pyridine-2-
carboxylate (46). A soln. of 44 (105 mg, 0.170 mmol) in AcOEt/MeOH 1:1 (1.8 ml) was treated with AcOH
(0.9 ml) and 10% Pd/C (50 mg), hydrogenated at 6 bar for 48 h, and filtered through Celite (washing with
MeOH/H2O 9 :1(20 ml)). Evaporation of the combined filtrates, FC (AcOEt/MeOH/H O 1:0 :0 ! 1 0 :1 :1 ),
2
lyophilisation, and drying gave 46 (38.5 mg, ca. 88%) as a colourless hygroscopic resin containing substantial
amounts of MeOH and H2O. The sample for microanalysis was dried for 4 d at 10À4 Torr. Rf (AcOEt/MeOH/
25
D
H2O 10 :1:1) 0.12. ‰aŠ À 21.6 (c ˆ 1.02, MeOH). UV (MeOH): 238 (3.95), 200 (3.67). IR (KBr): 3600 2400s
(br.), 2952m, 2924m, 1716s, 1636w, 1553m, 1442m, 1356m, 1334m, 1219s, 1138m, 1095s, 1011m, 945w, 902w, 834w,
805w, 769m. 1H-NMR (CD3OD, 300 MHz): 3.83 (s, MeO); 3.84 (dd, J ꢁ 3.7, 8.7, irrad. at 4.11 ! change, irrad. at
4.84 ! d, J ˆ 9.0, HÀC(7)); 3.89 (dd, J ˆ 5.9, 11.2, irrad. at 4.17 ! change, CHÀC(5)); 3.90 3.97 (m, irrad. at
4.11 ! change, irrad. at 4.17 ! change, HÀC(5)); 4.11 (dd, J ˆ 7.2, 9.0, irrad. at 3.84 ! d J ꢁ 6.5, HÀC(6)); 4.17
(dd, J ˆ 2.2, 11.2, CH'ÀC(5)); 4.84 (d, J ˆ 3.7, irrad. at 3.84 ! s, HÀC(8)); 8.01( s, HÀC(3)). 13C-NMR
(CD3OD, 75 MHz): see Table 6; additionally, 51.95 (q, MeO); 164.34 (s, CˆO). HR-MALDI-MS: 281.0742
‡
‡
(100, C10H14N2NaO6, [M ‡ Na] ; calc. 281.0749), 259.0928 (60, C10H15N2O6, [M ‡ H] ; calc. 259.0930), 227.0658
‡
(21, C9H11N2O5, [M À MeO] ; calc. 227.0668). Anal. calc. for C10H14N2O6 ¥ 0.6 MeOH ¥ 0.1H 2O (279.26): C
45.59, H 5.99, N 10.03; found: C 45.45, H 5.70, N 9.77.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-6,7,8-trihydroxy-5-(hydroxymethyl)imidazo[1,2-a]pyridine-2-carboxylic
Acid (47). A soln. of 46 (25 mg, 96.8 mmol) in 0.4m soln. of KOH in EtOH/H2O 4 :1(1ml) was heated at 50 8 for
‡
3 h, evaporated, taken up in H2O (3 ml), and applied to ion-exchange chromatography (Amberlite CG-120, H
form, elution with 0.1m aq. NH3). Lyophilisation gave 47 (19.5 mg, 83%) as a colourless hygroscopic resin. Rf
25
D
(AcOEt/MeOH/H2O 3 :1:1) 0.13. ‰aŠ ˆ À51.3 (c ˆ 0.74, H2O). UV (H2O): 226 (3.96), 193 (3.99). IR (KBr):
3600 2400s (br.), 2918m, 2857m, 1619s, 1575s, 1544s, 1434m, 1398s, 1337m, 1265m, 1183m, 1094s, 1065s, 1000m,
902m, 835m, 775m, 724m. 1H-NMR (D2O, 300 MHz): 3.84 (dd, J ˆ 3.4, 9.7, HÀC(7)); 3.82 3.89 (m, HÀC(5));

Helvetica Chimica Acta Vol. 86 (2003)
3507
3.89 (dd, J ˆ 3.4, 12.1, CHÀC(5)); 4.04 4.14 (m, HÀC(6), CH'ÀC(5)); 4.79 (d, J ˆ 3.4, HÀC(8)); 7.53
(s, HÀC(3)). 13C-NMR (D2O, 75 MHz): see Table 6; additionally, 169.88 (s, CˆO). HR-MALDI-MS: 289.0405
‡
‡
(12, C9H11N2Na2O6, [M À H ‡ 2 Na] ; calc. 289.0412); 267.0584 (51, C9H12N2NaO6, [M ‡ Na] ; calc. 267.0593);
‡
‡
245.0768 (100, C9H13N2O6, [M ‡ H] ; calc. 245.0774), 227.0657 (23, C9H11N2O5, [M À OH] ; calc. 227.0668).
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyridine-2-
carbonitrile (48). a) A soln. of 20 (235 mg, 0.342 mmol) in THF (2.3 ml) was treated at 08 with 1m EtMgBr soln.
in THF (1.18 ml, 1.18 mmol), stirred under Ar for 15 min, treated with a suspension of TsCN (620 mg,
3.42 mmol) in THF (4.7 ml), and stirred at 08 ! 238 for 4 h. The mixture was cooled to 08, treated with sat.
NH4Cl soln. (10 ml), diluted with Et2O (50 ml), and washed with sat. NH4Cl soln. (3 Â 30 ml). The combined
aq. layers were extracted with Et2O (2 Â 20 ml). The combined org. layers were washed with H2O (50 ml) and
brine (50 ml), dried (MgSO4), filtered, and evaporated. FC (hexane/AcOEt 5 :1 ! 3 :1) gave 48 (147 mg, 73%).
Colourless oil.
b) A suspension of 20 (50 mg, 72.8 mmol), Zn(CN)2 (17 mg, 0.145 mmol) and [Pd(PPh3)4] (25 mg,
21.6 mmol) in degassed DMF (0.2 ml) was stirred at 1508 for 1h. The mixture was cooled to r.t., diluted with
AcOEt (15 ml), and washed with sat. NH4Cl soln. (3 Â 10 ml). The combined aq. layers were extracted with
AcOEt (2 Â 15 ml). The combined org. layers were washed with H2O (20 ml) and brine (20 ml), dried (MgSO4),
filtered, and evaporated. FC (hexane/AcOEt 2 :1 ! 1:1 ! 0 :1) gave 48 (17 mg, 40%) and 17 (11 mg, 27%).
25
D
Data of 48: Rf (hexane/AcOEt 2 :1) 0.60. ‰aŠ ˆ À43.1( c ˆ 1.02, CHCl3). UV (CHCl3): 259 (3.02), 240
(3.55). IR (CHCl3): 3157w, 3090w, 3068w, 3024m, 3016m, 2927w, 2870m, 2238m, 1952w, 1879w, 1811w, 1730w,
1603w, 1531w, 1497w, 1455m, 1364m, 1266m, 1098s, 1028s, 91 3w. 1H-NMR (CDCl3, 300 MHz): see Table 7;
additionally, 4.43 (d, J ˆ 12.5, PhCH); 4.47 (d, J ˆ 12.8, PhCH); 4.56 (d, J ˆ 12.1, PhCH); 4.60 (d, J ˆ 12.8,
PhCH); 4.65 (d, J ˆ 12.1, PhCH); 4.68 (d, J ˆ 11.5, PhCH); 4.76 (d, J ˆ 12.8, PhCH); 4.94 (d, J ˆ 11.2, PhCH);
7.22 7.44 (m, 20 arom. H). 13C-NMR (CDCl3, 75 MHz): see Table 5; additionally, 70.49, 71.00 (2t, PhCH2,
CH2ÀC(5)); 72.06 (t, PhCH2); 73.34 (t, PhCH2); 74.78 (t, PhCH2); 114.11, 114.76 (2s, C(2), CꢀN); 127.72
128.52 (several d incl. C(3)); 136.77 (s), 137.22 (2s), 137.34 (s). HR-MALDI-MS: 624.2254 (4, C37H35KN3O4,
‡
‡
[M ‡ K] ; calc. 624.2264); 608.2527 (100, C37H35N3NaO4, [M ‡ Na] ; calc. 608.2525); 586.2707 (62, C37H36N3O4,
‡
‡
[M ‡ H] ; calc. 586.2706); 478.2111 (53, C30H28N3O3, [M À BnO] ; calc. 478.2131). Anal. calc. for C37H35N3O4
(585.71): C 75.88, H 6.02, N 7.17; found: C 75.90, H 6.12, N 7.24.
(5R,6R,7S,8R)-6,7,8-Tris(benzyloxy)-5-[(benzyloxy)methyl]-5,6,7,8-tetrahydro-2-(1H-tetrazol-5-yl)imida-
zo[1,2-a]pyridine (49). At 08, a soln. of 2m Me3Al in toluene (0.34 ml, 0.68 mmol) in toluene (1ml) was treated
with Me3SiN3 (90 ml, 0.684 mmol), stirred for 10 min, and treated dropwise with a soln. of 48 (81mg,
0.138 mmol) in toluene (1 ml). The mixture was stirred at 808 for 1.5 h, cooled to 08, treated with sat. NH4Cl
soln. (5 ml), diluted with AcOEt (40 ml), and washed with sat. NH4Cl soln. (3 Â 30 ml). The combined aq.
layers were extracted with AcOEt (2 Â 25 ml). The combined org. layers were washed with H2O (50 ml) and
brine (50 ml), dried (Na2SO4), filtered, and evaporated. The crude product (77 mg, a single compound
according to the 1H-NMR spectrum) was precipitated from hexane/AcOEt 3 :1(4 ml) at À 508 to afford after
drying 49 (66 mg, ca. 76%) as a colourless solid containing substantial amounts of H2O. The sample for
microanalysis was dried for 4 d at 10À4 Torr. Rf (AcOEt/MeOH 5 :1) 0.21. Rf (CHCl3/MeOH/AcOH 16 :1 :1)
25
D
0.61. M.p. 116.2 118.18. ‰aŠ ˆ ‡7.9 (c ˆ 0.79, CHCl3). UV (CHCl3): 248 (4.21). IR (CHCl3): 3200 2400m
(br.), 3163w, 3089m, 3067m, 3033m, 3011m, 2959m, 2905m, 2867m, 1952w, 1878w, 1812w, 1629m, 1527w, 1496m,
1454m, 1421w, 1364m, 1337m, 1262s, 1097s, 1026s, 963m, 91 2w. 1H-NMR (CDCl3, 300 MHz): see Table 7;
additionally, 4.51(br. s, PhCH2); 4.52 (d, J ˆ 12.1, PhCH); 4.63 (d, J ˆ 12.1, PhCH); 4.64 (d, J ˆ 11.2, PhCH);
4.71( d, J ˆ 12.1, PhCH); 4.84 (d, J ˆ 11.8, PhCH); 4.98 (d, J ˆ 11.5, PhCH); 7.01 7.03 ( m, 3 arom. H); 7.07 7.10
(m, 2 arom. H); 7.24 7.36 (m, 13 arom. H); 7.39 7.42 (m, 2 arom. H). 13C-NMR (CDCl3, 75 MHz): see Table 5;
additionally, 70.07, 71.45 (2t, PhCH2, CH2ÀC(5)); 72.04 (t, PhCH2); 73.39 (t, PhCH2); 74.73 (t, PhCH2); 127.37
128.50 (several d); 136.89 (2s); 137.14, 137.44 (2s); 149.32 (s, C(5) of CHN4). HR-MALDI-MS: 673.2530 (6,
‡
‡
C37H35N6Na2O4, [M À H ‡ 2 Na] ; calc. 673.2515), 651.2730 (93, C37H36N6NaO4, [M ‡ Na] ; calc. 651.2696),
‡
‡
629.2878 (100, C37H37N6O4, [M ‡ H] ; calc. 629.2876), 623.2647 (48, C37H36N4NaO4, [M À N2 ‡ Na] ; calc.
‡
‡
623.2634), 601.2822 (62, C37H37N4O4, [M ‡ H À N2] ; calc. 601.2815), 572.2656 (10, C37H36N2O4, [M À 2 N2] ;
‡
calc. 572.2675), 521.2292 (6, C30H29N6O3, [M À BnO] ; calc. 521.2301), 493.2235 (58, C30H29N4O3, [M À BnO À
‡
‡
N2] ; calc. 493.2239), 464.2089 (14, C30H28N2O3, [M À BnOH À 2 N2] ; calc. 464.2100). Anal. calc. for
C37H35N3O4 ¥ 1.5 H2O (655.76): C 67.77, H 5.99, N 12.82; found: C 68.03, H 6.04, N 12.82.
(5R,6R,7S,8R)-5,6,7,8-Tetrahydro-5-(hydroxymethyl)-2-(1H-tetrazol-5-yl)imidazo[1,2-a]pyridine-6,7,8-tri-
ol (50). A soln. of 49 (35 mg, 55.7 mmol) in CH2Cl2 (1.4 ml) was treated at À 788 with 1m BCl3 in CH2Cl2
(0.88 ml, 0.88 mmol), stirred until the mixture had reached a temp. of 108 (ca. 5 h), cooled to À 788, treated with
H2O (2 ml), and evaporated. The residue was taken up in H2O (3 ml) and applied to ion-exchange column

3508
Helvetica Chimica Acta Vol. 86 (2003)
‡
(Amberlite CG-120, H form, elution with 0.1m aq. NH3). Lyophilisation gave 50 (12.7 mg, 85%). Colourless
25
D
hygroscopic resin. Rf (AcOEt/MeOH/AcOH 7:5 :1) 0.10. ‰aŠ ˆ À33.8 (c ˆ 0.57, MeOH). UV (MeOH): 233
(3.91). IR (KBr): 3600 2400s (br.), 2930m, 1630m, 1519w, 1452m, 1401m, 1333m, 1246m, 1200m, 1097s, 965w,
904m, 873w. 1H-NMR (D2O, 300 MHz): 3.98 4.06 (m, irrad. at 5.00 ! change, HÀC(7), HÀC(5)); 4.08
(dd, J ˆ 3.1, 13.7, CHÀC(5)); 4.23 4.33 (m, HÀC(6), CH'ÀC(5)); 5.00 (d, J ˆ 3.4, HÀC(8)); 7.74 (s, HÀC(3)).
13C-NMR (D2O, 75 MHz): see Table 6; s for CHN4 hidden by the noise. HR-MALDI-MS: 313.0307 (15,
‡
‡
C9H11N6Na2O4, [M À H ‡ 2 Na] ; calc. 313.0637), 291.0807 (38, C9H12N6NaO4, [M ‡ Na] ; calc. 291.0818),
‡
‡
269.0991(100, C 9H13N6O4, [M ‡ H] ; calc. 269.0998), 241.0933 (21, C9H13N4O4, [M ‡ H À N2] ; calc. 241.0937),
‡
‡
212.1441 (90, C9H12N2O4, [M À 2 N2] ; calc. 212.0797), 198.9984 (53, C8H11N2O4, [M À CHN4] ; calc. 199.0719).
Inhibition Studies. Determination of the inhibition constants (Ki) or the IC50 values was performed with a
range of inhibitor concentrations (typically 4 7 concentrations), which bracket the Ki or IC50 value, and
substrate concentrations, which bracket the KM value of each enzyme (for Ki, typically 5 7 concentrations), or
correspond to it (for IC50).
a) Inhibition of Snail b-Mannosidase. KM ˆ 0.42 0.80. Inhibition constants (Ki) and IC50 values were
determined at 258 at an enzyme concentration of 0.048 units/ml, with a 0.05m acetate buffer (pH 4.5) and 4-
nitrophenyl b-d-mannopyranoside as the substrate. The enzymatic reaction was started after incubation of the
enzyme (100 ml) in presence of the inhibitor (50 ml) during 1h at 25 8, by the addition of the substrate (50 ml).
The enzyme reaction was quenched by addition of 0.2m borate buffer (pH 9.2, 100 ml) after 5 min, and the
absorption at 405 nm was taken as rate for the hydrolysis of the substrate. IC50 Values were determined by
plotting the reciprocal value of the rate of substrate hydrolysis vs. the inhibitor concentration. After fitting a
straight line to the data by linear regression, the negative [I] intercept of this plot provided the appropriate IC50
value. Ki Values were determined by taking the slopes from the LineweaverÀBurk plots [59] and plotting them
vs. the inhibitor concentrations [60]. After fitting a straight line to the data by linear regression, the negative [I]
intercept of this plot provided the appropriate Ki value.
b) Inhibition of Jack Beans a-Mannosidase. KM ˆ 1.8 2.8 ([61]: 2.5 mm). As described in a, inhibition
studies were carried out at 378 at an enzyme concentration of 0.086 units/ml, with a 0.05m acetate buffer (pH
4.5), containing 2 mmol of ZnCl2 and 4-nitrophenyl a-d-mannopyranoside as the substrate. The enzymatic
reaction was started after the incubation at 378 for 1h.
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[18] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 1975, 16, 4467.
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Received July 7, 2003