Hexafluoroacetone as protecting and activating reagent. Glycosylated malic, citramalic, and thiomalic acid derivatives, new glycosylated building blocks for drug design

Article abstract of DOI:10.1007/s00706-004-0187-5

Glycosylated α-hydroxy and α-mercapto acids have been synthesized starting from malic/citramalic/thiomalic acid and Ac ₄-β-D-Glc-NH₂/Bzl₄-β-D-Glc-NH ₂ using hexafluoroacetone as protecting and activating reagent

Full text of DOI:10.1007/s00706-004-0187-5

Monatshefte f€ur Chemie 135, 1225–1242 (2004)
DOI 10.1007/s00706-004-0187-5
Hexafluoroacetone as Protecting
and Activating Reagent. Glycosylated
Malic, Citramalic, and Thiomalic Acid
Derivatives, New Glycosylated Building
Blocks for Drug Design [1]
ꢀ;#
¨
Christoph Bottcher, Jan Spengler, and Klaus Burger
Department of Organic Chemistry, University of Leipzig, D-04103 Leipzig, Germany
Received January 7, 2004; accepted February 2, 2004
Published online July 23, 2004 # Springer-Verlag 2004
Summary. Glycosylated ꢀ-hydroxy and ꢀ-mercapto acids have been synthesized starting from malic=
citramalic=thiomalic acid and Ac4-ꢁ-D-Glc-NH2=Bzl4-ꢁ-D-Glc-NH2 using hexafluoroacetone as pro-
tecting and activating reagent.
Keywords. ꢀ-Hydroxy acids; ꢀ-Mercapto acids; Dielectrophiles; Glycosylamines; Maleimido
sugars; 3-Hydroxysuccinimido sugars; N-Glycosylated depsipeptides; ꢀ-Hydroxyacylamino acids;
ꢀ-Mercaptoacylamino acids.
Introduction
Glycoproteins and glycopeptides are ubiquitous in nature. They play a key role in
various biological processes both within cells and at cell surfaces. These include
protein transport, cell adhesion, and signal transduction [2]. Furthermore, glyco-
sylation influences properties of peptides and proteins such as solubility, thermal
and proteolytical stability [3] as well as conformation and folding [4]. Aberrant
glycosylation of cellular proteins and glycolipids are associated with various dis-
eases, including cancer [5]. Another remarkable feature are the enhanced binding
properties of glycoclusters [6]. Therefore, glycoconjugates are promising candi-
dates for drug design [7].
Deciphering the roles of glycoproteins in controlled studies requires convenient
synthetic access to a large number of glycoconjugates with different binding
motifs. Glycoconjugates isolated from biological sources are microheterogeneous
ꢀ
Corresponding author. E-mail: burger@organik.chemie.uni-leipzig.de
Dedicated to Prof. Dr. Horst Wilde on the occasion of his 65th birthday
#

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C. Bottcher et al.
1226
and cannot be applied for mechanistic studies. Therefore, the development of new
methodologies for the assembly of homogeneous glycopeptidomimetics by che-
moselective ligation is of current interest. Although glycosylated ꢀ-hydroxy acids
are known for some time, they received little attention as building blocks for
peptide and depsipeptide modification. Fisher et al. [8] reported on a considerable
improvement of the pharmacokinetic properties of the peptidic Renin inhibitor
Ditekiren on N-terminal incorporation of N-glycosylated malic and tartaric acid.
Risley et al. [9] synthesized a series of ꢁ-N-glycosylasparagine analogues, includ-
ing N-glycosylated malic acid derivatives. As protective groups for site-selective ꢁ-
functionalization of malic acid acetone [8, 10] and chloral have been used [9, 11].
As part of an ongoing program we synthesized new types of building blocks for
glycopeptide modification, including N-glycosylated ꢀ-hydroxy acid derivatives
[12] testing new protection=activation concepts, like the ‘‘hexafluoroacetone
route’’ [13], since the choice of the protecting group is crucial for the success in
the synthesis of glycopeptides [14].
Results and Discussion
ꢀ-Hydroxy and ꢀ-mercapto acids, including multifunctional species like malic
(1a), citramalic (1b), and thiomalic acid (1c), react with hexafluoroacetone in
DMSO or DMF at room temperature to give five-membered lactones 2 (Scheme
1) [15–17]. The reaction proceeds quantitatively, no six-membered lactone could
be identified by NMR spectroscopy in the crude material. However, 10–15% were
lost during the work-up procedure, because of the water solubility of compounds 2.
In one step, protection of both the ꢀ-hydroxy and the adjacent carboxy group
is achieved. Concomitantly, the ꢀ-carboxy group is selectively activated toward
nucleophiles. The ꢁ-carboxy groups of malic, citramalic, and thiomalic acid re-
main unaffected and can be derivatized in a consecutive step [18]. Compounds 2
can be easily prepared in a 50–100 g scale. On exclusion of moisture 2,2-bis(tri-
fluoromethyl)-1,3-dioxolan-4-ones as well as 2,2-bis(trifluoromethyl)-1,3-oxathio-
lan-5-ones can be stored at ꢁ30ꢂC for months without decomposition.
Scheme 1

Hexafluoroacetone as Protecting and Activating Reagent
1227
Scheme 2
Upon treatment with thionyl chloride or DAST (diethylaminosulfur trifluoride),
compounds 2 can be transformed into ꢁ-acid chlorides 3 [19] and ꢁ-acid fluorides
4 [20], respectively (Scheme 1). Compounds of type 3 and 4 represent a new class
of dielectrophiles having two centers of different reactivity. Recently, N-protected
amino acid chlorides and amino acid fluorides have received growing attention as
acylating agents in N-glycopeptide synthesis [21]. Therefore, we became interested
in studying the efficiency of compounds 3 and 4 as double acyl transfer reagents.
As models for acyl acceptors we chose glycosyl amines Ac4-ꢁ-D-Glc-NH2 (5a)
[22] and Bzl4-ꢁ-D-Glc-NH2 (5b) [23].
We found that ꢁ-acid chlorides 3a, 3b and glycosylamines 5a, 5b, which are
weak nucleophiles, react site-selectively at 0ꢂC in DCM (dichloromethane) in the
presence of one equivalent of pyridine or 2,6-lutidine to give the N-acylated pro-
ducts 6a–6d within minutes in high yields (73–91%), while the lactone moiety
remains unaffected, acting as protecting group (Scheme 2).
1H NMR analysis (300 MHz) of the crude products reveals that the ꢁ-anomer
(3JH-1=H-2 ¼ 9.0–9.3 Hz) is formed exclusively in the case of 6a–6c. Whereas for
6d, after isolation of the ꢁ-anomer by crystallization, the ꢀ-anomer can be detected
by 1H NMR (3JH-1=H-2 ¼ 5.7 Hz) and TLC in the concentrated mother liquor. Puri-
fication of compounds 6 by crystallization is the method of choice. On work-up
by column chromatography the yields are lower. When stronger bases like NEM
(N-ethylmorpholine) and DIEA (diisopropylethylamine) are used a competing retro
Michael addition is the reason for decreasing yields (40–60%) [24].
The acid fluorides 4a, 4b are noticeable less reactive than the corresponding
acid chlorides 3a, 3b. Nevertheless, with 4a, 4b a clean and site-selective acylation
of 5a, 5b can be achieved at 0ꢂC in the presence of pyridine. Again, on application
of stronger bases like NEM and DIEA, the yields are lower.
On treatment with bases compounds 6a–6d undergo an intramolecular cyclo-
condensation. When the cyclization process is performed in the presence of pyri-
dine in boiling chloroform lactones 6a–6d are transformed to give stereoselectively
3-hydroxysuccinimido sugars 7a–7d in very good yields, which can be purified by
column chromatography (Scheme 2).
However, when a solution of 6a was treated in ethyl acetate with stronger bases
like NEM, DIEA, or DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) a diastereomeric
mixture of 7a, together with maleimido sugar 8a was obtained (Scheme 3, Table 1)
[25]. 6b reacts analogously. Since there is no ꢀ-proton (R ¼ CH3) present, no
epimerization can take place.

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1228
Scheme 3
Table 1. Product ratio 7a=8a, (3S)-7a=(3R)-7a, and 7b=8b on treatment of 6a, 6b with different bases
Base
Product ratioa
Yield=%
7a þ 8a
Ratiob
Product ratioa
Yield=%
7b þ 8b
7a=8a
(3S)-7a=(3R)-7a
7b=8b
DBU
DIEA
NEM
5:1
3:1
57
68
73
5:3
7:3
7:3
4:1
65
68
72
15:1
25:1
8b n.d.
a
Determined by integration of the 1H NMR spectra of the crude products; b determined by integra-
1
tion of the H NMR spectra of an isolated diastereomeric mixture 7a
Finally, we demonstrated that glycosylated hexafluoroacetone-protected ꢀ-hy-
droxy acid derivatives 6a–6d are excellent acyl transfer reagents. With amino acid
and dipeptide esters or amides, they react to give N-glycoconjugates 9 (Scheme 4)
which can be used as building blocks for the construction of libraries of glycosylated
depsipeptides which we suggest to be an interesting new class of drug candidates. To
the best of our knowledge glycosylated depsipeptides are unknown.
As by-products of the aminolytic cleavage 7a–7d are formed in variable yields.
In all cases studied so far, chromatographic separation of by-products 7 from
compounds 9 was achieved without problems. As expected, the sterically more de-
manding compounds 6b and 6d (R2 ¼ CH3) exhibit lower reactivity toward N-
nucleophiles. Consequently, an increasing tendency to undergo the intramolecular
ring closure is observed. Furthermore, the amount of by-products is increasing with
the steric demand of the side-chain of the amino acid derivatives which act as
nucleophiles (Table 2).
The product ratio of the aminolytic ring opening can be influenced by the
solvent used. So far DMF was the best solvent for the synthesis of N-glycosylated
dipeptide amides from 6b and H-Phe-NH2.
Mercapto carboxylic acids have been isolated from biologically active naturally
occurring peptides [26]. Furthermore, mercapto acids as well as acylmercapto
acids have been introduced as a new class of monomers for the construction of
new types of peptidomimetics only recently [17, 27]. A ꢁ-mercapto acid is a sub-
unit of Captopril, a classical drug for treatment of hypertension [28]. Likewise,
an ꢀ-mercapto acid subunit is present in Omaprilat and Gemopatrilat. Both are
vasopeptidase inhibitors, currently under clinical evaluation [29]. Compounds con-
taining mercapto or acylmercapto subunits exhibit strong inhibitor activities on
metal-containing enzymes [30].

Hexafluoroacetone as Protecting and Activating Reagent
1229
Scheme 4
Table 2. Product ratio 9=7 obtained on treatment of compounds 6a–6d with amino acid esters and
dipeptide esters
Educt
Nucleophile
H-Xaa-R3
Product
Product ratio
Yield=%
9 þ 7
9:7
6a
6a
6a
6a
6a
6a
6b
6b
6b
6b
6b
6b
6c
6c
6c
6d
6d
6d
H-Gly-OtBu
H-Ala-OtBu
H-Val-OtBu
H-Phe-OtBu
H-Pro-OtBu
H-Phe-NH2
H-Gly-OtBu
H-Ala-OtBu
H-Val-OtBu
H-Phe-OtBu
H-Pro-OtBu
H-Phe-NH2
H-Phe-OtBu
H-Pro-OtBu
H-Phe-Ala-OtBu
H-Phe-OtBu
H-Pro-OtBu
H-Phe-Ala-OtBu
9a=1
9a=2
9a=3
9a=4
9a=5
9a=6
9b=1
9b=2
9b=3
9b=4
–
7a n.d.
9.3:1
76
72
82
80
72
80
78
72
81
82
76
80
78
74
67
69
82
88
6.5:1
7.0:1
7a n.d.
7a n.d.
3.9:1
1.8:1
1.4:1
1.1:1
<1:20
1.4:1
9b=5
9c=1
9c=2
9c=3
9d=1
9d=2
9d=3
7c n.d.
7c n.d.
7c n.d.
5.2:1
1:1.4
4.2:1
Scheme 5

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The hexafluoroacetone route can also be applied for the synthesis of the so far
undescribed N-glycosylated thioanalogues. Glycosylated 2,2-bis(trifluoromethyl)-
1,3-oxathiolan-5-ones 10 are slightly less reactive than 2,2-bis(trifluoromethyl)-
1,3-dioxolan-4-ones 6. Thiomalic acid was introduced as a racemate, consequently
the products obtained were diastereomeric mixtures (Scheme 5).
Since a growing number of reports focus on peptidomimetics as potential drug
candidates, built from two or more different types of monomers [31], the devel-
opment of new types of building blocks, like ꢀ-mercapto acids, adds a new facette
to peptide and depsipeptide modification [17].
Conclusion
We described a preparatively simple access to N-glycosylated ꢀ-hydroxy and ꢀ-
mercapto acids as well as to N-glycosylated ꢀ-hydroxyacyl and ꢀ-mercaptoacyl
amino acid derivatives. They represent new types of building blocks for the synthe-
sis of depsipeptide surrogates and their thioanalogues in solution and on solid
phase [32].
Experimental
General
Solvents were purified and dried prior to use. Reagents were used as purchased. TLC was performed
on Silica Gel 60 F254 (Merck) with detection by UV light or phosphomolybdic acid=ceric sulphate in
5% aqueous sulfuric acid followed by heating. Flash column chromatography was performed using
silica gel (32–63ꢂm) with solvent systems given in the text. Melting points (uncorrected) were deter-
mined on a Boetius heating table. Optical rotation indices were measured using a Schmidt & Haensch
Polartronic-D polarimeter in a 5 cm cell. 1H (200MHz, 300 MHz, 400 MHz, 600 MHz), 13C (50 MHz,
75MHz, 100 MHz), and 19F (188 MHz, 282 MHz) NMR spectra were recorded on a Varian Gemini
2000, Gemini 300, Bruker DRX-400 and Bruker AVANCE DRX-600 spectrometer, respectively. TMS
1
was used as reference for H and 13C NMR spectra (internal), and CF3COOH for 19F NMR spectra
(external). IR spectra were obtained with a FTIR spectrometer (Genesis ATI Mattson=Unicam). Mass
spectra were recorded on a Finnigan ZAB-HSQ spectrometer (FAB-matrix: 3-NBA).
Synthesis of N-Glycosylated Malic and Citramalic Acid Derivatives
Protocol 1. A solution of 3 (1 equiv.) in dry DCM (5cm3 per 1 mmol) was cooled to 0ꢂC. Then a
freshly prepared solution of the corresponding ꢁ-D-glycosylamine 5 (1 equiv.) and pyridine (1 equiv.)
in DCM (5cm3 per 1 mmol) was added over a period of 30min. After stirring the mixture for 1 h at 0ꢂC
DCM was added (20 cm3 per 1 mmol). The organic layer was washed with ice-cold citric acid (10%
solution) and ice water (10 cm3 per 1 mmol). After drying with MgSO4, the solvent was removed and
the crude product recrystallized.
Protocol 2. A solution of 6 (1 equiv.) in dry CHCl3 (20 cm3 per 1 mmol) was heated after addition
of pyridine (5 equiv.) under reflux for 16h. Then CHCl3 (40 cm3 per 1 mmol) was added and the
organic layer was washed with citric acid (10% solution) and water (10 cm3 per 1 mmol). After drying
the organic layer with MgSO4 the solvent was removed and the crude product purified by crystal-
lization or flash chromatography.
Protocol 3. A solution of 6 (1 equiv.) in dry ethyl acetate (10 cm3 per 1 mmol) was treated with a
base (1 equiv.) at room temperature until the starting material was consumed (TLC analysis). Then

Hexafluoroacetone as Protecting and Activating Reagent
1231
ethyl acetate was added (20 cm3 per 1 mmol) and the organic layer was extracted with citric acid (10%
solution) and water (10 cm3 per 1 mmol). After drying with MgSO4 the solvent was evaporated and the
residue purified by flash chromatography.
Protocol 4. To a solution of the amino acid tert-butylester hydrochloride (1.2 equiv.) and NEM (1.2
equiv.) in dimethylformamide (DMF) (5cm3 per 1 mmol) a solution of 6 (1 equiv.) in ethyl acetate
(5cm3 per 1 mmol) was added. The mixture was stirred at room temperature until the starting material
was consumed (TLC analysis). Then the solvent was evaporated in vacuo and the residue dissolved in
CHCl3 (50 cm3 per 1 mmol). The organic layer was washed with citric acid (10% solution), water, and
brine (10cm3 per 1 mmol). After drying with MgSO4 the organic solvent was removed and the residue
purified by column chromatography.
N-(2,3,4,6-Tetra-O-acetyl-ꢁ-D-glucopyranosyl)-2-[(5S)-4-oxo-2,2-
bis(trifluoromethyl)-1,3-dioxolan-5-yl]acetamide (6a, C21H23F6NO13)
3a (1.85 g, 6.16mmol) and 5a (2.14 g, 6.16 mmol) were reacted due to protocol 1. Purification by
crystallization from CHCl3=petroleum ether. Yield 3.35g (89%), colorless needles, mp 165–166ꢂC,
[ꢀ]D ¼ ꢁ1ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.5, DCM); 1H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 2.02 (s, 6H), 2.03
(s, 3H), 2.07 (s, 3H) (4OAc), 2.61 (dd, 1H, J ¼ 8.5, 16.2Hz, CH2Mal), 2.93 (dd, 1H, J ¼ 2.8, 16.2Hz,
CH2Mal), 3.84 (m, 1H, 5-H), 4.08 (dd, 1H, J ¼ 2.1, 12.3Hz, 6-Ha), 4.28 (dd, 1H, J ¼ 4.8, 12.3Hz, 6-
Hb), 4.90 (dd, 1H, J ¼ 9.6, 9.6Hz, 2-H), 5.04 (dd, 1H, J ¼ 9.6, 9.9 Hz, 4-H), 5.16 (dd, 1H, J ¼ 2.8,
8.5 Hz, CHMal), 5.27 (dd, 1H, J ¼ 9.3, 9.6 Hz, 1-H), 5.31 (dd, 1H, J ¼ 9.6, 9.6 Hz, 3-H), 6.06 (d, 1H,
J ¼ 9.3 Hz, 1-NH) ppm; 19F NMR (CDCl3, 282MHz): ꢃ ¼ ꢁ3.14 (q, 3F, J ¼ 9.0 Hz), ꢁ2.86 (q, 3F,
J ¼ 9.0 Hz) ppm; 13C NMR (CDCl3, 75 MHz, HETCOR): ꢃ ¼ 20.76, 20.97, 21.00, 21.11 (4OAc),
38.48 (CH2Mal), 61.16 (6-CH2), 68.66 (4-CH), 71.12 (2-CH), 72.26 (CHMal), 72.92 (3-CH), 74.31
(5-CH), 78.79 (1-CH), 98.19 (sept, J ¼ 36 Hz), 119.23 (q, J ¼ 286 Hz), 120.03 (q, J ¼ 289 Hz), 167.04,
167.45, 170.06, 170.25, 171.06, 171.58 ppm; IR (KBr): ꢄꢀ¼ 1854, 1753, 1706, 1543cmꢁ1; MS (FAB):
m=z ¼ 612.1 [M þ H]þ.
N-(2,3,4,6-Tetra-O-acetyl-ꢁ-D-glucopyranosyl)-2-[(5S)-5-methyl-4-oxo-
2,2-bis(trifluoromethyl)-1,3-dioxolan-5-yl]acetamide (6b, C22H25F6NO13)
3b (2.10 g, 6.68 mmol) and 5a (2.32 g, 6.68 mmol) were reacted due to protocol 1. Purification by
crystallization from ethyl acetate=petroleum ether. Yield 3.80g (91%), colorless needles, mp
1
106–108ꢂC, [ꢀ]D ¼ ꢁ8ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.5, CHCl3); H NMR (CDCl3, 300 MHz): ꢃ ¼ 1.72 (s,
3H, CH3Citr), 1.99 (s, 3H), 2.00 (s, 3H), 2.02 (s, 3H), 2.06 (s, 3H) (4OAc), 2.67 (d, 1H, J ¼ 15.0Hz,
CH2Citr), 2.77 (d, 1H, J ¼ 15.0Hz, CH2Citr), 3.79 (ddd, 1H, J ¼ 1.8, 4.8, 9.9 Hz, 5-H), 4.01 (dd, 1H,
J ¼ 1.8, 12.3Hz, 6-Ha), 4.28 (dd, 1H, J ¼ 4.8, 12.3 Hz, 6-Hb), 4.87 (dd, 1H, J ¼ 9.6, 9.6 Hz, 2-H), 4.97
(dd, 1H, J ¼ 9.6, 9.9 Hz, 4-H), 5.22 (dd, 1H, J ¼ 9.3, 9.3 Hz), 5.24 (dd, 1H, J ¼ 9.6, 9.3 Hz) (1,3-H),
6.81 (d, 1H, J ¼ 9.3 Hz, 1-NH) ppm; 19F NMR (CDCl3, 282 MHz): ꢃ ¼ ꢁ2.63 (q, 3F, J ¼ 9.0 Hz),
ꢁ2.08 (q, 3F, J ¼ 9.0 Hz) ppm; 13C NMR (CDCl3, 75MHz): ꢃ ¼ 20.28, 20.47, 20.52, 20.59 (4OAc),
22.54 (CH3Citr), 43.53 (CH2Citr), 61.88 (6-CH2), 68.20, 70.25, 72.83, 73.75 (2,3,4,5-CH), 77.93 (1-CH),
79.96 (CCitr), 97.14 (sept, J ¼ 36 Hz), 119.0 (q, J ¼ 290 Hz), 119.1 (q, J ¼ 287 Hz), 166.51, 169.10,
169.68, 169.93, 170.49, 170.72 ppm; IR (KBr): ꢄꢀ¼ 1843, 1755, 1710, 1541cmꢁ1; MS (FAB):
m=z ¼ 626.1 [M þ H]þ.
N-(2,3,4,6-Tetra-O-benzyl-ꢁ-D-glucopyranosyl)-2-[(5S)-4-oxo-2,2-
bis(trifluoromethyl)-1,3-dioxolan-5-yl]acetamide (6c, C41H39F6NO9)
3a (802 mg, 2.67 mmol) and 5b (1.44 g, 2.67mmol) were reacted due to protocol 1. Purification by
crystallization from CHCl3=petroleum ether. Yield 1.70 g (79%), colorless crystals, mp 161–162ꢂC,

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C. Bottcher et al.
1232
[ꢀ]D ¼ ꢁ11ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 2.0, CH2Cl2); 1H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 2.41 (dd, 1H,
J ¼ 7.9, 16.6Hz, CH2Mal), 2.67 (dd, 1H, J ¼ 3.0, 16.6Hz, CH2Mal), 3.37 (dd, 1H, J ¼ 9.0, 9.0Hz, 2-H),
3.53 (m, 1H, 5-H), 3.69 (dd, 1H, J ¼ 1.8, 10.7 Hz, 6-Ha), 3.72–3.80 (m, 3H, 3-H, 4-H, 6-Hb), 4.46 (d,
1H, J ¼ 12.1Hz, CH2Ph), 4.54 (d, 1H, J ¼ 10.8 Hz, CH2Ph), 4.61 (d, 1H, J ¼ 12.1Hz, CH2Ph), 4.65 (d,
1H, J ¼ 11.7 Hz, CH2Ph), 4.83 (d, 1H, J ¼ 11.7Hz, CH2Ph), 4.84 (d, 1H, J ¼ 10.8Hz, CH2Ph), 4.93 (s,
2H, CH2Ph), 5.09 (dd, 1H, J ¼ 9.0, 9.0Hz, 1-H), 5.16 (dd, 1H, J ¼ 3.0, 7.9 Hz, CHMal), 5.58 (d, 1H,
J ¼ 9.0 Hz, 1-NH), 7.15–7.38 (m, 20H, Harom); 19F NMR (CDCl3, 282 MHz): ꢃ ¼ ꢁ3.01 (q, 3F,
J ¼ 9.0 Hz), ꢁ2.69 (q, 3F, J ¼ 9.0 Hz) ppm; 13C NMR (CDCl3, 75 MHz, HMQC): ꢃ ¼ 37.87 (CH2Mal),
68.16 (6-CH2), 71.78 (CHMal), 73.73, 74.68, 75.09, 75.97 (4CH2Ph), 76.53 (5-CH), 77.58 (4-CH),
79.10 (1-CH), 79.49 (2-CH), 86.09 (3-CH), 97.77 (sept, J ¼ 36 Hz), 118.94 (q, J ¼ 288 Hz), 119.66 (q,
J ¼ 290 Hz), 127.9–129.1, 137.76, 137.97, 138.11, 138.35 (Carom), 166.30, 167.47 ppm; IR (KBr):
ꢄꢀ¼ 1851, 1673, 1547 cmꢁ1; MS (FAB): m=z ¼ 826.2 [M þ Na]þ.
N-(2,3,4,6-Tetra-O-benzyl-ꢁ-D-glucopyranosyl)-2-[(5S)-5-methyl-4-
oxo-2,2-bis(trifluoromethyl)-1,3-dioxolan-5-yl]acetamide (6d, C42H41F6NO9)
3b (1.18 g, 3.75mmol) and 5b (2.02 g, 3.74 mmol) were reacted due to protocol 1. Purification by
crystallization from ethyl acetate=petroleum ether. Yield 2.23g (73%), colorless crystals, mp 129–
131ꢂC, [ꢀ]D ¼ ꢁ17ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 2.0, CHCl3); 1H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.68 (s,
3H, CH3Citr), 2.57 (d, 1H, J ¼ 15.0Hz, CH2Citr), 2.66 (d, 1H, J ¼ 15.0Hz, CH2Citr), 3.41 (m, 1H, 2-H),
3.55 (m, 1H, 5-H), 3.73 (dd, 1H, J ¼ 1.8, 10.5 Hz, 6-Ha), 3.77–3.82 (m, 3H, 3-H, 4-H, 6-Hb), 4.52 (d,
1H, J ¼ 12.0Hz, CH2Ph), 4.57 (d, 1H, J ¼ 10.8 Hz, CH2Ph), 4.67 (d, 1H, J ¼ 12.0Hz, CH2Ph), 4.69 (d,
1H, J ¼ 11.4 Hz, CH2Ph), 4.86 (d, 1H, J ¼ 10.8Hz, CH2Ph), 4.88 (d, 1H, J ¼ 11.7Hz, CH2Ph), 4.91 (s,
2H, CH2Ph), 5.17 (dd, 1H, J ¼ 9.3, 9.0 Hz, 1-H), 5.80 (d, 1H, J ¼ 9.0 Hz, 1-NH), 7.16–7.38 (m, 20H,
Harom); 19F NMR (CDCl3, 282 MHz): ꢃ ¼ ꢁ2.68 (q, 3F, J ¼ 9.0 Hz), ꢁ2.29 (q, 3F, J ¼ 9.0 Hz) ppm;
13C NMR (CDCl3, 75 MHz, HETCOR, APT): ꢃ ¼ 22.48 (CH3Citr), 44.43 (CH2Citr), 68.32 (6-CH2),
73.90, 74.91, 75.25, 76.06 (4CH2Ph), 76.76 (5-CH), 77.76 (4-CH), 79.10 (1-CH), 80.25 (CCitr), 80.79
(2-CH), 86.19 (3-CH), 97.30 (sept, J ¼ 36 Hz), 119.35 (q, J ¼ 289Hz), 128.0–128.8, 137.97, 138.18,
138.25, 138.50 (Carom), 166.04, 169.35 ppm; IR (KBr): ꢄꢀ¼ 1846, 1668, 1558cmꢁ1: MS (FAB):
m=z ¼ 840.3 [M þ Na]þ, 818.3 [Mþ H]þ.
From the mother liquor 20 mg of the ꢀ-anomer were isolated and spectroscopically fully character-
ized. Separation by flash chromatography (ethyl acetate=petroleum ether ¼ 1=4, Rf (6d-a) ¼ 0.35, Rf (6d-
b ¼ 0.30);1H NMR(CDCl3, 600 MHz, COSY):ꢃ ¼ 1.63 (s, 3H, CH3Citr),2.69(s, 2H, CH2Citr), 3.49–3.52
(m, 2H, 3,5-H), 3.56 (dd, 1H, J ¼ 1.5, 11.1Hz, 6-Ha), 3.62 (dd, 1H, J ¼ 9.9, 9.6 Hz, 4-H), 3.65 (dd, 1H,
J ¼ 3.6, 11.1Hz, 6-Hb), 3.74 (dd, 1H, J ¼ 5.7, 9.6 Hz, 2-H), 4.38 (d, 1H, J ¼ 12.5Hz, CH2Ph), 4.45(d, 1H,
J ¼ 11.1Hz, CH2Ph), 4.49–4.56 (m, 3H, CH2Ph), 4.69 (d, 1H, J ¼ 11.1Hz, CH2Ph), 4.71 (d, 1H, J ¼
11.1Hz, CH2Ph), 4.80 (d, 1H, J ¼ 11.1Hz, CH2Ph), 5.66 (dd, 1H, J ¼ 5.7, 6.6 Hz, 1-H), 6.41 (d, 1H,
J ¼ 6.6 Hz, 1-NH), 7.06–7.34 (m, 20H, Harom) ppm; 19F NMR (CDCl3, 282MHz): ꢃ ¼ ꢁ2.76 (q, 3F,
J ¼ 9.0 Hz), ꢁ2.34 (q, 3F, J ¼ 9.0 Hz) ppm; 13C NMR (CDCl3, 75MHz, HMQC, APT): ꢃ ¼ 22.46
(CH3Citr), 44.37 (CH2Citr), 68.34 (6-CH2), 71.77 (5-CH), 72.96, 73.65, 74.93 (3CH2Ph), 75.28 (1-CH),
75.67 (CH2Ph), 76.96 (4-CH), 77.41 (2-CH), 79.99 (CCitr), 82.02 (3-CH), 97.26 (sept, J ¼ 36Hz), 119.21
(q, J ¼ 289 Hz), 127.7–128.7, 137.20, 138.03, 138.27, 138.34 (Carom), 166.52, 169.45 ppm.
(3S)-3-Hydroxy-1-(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)pyrrolidin-
2,5-dione (7a, C18H23NO12)
6a (611 mg, 1.00 mmol) was heated with pyridine (396 mg, 5.00 mmol) in dry CHCl3 under reflux for
16h due to protocol 2. Purification by flash chromatography (ethyl acetate=petroleum ether ¼ 4=1,
Rf ¼ 0.38). Yield 350 mg (79%), needles from ethyl acetate=petroleum ether, mp 174–176ꢂC,
[ꢀ]D ¼ ꢁ33ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.0, acetone); 1H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.95 (s,

Hexafluoroacetone as Protecting and Activating Reagent
1233
3H), 2.00 (s, 3H), 2.03 (s, 3H), 2.06 (s, 3H) (4OAc), 2.63 (dd, 1H, J ¼ 4.5, 18.3Hz, CH2Mal), 3.06 (dd,
1H, J ¼ 8.4, 18.3Hz, CH2Mal), 3.80 (m, 1H, 5-H), 4.14–4.18 (m, 2H, 6-H2), 4.56 (dd, 1H, J ¼ 4.5,
8.4 Hz, CHMal), 5.18 (dd, 1H, J ¼ 9.6, 9.6 Hz, 4-H), 5.26 (dd, 1H, J ¼ 9.6, 9.0 Hz, 3-H), 5.27 (d, 1H,
J ¼ 9.3 Hz, 1-H), 5.86 (dd, 1H, J ¼ 9.3, 9.3 Hz, 2-H) ppm; 13C NMR (CDCl3, 75 MHz): ꢃ ¼ 20.55,
20.66 (2c), 20.81 (4OAc), 37.14 (CH2Mal), 61.77 (6-CH2), 66.49, 67.82, 67.90, 73.33, 74.83 (2,3,4,5-
CH, CHMal), 78.29 (1-CH), 169.55, 169.86, 170.24, 170.87, 172.61, 176.53ppm; IR (KBr): ꢄꢀ¼ 3430,
1751, 1628 cmꢁ1; MS (FAB): m=z ¼ 446.1 [Mþ H]þ.
(3S)-3-Hydroxy-3-methyl-1-(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)pyrrolidin-
2,5-dione (7b, C19H25NO12)
6b (625 mg, 1.00mmol) was heated with pyridine (396mg, 5.00 mmol) in dry CHCl3 under reflux for
16h due to protocol 2. Purification by crystallization from ethyl acetate=petroleum ether. Yield 361 mg
1
(79%), mp 182–184ꢂC, [ꢀ]D ¼ ꢁ16ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 2.0, CHCl3); H NMR (CDCl3, 300MHz,
COSY): ꢃ ¼ 1.53 (s, 3H, CH3Citr), 1.97 (s, 3H), 2.03 (s, 3H), 2.06 (s, 3H), 2.09 (s, 3H) (4OAc),
2.75 (d, 1H, J ¼ 18.0Hz, CH2Citr), 2.86 (d, 1H, J ¼ 18.0Hz, CH2Citr), 3.43 (s, 1H, OH), 3.82 (m,
1H, 5-H), 4.18–4.21 (m, 2H, 6-H2), 5.22 (dd, 1H, J ¼ 9.6, 9.6Hz, 4-H), 5.28 (d, 1H, J ¼ 9.3 Hz, 1-H),
5.30 (dd, 1H, J ¼ 9.3, 9.6 Hz, 3-H), 5.88 (dd, 1H, J ¼ 9.3, 9.3 Hz, 2-H) ppm; 13C NMR (CDCl3,
75MHz): ꢃ ¼ 20.48, 20.65 (2c), 20.81 (4OAc), 24.74 (CH3Citr), 43.34 (CH2Citr), 61.80 (6-CH2),
67.89 (2c), 71.98, 73.26, 74.79 (2,3,4,5-CH, CCitr), 78.35 (1-CH), 169.54, 169.77, 170.21, 170.86,
172.35, 178.28 ppm; IR (KBr): ꢄꢀ¼ 3450, 1735, 1730cmꢁ1; MS (FAB): m=z ¼ 460.1 [M þ H]þ.
(3S)-3-Hydroxy-1-(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyranosyl)pyrrolidin-
2,5-dione (7c, C38H39NO8)
6c(402mg, 0.50 mmol)was heatedwithpyridine(198mg, 2.50mmol)indry CHCl3 under refluxfor 16h
due to protocol 2. Purification by flash chromatography (ethyl acetate=petroleum ether ¼ 1=1, Rf ¼ 0.39).
Yield 268 mg (84%), needles from ethyl acetate=petroleum ether, mp 118–119ꢂC; [ꢀ]D ¼
ꢁ30ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 0.9, CH2Cl2); 1H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 2.40 (dd, 1H, J ¼ 5.1,
18.0Hz, CH2Mal), 2.92 (br.s, 1H, CH2Mal), 3.58 (m, 1H, 5-H), 3.64–3.75 (m, 4H, 3,4-H, 6-H2), 4.46–4.60
(m, 6H, 2-H, CHMal, 4CH2Ph), 4.83 (d, 1H, J ¼ 10.5Hz, CH2Ph), 4.85 (d, 1H, J ¼ 12.0 Hz, CH2Ph), 4.91
(s, 2H, CH2Ph), 5.05 (d, 1H, J ¼ 9.3 Hz, 1-H), 7.17–7.35 (m, 20H, Harom) ppm; 13C NMR (CDCl3,
75MHz, APT): ꢃ ¼ 37.29 (CH2Mal), 66.65 (CHMal), 68.94 (6-CH2), 73.72, 75.27, 75.44, 75.97 (4CH2Ph),
77.43, 77.91, 78.24 (2,4,5-CH), 80.03 (1-CH), 86.82 (3-CH), 127.9–128.8, 138.18, 138.27, 138.63
(Carom), 173.10, 177.83 ppm; IR (KBr): ꢄꢀ¼ 3500, 1760cmꢁ1; MS (FAB): m=z ¼ 638.2 [M þ H]þ.
(3S)-3-Hydroxy-3-methyl-1-(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyranosyl)pyrrolidin-
2,5-dione (7d, C39H41NO8)
6d (409 mg, 0.50mmol) was heated with pyridine (198mg, 2.50 mmol) in dry CHCl3 under reflux for
16h due to protocol 2. Purification by flash chromatography (ethyl acetate=petroleum ether ¼ 1=2,
Rf ¼ 0.26). Yield 287 mg (88%), oil which crystallizes within a few days, mp 151–152ꢂC,
1
[ꢀ]D ¼ ꢁ9ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.4, CHCl3); H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.43 (br.s, 3H,
CH3Citr), 2.56 (br.d, 1H, J ¼ 18.0Hz, CH2Citr), 2.72 (br.d, 1H, J ¼ 18.0 Hz, CH2Citr), 3.65 (m, 1H, 5-H),
3.72–3.83 (m, 4H, 3,4-H, 6-H2), 4.55 (d, 1H, J ¼ 12.0Hz, CH2Ph), 4.61–4.69 (m, 4H, 2-H, 3CH2Ph),
4.89 (d, 1H, J ¼ 10.8Hz, CH2Ph), 4.90 (d, 1H, J ¼ 11.4 Hz, CH2Ph), 4.93 (d, 1H, J ¼ 11.4Hz, CH2Ph),
4.98 (d, 1H, J ¼ 11.4 Hz, CH2Ph), 5.15 (br.d, 1H, J ¼ 9.0 Hz, 1-H), 7.22–7.39 (m, 20H, Harom) ppm;
13C NMR (CDCl3, 75 MHz, APT): ꢃ ¼ 25.44 (br., CH3Citr), 43.28 (br., CH2Citr), 68.65 (6-CH2), 72.00,
73.52, 75.07, 75.26, 75.74 (4CH2Ph, CCitr), 76.99, 77.84, 78.32, 79.88 (br.), 86.65 (1,2,3,4,5-CH),
127.9–128.8, 138.19, 138.39, 138.52, 138.57 (Carom), 173.13, 179.62 ppm; IR (KBr): ꢄꢀ¼ 3500,
1728 cmꢁ1. MS (FAB): m=z ¼ 652.3 [Mþ H]þ.

€
C. Bottcher et al.
1234
1-(2,3,4,6-Tetra-O-acetyl-ꢁ-D-glucopyranosyl)-1H-pyrrol-2,5-dione (8a, C18H21NO11)
A solution of 6a (611 mg, 1.00mmol) in dry ethyl acetate was stirred at room temperature with DIEA
(129 mg, 1.00mmol) due to protocol 3. Reaction time: 2 d. Purificaton by flash chromatography (ethyl
acetate=petroleum ether¼ 3=1). Yield 72 mg (17%) 8a (Rf ¼ 0.44), mp 139–141ꢂC, [ꢀ]D ¼ ꢁ5ꢂ cm3
g
ꢁ1 dmꢁ1 (c ¼ 1.2, CHCl3) and 226 mg (51%) of a diastereomeric mixture of (3S)-7a and (3R)-7a (ratio
7:3, Rf ¼ 0.25); 1H NMR (CDCl3, 300 MHz): ꢃ ¼ 1.94 (s, 3H), 2.01 (s, 3H), 2.04 (s, 3H), 2.07 (s, 3H)
(4OAc), 3.79 (m, 1H, 5-H), 4.17–4.20 (m, 2H, 6-H2), 5.20 (dd, 1H, J ¼ 9.6, 9.6 Hz, 4-H), 5.22 (d, 1H,
J ¼ 9.3 Hz, 1-H), 5.27(dd, 1H, J ¼ 9.6,9.0 Hz, 3-H), 5.89(dd, 1H, J ¼ 9.3, 9.3Hz, 2-H), 6.75(s, 2H, Holef
)
ppm; 13C NMR (CDCl3, 75MHz): ꢃ ¼ 20.55, 20.69, 20.71, 20.84 (4OAc), 61.80 (6-CH2), 67.91, 68.11,
73.63, 74.66 (2,3,4,5-CH), 77.62 (1-CH), 134.78, 168.71, 169.34, 169.48, 170.23, 170.77ppm; IR (KBr):
ꢄꢀ¼ 1751, 1728, 1628 cmꢁ1; MS (FAB): m=z ¼ 450.1 [M þ Na]þ, 428.1 [Mþ H]þ.
3-Methyl-1-(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)-1H-pyrrol-2,5-dione
(8b, C19H23NO11)
A solution of 6b (625 mg, 1.00mmol) in dry ethyl acetate was stirred at room temperature with DBU
(152 mg, 1.00 mmol) due to protocol 3. Reaction time: 1 d. Purification by flash chromatography (ethyl
acetate=petroleum ether ¼ 3=2). Yield 52mg (12%) 8b (Rf ¼ 0.40), mp 143–145ꢂC, [ꢀ]D ¼
1
ꢁ8ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 0.6, CHCl3) and 242 mg (53%) 7b (Rf ¼ 0.22); H NMR (CDCl3, 600MHz):
ꢃ ¼ 1.92 (s, 3H), 2.00 (s, 3H), 2.03 (s, 3H), 2.05 (s, 3H) (4OAc), 2.07 (d, 3H, J ¼ 2.0 Hz, CH3), 3.78
(ddd, 1H, J ¼ 2.3, 4.7, 9.9 Hz, 5-H), 4.13 (dd, 1H, J ¼ 2.3, 12.6Hz, 6-Ha), 4.17 (dd, 1H, J ¼ 4.7,
12.6Hz, 6-Hb), 5.18 (dd, 1H, J ¼ 9.6, 9.6 Hz, 4-H), 5.19 (d, 1H, J ¼ 9.3 Hz, 1-H), 5.25 (dd, 1H, J ¼ 9.3,
9.3 Hz, 3-H), 5.89 (dd, 1H, J ¼ 9.3, 9.3 Hz, 2-H), 6.36 (m, 1H, Holef) ppm; 13C NMR (CDCl3,
150 MHz): ꢃ ¼ 11.19 (CH3), 20.57, 20.68, 20.70, 20.82 (4OAc), 61.82 (6-CH2), 67.90, 68.07, 73.71,
74.53 (2,3,4,5-CH), 77.59 (1-CH), 128.13, 146.46, 168.71, 169.29, 169.48, 169.82, 170.27,
170.77 ppm; IR (KBr): ꢄꢀ¼ 1753, 1728 cmꢁ1; MS (FAB): m=z ¼ 442.1 [Mþ H]ꢁ1
.
tert-Butyl N-{(2S)-2-hydroxy-1,4-dioxo-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)-
amino]butyl}glycinate (9a=1, C24H36N2O14)
t
ꢀ
6a(306mg, 0.50 mmol) was reacted withHCl H-Gly-O Bu(101mg, 0.60 mmol) inthe presenceofNEM
(69 mg, 0.60mmol) due to protocol 4. Reaction time: 1 d. Purification by flash chromatography (ethyl
acetate, Rf ¼ 0.36). Yield 220 mg (76%), foam, [ꢀ]D ¼ ꢁ6ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.0, CHCl3); 1H NMR
(CDCl3, 300 MHz): ꢃ ¼ 1.51 (s, 9H, CH3tBu), 2.06 (s, 3H), 2.07 (s, 3H), 2.09 (s, 3H), 2.11 (s, 3H) (4OAc),
2.63 (dd, 1H, J ¼ 7.8, 15.9Hz, CH2Mal), 2.88 (dd, 1H, J ¼ 3.6, 15.9Hz, CH2Mal), 3.88 (m, 1H, 5-H), 3.97
(d, 2H, J ¼ 5.7 Hz, CH2Gly), 4.13 (dd, 1H, J ¼ 1.8, 12.3Hz, 6-Ha), 4.33 (dd, 1H, J ¼ 4.5, 12.3 Hz, 6-Hb),
4.49 (m, 1H, CHMal), 4.57 (br.s, 1H, OH), 5.00 (dd, 1H, J ¼ 9.6, 9.6Hz), 5.11 (dd, 1H, J ¼ 9.9, 9.6Hz),
5.34 (dd, 1H, J ¼ 9.6, 9.0 Hz), 5.35 (dd, 1H, J ¼ 9.6, 9.3Hz) (1,2,3,4-H), 7.12 (d, 1H, J ¼ 9.0 Hz, 1-NH),
7.42 (t, 1H, J ¼ 5.7 Hz, NHGly) ppm; 13C NMR (CDCl3, 75MHz, APT): ꢃ ¼ 20.86 (2c), 20.92, 21.01
(4OAc), 28.31 (CH3tBu), 39.77 (CH2Mal), 41.89 (CH2Gly), 61.93 (6-CH2), 68.33, 69.09, 70.76, 73.02,
73.92 (2,3,4,5-CH, CHMal), 78.10 (1-CH), 82.75 (CtBu), 169.15, 169.82, 170.24, 170.94, 171.34, 172.57,
174.75 ppm; IR (KBr): ꢄꢀ¼ 3400, 1751, 1676, 1535 cmꢁ1; MS (FAB): m=z ¼ 577.2 [Mþ H]þ.
tert-Butyl N-{(2S)-2-hydroxy-1,4-dioxo-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)-
amino]butyl}alaninate (9a=2, C25H38N2O14)
t
ꢀ
6a (611 mg, 1.00mmol) was reacted withHCl H-Ala-O Bu(218mg, 1.20mmol)in the presence of NEM
(138 mg, 1.20 mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography (ethyl
acetate=petroleum ether ¼ 5=1). Yield 30mg (7%) 7a (Rf ¼ 0.30) and 382 mg (65%) 9a=2 (Rf ¼ 0.23),
1
foam, [ꢀ]D ¼ ꢁ4ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.2, CHCl3); H NMR (CDCl3, 300 MHz): ꢃ ¼ 1.40 (d, 3H,

Hexafluoroacetone as Protecting and Activating Reagent
1235
J ¼ 7.2 Hz, CH3Ala), 1.48(s, 9H, CH3tBu), 2.03 (s, 3H),2.05(s, 3H), 2.09 (s, 3H), 2.10(s, 3H) (4OAc),2.55
(dd, 1H, J ¼ 8.1, 15.9 Hz, CH2Mal), 2.85 (dd, 1H, J ¼ 3.3, 15.9Hz, CH2Mal), 3.88 (m, 1H, 5-H), 4.11 (dd,
1H, J ¼ 2.1, 12.6Hz, 6-Ha), 4.31 (dd, 1H, J ¼ 4.5, 12.3Hz, 6-Hb), 4.41–4.46 (m, 2H, ꢀ-CHAla, CHMal),
4.51 (d, 1H, J ¼ 5.7 Hz, OH), 4.97 (dd, 1H, J ¼ 9.6, 9.6 Hz), 5.09 (dd, 1H, J ¼ 9.9, 9.6 Hz), 5.32 (dd, 1H,
J ¼ 9.3, 9.3 Hz), 5.34 (dd, 1H, J ¼ 9.6, 9.6 Hz) (1,2,3,4-H), 7.07 (d, 1H, J ¼ 9.3 Hz, 1-NH), 7.39 (d, 1H,
J ¼ 7.8 Hz, NHAla) ppm; 13C NMR (CDCl3, 75 MHz, APT): ꢃ ¼ 15.51 (CH3Ala), 20.67 (2c), 20.72, 20.82
(4OAc), 28.04 (CH3tBu), 39.57 (CH2Mal), 48.56 (CHAla), 61.77 (6-CH2), 68.20, 68.87, 70.60, 72.86, 73.73
(2,3,4,5-CH, CHMal), 77.92 (1-CH), 82.16 (CtBu), 169.64, 170.09, 170.76, 171.10, 171.88, 171.91,
172.50 ppm; IR (KBr): ꢄꢀ¼ 3400, 1753, 1668, 1533 cmꢁ1; MS (FAB): m=z ¼ 591.2 [Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)-
amino]butyl}valinate (9a=3, C27H42N2O14)
t
ꢀ
6a (611 mg, 1.00mmol) and HCl H-Val-O Bu (252mg, 1.20mmol) were reacted in the presence of NEM
(138 mg, 1.20mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(CHCl3=petroleum ether=MeOH¼ 10=5=1). Yield 48 mg (11%) 7a (Rf ¼ 0.33) and 440 mg (71%)
1
9a=3 (Rf ¼ 0.26), foam, [ꢀ]D ¼ þ5ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.2, CHCl3); H NMR (CDCl3, 300MHz):
Val
ꢃ ¼ 0.93 (d, 3H, J ¼ 6.9 Hz, ꢅ-CH3 ), 0.95 (d, 3H, J ¼ 6.6 Hz, ꢅ0-CH3Val), 1.49 (s, 9H, CH3tBu), 2.03
(s, 3H), 2.05 (s, 3H), 2.09 (s, 3H), 2.10 (s, 3H) (4OAc), 2.20 (m, 1H, ꢁ-CHVal), 2.58 (dd, 1H, J ¼ 7.8,
15.9Hz, CH2Mal), 2.86 (dd, 1H, J ¼ 3.3, 15.9 Hz, CH2Mal), 3.87 (m, 1H, 5-H), 4.10 (dd, 1H, J ¼ 1.8,
12.3Hz, 6-Ha), 4.31 (dd, 1H, J ¼ 4.2, 12.3Hz, 6-Hb), 4.39–4.43 (m, 2H, ꢀ-CHVal, CHMal), 4.55 (br.s, 1H,
OH), 4.96(dd, 1H, J ¼ 9.6, 9.6 Hz), 5.08 (dd, 1H, J ¼ 9.6, 9.9 Hz), 5.29 (dd, 1H, J ¼ 9.0, 9.3 Hz), 5.37 (dd,
1H, J ¼ 9.6, 9.6 Hz) (1,2,3,4-H), 6.89 (d, 1H, J ¼ 9.3 Hz, 1-NH), 7.29 (d, 1H, J ¼ 9.0 Hz, NHVal) ppm; 13
C
NMR (CDCl3, 75 MHz, APT): ꢃ ¼ 17.60 (ꢅ-CH3 ), 19.03 (ꢅ0-CH3Val), 20.66 (2c), 20.74, 20.81 (4OAc),
28.12 (CH3tBu), 31.51 (ꢁ-CHVal), 39.39 (CH2Mal), 57.30 (ꢀ-CHVal), 61.72 (6-CH2), 68.18, 69.13, 70.52,
72.80, 73.70 (2,3,4,5-CH, CHMal), 77.93 (1-CH), 82.13 (CtBu), 169.62, 170.07, 170.68, 170.75, 171.19,
172.22, 172.71 ppm; IR (KBr): ꢄꢀ¼ 3400, 1753, 1672, 1526cmꢁ1; MS (FAB): m=z ¼ 619.3 [Mþ H]þ.
Val
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)-
amino]butyl}phenylalaninate (9a=4, C31H42N2O14)
t
ꢀ
6a(306mg, 0.50mmol)andHCl H-Phe-O Bu(155mg,0.60 mmol)werereactedinthepresenceofNEM
(69 mg, 0.6 mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(CHCl3=MeOH ¼ 10=1). Yield 22 mg (10%) 7a (Rf ¼ 0.30) and 233 mg (70%) 9a=4 (Rf ¼ 0.21), foam,
1
[ꢀ]D ¼ þ23ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.2, CHCl3); H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.49 (s, 9H,
CH3tBu), 1.99 (s, 3H), 2.00 (s, 3H), 2.04 (s, 3H), 2.05 (s, 3H) (4OAc), 2.39 (dd, 1H, J ¼ 8.3, 15.9Hz,
CH2Mal), 2.74 (dd, 1H, J ¼ 3.3, 15.9Hz, CH2Mal), 3.03–3.07 (m, 2H, ꢁ-CH2Phe), 3.84 (ddd, 1H, J ¼ 2.1,
4.2, 9.9Hz, 5-H), 4.05 (dd, 1H, J ¼ 2.1, 12.3Hz, 6-Ha), 4.27(dd, 1H, J ¼ 4.2, 12.3Hz, 6-Hb), 4.35(m, 1H,
CHMal), 4.45 (d, 1H, J ¼ 6.0 Hz, OH), 4.69 (m, 1H, ꢀ-CHPhe), 4.93 (dd, 1H, J ¼ 9.6, 9.6 Hz, 2-H), 5.05
(dd, 1H, J ¼ 9.9, 9.3 Hz, 4-H), 5.25(dd, 1H, J ¼ 9.3, 9.3 Hz, 1-H), 5.30(dd, 1H, J ¼ 9.6, 9.6 Hz, 3-H), 6.97
(d, 1H, J ¼ 9.3 Hz, 1-NH), 7.13–7.30 (m, 6H, Harom, NHPhe) ppm; 13C NMR (CDCl3, 75MHz, HET-
COR): ꢃ ¼ 20.83 (2c), 20.91, 20.99 (4OAc), 28.18 (CH3tBu), 38.46 (ꢁ-CH2Phe), 39.58 (CH2Mal), 53.57 (ꢀ-
CHPhe), 61.90 (6-CH2), 68.34 (4-CH), 69.10 (CHMal), 70.74 (2-CH), 72.97 (3-CH), 73.88 (5-CH), 78.10
(1-CH), 82.69 (CtBu), 127.28, 128.68, 129.76, 136.28 (Carom), 169.81, 170.23, 170.51, 170.93, 171.34,
172.02, 172.65 ppm; IR (KBr): ꢄꢀ¼ 3400, 1749, 1670, 1525cmꢁ1; MS (FAB): m=z ¼ 667.3 [Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)-
amino]butyl}prolinate (9a=5, C27H40N2O14)
t
ꢀ
6a (611 mg, 1.00mmol) and HCl H-Pro-O Bu (249 mg, 1.20 mmol) were reacted in the presence of
NEM (138mg, 1.20 mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromato-

€
C. Bottcher et al.
1236
graphy (ethyl acetate, Rf ¼ 0.29). Yield 442 mg (72%), foam, [ꢀ]D ¼ ꢁ40ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.1,
1
CHCl3); H NMR (CDCl3, 300 MHz, 298 K, COSY): rotamers, ratio 5:1, ꢃ (major rotamer)¼ 1.41
(s, 9H, CH3tBu), 1.99 (s, 3H), 2.01 (s, 3H), 2.03 (s, 3H), 2.06 (s, 3H) (4OAc), 1.85–2.25 (m, 4H,
ꢅ,ꢁ-CH2Pro), 2.35 (dd, 1H, J ¼ 9.3, 14.4 Hz, CH2Mal), 2.54 (dd, 1H, J ¼ 3.0, 14.4Hz, CH2Mal),
3.48–3.63 (m, 2H, ꢃ-CH2Pro), 3.82 (m, 1H, 5-H), 3.97 (d, 1H, J ¼ 7.8 Hz, OH), 4.07 (dd, 1H, J ¼ 2.4,
12.6Hz, 6-Ha), 4.25 (dd, 1H, J ¼ 4.2, 12.6 Hz, 6-Hb), 4.42 (m, 1H, ꢀ-CHPro), 4.58 (m, 1H, CHMal),
4.99 (dd, 1H, J ¼ 9.0, 9.3Hz, 2-H), 5.06 (dd, 1H, J ¼ 9.6, 9.6 Hz, 4-H), 5.27 (dd, 1H, J ¼ 9.3, 9.0 Hz,
1-H), 5.31 (dd, 1H, J ¼ 9.6, 9.6 Hz, 3-H), 7.38 (d, 1H, J ¼ 9.0 Hz, 1-NH) ppm; 13C NMR (CDCl3,
75MHz, HETCOR): ꢃ (major rotamer)¼ 20.85 (2c), 20.93, 20.98 (4OAc), 25.08 (ꢅ-CH2Pro), 28.18
(CH3tBu), 29.05 (ꢁ-CH2Pro), 41.82 (CH2Mal), 46.92 (ꢃ-CH2Pro), 60.07 (ꢀ-CHPro), 62.15 (6-CH2),
67.41 (CHMal), 68.48 (4-CH), 70.43 (2-CH), 73.26 (3-CH), 73.83 (5-CH), 78.23 (1-CH), 81.94
(CtBu), 169.83, 170.21, 170.83, 170.88, 171.12, 171.20, 171.71 ppm; IR (KBr): ꢄꢀ¼ 3400, 1749,
1691, 1643, 1541cmꢁ1; MS (FAB): m=z ¼ 617.1 [M þ H]þ.
N-{(2S)-1,4-Dioxo-2-hydroxy-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)amino]butyl}-
phenylalanine amide (9a=6, C27H35N3O13)
ꢀ
6a (306mg, 0.50 mmol) and HCl H-Phe-NH2 (121mg, 0.60 mmol) were reacted in the presence of
NEM (69 mg, 0.60 mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromato-
graphy (CHCl3=MeOH¼ 20=3, Rf ¼ 0.30). Yield: 244 mg (80%), foam, [ꢀ]D ¼ þ17ꢂ cm3 gꢁ1 dmꢁ1
1
(c ¼ 1.2, CHCl3); H NMR (CDCl3, 300 MHz): ꢃ ¼ 2.04 (s, 3H), 2.05 (s, 3H), 2.06 (s, 6H) (4OAc),
2.22 (dd, 1H, J ¼ 9.6, 15.9 Hz, CH2Mal), 2.65 (dd, 1H, J ¼ 3.0, 15.9Hz, CH2Mal), 3.04 (dd, 1H,
J ¼ 7.5, 13.8Hz, ꢁ-CH2Phe), 3.15 (dd, 1H, J ¼ 6.0, 13.8Hz, ꢁ-CH2Phe), 3.86 (m, 1H, 5-H), 4.12
(dd, 1H, J ¼ 1.8, 12.6Hz, 6-Ha), 4.30 (dd, 1H, J ¼ 4.5, 12.6Hz, 6-Hb), 4.38 (m, 1H, CHMal), 4.66
(m, 1H, ꢀ-CHPhe), 5.00 (dd, 1H, J ¼ 9.6, 9.6 Hz), 5.11 (dd, 1H, J ¼ 9.9, 9.6 Hz), 5.30 (dd, 1H,
J ¼ 9.3, 9.3 Hz), 5.34 (dd, 1H, J ¼ 9.6, 9.6 Hz) (4,3,2,1-H), 6.46 (s, 1H, CONH2), 6.60 (s, 1H,
CONH2), 7.23–7.35 (m, 5H, Harom), 7.53 (d, 1H, J ¼ 9.3Hz, 1-NH), 7.61 (d, 1H, J ¼ 8.4 Hz,
NHPhe) ppm; 13C NMR (CDCl3, 75 MHz): ꢃ ¼ 20.84 (2c), 20.95 (2c) (4OAc), 38.22 (ꢁ-CH2Phe),
40.09 (CH2Mal), 54.26 (ꢀ-CHPhe), 61.95 (6-CH2), 68.35, 68.88, 70.75, 73.17, 73.89 (CHMal, 5,4,3,2-
CH), 78.04 (1-CH), 127.43, 128.97, 129.54, 136.50 (Carom), 169.91, 170.27, 171.05, 171.32,
172.49, 173.50, 172.25ppm; IR (KBr): ꢄꢀ¼ 3400, 1749, 1668, 1527 cmꢁ1; MS (FAB): m=z ¼ 610.3
[Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyra-
nosyl)amino]butyl}glycinate (9b=1, C25H38N2O14)
t
ꢀ
6b (625 mg, 1.00 mmol) and HCl H-Gly-O Bu (201 mg, 1.20mmol) were reacted in the presence of
NEM (138 mg, 1.20mmol) due to protocol 4. Reaction time: 1 d. Purification by flash chromatography
(ethyl acetate=petroleum ether ¼ 5=1). Yield 74mg (16%) 7b (Rf ¼ 0.30) and 369 mg (62%) 9b=1
(Rf ¼ 0.19), foam, [ꢀ]D ¼ þ25ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 2.0, CHCl3); 1H NMR (CDCl3, 300 MHz, COSY):
ꢃ ¼ 1.36 (s, 3H, CH3Citr), 1.45 (s, 9H, CH3tBu), 1.98 (s, 3H), 2.00 (s, 3H), 2.05 (s, 3H), 2.07 (s, 3H)
(4OAc), 2.43 (d, 1H, J ¼ 15.3Hz, CH2Citr), 2.85 (d, 1H, J ¼ 15.3 Hz, CH2Citr), 3.78 (ddd, 1H, J ¼ 1.8,
4.2, 9.9Hz, 5-H), 3.79 (dd, J ¼ 5.4, 18.0Hz, CH2Gly), 3.89 (dd, 1H, J ¼ 5.4, 18.0Hz, CH2Gly), 4.05 (dd,
1H, J ¼ 1.8, 12.3Hz, 6-Ha), 4.26 (dd, 1H, J ¼ 4.2, 12.3Hz, 6-Hb), 4.92 (dd, 1H, J ¼ 9.6, 9.6 Hz, 2-H),
5.03 (dd, 1H, J ¼ 9.6, 9.6 Hz, 4-H), 5.19–5.28 (m, 3H, 1,3-H, OH), 7.08 (d, 1H, J ¼ 9.3 Hz, 1-NH),
7.34 (t, 1H, J ¼ 5.4 Hz, NHGly) ppm; 13C NMR (CDCl3, 75MHz, HETCOR): ꢃ ¼ 20.83 (2c), 20.90,
20.99 (4OAc), 26.76 (CH3Citr), 28.30 (CH3tBu), 42.10 (CH2Gly), 43.54 (CH2Citr), 61.92 (6-CH2), 68.29
(4-CH), 70.43 (2-CH), 73.00 (3-CH), 73.92 (5-CH), 74.81 (CCitr), 77.91 (1-CH), 82.55 (CtBu), 168.81,
169.76, 170.20, 170.90, 171.42, 172.42, 175.85 ppm; IR (KBr): ꢄꢀ¼ 3400, 1751, 1670, 1533cmꢁ1; MS
(FAB): m=z ¼ 591.2 [M þ H]þ.

Hexafluoroacetone as Protecting and Activating Reagent
1237
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyra-
nosyl)amino]butyl}alaninate (9b=2, C26H40N2O14)
t
ꢀ
6b (625 mg, 1.00mmol) and HCl H-Ala-O Bu (218 mg, 1.20 mmol) were reacted in the presence of
NEM (138 mg, 1.20mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(CHCl3=petroleum ether=MeOH¼ 10=5=1). Yield 276mg (46%) 9b=2 (Rf ¼ 0.36), foam, [ꢀ]D ¼
þ22ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.5, CHCl3) and 119 mg (26%) 7b (Rf ¼ 0.26).
9b=2:1H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.33 (d, 3H, J ¼ 7.2 Hz, CH3Ala), 1.35 (s, 3H,
CH3Citr), 1.43 (s, 9H, CH3tBu), 1.99 (s, 3H), 2.00 (s, 3H), 2.06 (s, 3H), 2.12 (s, 3H) (4OAc), 2.42
(d, 1H, J ¼ 15.3Hz, CH2Citr), 2.81 (d, 1H, J ¼ 15.3 Hz, CH2Citr), 3.77 (ddd, 1H, J ¼ 2.1, 4.2, 9.9 Hz, 5-
H), 4.05 (dd, 1H, J ¼ 2.1, 12.3 Hz, 6-Ha), 4.24–4.30 (m, 2H, ꢀ-CHAla, 6-Hb), 4.92 (dd, 1H, J ¼ 9.6,
9.6 Hz, 2-H), 5.04 (dd, 1H, J ¼ 9.6, 9.6 Hz, 4-H), 5.17 (s, 1H, OH), 5.18 (dd, 1H, J ¼ 9.0, 9.3Hz, 1-H),
5.28 (dd, 1H, J ¼ 9.6, 9.3Hz, 3-H), 6.81 (d, 1H, J ¼ 9.0 Hz, 1-NH), 7.23 (d, 1H, J ¼ 7.5 Hz, NHAla
)
ppm; 13C NMR (CDCl3, 75 MHz, APT): ꢃ ¼ 18.39 (CH3Ala), 20.68 (2c), 20.73, 20.83 (4OAc), 26.23
(CH3Citr), 28.05 (CH3tBu), 43.18 (CH2Citr), 48.66 (ꢀ-CHAla), 61.69 (6-CH2), 68.15, 70.20, 72.65, 73.78
(2,3,4,5-CH), 74.68 (CCitr), 77.84 (1-CH), 81.92 (CtBu), 169.61, 170.05, 170.72, 171.53, 171.71,
173.52, 174.94 ppm; IR (KBr): ꢄꢀ¼ 3400, 1751, 1666, 1533cmꢁ1; MS (FAB): m=z ¼ 605.2 [Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-
glucopyranosyl)amino]butyl}valinate (9b=3, C28H44N2O14)
t
ꢀ
6b (312 mg, 0.50mmol) and HCl H-Val-O Bu (126mg, 0.60mmol) were reacted in the presence of
NEM (69 mg, 0.60 mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(CHCl3=petroleum ether=MeOH¼ 10=3=1). Yield 149 mg (47%) 9b=3 (Rf ¼ 0.38), foamy solid,
[ꢀ]D ¼ þ23ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.6, CHCl3) and 80mg (34%) 7b (Rf ¼ 0.24).
9b=3: 1H NMR (CDCl3, 300 MHz): ꢃ ¼ 0.92 (d, 3H, J ¼ 6.9 Hz, ꢅ-CH3Val), 0.93 (d, 3H, J ¼ 6.9 Hz,
ꢅ0-CH3Val), 1.39 (s, 3H, CH3Citr), 1.48 (s, 9H, CH3tBu), 2.04 (s, 3H), 2.05 (s, 3H), 2.10 (s, 3H), 2.17 (s,
3H) (4OAc), 2.18 (m, 1H, ꢁ-CHVal), 2.45 (d, 1H, J ¼ 15.3Hz, CH2Citr), 2.86 (d, 1H, J ¼ 15.3Hz,
CH2Citr), 3.82 (m, 1H, 5-H), 4.09 (dd, 1H, J ¼ 2.1, 12.3Hz, 6-Ha), 4.27–4.35 (m, 2H, ꢀ-CHVal, 6-Hb),
4.96 (dd, 1H, J ¼ 9.6, 9.6Hz, 2-H), 5.08 (dd, 1H, J ¼ 9.6, 9.9 Hz, 4-H), 5.16 (dd, 1H, J ¼ 9.0, 9.3 Hz, 1-
H), 5.31 (dd, 1H, J ¼ 9.6, 9.3 Hz, 3-H), 5.35 (s, 1H, OH), 6.73 (d, 1H, J ¼ 8.7 Hz, NHVal), 7.25 (d, 1H,
Val
J ¼ 9.3 Hz, 1-NH) ppm; 13C NMR (CDCl3, 75 MHz, APT): ꢃ ¼ 17.47 (ꢅ-CH3 ), 19.07 (ꢅ0-CH3Val),
20.70 (2c), 20.80, 20.84 (4OAc), 26.26 (CH3Citr), 28.14 (CH3tBu), 31.42 (ꢁ-CHVal), 43.17 (CH2Citr),
57.42 (ꢀ-CHVal), 61.66 (6-CH2), 68.19, 70.09, 72.58, 73.72 (2,3,4,5-CH), 75.07 (CCitr), 77.97 (1-CH),
81.95 (CtBu), 169.63, 170.08, 170.56, 170.73, 171.83, 173.77, 175.19 ppm; IR (KBr): ꢄꢀ¼ 3400, 1751,
1668, 1524 cmꢁ1; MS (FAB): m=z ¼ 633.3 [Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-
glucopyranosyl)amino]butyl}phenylalaninate (9b=4, C32H44N2O14)
t
ꢀ
6b (625mg, 1.00 mmol) and HCl H-Phe-O Bu (309mg, 1.20 mmol) were reacted in the presence of
NEM (138 mg, 1.20mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(CHCl3=petroleum ether=MeOH¼ 10=5=1). Yield 290 mg (43%) 9b=4 (Rf ¼ 0.36), foamy solid,
[ꢀ]D ¼ þ43ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.6, CHCl3) and 180 mg (39%) 7b (Rf ¼ 0.25).
9b=4: H NMR (CDCl3, 300 MHz): ꢃ ¼ 1.35 (s, 3H, CH3Citr), 1.39 (s, 9H, CH3tBu), 2.02 (s, 3H),
1
2.04 (s, 3H), 2.08 (s, 3H), 2.11 (s, 3H) (4OAc), 2.44 (d, 1H, J ¼ 15.6Hz, CH2Citr), 2.79 (d, 1H,
J ¼ 15.6Hz, CH2Citr), 2.99–3.15 (m, 2H, ꢁ-CH2Phe), 3.82 (m, 1H, 5-H), 4.08 (dd, 1H, J ¼ 1.5,
12.6Hz, 6-Ha), 4.32 (dd, 1H, J ¼ 4.2, 12.6Hz, 6-Hb), 4.62 (m, 1H, ꢀ-CHPhe), 4.96 (dd, 1H, J ¼ 9.6,
9.6 Hz, 2-H), 5.08 (dd, 1H, J ¼ 9.6, 9.9 Hz, 4-H), 5.19 (dd, 1H, J ¼ 9.3, 9.3 Hz, 1-H), 5.29 (s, 1H, OH),
5.31 (dd, 1H, J ¼ 9.6, 9.3 Hz, 3-H), 6.64 (d, 1H, J ¼ 9.0 Hz, 1-NH), 7.21–7.36 (m, 6H, NHPhe, Harom
)
ppm; 13C NMR (CDCl3, 75 MHz, APT): ꢃ ¼ 20.62, 20.64, 20.69, 20.78 (4OAc), 26.19 (CH3Citr), 27.98

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C. Bottcher et al.
1238
(CH3tBu), 38.18 (ꢁ-CH2Phe), 42.93 (CH2Citr), 53.51 (ꢀ-CHPhe), 61.68 (6-CH2), 68.11, 70.13, 72.67,
73.71 (2,3,4,5-CH), 74.66 (CCitr), 77.72 (1-CH), 82.25 (CtBu), 127.07, 128.55, 129.58, 136.13 (Carom),
169.57, 169.98, 170.05, 170.69, 171.38, 173.45, 174.85 ppm; IR (KBr): ꢄꢀ¼ 3400, 1755, 1672,
1521 cmꢁ1; MS (FAB): m=z ¼ 681.3 [Mþ H]þ.
N-{(2S)-1,4-Dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-glucopyranosyl)-
amino]butyl}phenylalanine amide (9b=5, C28H37N3O13)
ꢀ
6b (625mg, 1.00 mmol) and HCl H-Phe-NH2 (241mg, 1.20mmol) were reacted in the presence of
NEM (138 mg, 1.20mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(gradient elution, CHCl3=MeOH¼ 15=1 ! 10=1). Yield 150mg (33%) 7b (Rf ¼ 0.60) and 290 mg
1
(47%) 9b=5 (Rf ¼ 0.15), foamy solid, [ꢀ]D ¼ þ3ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.5, CHCl3); H NMR (CDCl3,
300 MHz): ꢃ ¼ 1.30 (s, 3H, CH3Citr), 2.00 (s, 3H), 2.02 (s, 3H), 2.05 (s, 3H), 2.07 (s, 3H) (4OAc), 2.44
(d, 1H, J ¼ 15.6Hz, CH2Citr), 2.71 (d, 1H, J ¼ 15.6Hz, CH2Citr), 3.11–3.16 (m, 2H, ꢁ-CH2Phe), 3.81
(m, 1H, 5-H), 4.06 (dd, 1H, J ¼ 1.8, 12.6Hz, 6-Ha), 4.29 (dd, 1H, J ¼ 4.2, 12.6 Hz, 6-Hb), 4.46 (m, 1H,
ꢀ-CHPhe), 4.92 (dd, 1H, J ¼ 9.6, 9.6 Hz, 2-H), 5.05 (dd, 1H, J ¼ 9.6, 9.9Hz, 4-H), 5.16 (dd, 1H,
J ¼ 9.3, 9.3 Hz, 1-H), 5.21 (s, 1H, OH), 5.29 (dd, 1H, J ¼ 9.6, 9.6Hz, 3-H), 5.84 (s, 1H, NH2Phe),
6.06 (s, 1H, NH2Phe), 7.15 (d, 1H, J ¼ 9.0 Hz, 1-NH), 7.21–7.34 (m, 5H, Harom), 7.42 (d, 1H,
J ¼ 8.4 Hz, NHPhe) ppm; 13C NMR (CDCl3, 75MHz, APT): ꢃ ¼ 20.86 (2c), 20.93, 20.97 (4OAc),
26.04 (CH3Citr), 37.51 (ꢁ-CH2Phe), 43.40 (CH2Citr), 54.76 (ꢀ-CHPhe), 61.89 (6-CH2), 68.31, 70.50,
73.08, 73.89 (2,3,4,5-CH), 74.62 (CCitr), 77.78 (1-CH), 127.30, 128.99, 129.57, 137.05 (Carom), 169.85,
170.24, 170.91, 171.41, 173.33 (2c), 175.95 ppm; IR (KBr): ꢄꢀ¼ 3400, 1751, 1670, 1522 cmꢁ1; MS
(FAB): m=z ¼ 624.2 [M þ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-4-[(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyranosyl)-
amino]butyl}phenylalaninate (9c=1, C51H58N2O10)
t
ꢀ
6c (804mg, 1.00mmol) and HCl H-Phe-O Bu (309 mg, 1.20 mmol) were reacted in the presence of
NEM (138 mg, 1.20mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(ethyl acetate=petroleum ether ¼ 3=2, Rf ¼ 0.29). Yield 669 mg (78%), thin needles, mp 128–130ꢂC,
1
[ꢀ]D ¼ þ1ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.4, CHCl3); H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.40 (s, 9H,
CH3tBu), 2.30 (dd, 1H, J ¼ 8.2, 16.1Hz, CH2Mal), 2.66 (dd, 1H, J ¼ 3.6, 16.1Hz, CH2Mal), 3.08–3.12
(m, 2H, ꢁ-CH2Phe), 3.40 (m, 1H, 2-H), 3.54 (m, 1H, 5-H), 3.68–3.75 (m, 4H, 3,4-H, 6-H2), 4.38 (m,
1H, CHMal), 4.44 (d, 1H, J ¼ 12.3Hz, CH2Ph), 4.50 (d, 1H, J ¼ 11.1Hz, CH2Ph), 4.60 (d, 1H,
J ¼ 12.3Hz, CH2Ph), 4.61 (br.s, 1H, OH), 4.68 (d, 1H, J ¼ 12.0Hz, CH2Ph), 4.70 (m, 1H, ꢀ-CHPhe),
4.81 (d, 1H, J ¼ 11.1 Hz, CH2Ph), 4.83 (d, 1H, J ¼ 12.0Hz, CH2Ph), 4.90 (s, 2H, CH2Ph), 5.08 (dd,
1H, J ¼ 9.3, 9.3 Hz, 1-H), 5.96 (d, 1H, J ¼ 9.3 Hz, 1-NH), 7.17–7.42 (m, 26H, NHPhe, Harom) ppm; 13
C
NMR (CDCl3, 75 MHz, HETCOR, APT): ꢃ ¼ 28.22 (CH3tBu), 38.57 (ꢁ-CH2Phe), 39.17 (CH2Mal),
53.62 (ꢀ-CHPhe), 68.32 (6-CH2), 68.98 (CHMal), 73.86, 74.87, 75.25, 76.04 (4CH2Ph), 76.70 (5-
CH), 77.77 (4-CH), 78.91 (1-CH), 79.71 (2-CH), 82.58 (CtBu), 86.34 (3-CH), 127.2–129.9, 136.43,
137.98, 138.09, 138.28, 138.59 (Carom), 170.47, 172.03, 172.54 ppm; IR (KBr): ꢄꢀ¼ 3400, 1730, 1662,
1525 cmꢁ1; MS (FAB): m=z ¼ 859.4 [Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-4-[(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyranosyl)-
amino]butyl}prolinate (9c=2, C47H56N2O10)
t
ꢀ
6c (402 mg, 0.50mmol) and HCl H-Pro-O Bu (125 mg, 0.60mmol) were reacted in the presence of
NEM (69 mg, 0.60 mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
(ethyl acetate=petroleum ether ¼ 2=1, Rf ¼ 0.23). Yield 298mg (74%), foamy solid, [ꢀ]D ¼
ꢁ21ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.1, CHCl3); 1H NMR (CDCl3, 300 MHz, 298 K, COSY): rotamers,

Hexafluoroacetone as Protecting and Activating Reagent
1239
ratio 5:1, ꢃ (major rotamer)¼ 1.49 (s, 9H, CH3tBu), 1.82–2.24 (m, 4H, ꢁ,ꢅ-CH2Pro), 2.45 (dd, 1H,
J ¼ 8.7, 14.8Hz, CH2Mal), 2.57 (dd, 1H, J ¼ 3.6, 14.8 Hz, CH2Mal), 3.38–3.51 (m, 3H, 2-H, ꢃ-CH2Pro),
3.55 (m, 1H, 5-H), 3.68–3.75 (m, 4H, 3,4-H, 6-H2), 4.08 (d, 1H, J ¼ 7.4Hz, OH), 4.43 (dd, 1H,
J ¼ 5.1, 8.4Hz, ꢀ-CHPro), 4.50 (d, 1H, J ¼ 12.0 Hz, CH2Ph), 4.52 (m, 1H, CHMal), 4.58 (d, 1H, J ¼
10.8Hz, CH2Ph), 4.64 (d, 1H, J ¼ 12.0Hz, CH2Ph), 4.84–4.89 (m, 3H, CH2Ph), 4.91 (d, 1H,
J ¼ 11.1Hz, CH2Ph), 4.96 (d, 1H, J ¼ 11.1Hz, CH2Ph), 5.25 (dd, 1H, J ¼ 9.3, 9.3 Hz, 1-H), 7.10
(d, 1H, J ¼ 9.3Hz, 1-NH), 7.29–7.41 (m, 20H, Harom) ppm; 13C NMR (CDCl3, 75 MHz, APT): ꢃ
(major rotamer) ¼ 25.13 (ꢅ-CH2Pro), 28.28 (CH3tBu), 29.11 (ꢁ-CH2Pro), 42.26 (CH2Mal), 46.95
(ꢃ-CH2Pro), 60.24 (ꢀ-CHPro), 67.00 (CHMal), 68.66 (6-CH2), 73.77, 75.05, 75.24, 75.95 (4CH2Ph),
76.62, 77.86, 79.33, 81.26 (5,4,2,1-CH), 82.05 (CtBu), 86.15 (3-CH), 127.97–128.84, 138.12, 138.41,
138.57, 138.75 (Carom), 170.88, 171.05, 171.60ppm; IR (KBr): ꢄꢀ¼ 3400, 1737, 1647, 1542cmꢁ1; MS
(FAB): m=z ¼ 809.4 [M þ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-4-[(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyranosyl)-
amino]butyl}phenylalanylalaninate (9c=3, C54H63N3O11)
A solution of Z-Phe-Ala-OtBu (277 mg, 0.65mmol) in ethyl acetate (40 cm3) was vigorously stirred for
4 h in an atmosphere of hydrogen in the presence of 100 mg of 10% Pd=C catalyst. After filtration and
removal of the solvent in vacuo the remaining residue was reacted with 6c (434mg, 0.54mmol) in the
presence of NEM (75 mg, 0.65 mmol) due to protocol 4. Reaction time: 3 d. Purification by flash
chromatography (ethyl acetate=petroleum ether ¼ 5=2, Rf ¼ 0.27). Yield 336 mg (67%), needles, mp
171–173ꢂC, [ꢀ]D ¼ ꢁ21ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 2.7, CHCl3); 1H NMR (CDCl3, 300MHz, COSY):
ꢃ ¼ 1.31 (d, 3H, J ¼ 7.2 Hz, CH3Ala), 1.44 (s, 9H, CH3tBu), 2.17 (dd, 1H, J ¼ 8.7, 15.9Hz, CH2Mal),
2.59 (dd, 1H, J ¼ 3.6, 15.9Hz, CH2Mal), 3.01–3.15 (m, 2H, ꢁ-CH2Phe), 3.36 (dd, 1H, J ¼ 9.0, 9.0 Hz, 2-
H), 3.51 (m, 1H, 5-H), 3.64–3.77 (m, 4H, 3,4-H, 6-H2), 4.32–4.37 (m, 2H, CHMal, ꢀ-CHAla), 4.43 (d,
1H, J ¼ 12.3Hz, CH2Ph), 4.49 (d, 1H, J ¼ 10.8 Hz, CH2Ph), 4.57 (d, 1H, J ¼ 12.3Hz, CH2Ph), 4.60
(m, 1H, ꢀ-CHPhe), 4.65 (d, 1H, J ¼ 12.0 Hz, CH2Ph), 4.79 (d, 1H, J ¼ 10.8Hz, CH2Ph), 4.80 (d, 1H,
J ¼ 12.0Hz, CH2Ph), 4.89 (s, 2H, CH2Ph), 5.03 (dd, 1H, J ¼ 9.0, 9.3 Hz, 1-H), 5.90 (d, 1H, J ¼ 9.0 Hz,
1-NH), 6.49 (d, 1H, J ¼ 6.9 Hz, NHAla), 7.10–7.36 (m, 26H, NHPhe, Harom) ppm; 13C NMR (CDCl3,
75MHz, APT): ꢃ ¼ 18.64 (CH3Ala), 28.23 (CH3tBu), 38.43 (ꢁ-CH2Phe), 39.46 (CH2Mal), 49.10 (ꢀ-
CHAla), 54.31 (ꢀ-CHPhe), 68.37 (6-CH2), 68.97 (CHMal), 73.78, 74.93, 75.24, 76.03 (4CH2Ph),
76.68, 77.80, 79.00, 80.09 (5,4,2,1-CH), 82.28 (CtBu), 86.24 (3-CH), 127.2–129.7, 136.69, 137.91,
138.14, 138.27, 138.59 (Carom), 170.25, 171.99, 172.34, 172.81 ppm; IR (KBr): ꢄꢀ¼ 3400, 1736, 1645,
1544 cmꢁ1; MS (FAB): m=z ¼ 952.4 [Mþ Na]þ, 930.4 [Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyra-
nosyl)amino]butyl}phenylalaninate (9d=1, C52H60N2O10)
t
ꢀ
6d (409mg, 0.50 mmol) and HCl H-Phe-O Bu (155mg, 0.60 mmol) were reacted in the presence of
NEM (69 mg, 0.60 mmol) due to protocol 4. Reaction time: 3 d. Purification by flash chromatography
(gradient elution, ethyl acetate=petroleum ether ¼ 1=2 ! 1=1). Yield: 35mg (11%) 7d (Rf ¼ 0.19) and
251 mg (58%) 9d=1 (Rf ¼ 0.10), crystalline solid, mp 121–122ꢂC, [ꢀ]D ¼ þ24ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.4,
CHCl3); 1H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.42 (s, 3H, CH3Citr), 1.44 (s, 9H, CH3tBu), 2.37 (d,
1H, J ¼ 15.6Hz, CH2Citr), 2.75 (d, 1H, J ¼ 15.6Hz, CH2Citr), 2.99–3.14 (m, 2H, ꢁ-CH2Phe), 3.41 (m,
1H, 2-H), 3.56 (m, 1H, 5-H), 3.74–3.80 (m, 4H, 3,4-H, 6-H2), 4.50 (d, 1H, J ¼ 12.0Hz, CH2Ph), 4.56
(d, 1H, J ¼ 10.8Hz, CH2Ph), 4.66 (d, 1H, J ¼ 12.0Hz, CH2Ph), 4.70 (m, 1H, ꢀ-CHPhe), 4.77–4.88 (m,
3H, CH2Ph), 4.95 (s, 2H, CH2Ph), 5.12 (dd, 1H, J ¼ 9.3, 9.0 Hz, 1-H), 5.64 (s, 1H, OH), 6.04 (d, 1H,
J ¼ 9.0 Hz, 1-NH), 7.16–7.45 (m, 26H, NHPhe, Harom) ppm; 13C NMR (CDCl3, 75 MHz, APT):
ꢃ ¼ 26.38 (CH3Citr), 28.05 (CH3tBu), 38.22 (ꢁ-CH2Phe), 42.79 (CH2Citr), 53.38 (ꢀ-CHPhe), 68.36 (6-
CH2), 73.86, 74.58, 74.79, 75.24, 76.04 (4CH2Ph, CCitr), 76.70, 77.78, 78.87, 79.64 (5,4,2,1-H), 82.30

€
C. Bottcher et al.
1240
(CtBu), 86.27 (3-CH), 127.2–129.6, 136.39, 138.02, 138.08, 138.31, 138.60 (Carom), 170.37, þ173.20,
175.14 ppm; IR (KBr): ꢄꢀ¼ 3400, 1732, 1659, 1518 cmꢁ1; MS (FAB): m=z ¼ 873.4 [Mþ H]
.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyra-
nosyl)amino]butyl}prolinate (9d=2, C48H58N2O10)
t
ꢀ
6d (409 mg, 0.50 mmol) and HCl H-Pro-O Bu (125 mg, 0.60 mmol) were reacted in the presence of
NEM (69 mg, 0.60 mmol) due to protocol 4. Reaction time: 4 d. Purification by flash chromatography
(ethyl acetate=petroleum ether ¼ 3=4). Yield: 155 mg (48%) 7d (Rf ¼ 0.32) and 141 mg (34%) 9d=2
1
(Rf ¼ 0.10), foamy solid, [ꢀ]D ¼ þ10ꢂ cm3 gꢁ1 dmꢁ1 (c ¼ 1.4, CHCl3); H NMR (CDCl3, 400 MHz,
Citr
tBu
tBu
300 K, COSY): rotamers, ratio 3:1, ꢃ ¼ 1.32 (s, CH3 min), 1.38 (s, CH3 maj), 1.40 (s, CH3 min),
Citr
1.44 (s, CH3 maj), 1.70–1.92 (m, ꢁ,ꢅ-CH2 maj, ꢅ-CH2 min), 2.02–2.09 (m, ꢁ-CH2 min), 2.24 (d,
Pro
Pro
Pro
Citr
Citr
Citr
J ¼ 15.2Hz, CH2 min), 2.28 (d, J ¼ 14.8Hz, CH2 maj), 2.86 (d, J ¼ 15.2Hz, CH2 min), 2.93 (d,
Citr
Pro
J ¼ 14.8Hz, CH2 maj), 3.32–3.36 (m, 2-H), 3.39–3.46 (m, 5-H, ꢃ-CH2 min), 3.63–3.70 (m, 3,4-H,
Pro
Pro
6-H2), 3.77 (m, ꢃ-CH2 maj), 3.91 (m, ꢃ-CH2 maj), 4.10 (dd, J ¼ 3.9, 8.2 Hz, ꢀ-CHPromaj), 4.41 (d,
J ¼ 12.0Hz, CH2Phmin), 4.42 (d, J ¼ 12.0Hz, CH2Phmaj), 4.46 (d, J ¼ 11.0 Hz, CH2Phmin þ maj), 4.55
(d, J ¼ 12.0Hz, CH2Phmin), 4.56 (d, J ¼ 12.0Hz, CH2Phmaj), 4.67 (d, J ¼ 10.4Hz, CH2Phmin þ maj),
4.73 (ꢀ-CHPromin), 4.74–4.86 (4 CH2Phmin þ maj), 5.11 (dd, J ¼ 9.3, 9.3Hz, 1-H), 5.65 (br.s, OHmaj),
5.79 (br.s, OHmin), 5.99 (d, J ¼ 9.3 Hz, 1-NHmin), 6.21 (d, J ¼ 9.3Hz, 1-NHmaj), 7.07–7.30 (Harom
)
Pro
ppm; 13C NMR (CDCl3, 75 MHz, 300K, HETCOR, APT): ꢃ ¼ 21.17 (ꢅ-CH2 min), 25.41
(CH3 maj), 25.62 (ꢅ-CH2 maj), 26.16 (CH3 min), 28.18 (ꢁ-CH2 maj), 28.30 (CH3tBu), 32.12
Citr
Pro
Citr
Pro
Pro
Citr
Citr
Pro
Pro
(ꢁ-CH2 min), 44.71 (CH2 min), 45.30 (CH2 maj), 48.36 (ꢃ-CH2 min), 48.62 (ꢃ-CH2 maj),
61.33 (ꢀ-CHPromin), 61.46 (ꢀ-CHPromaj), 68.51 (6-CH2), 73.84 (CH2Ph), 74.74 (CCitr), 75.00, 75.25,
76.00 (3CH2Ph), 76.58 (5-CHmin), 76.74 (5-CHmaj), 77.69 (4-CH), 78.89 (1-CHmin), 79.08 (1-CHmaj),
80.53 (2-CHmin), 80.90 (2-CHmaj), 81.10 (CtBumaj), 81.35 (CtBumin), 86.06 (3-CH), 127.94–129.24,
138.06, 138.34 (2c), 138.72 (Carom), 171.86, 172.41, 173.22, 173.63, 173.93ppm; IR (KBr): ꢄꢀ¼ 3400,
1732, 1628, 1552 cmꢁ1; MS (FAB): m=z ¼ 823.4 [Mþ H]þ.
tert-Butyl N-{(2S)-1,4-dioxo-2-hydroxy-2-methyl-4-[(2,3,4,6-tetra-O-benzyl-ꢁ-D-glucopyra-
nosyl)amino]butyl}phenylalanylalaninate (9d=3, C55H65N3O11)
A solution of Z-Phe-Ala-OtBu (256 mg, 0.60mmol) in ethyl acetate (40 cm3) was vigorously stirred for
4 h in an atmosphere of hydrogen in the presence of 100 mg of 10% Pd=C. After filtration and removal
of the organic solvent in vacuo the remaining residue was reacted with 6d (409mg, 0.50 mmol) in
the presence of NEM (69 mg, 0.60mmol) due to protocol 4. Reaction time: 5 d. Purification by flash
chromatography (ethyl acetate=petroleum ether ¼ 1=1). Yield: 54 mg (17%) 7d (Rf ¼ 0.46) and
337 mg (71%) 9d=3 (Rf ¼ 0.27), crystalline solid, mp 154–156ꢂC; [ꢀ]D ¼ ꢁ3ꢂ cm3 gꢁ1 dmꢁ1
(c ¼ 2.5, CHCl3); H NMR (CDCl3, 300 MHz, COSY): ꢃ ¼ 1.34 (d, 3H, J ¼ 7.2 Hz, CH3Ala), 1.40
1
(s, 3H, CH3Citr), 1.49 (s, 9H, CH3tBu), 2.31 (d, J ¼ 15.6 Hz, CH2Citr), 2.69 (d, J ¼ 15.6Hz, CH2Citr),
3.04 (dd, 1H, J ¼ 6.3, 13.8Hz, ꢁ-CH2Phe), 3.20 (dd, 1H, J ¼ 6.3, 13.8Hz, ꢁ-CH2Phe), 3.38 (m, 1H, 2-
H), 3.54 (m, 1H, 5-H), 3.71–3.81 (m, 4H, 3,4-H, 6-H2), 4.39 (m, 1H, ꢀ-CHAla), 4.49 (d, 1H,
J ¼ 12.3Hz, CH2Ph), 4.55 (d, 1H, J ¼ 10.5 Hz, CH2Ph), 4.56 (m, 1H, ꢀ-CHPhe), 4.64 (d, 1H,
J ¼ 12.3Hz, CH2Ph), 4.76 (d, 1H, J ¼ 11.4Hz, CH2Ph), 4.83 (d, 1H, J ¼ 11.4Hz, CH2Ph), 4.85 (d,
1H, J ¼ 10.5 Hz, CH2Ph), 4.94 (s, 2H, CH2Ph), 5.08 (dd, 1H, J ¼ 9.3, 9.0 Hz, 1-H), 5.55 (s, 1H, OH),
5.94 (d, 1H, J ¼ 9.0 Hz, 1-NH), 6.54 (d, 1H, J ¼ 6.9 Hz, NHAla), 7.15–7.43 (m, 26H, NHPhe, Harom
)
ppm; 13C NMR (CDCl3, 75 MHz, APT): ꢃ ¼ 18.76 (CH3Ala), 26.55 (CH3Citr), 28.21 (CH3tBu), 37.72
(ꢁ-CH2Phe), 42.92 (CH2Citr), 49.01 (ꢀ-CHAla), 54.15 (ꢀ-CHPhe), 68.30 (6-CH2), 73.84, 74.58, 74.76,
75.24, 76.06 (4 CH2Ph, CCitr), 76.67, 77.76, 78.81, 79.56 (5,4,2,1-CH), 82.19 (CtBu), 86.24 (3-CH),
127.2–129.8, 136.56, 137.94, 138.03, 138.25, 138.52 (Carom), 170.02, 171.97, 173.02, 175.85 ppm; IR
(KBr): ꢄꢀ¼ 3400, 1732, 1653, 1528 cmꢁ1; MS (FAB): m=z ¼ 944.5 [Mþ H]þ.

Hexafluoroacetone as Protecting and Activating Reagent
1241
Synthesis of N-Glycosylated Derivatives of Thiomalic Acid
N-(2,3,4,6-Tetra-O-acetyl-ꢁ-D-glucopyranosyl)-2-[(4RS)-5-oxo-2,2-bis(trifluoromethyl)-1,3-
oxathiolan-4-yl]acetamide (10, C21H23F6NO12S)
3c (2.66 g, 8.40 mmol) and 5a (2.92 g, 8.40mmol) were reacted due to protocol 1. Purification by flash
chromatography (ethyl acetate=petroleum ether ¼ 1=1, Rf ¼ 0.25, both diastereomers). Yield 3.90g
(74%), recrystallization from toluene, mp 77–78ꢂC; 1H NMR (CDCl3, 300 MHz): mixture of diaster-
eomers, ratio 1:1, ꢃ ¼ 2.03 (s, 6H), 2.04 (s, 6H), 2.07 (s, 6H), 2.09 (s, 6H) (OAc), 2.68 (dd, 1H,
J ¼ 11.4, 16.8Hz), 2.81 (dd, 1H, J ¼ 9.9, 16.8Hz), 3.08 (dd, 1H, J ¼ 4.2, 16.8Hz), 3.25 (dd, 1H,
J ¼ 3.3, 16.8 Hz) (CH2Thiomal), 3.81 (ddd, 2H, J ¼ 2.1, 4.5, 9.9 Hz, 5-H), 4.06–4.11 (m, 2H, 6-Ha), 4.29
(dd, 1H, J ¼ 4.5, 12.3Hz, 6-Hb), 4.33 (dd, 1H, J ¼ 4.5, 12.3Hz, 6-Hb), 4.49–4.54 (m, 2H, CHThiomal),
4.90 (dd, 2H, J ¼ 9.6, 9.3 Hz), 5.06 (dd, 1H, J ¼ 9.9, 9.6 Hz), 5.07 (dd, 1H, J ¼ 9.9, 9.6 Hz), 5.20 (dd,
1H, J ¼ 9.3, 9.3 Hz), 5.22 (dd, 1H, J ¼ 9.3, 9.3 Hz), 5.31 (dd, 1H, J ¼ 9.6, 9.3Hz), 5.32 (dd, 1H,
J ¼ 9.6, 9.3 Hz) (1,2,3,4-H), 6.43 (d, 2H, J ¼ 9.0 Hz, 1-NH) ppm; 19F NMR (CDCl3, 282 MHz):
ꢃ ¼ 0.81–0.97 (m, 6F), 1.54 (q, 3F, J ¼ 9.0 Hz), 1.73 (q, 3F, J ¼ 9.0 Hz) ppm; 13C NMR (CDCl3,
75MHz): ꢃ ¼ 20.71, 20.75, 20.84, 20.86 (4OAc), 39.76, 40.05 (CH2Thiomal), 41.80, 41.85 (CHThiomal),
61.94 (6-CH2), 68.36 (4-CH), 70.90 (2-CH), 72.78, 72.84 (3-CH), 73.97, 74.04 (5-CH), 78.47, 78.55
(1-CH), 83.87 (sept, J ¼ 35.0Hz), 121.00 (q, J ¼ 283.0 Hz), 121.10 (q, J ¼ 283.0 Hz), 168.93, 169.14,
169.91 (2c), 170.11 (2c), 170.61, 170.69, 170.93, 170.96, 171.21, 171.35 ppm; IR (KBr): ꢄꢀ¼ 1817,
1754, 1799, 1543 cmꢁ1; MS (FAB): m=z ¼ 628.1 [Mþ H]þ.
N-{(2RS)-1,4-Dioxo-2-mercapto-4-[(2,3,4,6-tetra-O-acetyl-ꢁ-D-
glucopyranosyl)amino]butyl}-phenylalanine amide (11, C27H35N3O12S)
ꢀ
NEM (138 mg, 1.20mmol) due to protocol 4. Reaction time: 2 d. Purification by flash chromatography
10 (627mg, 1.00 mmol) and HCl H-Phe-NH2 (241mg, 1.20 mmol) were reacted in the presence of
1
(CHCl3=MeOH ¼ 10=1, Rf ¼ 0.25, both diastereomers). Yield 506 mg (81%), foamy solid; H NMR
(CD3OD, 300 MHz): mixture of diastereomers, ratio 1:1, ꢃ ¼ 2.00–2.05 (several s, 24H, OAc), 2.59
(dd, 1H, J ¼ 7.2, 15.9Hz, CH2Thiomal), 2.69 (dd, 1H, J ¼ 6.9, 12.6Hz, CH2Thiomal), 2.85–3.24 (m, 6H,
CH2Thiomal, ꢁ-CH2Phe), 3.73–3.81 (m, 2H, CHThiomal), 3.93–3.40 (m, 2H, 5-H), 4.08–4.15 (m, 2H, 6-
Ha), 4.25–4.32 (m, 2H, 6-Hb), 4.56 (dd, 1H, J ¼ 5.7, 8.7 Hz, ꢀ-CHPhe), 4.64 (dd, 1H, J ¼ 4.8, 9.3Hz, ꢀ-
CHPhe), 4.97–5.11 (m, 4H, 2,4-H), 5.33–5.42 (m, 4H, 1,3-H), 7.23–7.35 (m, 10H, Harom) ppm; 13C
NMR (CD3OD, 75 MHz): ꢃ ¼ 19.50, 19.57, 19.60 (OAc), 37.15, 37.33 (ꢁ-CH2Phe, CH2Thiomal), 41.13
(CHThiomal), 54.63, 55.03 (ꢀ-CHPhe), 62.04 (6-CH2), 68.47, 70.86, 70.96, 73.51, 73.60, 73.65 (2,3,4,5-
CH), 77.59, 77.68 (1-CH), 126.63, 126.69, 128.35, 128.40, 129.27, 129.35, 137.46 (Carom), 170.23,
170.38, 170.51, 171.23, 171.74, 171.98, 173.04, 173.50, 174.65, 174.96ppm; IR (KBr): ꢄꢀ¼ 1749,
1664, 1525 cmꢁ1; MS (FAB): m=z ¼ 626.2 [Mþ H]þ.
Acknowledgements
We thank Deutsche Forschungsgemeinschaft (Bu 277=21-1) and Stiftung Volkswagenwerk, Hannover,
for financial support.
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