A practical and simple synthesis of (2S,5R)- and (2S,5S)-5-hydroxylysine and of a related α-amino acid required for the synthesis of the collagen cross-link pyridinoline

Article abstract of DOI:10.1016/j.tetasy.2004.06.004

A four step synthesis of (2S,5R)- and (2S,5S)-5-hydroxylysine using Williams' glycine template methodology for controlling the stereogenicity at the α-position is reported. This route offers the possibility for the synthesis of all possible isomers of 5-hydroxylysine and of an important α-amino acidic iodohydrin required for the construction of the hydroxylated side chain of the collagen cross-link pyridinoline.

Full text of DOI:10.1016/j.tetasy.2004.06.004

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 15 (2004) 2091–2096
A practical and simple synthesis of (2S,5R)- and (2S,5S)-
5-hydroxylysine and of a related a-amino acid required for
the synthesis of the collagen cross-link pyridinoline
Pietro Allevia,* and Mario Anastasiab
a
ꢀ
Dipartimento di Medicina, Chirurgia e Odontoiatria, Universitꢀa di Milano, via A. Di Rudinı 8, I-20142 Milano, Italy
bDipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Universitꢀa di Milano, via Saldini 50, I-20133 Milano, Italy
Received 31 May 2004; accepted 4 June 2004
Available online
Abstract—A four step synthesis of (2S,5R)- and (2S,5S)-5-hydroxylysine using Williams’ glycine template methodology for con-
trolling the stereogenicity at the a-position is reported. This route offers the possibility for the synthesis of all possible isomers of
5-hydroxylysine and of an important a-amino acidic iodohydrin required for the construction of the hydroxylated side chain of the
collagen cross-link pyridinoline.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1.Introduction
pyranosyl-(1 fi 2)-b-
D
-galactopyranosyl residue2 to
afford galactosyl-O-hydroxylysine (5R-GaHyl) 5 or
glucosylgalactosyl-O-hydroxylysine (5R-GGaHyl) 6.
Moreover, during maturation of collagen, its (2S,5R)-5-
hydroxylysine residues interact with those of an adjacent
lysine and/or hydroxylysine and form some important
cross-links which, during collagen turnover, generate
deoxypyridinoline 7 and pyridinolines 8a and 8b. In all
cases during collagen degradation, (2S,5R)-5-hydroxy-
lysine 1 and collagen cross-links 7 and 8 are not meta-
bolised but are excreted in human urine mainly as
glycosides 5, 6 and 8b (Fig. 2).3;4 Thus, after an acidic
hydrolysis, the total levels of the amino acid and of
collagen cross-links are measured in this medium to
evaluate the collagen breakdown5 and to aid diagnosis
of osteoporosis and of other metabolic bone diseases.6
Under these conditions some amount of the isomerised
(2R,5R)-5-hydroxylysine 4 also forms and must be
evaluated.5
(2S,5R)-5-Hydroxylysine (
L
-normal-5-hydroxylysine) 1
is the natural isomer of four possible 2,6-diamino-5-
hydroxyhexanoic acids 1–4 (Fig. 1) and it is exclusive to
collagen protein, which is formed by posttranslational
hydroxylation of some lysine residues.1
In collagen, (2S,5R)-5-hydroxylysine 1 can be glycosyl-
ated with either b-
D
-galactopyranosyl or an a-D-gluco-
OH
OH
-O2C
NH2
-O2C
NH2
+
+
NH3
NH3
1 (2S,5R)-5-Hydroxylysine
2 (2S,5S)-5-Hydroxylysine
L-normal
L-allo
OH
OH
-O2C
NH2
-O2C
NH2
(2S,5R)-5-Hydroxylysine 1 is commercially available
both in enantiomerically pure form and as a mixture
with its possible isomers 2–4 (Fig. 1). Moreover, the
pure enantiomer 1 is quite expensive, since it is produced
by tedious procedures from gelatine acid hydrolysates,7
or it is isolated from a mixture of isomers by very
laborious methods, involving the fractionated crystalli-
zation of appropriate derivatives.8 In addition, the use
of (2S,5R)-5-hydroxylysine 1 in the synthesis of collagen
metabolites9 or of peptides10 requires lengthy procedures
+
+
NH3
NH3
3 (2R,5S)-5-Hydroxylysine 4 (2R,5R)-5-Hydroxylysine
D-normal D-allo
Figure 1.
* Corresponding author. Tel.: +39-02-7064-5231; fax: +39-02-5031-
6040; e-mail: pietro.allevi@unimi.it
0957-4166/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.06.004

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P. Allevi, M. Anastasia / Tetrahedron: Asymmetry 15 (2004) 2091–2096
NH2
Ph
Ph
Ph
NH2
OH
O
OH
O
HO
HO
Ph
Ph
Ph
HO
HO
O
O
O
O
O
iii
ii
i
BocN
BocN
BocN
OH
O
O
O
O
+
O
+
O
NH3
HO
NH3
OH
-
-
CO2
CO2
11a: 3'R
11b: 3'S
10
9
5
OH
6
HO
Ph
+
+
NH3
NH3
Ph
O
OH
-
-
+
+
iv
CO2
CO2
NH3
NH3
BocN
-O2C
NH2
-O
O
O
-O
OH
-
-
+
CO2
CO2
N3
NH3
N+
N+
12a
1
+
Ph
OG
Ph
H3N+
H3N+
OH
O
-
-
iv
CO2
a:G = H
b: G = GlucosylGalactosyl
-O2C
NH2
CO2
BocN
7
8
OH
+
NH3
N3
2
12b
Figure 2.
Scheme 1. Reagents and conditions: (i) CH2@CH(CH2)2I,
(Me3Si)2NLi, THF-HMPA, )78 to )40 °C, 4 h; (ii) m-ClPBA, 1,2-
dichloroethane-buffer pH ¼ 7, room temp., 12 h; (iii) NaN3–NH4Cl,
MeOCH2CH2OH, 50 °C, 4.5 h; (iv) TFA–H2O (95:5), room temp., 1 h,
H2, Pd/C, H2O–MeOH–HCl.
for protection prior to its use. Thus, in recent years,
there has been a renewed interest for the preparation11
not only for free and glycosylate hydroxylysines 1, 5 and
6 but also for their epimers, as possible internal stan-
dards in clinical analyses of collagen metabolites. In
addition protected hydroxylysines are important for the
synthesis the collagen cross-links pyridinolines 8a and
8b, both needed for studies in clinical chemistry and
biochemistry.11b;12 Moreover, despite the apparent sim-
plicity of the (2S,5R)-5-hydroxylysine 1 molecule, to
date there is no short synthesis of this amino acid. In
fact, the most recent synthetic strategies involve multi-
step, direct or convergent, procedures and often also the
separations of diastereomers is laborious. This is due to
the fact that in all these approaches the a-stereogenic
center cannot efficiently direct the stereoselective intro-
duction of the second stereogenic center at C-5
position.11a;d;13
the key compound of the synthesis (Scheme 1). Our idea
was that this masked amino acid, by means of its car-
bonyl group, could form an intramolecular hydrogen
bond in each of the hydroxylated epimers previewed as
intermediates in our synthetic procedure (Scheme 1).
This should increase the differences of polarity between
the epimers and avoid the tedious separation of stereo-
isomers by subsidiary methods. In fact, the alkylation
of the oxazinone 914 with homoallyl iodide, at low
temperature, in the presence of lithium bis(trimethylsil-
yl)amide, gave the homoallyloxazinone 10 in satisfac-
tory yield, according to the Williams’ results,14 without
any detectable amount of the epimeric alkylation
product in the crude reaction mixture (1H NMR anal-
ysis in DMSO-d6 at 393 K, Scheme 1). The homoallyl-
oxazinone 10 was then epoxidized by simple treatment
with 3-chloroperbenzoic acid to afford a diastereomeric
mixture (1:1; HPLC of the crude product) of epoxides
11a and 11b, in quantitative yield. These epoxides, even
if resistant to all efforts of separation (TLC, column
chromatography, crystallization), by reaction with so-
dium azide in the presence of ammonium chloride, af-
ford a mixture of the hydroxyazides 12a and 12b, which
could be easily separated by simple rapid chromato-
graphy on silica gel, due to their different polarities
(TLC on silica, eluting with dichloromethane–acetone;
100:2; v/v). Initially, the structure 12a was assigned
tentatively to the less polar compound, however this
assignment was subsequently substantiated by trans-
forming the hydroxyazide 12a into (2S,5R)-5-hydroxy-
lysine 1.
As a result of our continuing interest in the synthesis of
collagen cross links,12 we report herein a simple four
steps procedure for the synthesis of both (2S,5R)-5-
hydroxylysine 1 and of (2S,5S)-5-hydroxylysine 2, based
on the use of diphenyloxyazinones, Williams’ glycine
templates.14 Moreover the commercial availability15 of
both enantiomers of the starting oxazinone renders the
procedure adaptable to preparing also the correspond-
ing (2R)-hydroxylysines 3 and 4. In addition we report
the convenient preparation of a masked (2S,5R)-5-
hydroxylysine, which helps to solve another synthetic
problem associated to the construction of the hydroxyl-
ated side chain of pyridinoline 8a, deriving from 5-
hydroxylysine.12
2.Results and discussion
Our very simple and short protocol (Scheme 1) uses the
glycine template 9 for the preparation, according to the
Williams’ procedure,14 of the homoallyloxazinone 10,
In the same way, the epimeric structure 12b was assigned
to the more polar hydroxyazide.

P. Allevi, M. Anastasia / Tetrahedron: Asymmetry 15 (2004) 2091–2096
2093
+
Each hydroxyazide was then transformed in one-pot
NH3
into the corresponding 5-hydroxylysine 1 or 2 by simple
treatment with trifluoroacetic acid followed by hydro-
genation over Pd on carbon14a (Scheme 1). The obtained
(2S,5R)-5-hydroxylysine 1 and of (2S,5S)-5-hydroxyly-
sine 2 showed an high stereoisomeric purity (>98%;
GLC on a suitable chiral column, see experimental) and
all other physicochemical properties (specific rotation,
13C NMR) were in agreement with those reported.11c;d;e
-
+
+
CO2
NH3
NH3
-O
-
-
+
CO2
CO2
NH3
-O
-
N
CO2
+
I
N+
OH
OH
H3N+
Interestingly, the mixture of epoxides 11 could be
opened, by treatment with sodium iodide, to the mixture
of easily separable iodohydrins of assigned structures
13a and 13b (Scheme 2).
-
CO2
O
O
BocN
Ph
Ph
These epimeric iodohydrins show a different polarity on
silica gel and can be separated by rapid chromatography
on silica. Their structure was easily demonstrated by
simple separate transformation into the corresponding
hydroxyazides 12a and 12b, described above (Scheme 2).
Scheme 3.
important iodohydrin 13a, required by many protocols
for the construction of pyridinoline hydroxylated side
chain.12
Ph
Ph
O
ii
4.Experimental
4.1. General
12a
BocN
O
OH
Ph
I
Ph
less polar
13a
O
i
Nuclear magnetic resonance spectra were recorded on a
Bruker AM-500 spectrometer operating at 500.13 MHz
for 1H and 125.76 MHz for 13C. Chemical shifts are
reported in parts per million (ppm, d units) relative to
CHCl3 fixed at 7.24 ppm or to HDO fixed at 4.54 ppm
for the 1H spectra and relative to dioxane fixed at
+
BocN
O
Ph
O
Ph
O
ii
12b
BocN
11a and 11b
O
OH
I
1
67.60 ppm for the 13C spectra. H NMR data are tabu-
more polar
13b
lated in the following order: number of protons, multi-
plicity (s, singlet; d, doublet; br s, broad singlet; m,
multiplet), coupling constant(s) in hertz, assignment of
proton(s). IR spectra were determined with a Perkin–
Elmer 1420 infrared recording spectrophotometer.
Optical rotations were taken at 25 °C on a Perkin–Elmer
241 polarimeter. Chiral GLC analyses were carried out
Scheme 2. Reagents and conditions: (i) NaI, THF–AcOH, room
temp., 1 h; (ii) NaN3, DMF, room temp., 12 h.
The iodohydrin 13a is a very useful masked hydroxy-
lysine since has a structure required in many synthesis of
the pyridinoline 8. In fact, it allows the construction of
the hydroxylated side chain of the pyridinoline by
alkylation of the nitrogen atom of an appropriate 4,5-
disubstituted-3-hydroxypyridine (Scheme 3).12
on
a Hewlett-Packard 5890 gas chromatography
equipped with a octakis(3-O-butyryl-2,6-di-O-pentyl)-c-
cyclodextrin (Lipodex E)16 capillary column (25 m,
0.25 mm ID, purchased from Macherey-Nagel); carrier
gas was He set at 85 kPa column head pressure and the
column temperature was set at 170 °C. HPLC analyses
were carried out on a chiral column (LiChroCART 250-
4 (R,R)-Whelk-01, 5 lm, Merck, eluent hexane–2-pro-
panol 60:40, v/v; the flow rate was 1 mL/min and the
detection was performed at 221 nm. All reactions were
monitored by thin-layer chromatography (TLC) carried
out on 0.25 mm E. Merck silica gel plates (60 F254) using
UV light, 50% sulfuric acid or 0.2% ninhydrin in ethanol
and heat as developing agent. Merck 230–400 mesh sil-
ica gel was used for flash column chromatography.17
Usual work-up refers to washing the organic layer with
water, drying over Na2SO4, and evaporating the solvent
under reduced pressure. Mass spectra were obtained
using a Finnigan LCQdeca (ThermoQuest) ion trap
mass spectrometer fitted with an electrospray source
(ESI).
3.Conclusion
Thus, the possibility herein reported for obtaining this
amino acidic iodohydrin 13a in a simple way is an
important self-consistent result for the chemistry of
collagen cross-links. This is evident from the docu-
mented difficulties in preparing similar iodohydrins,12
which only recently have been obtained in a relatively
satisfactory way according to some methods set-up in
our laboratory.12h
In conclusion, herein we have reported a very short
synthesis of enantiopure (2R,5R)- and (2R,5S)-5-hy-
droxylysines 1 and 2, using a methodology which also
allows the preparation of the corresponding (2R)-
enantiomers 3 and 415 and permits the preparation of an

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P. Allevi, M. Anastasia / Tetrahedron: Asymmetry 15 (2004) 2091–2096
4.2. GLC analysis of 5-hydroxylysines on a chiral column
(920 mg, 88.7%) in a 1:1 ratio (HPLC: 7.7 and 9.5 min)
23
D
as a white solid: mp 125–127 °C; ½aŠ ¼ À57 (c 1,
1
5-Hydroxylysines (1–2 mg) were esterified with methan-
olic HCl (1 M; 0.2 mL; 25 °C; 12 h). The solvent was
removed under a nitrogen stream and the residue was
treated with a 50% mixture of (CF3CO)2O in CF3CO2H
(0.2 mL; 25 °C; 2 h). After removal of the solvent, the
residue (tris-trifluoroacetates of 5-hydroxylysine methyl
ester) was dissolved in AcOEt and injected.
CHCl3); H NMR (303 K, CDCl3): d 7.25–6.95 (2 · 8H,
aromatics), 6.54 (2 · 2H, d, J ¼ 7:2, aromatics), 5.92
(2 · 1H, m, 6-H), 5.02 (2 · 1H, m, 3-H), 4.99 (2 · 1H, m,
5-H), 3.03 (2 · 1H, m, 30-H), 2.80 (1H, dd, J ¼ 4:9 and
4.0, 40-Ha), 2.78 (1H, dd, J ¼ 4:9 and 4.0, 40-Ha), 2.59
(1H, dd, J ¼ 4:9 and 2.6, 40-Hb), 2.57 (1H, dd, J ¼ 4:9
and 2.6, 40-Hb), 2.33 (2 · 1H, m, 20-Ha), 2.09 (2 · 1H, m,
20-Hb), 1.98 (2 · 1H, m, 10-Ha), 1.78 (1H, m, 10-Hb), 1.69
(1H, m, 10-Hb), 1.08 [9H, s, C(CH3)3], 1.06 [9H, s,
C(CH3)3]; ESI-MS m=z (relative intensity): 446.2 (100,
M+Naþ), 390.2 (60, M+Naþ)56). Anal. Calcd for
C25H29NO5: C, 70.90; H, 6.90; N, 3.31. Found: C, 70.73;
H, 7.05; N, 3.25.
In the used analyses conditions (see general), the deriv-
atives showed the following retention times: 23.35 min
for (2R,5R)-5-hydroxylysine 4; 24.26 min for (2S,5R)-5-
hydroxylysine 1, 24.59 min for (2S,5S)-5-hydroxylysine
2 and 28.67 min for (2R,5S)-5-hydroxylysine 3.
4.3. tert-Butyl (3S,5S,6R)-3-(3-butenyl)-2-oxo-5,6-diphen-
yl-1,4-oxazinane-4-carboxylate 10
4.5. tert-Butyl (3S,5S,6R)-3-[(3R)-4-azido-3-hydroxy-
butyl]-2-oxo-5,6-diphenyl-1,4-oxazinane-4-carboxylate 12a
and tert-butyl (3S,5S,6R)-3-[(3S)-4-azido-3-hydroxybutyl]-
2-oxo-5,6-diphenyl-1,4-oxazinane-4-carboxylate 12b
The homologate oxazinone 10 was prepared according
to the method of Williams and co-workers.14 Starting
with a stirred solution of the lactone 915 (10.1 g, 30 mmol)
and 4-iodobutene (27.3 g, 150 mmol), in anhydrous THF
(225 mL) and HMPA (22.5 mL), cooled to )78 °C, lith-
ium bis(trimethylsilyl)amide (45 mL of a 1 M solution in
dichloromethane, 45 mmol) was added dropwise, under
argon. After 10 min the reaction mixture was stirred at
)40 °C for 4 h. At this time, the reaction was quenched
with ethyl acetate and poured into a mixture of ethyl
acetate (50 mL) and an aqueous solution of NH4Cl
(50 mL, 1 M). The organic layer were worked up to
afford a crude residue which was chromatographed to
afford the title compound 10 (7.3 g, 60%). Compound 10
To a solution of the epoxides 11 (600.0 mg, 1.42 mmol)
in ethylene glycol mono methyl ether, NaN3 (272.0 mg,
4 mmol) and NH4Cl (60 mg, 1.07 mmol) were added and
the mixture was heated at 50 °C for 4.5 h. At this time,
the mixture was cooled at room temperature and poured
into water to afford a solid, which was filtered and
chromatographed (eluting with dichloromethane–ace-
tone, 100:2; v/v) to afford first the (30R)-hydroxyazide
12a (268 mg, 40.4%): mp 110–112 °C (from methanol–
23
water); ½aŠ ¼ À57:0 (c 1, CHCl3); 1H NMR (295 K,
D
DMSO-d6): d 7.26–6.69 (8H, aromatics), 6.54 (2H, d,
J ¼ 7:9, aromatics), 5.89 (1H, d, J ¼ 2:8, 6-H), 4.98
(1H, d, J ¼ 2:8, 5-H), 4.96 (1H, dd, J ¼ 7:0 and 3.7, 3-
H), 4.17 (1H, m, 30-H), 3.55 (1H, br s, OH), 3.37 (1H,
dd, J ¼ 12:4 and 3.3, 40-Ha), 3.29 (1H, dd, J ¼ 12:4 and
7.2, 40-Hb), 2.30 (1H, m, 20-Ha), 2.14 (1H, m, 20-Hb),
1.78 (1H, m, 10-Ha), 1.68 (1H, m, 10-Hb), 1.10 [9H, s,
C(CH3)3]; ESI-MS m=z (relative intensity): 955.1 (54,
M+M+Naþ), 489.2 (100, M+Naþ). Anal. Calcd for
C25H30N4O5: C, 64.36; H, 6,48; N, 12,01. Found: C,
64.28; H, 6.44; N, 12.11.
showed: mp 148–152 °C (from methanol–diisopropyl
23
ether); ½aŠ ¼ À57 (c 0.5, CHCl3) [lit.14a mp 157–152 °C;
D
23
D
½aŠ ¼ À56:7 (c 0.54; CH2Cl2)]; 1H NMR (393 K,
DMSO-d6): d 7.25–7.05 (8H, aromatics), 6.56 (2H, d,
J ¼ 7:7, aromatics), 6.18 (1H, d, J ¼ 3:2, 6-H), 5.92 (1H,
ddt, J ¼ 16:6, 10.2 and 6.5, 30-H), 5.16 (1H, d, J ¼ 3:2, 5-
H), 5.15 (1H, dd, J ¼ 16:6 and 1.7, 40-Ha), 5.05 (1H, dd,
J ¼ 10:2 and 1.7, 40-Hb), 4.82 (1H, dd, J ¼ 7:0 and 7.0,
3-H), 2.34–2.23 (2H, m, 20-H2), 2.22–2.17 (2H, m, 10-H2),
1.19 [9H, s, C(CH3)3]; ESI-MS m=z (relative intensity):
837.0 (40, M+M+Naþ), 430.2 (100, M+Naþ). Anal.
Calcd for C25H29NO4: C, 73.68; H, 7.17; N, 3.44. Found:
C, 73.92; H, 7.24; N, 3.31.
Further elution afforded the (30S)-hydroxyazide 12b
(263 mg, 39.8%): mp 106–108 °C (from methanol–
23
D
1
water); ½aŠ ¼ À52:0 (c 1, CHCl3); H NMR (295 K,
DMSO-d6): d 7.25–6.74 (8H, aromatics), 6.54 (2H, d,
J ¼ 7:4, aromatics), 5.89 (1H, d, J ¼ 2:7, 6-H), 5.05
(1H, dd, J ¼ 8:6 and 5.4, 3-H), 4.99 (1H, d, J ¼ 2:6, 5-
H), 3.91 (1H, m, 30-H), 3.37 (1H, dd, J ¼ 12:3 and 3.8,
40-Ha), 3.31 (1H, dd, J ¼ 12:3 and 6.8, 40-Hb), 2.31 (1H,
m, 20-Ha), 2.07 (1H, m, 20-Hb), 1.80 (2H, m, 10-H2), 1.09
[9H, s, C(CH3)3]; ESI-MS m=z (relative intensity): 955.1
(51, M+M+Naþ), 489.2 (100, M+Naþ). Anal. Calcd for
C25H30N4O5: C, 64.36; H, 6.48; N, 12,01. Found: C,
64.52; H, 6.34; N, 11.87.
4.4. tert-Butyl (3S,5S,6R)-3-[(3R)-3,4-epoxybutyl]-2-oxo-
5,6-diphenyl-1,4-oxazinane-4-carboxylate 11a and tert-
butyl (3S,5S,6R)-3-[(3S)-3,4-epoxybutyl]-2-oxo-5,6-di-
phenyl-1,4-oxazinane-4-carboxylate 11b
To a solution of the homoallyloxazinone 10 ( 1 g,
2.45 mmol) and 3-chloroperbenzoic acid (1.02 g, 50%,
2.95 mmol) in 1,2-dichloroethane (60 mL), a buffered
phosphate solution (120 mL, pH ¼ 7) was added and the
mixture was shaken for 12 h at room temperature. At
this time the organic phase was separated and worked
up to afford a crude residue, which was chromato-
graphed (eluting with hexane–AcOEt 75:25) to afford an
unseparable mixture of the epoxides 11a and 11b
4.6. (2S,5R)-5-Hydroxylysine monohydrochloride 1
The hydroxyazide 12a (150 mg; 0.32 mmol) was dis-
solved in CF3COOH–H2O (5 mL; 95:5; v/v) and the

P. Allevi, M. Anastasia / Tetrahedron: Asymmetry 15 (2004) 2091–2096
2095
solution was stirred for 1 h at room temperature. At this
time, a solution of CH3OH–H2O–HCl (8:3:1; v/v/v,
120 mL) was added and the resulting solution was
hydrogenated at room temperature for 24 h at 25 °C, in
the presence of Pd on carbon (80 mg, 10%). Filtration of
the catalyst through Celite, evaporation of the solvent
afforded a residue, which was dissolved in water
(1.5 mL) and the pH adjusted to 6.5–7.0. The addition of
EtOH and the storage at 0 °C effected the precipitation
of (2S,5R)-5-hydroxylysine 1 as the monohydrochloride
Further elution affords the iodohydrin 13b (600 mg,
23
1
47%); mp 155–156 °C; ½aŠ ¼ À44:7 (c 1, CHCl3); H
D
NMR (295 K, DMSO-d6): d 7.27–6.97 (8H, aromatics),
6.55 (2H, d, J ¼ 7:5, aromatics), 5.92 (1H, d, J ¼ 2:8, 6-
H), 5.06 (1H, dd, J ¼ 9:0 and 5.6, 3-H), 5.00 (1H, d,
J ¼ 2:8, 5-H), 3.68 (1H, m, 30-H), 3.42 (1H, dd, J ¼ 9:8
and 3.5, 40-Ha), 3.31 (1H, dd, J ¼ 9:8 and 6.3, 40-Hb),
2.59 (1H, br s, OH), 2.35 (1H, m, 20-Ha), 2.07 (1H, m, 20-
Hb), 1.95–1.84 (2H, overlapping, 10-Ha and H10-Hb),
1.09 [9H, s, C(CH3)3]. Anal. Calcd for C25H30INO5: C,
54.45; H, 5.48; N, 2.54. Found: C, 54.38; H, 5.32; N,
2.55.
(56.0 mg, 88%): ½aŠ ¼ þ15:0 (c 1, HCl 6 M), [lit.11c
D
1
½aŠ ¼ þ15:2 (c 2)]; H NMR (D2O): d 3.69 (1H, m, 5-
D
H), 3.59 (1H, dd, J ¼ 6:1, 6.1, 2-H), 2.97 (1H, dd,
J ¼ 13:3, 3.1, 6-Ha), 2.73 (1H, dd, J ¼ 13:3, 9.6, 6-Hb),
1.87 (1H, m, 3-Ha), 1.72 (1H, m, 3-Hb), 1.45–1.38 (2H,
overlapping, 4-H2); 13C NMR (D2O): d 175.37 (C-1),
68.27 (C-5), 55.43 (C-2), 45.35 (C-6), 30.56 (C-4), 27.59
(C-3). Anal. Calcd for C6H15ClN2O3: C, 36.28; H, 7.61;
N, 14.10. Found: C, 36.35; H, 7.69; N, 14.08.
4.9. Preparation of tert-butyl (3S,5S,6R)-3-[(3R)-4-azido-
3-hydroxybutyl]-2-oxo-5,6-diphenyl-1,4-oxazinane-4-carb-
oxylate 12a and tert-butyl (3S,5S,6R)-3-[(3S)-4-azido-3-
hydroxybutyl]-2-oxo-5,6-diphenyl-1,4-oxazinane-4-carb-
oxylate 12b from the analogues iodohydrins 13a and 13b
Each iodohydrin 13a and 13b (100 mg; 0.18 mmol) was
dissolved in DMF (1 mL) and treated with NaN3
(23.30 mg; 0.36 mmol) at room temperature for 12 h.
Then the reaction mixture was poured into ice cold
water and extracted with AcOEt to afford, after usual
work-up, the appropriate crystalline hydroxyazide. In
particular, starting from the iodohydrin 13a, the azide
4.7. (2S,5S)-5-Hydroxylysine monohydrochloride 2
The hydroxyazide 12b (150 mg; 0.32 mmol) was dis-
solved in CF3COOH–H2O (5 mL; 95:5; v/v) and reacted
as described for the isomer 12a to afford (2S,5S)-5-
hydroxylysine monohydrochloride 2 (49.2 mg, 78%):
½aŠ ¼ þ25:5 (c 1, HCl 6 M) [lit.11c ½aŠ ¼ þ25:8 (c 2)];
12a was obtained (68 mg, 81%); mp 109–111 °C (from
D
D
23
1H NMR (D2O): d 3.68 (1H, m, 5-H), 3.56 (1H, dd,
J ¼ 5:7, 5.7, 2-H), 2.96 (1H, dd, J ¼ 13:1, 1.7, 6-Ha),
2.73 (1H, dd, J ¼ 13:1, 10.0, 6-Hb), 1.84 (1H, m, 3-Ha),
1.73 (1H, m, 3-Hb), 1.49 (1H, m, 4-Ha), 1.33 (1H, m, 4-
Hb); 13C NMR (D2O): d 175.38 (C-1), 68.16 (C-5), 55.47
(C-2), 45.35 (C-6), 30.64 (C-4), 27.59 (C-3). Anal. Calcd
for C6H15ClN2O3: C, 36.28; H, 7.61; N, 14.10. Found:
C, 36.18; H, 7.45; N, 14.23.
methanol–water); ½aŠ ¼ À56:2 (c 1, CHCl3); identical
D
in all respect with that described above. Starting from
the iodohydrin 13b, the azide 12b was obtained (70 mg,
83%); mp 106–108 °C (from methanol–water);
23
½aŠ ¼ À51:4 (c 1, CHCl3); identical in all respect with
D
that described above.
Acknowledgements
This work was supported financially by Italian MIUR
ꢀ
(Ministero dell’Istruzione, dell’Universita e della Ric-
erca).
4.8. tert-Butyl (3S,5S,6R)-3-[(3R)-3-hydroxy-4-iodobutyl]-
2-oxo-5,6-diphenyl-1,4-oxazinane-4-carboxylate 13a and
tert-butyl (3S,5S,6R)-3-[(3S)-3-hydroxy-4-iodobutyl]-2-
oxo-5,6-diphenyl-1,4-oxazinane-4-carboxylate 13b
References and notes
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at room temperature. After 1 h the solution was poured
in a cold aqueous solution of NaHCO3 and extracted
with ethyl acetate. After usual work-up, the crude resi-
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23
D
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