A chiron approach towards the synthesis of 3-hydroxy lysine and its derivatives

Article abstract of DOI:10.1016/j.bmc.2013.02.013

A general and efficient route towards the synthesis of three derivatives of structurally and functionally important amino acid, lysine is reported. Chemoselective reduction of aldehydic functionality in C-3-azido conjugated aldehyde 4, under Luche condition, is the key step in the synthetic sequence. The lysine derivative, (2S,3R)-2,6-diazido-3-hydroxy-hex-4-ene-oic acid 9 could be used to prepare switch peptide using Staudinger reaction, while the unprotected (2S,3R)-2,6-diamino-3-hydroxy-hexanoic acid hydrochloride 10 is a proven reaction intermediate towards the synthesis of natural product (-)-Balanol.

Full text of DOI:10.1016/j.bmc.2013.02.013

Accepted Manuscript
A Chiron Approach Towards the Synthesis of 3-Hydroxy Lysine and Its Deriv‐
atives
K.S. Ajish Kumar
PII:
S0968-0896(13)00137-5
DOI:
http://dx.doi.org/10.1016/j.bmc.2013.02.013
BMC 10608
Reference:
To appear in:
Bioorganic & Medicinal Chemistry
Please cite this article as: Ajish Kumar, K.S., A Chiron Approach Towards the Synthesis of 3-Hydroxy Lysine and
Its Derivatives, Bioorganic & Medicinal Chemistry (2013), doi: http://dx.doi.org/10.1016/j.bmc.2013.02.013
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A Chiron Approach Towards the Synthesis of 3-Hydroxy Lysine and Its Derivatives
K. S. Ajish Kumar*
Bio-organic Division, Bhabha Atomic Research Centre,
Trombay, Mumbai- 400085
Email: ajish@barc.gov.in
Abstract
A general and efficient route towards the synthesis of three derivatives of structurally and
functionally important amino acid, lysine is reported. Chemoselective reduction of aldehydic
functionality in C-3-azido conjugated aldehyde 4, under Luche condition, is the key step in
the synthetic sequence. The lysine derivative, (2S,3R)-2,6-diazido-3-hydroxy-hex-4-ene-oic
acid 9 could be used to prepare switch peptide using Staudinger reaction, while the
unprotected 3-hydroxy lysine 10 is a proven reaction intermediate towards the synthesis of
natural product (−)-Balanol.
1

Introduction
Synthesis of modified amino acids and its application in the construction of proteins or
molecules of biological importance, has been the subject of interest for last few decades.1
Ever since the discovery of native chemical ligation (NCL),2 wherein, unmodified amide
bonds are constructed in aqueous conditions, it is possible to synthesize peptides with few
tons of amino acid residues having modification at a specific site. The ability to obtain
peptides/proteins in workable quantities, as homogeneous and pure product, is the biggest
gain of this unique method. Considering the importance of modified amino acids, which is
also an important tool in synthesis and study of lantibiotics3 there has been particular interest
in the synthesis, biosynthesis, and activity studies of such amino acids.4 Among the unnatural
amino acids, the side chain modified with hydroxy derivative have received considerable
attention (Figure 1). Some of the commercially available hydroxy incorporated amino acids
include, 3-hydroxy derivatives of phenylalanine 1a, leucine 1b, valine 1c, lysine 1d and 4-
hydroxy derivatives of glutamine 2a, valine 2b, and lysine 2c. In addition to 3- and 4-
hydroxy lysines, 1d/2c, 5-hydroxy lysine, 2d is well known and is used for various
purposes.5 Recently, two different groups6 independently employed this amino acid or its
masked derivative as the starting material for the synthesis of δ-mercaptolysine, an amino
acid used for isopeptide chemical ligation (ICL).7 In NCL, for cysteine free ligations, the
presence of suitably positioned sulphydryl moiety in the amino acid side chain is one of the
criteria to be fulfilled. The above mentioned hydroxy amino acids, not only serve to
incorporate interesting modification in peptides and proteins, but also it could be utilized as
2

an important starting material for the synthesis of corresponding mercapto derivatives, a tool
for NCL.8
R
R1 2OH
R1
R2
R3
OH
H2N
OH
H2N
O
O
1a, R1 = Ph, R2 = H
1b, R1 = CH(CH3)2, R2 = H
1c, R1, R2 = CH3
2a, R1 = CONH2, R2 = H, R3 = OH
2b, R1 = H, R2 = CH3, R3 = OH
2c, R1 = CH2CH2NH2, R2 = H, R3 = OH
2d, R1 = CH(OH)CH2NH2, R2 = R3 = H
1d, R1 = CH2CH2CH2NH2, R2 = H
O
OH
HN
O
O
N
O
OH
HO
COOH
(−)-Balanol
OH
Figure 1: Hydroxy amino acids and (−)-Balanol
In addition, some of these amino acids are fragments of natural products for eg. stereo
isomers of 3-hydroxy leucine. (2S,3S)-3-hydroxy leucine, is an important amino acid present
in several peptide antibiotics like, azinthricin,9 A g3586c,10 and telomycin11 while, isomer
(2R,3S)-3-hydroxy leucine is present in lactacystin.12 Another isomer of leucine, (2S,3R)-3-
hydroxy leucine, is found to be a constituent of a macrocyclic peptide lactone antibiotic
lysobactin13 isolated from fermentations of Lysobacter Sp. ATCC 53042. 3-Hydroxy lysine,
is an interesting residue that has got wide applicability as protein marker for studying radical
induced protein oxidation.14 3-Hydroxy lysine is also as an important reaction intermediate
towards the synthesis of natural product (−)-Balanol,15 a potent protein kinase C (PKC)
inhibitor which is involved in cell growth, metabolism and differentiation.16 In short, these
3

unnatural hydroxy amino acids are either present in natural product or could easily be
transformed into moieties that are present in natural products/could be used in protein
synthesis. Citing the multiple application of 3-hydroxy lysine 1d, we here report, the
synthesis of different derivatives of this amino acid based on chiron approach, with D-
glucose as starting material. The synthetic strategy is planned, taking into account of the
multiple nucleophilic functionalities in hydroxy lysine, so that we can perform orthogonal
protection of choice at specific functional group required for Boc/Fmoc strategy. With this
objective, as a preliminary study, synthesis of (2S,3R)-2,6-diazido-3-hydroxy-hex-4-ene-oic
acid 9, (2S,3R)-2,6-diamino-3-hydroxy-hexanoic acid hydrochloride 10, and, (2S,3R)-6-
azido-2-N-benzyloxy carbonyl-3-O-formylo-hexanoic acid 13, is reported.
Results and Discussion
In the synthesis, as shown in scheme 1, D-glucose was transformed to azido aldehyde 3 as
reported by Tronchet et.al.17 The Wittig olefination of aldehyde
3
with
(Triphenylphosphoranylidene) acetaldehyde afforded the conjugated aldehyde 4 as the major
product in 79% yield. The aldehyde 4 possess multiple reaction sites sensitive to reduction in
conjugated olefin, azide, and aldehyde, therefore the selective reduction of aldehyde group is
required to incorporate the desired C-6 amino functionality of lysine. This key step of
chemoselective reduction of aldehydic functionality in C-3 azido conjugated aldehyde 4 was
achieved under Luche condition18 to give C-3-azido allyl alcohol 5. Subsequently, activation
of allylic hydroxy group in 5 using mesyl chloride and refluxing the resultant mesylate with
sodium azide in DMF yielded allylic azide 6 in 78% yield, over two steps. In order to
generate the required carboxylic acid functionality at C-1 position of lysine, the 1,2-acetonide
4

group in allylic azide 6 was deprotected using TFA-H2O (3:2) and the resultant hemiacetal
was subjected to periodate cleavage to yield azido aldehyde 7, that on oxidation using
NaClO2, NaH2PO4, and 30% H2O2 afforded the highly functionalized lysine derivative 8 in
68% yield (over three steps). The product 8 could serve as an interesting conformationally
constrained lysine, to study the folding of protein as well as in peptidomimetics
design/foldamers.19
O
O
(a)
(b)
O
O
H
H
D-glucose
O
O
O
O
N3
N3
3
4
OH
N3
O
O
(d)
(e)
(c)
N3
O
O
O
O
N3
N3
5
6
N3
NH3.Cl
OCHO
(g)
OH
(h)
RO
N3
HO
Cl.H3N
10
(−)-Balanol
H
OH
N3
O
O
O
7
8, R = CHO
(f)
9, R = H
Scheme 1: Synthesis of β-hydroxy lysine: (a) ref 17; (b) PPh3=CHCHO, CH2Cl2,
0 oC to 30 oC, 12 h; (c) NaBH4, CeCl3.7H2O, THF, -40 oC, 30 min; (d) i) MsCl,
TEA, CH2Cl2, 0 oC to 10 oC, 30 min, ii) NaN3, DMF, 80 oC, 1. 5 h; (e) i) TFA-
H2O (3:2), 0 oC-20 oC, 6 h, ii) NaIO4, acetone-water (4:1), 0 oC to 15 oC, 30 min,
iii) NaClO2, NaH2PO4, 30% H2O2, 0 oC to15 oC, 10 h; (f) LiOH (0.3 M), THF-
H2O (4:1), 0 oC, 1.5 h; (g) H2 (80 Psi), 10% Pd-C, MeOH-HCl, 25 oC, 12 h; (h)
ref 15.
To avoid the possible migration of formyl group during the conversion of azide 8 to amine 10
during hydrogenation it was thought to unmask the C-3 hydroxy group. Thus, Saponification
5

of amino acid 8 in the presence of 0.3 M LiOH in THF furnished (2S,3R)-2,6-diazido-3-
hydroxy-hex-4-ene-oic acid 9 in quantitative yield. Amino acid 9 is an interesting derivative
of lysine that could be used in the synthesis of switch peptide20 using Staudinger reaction.
Finally, hydrogenation of 9 (10% Pd-C, 80 psi) in methanol for 12 h at room temperature,
followed by purification, yielded hydroxy lysine 10 as a white solid in 59% yield.21 The
spectral and analytical data of 10 were in agreement with that reported, [observed
[α]D25 +17.41 (c 1.87, CH3OH), reported [α]D25 +16.90 (c 1.83, CH3OH)].21a Lampe et. al.
reported the synthesis of (−)-Balanol from amino acid 10 by transforming it to suitably
protected azepane.15 The structural confirmation of amino acid 10 also fixes the structural
integrity of the amino acid 8.
For Boc/Fmoc strategies of peptide synthesis the side chain functionalities of the
hydroxyl lysine should be orthogonally protected to make it useful for solid phase peptide
synthesis (SPPS). Hence, the utility of present strategy in the synthesis of orthogonally
protected lysine was also explored; as a proof of this a model amino acid 13 was targeted.
Thus, as shown in Scheme 2, the C-3-azido-allylic alcohol 5 was subjected to hydrogenation,
thereafter insitu protection of the resultant amine with benzyloxycarbonyl group afforded N-
protected amino alcohol 11, in 78% yield. The C-7 hydroxy functionality in 11 was
converted to azide 12, through mesylate pathway, in 76% yield.
6

OH
N3
(b)
O
O
(a)
5
O
O
O
CbzHN
O
CbzHN
11
12
N3
N3
OCHO
H
(c)
OHCO
CbzHN
CbzHN
OH
O
O
13
Scheme 2: Synthesis of orthogonally protected β-hydroxy lysine: (a) i) H2, 10%
Pd-C, MeOH-HCl, 25 oC, 12 h, ii) CbzCl, NaHCO3, MeOH-H2O (5:2), 5 h; (b) i)
MsCl, TEA, CH2Cl2, 0 oC to 10 oC, 30 min, ii) NaN3, DMF, 80 oC, 2 h; (c) i) TFA-
H2O (3:2), 0 oC-20 oC, 6 h, ii) NaIO4, acetone-water (4:1), 0 oC to 15 oC, 30 min,
iii) NaClO2, NaH2PO4, 30% H2O2, 0 oC to15 oC, 10 h.
Finally, treatment of 12 with TFA-H2O (3:2) yielded corresponding hemiacetal that on
metaperiodate cleavage, followed by oxidation, vide supra, yielded the required amino acid
13 in 69 % yield over 3 steps from azide 12. Similarly, one can incorporate Fmoc group in
the place of benzyloxy carbonyl group at the C-2 amine to make it a useful precursor for the
synthesis of amino acid derivative for Fmoc-SPPS. The lysine derivative 13 is suitably
protected to serve as an interesting intermediate towards the synthesis of (−)-Balanol.15
Conclusions
In summary, an efficient route towards the synthesis of three derivatives of hydroxy
functionalized lysine is reported, which has got wide range of application in the synthesis and
study of peptides/proteins and natural products. Work is in progress to synthesize other
possible orthogonally protected lysines, useful for both Boc and Fmoc SPPS, and also its
7

mercapto variant, useful for peptide ligation, which will be reported elsewhere. Hydroxy
lysine 10/13 can easily be transformed to biologically relevant natural product (−)-Balanol,
which completes its formal synthesis.
Experimental
General.
The IR spectra were recorded as a thin film (liquids) or as KBr pellets (solids) with a
1
13
Shimadzu FTIR-8400 spectrometer. The H (200 MHz) and C (50 MHz) NMR spectra,
were recorded with a Brooker Oxford instrument in CDCl3 or D2O. The elemental analyzes
were carried out with a Thermo-Electron Corporation CHNS analyzer model Flash-EA 1112.
The optical rotations were measured using a Jasco P1020 polarimeter. The thin layer
chromatography was performed on pre-coated plates (0.25 mm, silica gel 60 F254), and the
spots were visualized by UV light or spraying with 3.5% solution of 2,4-
dinitrophenylhydrazine in ethanol/H2SO4 or with basic aqueous KMnO4 solution followed by
heating.
3-Azido-1,2-O-isopropylidene-3,5,6,7-tetradeoxy-α-D-xylo-5-ene-hept-7-dialdose (4).
To a stirred solution of the azido aldehyde 3 (2.00 g, 9.38 mmol) in CH2Cl2 (60 mL) was
o
added PPh3=CHCHO (4.18 g, 12.19 mmol) at 0 ºC to 30 C for 12 h. After completion of
reaction (cf.TLC), the reaction mixture was evaporated in vacuo to give a residue, which on
column chromatography afforded 4 (1.77 g, 79%) as a thick liquid. Rf = 0.48 (EtOAc/hexane,
25
2:3); [α]D −23.5 (c 1.93, CHCl3); IR: 2104, 1727 cm-1; 1H NMR (200 MHz, CDCl3): δ 1.27
8

(s, 3H), 1.44 (s, 3H), 3.98 (d, J = 3.4 Hz, 1H), 4.67 (d, J = 3.7 Hz, 1H), 5.01-4.84 (m, 1H),
5.91 (d, J = 3.7 Hz, 1H), 6.38 (ddd, J = 15.8, 7.7, 1.6 Hz, 1H), 6.75 (dd, J = 15.8, 4.5 Hz,
13
1H), 9.54 (d, J = 7.7 Hz, 1H); C NMR (50 MHz, CDCl3): δ 26.4, 26.8, 67.7, 79.0, 83.9,
104.9, 112.8, 134.2, 148.9, 193.1. Anal.Calcd. for C10H13N3O4: C, 50.21; H, 5.48; N, 17.56.
Found: C, 50.24; H, 5.52; N, 17.64.
3-Azido-1,2-O-isopropylidene-7-hydroxy-3,5,6-trideoxy-α-D-xylo-hept-5-ene-furanose
(5).
o
To a solution of aldehyde 4 (1.10 g, 4.60 mmol) in THF (25 mL) at 30 C was added
CeCl3.7H2O (0.08 g, 2.30 mmol) and stirred for 10 min at same temperature. The reaction
mixture was cooled to −40 oC and a solution of NaBH4 (0.17 g, 4.60 mmol) in water (3 mL)
was added in intervals for a peroid of 20 min. After completion of reaction (cf.TLC) the
reaction mixture was decomposed using 1 N HCl (2 mL) and concentrated in vacuo, and
extracted with EtOAc (3 × 15 mL). The organic extract was washed with H2O (2 × 10 mL)
and brine (1 × 5 mL), and dried. Concentration of solvent followed by column
chromatography of the residue furnished 5 as a colourless thick liquid (0.94 g, 85%). Rf =
25
1
0.59 (EtOAc/hexane, 1:1); [α]D −65.5 (c 1.95, CHCl3); IR: 2106, 3410 (broad) cm−1; H
NMR (200 MHz, CDCl3): δ 1.30 (s, 3H), 1.49 (s, 3H), 2.00 (bs, exchangeable with D2O,
1H), 3.83 (d, J = 3.2 Hz, 1H), 4.18 (d, J = 4.8 Hz, 2H), 4.63 (d, J = 3.7 Hz, 1H), 4.73 (dd, J =
6.4, 3.1 Hz, 1H), 5.77 (ddt, J = 15.6, 6.5, 1.5 Hz, 1H), 5.89 (d, J = 3.7 Hz, 1H), 6.11 (dtd, J =
13
15.6, 4.9, 0.8 Hz, 1H); C NMR (50 MHz, CDCl3): δ 26.8, 27.2, 63.2, 68.5, 80.5, 84.3,
9

105.0, 112.7, 124.2, 135.9. Anal. calcd. for C10H15N3O4: C, 49.79; H, 6.27; N, 17.42. Found:
C, 49.81; H, 6.31; N, 17.49.
3,7-Diazido-1,2-O-isopropylidene-3,5,6,7-tetradeoxy-α-D-xylo-hept-5-ene-furanose (6).
To an ice cooled solution of 5 (1.00 g, 4.14 mmol) in CH2Cl2 (40 mL) was added triethyl
amine (0.75 mL, 5.39 mmol) followed by dropwise addition of methane sulphonyl chloride
(0.35 mL, 4.55 mmol), stirred for 15 min at the same temperature, brought to room
temperature, stirred for additional 10 min. The reaction mixture was diluted with cold water,
and extracted with CH2Cl2 (3 x 15 mL). The organic layer was dried over Na2SO4, and was
purified by flash column chromatography (15% EtOAc/hexane) to afford the corresponding
mesylate. To the mesylate dissolved in DMF was added sodium azide (0.67 g, 10.35 mmol)
o
and heated at 80 C for 1.5 h. After completion of reaction (cf.TLC), DMF was removed
under vacuo, and the residue was extracted with EtOAc (3 x 15 mL). The combined organic
layer was dried over Na2SO4, concentrated and purified using column chromatography to
give azide (6) as thick liquid (0.86 g, 78% over two steps); Rf = 0.50 (EtOAc/hexane, 3:7);
25
1
[α]D −30.15 (c 1.97, CHCl3); IR: 2102 cm−1; H NMR (200 MHz, CDCl3): δ 1.31 (s, 3H),
1.48 (s, 3H), 3.80-3.86 (m, 3H), 4.65 (d, J = 3.7 Hz, 1H), 4.74 (dd, J = 5.2, 3.6 Hz, 1H), 5.91
(d, J = 3.5 Hz, 1H), 5.75-6.05 (m, 2H); 13C NMR (50 MHz, CDCl3): δ 26.8, 27.3, 52.8, 68.4,
80.1, 84.4, 105.1, 112.9, 128.3, 129.4. Anal. calcd. for C10H14N6O3: C, 45.11; H, 5.30; N,
31.56. Found: C, 45.13; H, 5.27; N, 31.66.
(2S,3R)-2,6-diazido-3-O-formylo-hex-4-ene-oic acid (8).
10

A solution of 6 (0.45 g, 1.69 mmol) in TFA-H2O (7.00 mL, 3:2) was stirred at 0 ºC to 30 oC
for 6 h. TFA was removed azeotropically with toluene in vacuo to afford the crude
hemiacetal, was purified using flash column chromatography to afford hemi acetal (0.34 g,
89%). To the hemiacetal solution (0.34 g, 1.50 mmol) in acetone/water (10.00 mL, 9:1) at 0
ºC was added NaIO4 (0.36 g, 1.65 mmol). After stirring for 30 min, excess NaIO4 was
decomposed with ethylene glycol (0.10 mL), the mixture concentrated in vacuo, and the
residue was extracted with CHCl3 (3 × 10 mL) to get the crude α-aminal (0.38 g) 7 as a thick
liquid.
To a cooled (0 ºC) and stirred solution of α-aminal in CH3CN (20 mL) was added a solution
of NaH2PO4 (0.05 g, 0.30 mmol) in H2O (2 mL) and 30% H2O2 (0.22 mL, 1.65 mmol). The
mixture was cooled to 0 ºC, and NaClO2 (0.22 g, 2.40 mmol) in H2O (5 mL) was added
dropwise over a period of 0.5 h. The reaction mixture was stirred at 15 ºC and monitored
from the evolution of gas with a bubbler connected to the apparatus. After 10 h, the reaction
was decomposed by addition of a small amount of Na2SO4 (0.25 g) and extracted with
EtOAc (3 × 10 mL). Evaporation of solvent and column purification with EtOH/CHCl3 (5%)
gave 8 (0.27 g, 68% from 6) as a sticky gum. Rf = 0.30 (EtOAc); [α]D25−56.30 (c 1.89,
CHCl3); IR: 3352, 2105, 1737 cm-1; 1H NMR (200 MHz, CDCl3): δ 3.85 (d, J = 5.0 Hz, 2H),
4.04 (d, J = 3.2 Hz, 1H), 5.85 (s, 1H), 5.80-6.17 (m, 2H), 7.80-8.01 (bs, exchangeable with
D2O, 1H), 8.10 (s, 1H); 13C NMR (50 MHz, CDCl3): δ 52.2, 64.5, 73.4, 127.8, 131.3, 160.1,
172.4. Anal. calcd. for C7H8N6O4: C, 35.01; H, 3.36; N, 34.99. Found: C, 34.99; H, 3.39; N,
35.08.
11

(2S,3R)-2,6-diazido-3-hydroxy-hex-4-ene-oic acid (9).
o
A solution of 8 (0.13 g, 0.54 mmol) in THF at 0 C was hydrolyzed with 0.3 M LiOH (0.09
g, 2.16 mmol), LiOH solution was added in small portions over a period of 30 min, after 1h
of reaction at same temperature, sat. citric acid solution (4 mL) was added and extracted
using EtOAc (4 x 10 mL). The extract was dried over sodium sulphate, concentrated, and
purified using column chromatography to afford 9 as a thick liquid (0.11 g, 93%).
[α]D25−0.12 (c 1.00, CHCl3); IR: 3323, 2108, 1745 cm-1; 1H NMR (200 MHz, CDCl3): δ 3.84
(d, J = 4.3 Hz, 2H), 4.06 (d, J = 2.8 Hz, 1H), 4.76 (t, J = 3.1 Hz, 1H), 5.85-5.92 (m, 2H), 7.06
13
(bs, 2H, exchangeable with D2O); C NMR (50 MHz, CDCl3): δ 52.5, 66.5, 72.9, 127.9,
132.5, 173.1; Anal. Calcd. for C6H8N6O3: C, 33.97; H, 3.80; N, 39.61. Found: C, 33.96; H,
3.85; N, 39.68.
(2S,3R)-2,6-diamino-3-hydroxy-hexanoic acid. 2HCl (10).
The formyl free product 9 (0.10 g, 0.41 mmol) and 10% Pd/C (0.045 g) in MeOH: HCl (4:1
mL) was stirred under a H2 atmosphere at 80 psi for 12 h at 25 ºC. The catalyst was filtered
through a pad of Celite 545. The filterate was contentrated, washed using EtOAc and purified
using coloumn chromatography using (5% MeOH-H2O) to afford 10 as a white solid (0.065
o
o
25
g, 59%); mp 187-191 C [reported 188-192 C]20; [α]D +17.41 (c 1.87, CH3OH), reported
+16.90 (c 1.83, CH3OH)20; IR: 3350, 1733 cm-1; 1H NMR (200 MHz, D2O): δ 1.59-1.95 (m,
13
4H), 3.07 (t, J = 6.9 Hz, 2H), 4.06 (s, 1H), 4.14-4.34 (m, 1H); C NMR (50 MHz, D2O):
δ 23.3, 29.9, 38.9, 57.7, 68.4, 170.5. Anal. Calcd. for C6H16Cl2N2O3: C, 30.65; H, 6.86; N,
12

11.92. Found: C, 30.63; H, 6.89; N, 12.02.; ESI-MS: Calcd. for [C6H13N2O3 + 2Na]+: 207.06
Da, Observed: 206.98 Da.
3-N-benzyloxycarbonyl-7-hydroxy-1,2-O-isopropylidene-3,5,6-trideoxy-α-D-xylo-hept-
furanose (11).
To a stirred solution of azido alcohol 5 (1.75 g, 7.25 mmol) and 10% Pd/C (0.17 g) in MeOH
(10 mL) was stirred under a H2 (80 psi) atmosphere for 12 h at 25 ºC. The catalyst was
filtered through a pad of Celite 545. The filterate was contentrated and redissolved in MeOH-
H2O (15 mL, 4:1), and cooled to 0 oC, to it NaHCO3 (1.71 g, 20.44 mmol) and CbzCl (60%
solution in toluene) (2.00 mL, 14.50 mmol), was added sequentially and stirred to room
temperature for 5 h. After completion of reaction on tlc, reaction mixture was concentrated
and extracted using EtOAc (3 x 10 mL). The combined organic layer was kept over
anhydrous Na2SO4, concentrated under vacuo, and purified using column chromatography to
25
afford 11 as a thick liquid. (1.98 g, 78%). Rf = 0.40 (EtOAc/hexane, 3:2); [α]D −12.7 (c
1.15, CHCl3); IR: 3326, 1690 cm-1; 1H NMR (200 MHz, CDCl3) δ 1.24 (s, 3H), 1.48 (s, 3H),
1.50-1.70 (m, 4H), 2.15 (s, 1H, exchangeable with D2O), 3.60 (s, 2H), 4.07-4.29 (m, 2H),
4.48 (d, J = 3.7 Hz, 1H), 5.05 (s, 3H, one exchangeable with D2O), 5.75 (d, J = 3.8 Hz, 1H),
13
7.33 (s, 5H); C NMR (50 MHz, CDCl3): δ 24.9, 26.4, 26.7, 27.5, 58.5, 63.0, 67.9, 79.1,
85.3, 104.5, 112.4, 128.9, 129.0, 129.1, 136.6, 156.5. Anal. Calcd for C18H25NO6: C, 61.52;
H, 7.17; N, 3.99. Found: C, 61.55; H, 7.22; N, 4.10; ESI-MS: Calcd for.[C18H25NO6 + Na]+:
374.14 Da, Observed: 373.94 Da.
13

7-azido-3-N-benzyloxy carbonyl-1,2-O-isopropylidene-3,5,6,7-tetradeoxy-α-D-xylo-hept-
furanose (12).
To an ice cooled solution of 11 (1.53 g, 4.35 mmol) in CH2Cl2 (40 mL) was added triethyl
amine (0.79 mL, 5.66 mmol) followed by dropwise addition of methane sulphonyl chloride
(0.37 mL, 4.78 mmol), stirred for 15 min at the same temperature, brought to room
temperature, stirred for additional 10 min. The reaction mixture was diluted with cold water,
and extracted with CH2Cl2 (3 x 15 mL). The organic layer was washed sequentially with 1N
HCl (15 mL) and with brine (15 mL), dried over Na2SO4, and was purified by flash column
chromatography (20% EtOAc/hexane) to afford corresponding mesylate. To the mesylate
o
solution in DMF (7 mL) was added sodium azide (0.70 g, 10.87 mmol) and heated at 80 C
for 2 h. After completion of reaction (cf.TLC), DMF was removed under vacuo, and the
residue was extracted with EtOAc (3 x 15 mL). The combined organic layer was dried over
Na2SO4, concentrated and purified using column chromatography (10% EtOAc/hexane) to
give azide 12 as a thick liquid (1.24 g, 76%); Rf = 0.40 (EtOAc/hexane, 3:7); [α]D25 −9.80 (c
1.60, CHCl3); IR: 2109, 1695 cm-1; 1H NMR (200 MHz, CDCl3): δ 1.26 (s, 3H), 1.50 (s, 3H),
1.57-1.83 (m, 4H), 3.26 (d, J = 5.5 Hz, 2H), 4.16 (d, J = 7.4 Hz, 2H), 4.49 (d, J = 3.8 Hz,
1H), 4.81 (d, J = 9.2 Hz, 1H, exchangeable with D2O), 5.10 (s, 2H), 5.76 (d, J = 3.8 Hz, 1H),
13
7.34 (s, 5H); C NMR (50 MHz, CDCl3): δ 25.3, 25.4, 26.8, 27.1, 51.9, 58.6, 67.9, 78.7,
85.3, 104.5, 112.5, 128.9, 129.1, 129.3, 136.7, 156.5. Anal. calcd. for C18H24N4O5: C, 57.44;
H, 6.43; N, 14.88. Found: C, 57.48; H, 6.48; N, 14.95. ESI-MS: Calcd. for [C18H24N4O5 +
Na]+: 399.15 Da, Observed: 399.04 Da.
14

(2S,3R)-6-azido-2-N-benzyloxy carbonyl-3-O-formylo-hexanoic acid (13).
The procedure was similar to that followed for synthesis of 8 from 6. After column
purification of the extract afforded 13 as a thick liquid (0.22 g, 69% from 0.35 g of 12). Rf =
0.30 (EtOAc); [α]D25+14.71 (c 1.75, CHCl3); IR: 3352, 1733 cm-1; H NMR (200 MHz,
1
CDCl3): δ 1.58-1.78 (m, 4H), 3.27 (t, J = 6.2 Hz, 2H), 4.64 (dd, J = 9.7, 1.6 Hz, 1H), 5.13 (s,
2H), 5.52 (t, J = 5.7 Hz, 1H), 5.63 (d, J = 9.7 Hz, 1H), 7.35 (s, 5H), 7.97 (s, 1H), 8.72 (bs,
13
1H, exchangeable with D2O); C NMR (50 MHz, CDCl3): δ 25.3, 29.1, 51.4, 56.6, 68.3,
73.7, 128.8, 129.1, 129.3, 136.5, 157.4, 160.8, 173.7. Anal.calcd. for C15H18N4O6: C, 51.43;
H, 5.18; N, 15.99. Found: C, 51.46; H, 5.23; N, 16.07; ESI-MS: Calcd. for [C15H18N4O6
+Na]+: 373.10 Da, Observed: 372.99 Da.
Acknowledgment
AKS is thankful to Prof. S Chattopadhyay, Head, Bio-Organic Division, BARC, for his
constant support and encouragement. AKS gratefully acknowledges BRNS-DAE (Mumbai,
INDIA) for the award of K. S. Krishnan Research Associateship.
15

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18

A Chiron Approach Towards the Synthesis of 3-Hydroxy Lysine and Its Derivatives
K. S. Ajish Kumar*
Bio-organic Division, Bhabha Atomic Research Centre,
Trombay, Mumbai- 400085
Email: ajish@barc.gov.in
N3
RO
OH
N3
OH
O
O
8, R = CHO
D
-glucose
9, R = H
O
O
N3
R2
5
R3O
R1HN
OH
O
10, R1 = H; R2 = NH2; R3 = H
13, R1 = Cbz; R2 = N3; R3 =CHO
19