Total synthesis of the acetyl derivatives of lyxo-(2R,3R,4R)- phytosphingosine and (-)-jaspine B

Article abstract of DOI:10.1016/j.tetasy.2012.04.009

The total synthesis of acetyl derivatives of lyxo-(2R,3R,4R)- phytosphingosine and (-)-jaspine B using a Grignard reaction on sugar-imine and a Wittig reaction as the key steps.

Full text of DOI:10.1016/j.tetasy.2012.04.009

Tetrahedron: Asymmetry 23 (2012) 564–569
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Tetrahedron: Asymmetry
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Total synthesis of the acetyl derivatives of lyxo-(2R,3R,4R)-phytosphingosine
and (ꢀ)-jaspine B
⇑
Ganipisetti Srinivas Rao, Bandari Chandrasekhar, Batchu Venkateswara Rao
Organic and Biomolecular Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500607, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The total synthesis of acetyl derivatives of lyxo-(2R,3R,4R)-phytosphingosine and (ꢀ)-jaspine B using a
Grignard reaction on sugar-imine and a Wittig reaction as the key steps.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 9 March 2012
Accepted 5 April 2012
Available online 18 May 2012
1. Introduction
moiety in the tetrahydrofuran ring, which may be a key structural
feature for its biological activity. Our group reported that (ꢀ)-
Sphingoids are the characteristic structural unit of sphingoli-
pids and are basically long-chain amino-diol and amino-triol bases.
Sphingoids are important membrane constituents and play an
important role in cell regulation as well as signal transduction.1
Furthermore, glycosphingolipids show important biological activi-
ties such as antitumor,2a antiviral,2b antifungal,2c and cytotoxic
properties.2d Phytosphingosines, one of the major classes of
sphingoids, have been isolated and identified either separately or
as parts of sphingolipids from plants,3a marine organisms,3b–c fun-
gi,3d yeasts,3e and even mammalian tissues3f–k of the kidney,3g li-
ver,3h uterus,3i intestine,3j and skin.3k Phytosphingosines are one
of the most important and common species of the naturally occur-
ring sphingoid bases.4 Phytosphingosines themselves have also
been found to be bioactive lipids. For example, ribo-phytosphingo-
sine 1 is a potential heat stress signal in yeast cells.5 It has also
been confirmed that various diastereomers of phytosphingosines
1–4 exhibit different activities and metabolisms (Fig. 1).1b,6
Much effort has been devoted toward the synthesis of these
molecules for their use in biological studies. All of the diastereo-
mers of the phytosphingosines have been synthesized since they
have shown noticeable variation in their bioactivity.7 However,
all lyxo-phytosphingosines 2 and 3 have attracted much less atten-
tion from the synthetic community.8
jaspine B 8 showed promising results on MCF7 cells maybe
because of the cis-configuration of its amino and hydroxy groups
(erythro configuration).12a It has also shown better activity com-
pared to the trans-configuration.
The novel structural features and interesting biological activi-
ties of pachastrissamine have prompted chemists to develop sev-
eral syntheses for jaspine B 5, its stereoisomers 6–9, and its
analogues.13,14 Our group published the first total synthesis of jas-
pine B 5 and its C2 epimer 6.15 We also reported the synthesis of
ent-4-epi-jaspine B 7 and (ꢀ)-jaspine B 8 and their biological activ-
ities in comparison to jaspine B 5,12a and also synthesised 3-epi-
jaspine B 9.12b Recently we developed a common strategy for the
synthesis of
-ribose,7s jaspine
-ascorbicacid.8i
In continuation of our efforts in the stereoselective synthesis of
D-ribo-phytosphingosine 1 and 2-epi-jaspine B 6 from
D
B
5
and -lyxo-phytosphingosine from
D
2
L
bioactive azasugars,16 and carbasugars17 by using Grignard addition
reactions on sugar-imines, we herein report the application of the
above strategy for the development of efficient and common meth-
ods for the synthesis of N,O,O,O-tetra-acetyl lyxo-(2R,3R,4R)-phyto-
sphingosine 10 and N,O-diacetyl-(ꢀ)-jaspine B 11. The starting
material for our approach was D-glucose, which is an inexpensive
sugar and possesses the desired chirality.
In 2002, pachastrissamine 5 (jaspine B) (Fig. 2), the first natu-
rally occurring anhydrophytosphingosine derivative, was isolated
from the Okinawan marine sponge Pachastrissa sp. by Higa et al.9
In 2003, Debitus et al. isolated the same compound from a different
marine sponge, Jaspis sp. and named it jaspine B 5.10 This marine
natural product exhibited high cytotoxic activity against various
tumor cell lines in vitro.9,10 Delgado et al. reported that the potency
of the cytotoxicity is dependent on the stereochemistry of the tet-
rahydrofuran moiety.11 Jaspine B 5 has an erythro-amino alcohol
The retro-synthetic analysis of 10 and 11 is depicted in
Scheme 1. Compound 12 is a common intermediate for the synthe-
sis of 10 and 11 and it can be obtained from compound 13 after
appropriate manipulation. The amino group can be introduced by
nucleophilic addition on sugar-imine 14 and the required lipid
chain can be added by a Wittig olefination. Sugar-imine 14 can
be obtained from D-glucose.
2. Results and discussions
⇑
Our synthesis of 10 and 11 started from 13, which can be
prepared from commercially available D-glucose using our earlier
Corresponding author. Tel./fax: +91 40 27193003.
E-mail address: venky@iict.res.in (B. Venkateswara Rao).
0957-4166/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetasy.2012.04.009

G. Srinivas Rao et al. / Tetrahedron: Asymmetry 23 (2012) 564–569
565
NH2 OH
NH2 OH
NH2 OH
OH
NH2 OH
HO
HO
HO
HO
C14H29
C14H29
C14H29
C14H29
OH
OH
OH
2
3
1
4
D-lyxo-PHS
L-lyxo-PHS
D-arabino-PHS
D-ribo-PHS
Figure 1. Structures of the phytophingosines.
H2N
OH
H2N
OH
H2N
OH
H2N
OH
H2N
OH
C14H29
C14H29
C14H29
C14H29
2-epi-jaspine B
C14H29
O
O
O
O
O
8
9
5
7
6
3-epi-jaspine B
jaspine B
ent-4-epi-jaspine B
(-)-jaspine B
Figure 2. Structures of jaspine B and its structural isomers.
Ac
NH
OAc
C14H29
AcO
OAc
NHBn
tetraacetyl lyxo-PHS 10
O
O
OBn
BnHN
+
C12H25
HO
AcHN
OAc
O
BnO
12
OH
13
C14H29
diacetyl (-) jaspine B 11
O
OH
O
NBn
BnO
HO
O
OH
OH
O
O
HO
14
D-glucose
Scheme 1. Retro-synthetic analysis of acetyl derivatives of
L
-lyxo-phytosphingosine 10 and (ꢀ)-jaspine B 11.
NBnCbz
NHBn
O
O
O
ref.16c
b
O
a
D-glucose
O
O
BnO
BnO
15 (92%)
O
O
O
NBn
NBn
BnO
NH
NBnCbz
O
O
HO
O
O
c
d
O
OH
OH
O
O
O
BnO
BnO
16 (94%)
17 (92%)
18 (80%)
O
Ac
OAc
BnHN
HO
OBn
OBn
NBn
f
g
C12H25
e
C12H25
O
AcO
C14H29
OAc
10 (85%)
OH
12 (85%)
OH
19 (90%)
Scheme 2. Synthesis of the acetyl derivative of lyxo-phytosphingosine 10: Reagents and conditions: (a) Cbz-Cl, NaHCO3, MeOH, 1 h; (b) (i) O3, CH2Cl2, ꢀ78 °C, 30 min then
DMS, ꢀ78 °C to rt, 30 min; (ii) NaBH4, MeOH, 1 h; (c) NaH, THF, 30 min; (d) TFA–H2O, 0 °C to rt, 4 h; (e) (i) NaIO4, MeOH, H2O, rt, 1 h, (ii) C13H27Ph3P+Brꢀ, n-BuLi, THF, 0 °C, 1 h;
(f) 4 M NaOH, EtOH, reflux, 6 h; (g) (i) H2, Pd/C, MeOH, 6 h, (ii) Ac2O, Et3N, CH2Cl2, 6 h.

566
G. Srinivas Rao et al. / Tetrahedron: Asymmetry 23 (2012) 564–569
Boc
BocHN
OH
AcHN
OAc
NH
OH
BnHN
OBn
b
a
c
HO
C12H25
HO
C14H29
C14H29
21 (86%)
C14H29
11 (94%)
O
O
OH
20 (86%)
OH
12
Scheme 3. Synthesis of diacetyl (ꢀ)-jaspine B 11: Reagents and conditions: (a) (i) H2, Pd/C, MeOH, 6 h, (ii) (Boc)2O, Et3N, CH2Cl2, 2 h; (b) TsCl, Et3N, DMAP, CH2Cl2; (c) (i) TFA,
CH2Cl2, 2 h; (ii) (Ac)2O, Et3N, CH2Cl2, 4 h.
procedure (Scheme 2).16c The allylamine 13 was treated with CbzCl
in the presence of NaHCO3 in dry MeOH to afford compound 15.
Oxidative cleavage of terminal double bond in 15 with O3 in CH2Cl2
at ꢀ78 °C produced the aldehyde, which upon treatment with
NaBH4 in dry MeOH gave 16 in 94% yield. In order to protect the
primary hydroxyl group, compound 16 was treated with sodium
hydride to give the cyclic carbamate 17. Deprotection of the 2,3-
O-isopropylidene group in 17 was achieved using TFAꢁH2O to af-
ford hemiacetal 18. Oxidative cleavage of 18 with NaIO4 in
MeOHꢁH2O gave the aldehyde, which upon treatment with excess
Wittig reagent (C12H25P+Ph3Brꢀ in dry THF) at 0 °C, gave 19. Depro-
tection of the carbamate in 19 was achieved with 4 M NaOH to give
12; the stereochemistry of the double bond was confirmed as the
Z-isomer by 1H NMR coupling constants. Hydrogenation of com-
pound 12 in the presence of Pd/C in MeOH under a hydrogen atmo-
plet), number of proton(s), and coupling constant(s) J (Hz). 13C
NMR chemical shifts are expressed in ppm. Optical rotations were
measured with JASCO digital polarimeter. Accurate mass measure-
ment was performed on Q STAR mass spectrometer (Applied Bio-
systems, USA).
4.1. Benzyl benzyl((R)-1-((3aR,5R,6S,6aR)-6-(benzyloxy)-2,2-
dimethyltetrahydro-furo[2,3-d][1,3]dioxol-5-yl)allyl)carbamate
15
To a stirred solution of 13 (2.4 g, 6.1 mmol) in dry MeOH
(20 mL) was added sodium bicarbonate (1.02 g, 12.2 mmol) fol-
lowed by CbzCl (1.52 mL, 9.15 mmol) at 0 °C. The mixture was stir-
red at rt for 3 h. Next, MeOH was evaporated under reduced
pressure and reaction mixture was extracted with EtOAc and
water. The combined organic layers were washed with water and
brine, and dried over anhydrous Na2SO4. The solvent was removed
on a rotary evaporator and the resulting crude material was puri-
fied by column chromatography on silica gel by eluting with ethyl
acetate:hexane (1:9) to give 15 (2.96 g, 92%) as a colorless liquid.
sphere gave
L-lyxo-phytosphingosine 3. For the sake of
characterization, this was converted into acetyl derivative 10 by
using Ac2O in the presence of Et3N. The spectroscopic data of 10
were in good agreement with the reported values.18
For the synthesis of the acetyl derivative of (ꢀ)-jaspine B 11, the
following reactions were carried out (Scheme 3). Hydrogenation of
compound 12 using Pd/C in MeOH followed by protection of the
resultant amino functionality with (Boc)2O in the presence of
Et3N afforded carbamate 20. Regioselective tosylation of the pri-
mary hydroxy group of 20 prompted spontaneous cyclization to
give tetrahydrofuran derivative 21 (Scheme 3).13b Deprotection of
the Boc group in 21 with TFA/CH2Cl2 provided the (ꢀ)-jaspine B
8, which upon acetylation using Ac2O in the presence of excess
Et3N gave the acetyl derivative of (ꢀ)-jaspine B 11. The physical
properties of Boc protected (ꢀ)-jaspine B 21 and its diacetyl deriv-
ative 11 were in good agreement with the reported values.13e
½
a 2D6
ꢂ
¼ ꢀ49:2 (c 2.0, CHCl3); IR
m
max: 2985, 2932, 1695, 1455,
1413, 1374, 1247, 1215, 1074, 1024, 740, 699 cmꢀ1
;
1H NMR
(CDCl3, 300 MHz): d 7.00–7.41(m, 15H), 5.81–6.20 (m, 2H), 4.73–
5.31 (m, 5H), 4.32–4.66 (m, 5H), 4.02 (m, 1H), 3.59 (m, 1H),
1.17–1.42 (m, 6H); 13C NMR (CDCl3, 75 MHz): d 156.9, 138.3,
137.1, 136.1, 134.5, 128.2, 128.1, 127.8, 127.7, 127.6, 127.1,
116.9, 111.2, 104.7, 81.7, 81.2, 79.6, 71.5, 67.2, 57.7, 50.7, 26.4,
26.0 (because of the rotamers multiple peaks are observed in
NMR); ESIMS m/z: 530 [M+H]+; HRMS (ESI): Calcd for C32H36NO6
[M+H]+ 530.2542, found 530.2528.
4.2. Benzyl benzyl((R)-1-((3aR,5R,6S,6aR)-6-(benzyloxy)-2,2-
dimethyltetrahydro-furo[2,3-d][1,3]dioxol-5-yl)-2-
hydroxyethyl)carbamate 16
3. Conclusions
In conclusion we have successfully demonstrated a common
strategy for the synthesis of the acetyl derivatives of L-lyxo-phyto-
To a solution of compound 15 (2.0 g, 3.78 mmol) in CH2Cl2
(20 mL) at ꢀ78 °C, ozone gas was passed for 30 min (until the solu-
tion turns to a light blue color) and the reaction mixture was
quenched with dimethyl sulfide (1.0 mL, 7.56 mmol), stirred for
30 min, and the reaction mixture was washed with CH2Cl2
(2 ꢃ 20 mL). The combined organic layers were washed with water
and brine, and dried over anhydrous Na2SO4. The solvent was re-
moved on a rotary evaporator and the resulting crude aldehyde
was used in the next step without further purification.
sphingosine and (ꢀ)-jaspine B with good overall yields (16.8% and
13.7% respectively), from inexpensive and commercially available
D-glucose by using Grignard addition on a chiral sugar-imine and
a Wittig olefination. This strategy is also useful for making some
other analogues and isomers of phytosphingosine and jaspine B
with high stereoselectivity in order to study their activity.
4. Experimental
To the solution of the resulting crude aldehyde in dry MeOH
(20 mL) at 0 °C was added NaBH4 (142 mg, 3.78 mmol) and the
reaction mixture stirred for 2 h. The reaction mixture was
quenched with a saturated NH4Cl solution and the solvents were
removed in vacuo. The crude compound was partitioned between
CH2Cl2 and H2O. The aqueous layer was washed with CH2Cl2
(2 ꢃ 20 mL). The combined organic layers were washed with brine
and dried over anhydrous Na2SO4. The solvent was removed on a
rotary evaporator and the resulting crude material was purified
by column chromatography on silica gel by eluting with ethyl ace-
tate:hexane (1:4) to give compound 16 (1.91 g, 94% for two steps)
TLC was performed on Merck Kiesel gel 60, F254 plates (layer
thickness 0.25 mm). Column chromatography was performed on
silica gel (60–120 mesh) using ethyl acetate and hexane mixture
as the eluent. Melting points were determined on a Fisher John’s
melting point apparatus and are uncorrected. IR spectra were re-
corded on a Perkin–Elmer RX-1 FT-IR system. 1H NMR and 13C
NMR spectra were recorded using Varian Gemini-200 MHz, Bruker
Avance-300 MHz, and Varian Inova-500 MHz spectrometer. 1H
NMR data are expressed as chemical shifts in ppm followed by
multiplicity (s–singlet; d–doublet; t–triplet; q–quartet; m–multi-

G. Srinivas Rao et al. / Tetrahedron: Asymmetry 23 (2012) 564–569
567
as a colorless oil. ½a D26
ꢂ
¼ ꢀ59:3 (c 1.5, CHCl3); IR
m
max: 3469, 2929,
tinued for 2 h; after consumption of the starting material, metha-
nol was removed under reduced pressure, and the resulting
residue was diluted with H2O and washed with CH2Cl2
(2 ꢃ 10 mL). The combined organic layers were washed with satu-
rated aqueous NaHCO3 and brine, and dried over anhydrous
Na2SO4. The solvent was removed on a rotary evaporator and the
resulting crude aldehyde was used in the next step without any
purification.
1692, 1454, 1412, 1374, 1247, 1215, 1074, 1024, 740, 699 cmꢀ1
;
1H-NMR (CDCl3, 300 MHz): d 7.00–7.42 (m, 15H), 5.88 (br s, 1H),
5.00–5.30 (m, 2H), 4.30–5.00 (m, 6H), 4.17 (br d, 1H, J = 15.5 Hz),
3.94 (dd, 1H, J = 4.2 and 11.5 Hz), 3.55–3.85 (m, 2H), 1.67 (br s,
1H), 1.18–1.44 (m, 6H); 13C NMR (CDCl3, 75 MHz): d 156.9,
138.3, 137.0, 136.1, 128.5, 128.0, 127.8, 127.4, 111.8, 104.8, 82.1,
81.2, 78.8, 71.7, 67.6, 63.4, 58.1, 51.0, 29.6, 26.6, 26.2 (because of
the rotamers multiple peaks are observed in NMR); ESIMS m/z:
534 [M+H]+; HRMS (ESI): Calcd for C31H35NO7Na [M+Na]+
556.2311, found 556.2288.
To a precooled solution of Wittig salt C13H27Ph3P+Brꢀ (2.86 g,
5.46 mmol) in THF (30 mL) was slowly added n-BuLi (2.5 M in hex-
ane, 1.45 mL, 3.64 mmol) under N2 protection. The orange solution
was stirred for about 30 min, after which a solution of the above
crude aldehyde in dry THF (10 mL) was added dropwise under N2
protection. The mixture was stirred at this temperature for another
30 min, and quenched by saturated NH4Cl solution. The mixture
was diluted with water and extracted with EtOAc (3 ꢃ 20 mL).
The combined organic layer was washed with brine, and dried over
Na2SO4. The solvent was removed on a rotary evaporator and the
residue was purified by column chromatography on silica gel using
ethyl acetate:hexane (1:9) as the eluent to give pure compound 19
4.3. (R)-3-Benzyl-4-((3aR,5R,6S,6aR)-6-(benzyloxy)-2,2-
dimethyltetrahydrofuro[2,3-d][1,3]dioxol-5-yl)oxazolidin-2-
one 17
To an ice cooled, stirred solution of compound 16 (1.7 g,
3.18 mmol) in dry THF (15 mL), was slowly added NaH (0.26 g,
60% w/v dispersion in mineral oil, 6.37 mmol) over 5 min (portion-
wise). Then the reaction was allowed to return to room tempera-
ture and stirred for 2 h. The reaction mixture was quenched with
crushed ice and extracted with ethyl acetate (3 ꢃ 100 mL). The
combined organic extracts were washed with water and brine,
and dried over Na2SO4. The solvent was removed on a rotary evap-
orator and the residue was purified by column chromatography on
silica gel using ethyl acetate:hexane (1:4) as the eluent to give pure
(0.85 g, 90% for two steps) as a colorless oil. ½a D26
¼ ꢀ28:5 (c 1.0,
ꢂ
CHCl3); IR mmax: 2923, 2853, 1748, 1426, 1376, 1256, 1210, 1070,
1038, 880, 702; 1H-NMR (CDCl3, 300 MHz): d 7.09–7.30 (m, 10H),
5.57(m, 1H), 5.03 (dd, 1H, J = 10.3 Hz), 4.70 (d, 1H, J = 15.6 Hz),
4.46 (d, 1H, J = 11.2 Hz), 4.28 (m, 1H), 4.15 (d, 1H, J = 11.2 Hz),
3.95–4.05 (m, 2H), 3.82 (m, 1H), 3.72 (d, 1H, J = 6.8 Hz), 3.53 (m,
1H), 1.70–2.06 (m, 4H), 1.05–1.25 (m, 20H), 0.78 (t, 1H,
J = 6.6 Hz); 13C NMR (CDCl3, 75 MHz): d 158.6, 137.6, 137.5,
135.7, 128.7, 128.4, 128.0, 127.8, 124.9, 74.4, 70.0, 69.7, 62.01,
55.8, 45.9, 31.8, 29.6, 29.4, 29.2, 29.1, 28.7, 27.9, 22.6, 14.0; ESIMS
m/z: 522 [M+H]+; HRMS (ESI): Calcd for C33H48NO4 [M+H]+
522.3583, found 522.3598.
compound 17 (1.24 g, 92%) as a colorless liquid. ½a D26
¼ ꢀ39:7 (c
ꢂ
1.0, CHCl3); IR mmax: 2924, 1742, 1427, 1371, 1217, 1074, 1023,
744, 700 cmꢀ1 1H NMR (CDCl3, 300 MHz): d 7.12–7.36 (m, 10H),
;
5.88 (d, 1H, J = 3.8 Hz), 4.64 (d, 1H, J = 16.1 Hz), 4.60 (d, 1H,
J = 11.7 Hz), 4.52 (d, 1H, J = 3.8 Hz), 4.43 (dd, 1H, J = 6.7 and
9.2 Hz), 4.33 (d, 1H, J = 11.7 Hz), 4.28 (t, 1H, J = 3.3 Hz), 4.16–4.26
(m, 2H), 3.83 (td, 1H, J = 3.3 and 9.2 Hz), 3.74 (d, 1H, J = 3.4 Hz),
1.34 (s, 3H), 1.28 (s, 3H); 13C NMR (CDCl3, 75 MHz): d 158.5,
136.6, 136.0, 128.8, 128.6, 128.2, 127.7, 127.5, 112.0, 105.0, 82.4,
81.6, 77.0, 71.7, 63.8, 54.5, 46.5, 26.8, 26.3; ESIMS m/z: 426
[M+H]+; HRMS (ESI): Calcd for C24H28NO6 [M+H]+ 426.1916, found
426.1903.
4.6. (2R,3R,4R,Z)-2-(Benzylamino)-4-(benzyloxy)octadec-5-ene-
1,3-diol 12
Compound 19 (0.50 g, 0.95 mmol) was taken in EtOH (20 ml); to
this solution at room temperature was added aq 4 M NaOH
(1.5 mL), then it was heated at reflux for 12 h. After completion
of the reaction, it was neutralized with 1 M aq. HCl (6 mL) and ex-
tracted with EtOAc (2 ꢃ 20 mL). The combined organic layer was
washed with brine and dried over Na2SO4. The solvent was re-
moved on a rotary evaporator and the residue was purified by col-
umn chromatography on silica gel using ethyl acetate:hexane (2:3)
as the eluent to give pure compound 12 (0.40 g, 85% for two steps)
4.4. (R)-3-Benzyl-4-((2R,3R,4R,5S)-3-(benzyloxy)-4,5-
dihydroxytetrahydrofuran-2-yl)oxazolidin-2-one 18
Compound 17 (1.2 g, 2.82 mmol) was treated with 20 mL of
TFA:H2O (3:2) at 0 °C then the reaction mixture was warmed to
room temperature and stirred for 3 h. Solvents were removed by
three coevaporations with toluene (10 mL), and the residue was
purified by column chromatography on silica gel using ethyl ace-
tate:hexane (2:3) as the eluent to give pure compound 18
as a colorless oil. ½a D26
ꢂ
¼ ꢀ53:4 (c 1.0, CHCl3); IR
mmax: 3342, 2923,
2853, 1728, 1457, 1062, 735, 699 cmꢀ1; 1H-NMR (CDCl3, 300 MHz):
d 7.21–7.38 (m, 10H), 5.77 (m, 1H), 5.30 (dd, 1H, J = 9.4 and
10.4 Hz), 4.60 (d, 1H, J = 11.4 Hz), 4.29 (d, 1H, J = 11.4 Hz), 4.23
(m, 1H), 3.74–3.85 (m, 3H), 3.68 (m, 1H), 3.63 (m, 1H), 2.62–2.74
(m, 4H), 1.98–2.17 (m, 2H), 1.21–1.41 (m, 18H), 0.88 (t, 1H,
J = 7.2 Hz); 13C NMR (CDCl3, 75 MHz): d 137.3, 128.4. 128.3,
127.9, 127.8, 127.2, 125.4, 75.1, 73.9, 70.0, 60.1, 58.3, 50.9, 31.9,
29.6, 2 ꢃ 29.5, 29.4, 29.3, 28.1, 22.6, 14.1; ESIMS m/z: 496
[M+H]+; HRMS (ESI): Calcd for C32H50NO3 [M+H]+ 496.3790, found
496.3802.
(0.87 g, 80%) as a colorless liquid. ½a D26
ꢂ
¼ ꢀ18:9 (c 1.0, CHCl3); IR
m
max: 3389, 2924, 1720, 1443, 1241, 1105, 1073, 1026, 746,
701 cmꢀ1
;
1H NMR (CDCl3, 200 MHz): d 7.13–7.40 (m, 10H), 5.55
(d, 1H, J = 3.8 Hz), 4.84 (d, 1H, J = 15.5 Hz), 4.66 (d, 1H,
J = 11.7 Hz), 4.60 (dd, 1H, J = 2.0 and 5.5 Hz), 4.32–4.42 (m, 2H),
4.08–4.24 (m, 3H), 3.92 (dd, 1H, J = 2.0 and 5.5 Hz), 3.81 (m, 1H),
3.05 (br s, 1H); 13C-NMR (CDCl3, 75 MHz): d 159.1, 137.1, 135.4,
128.9, 128.5, 128.0, 2 x 127.9, 127.5, 96.3, 84.0, 76.1, 74.3, 71.7,
64.3, 54.5, 45.7; ESIMS m/z: 386 [M+H]+; HRMS (ESI): Calcd for
C
21H24NO6 [M+H]+ 386.1603, found 386.1588.
4.7. (2R,3R,4R)-2-Acetamidooctadecane-1,3,4-triyl triacetate 10
4.5. (R)-3-Benzyl-4-((1R,2R,Z)-2-(benzyloxy)-1-
hydroxyhexadec-3-enyl)oxazolidin-2-one 19
Compound 12 (0.2 g, 0.40 mmol) was taken in dry EtOH (5 mL)
and to it 1:1 Pd/C and Pd(OH)2 (20 mg) were added. The flask was
then purged with hydrogen and hydrogenated at room tempera-
ture for 24 h. The reaction mixture was filtered and the filtrate
was concentrated under reduced pressure to give a syrup, which
was acetylated as such with Et3N (0.17 mL, 1.2 mmol), Ac2O
To a stirred solution of compound 18 (0.70 g, 1.82 mmol) in
MeOH/H2O (15 mL, 2:1 v/v) were added NaIO4 (0.78 g, 3.64 mmol)
and saturated NaHCO3 solution (0.2 mL) at 0 °C. Stirring was con-

568
G. Srinivas Rao et al. / Tetrahedron: Asymmetry 23 (2012) 564–569
(0.18 mL, 0.72 mmol), and DMAP (5 mg) in CH2Cl2 (5 mL). The
reaction mixture was diluted with CH2Cl2 (25 mL) and washed
with saturated NH4Cl solution, brine, dried over anhydrous Na2SO4,
and the solvent was concentrated in vacuo to give the residue,
which was purified by column chromatography on silica gel by
eluting with ethyl acetate:hexane (3:7) to give tetraacetate deriv-
4.10. (2R,3R,4R)-4-Acetamido-2-tetradecyltetrahydrofuran-3-yl
acetate 11
To an ice cooled, stirred solution of compound 21 (0.08 g,
0.2 mmol) in dry CH2Cl2 (2 mL), was added TFA (2 mL). The reac-
tion was allowed to room temperature and stirred for 2 h. The vol-
atiles were removed on a rotary evaporator to give the residue,
which was then taken in dry CH2Cl2 (4 mL) and to it were added
Et3N (0.09 mL, 0.6 mmol), Ac2O (0.03 mL, 0.3 mmol) and DMAP
(2 mg). After the completion of addition, the reaction was allowed
to return to room temperature and stirred for 4 h. The reaction
mixture was diluted with CH2Cl2 (30 mL) and the organic layer
was washed with saturated aq.NH4Cl solution, water and brine,
and dried over anhydrous Na2SO4. The solvent was removed on a
rotary evaporator and the residue was purified by column chroma-
tography on silica gel using ethyl acetate:hexane (1:2) as the elu-
ative 10 (0.17 g, 85%, for two steps) as
a
yellow syrup.
¼ þ4:3 (c 0.5, CHCl3)}; IR
;
max: 2924, 2854, 1741, 1659, 1543, 1370, 1221, 1044 cmꢀ1 1H
½
a 2D6
ꢂ
¼ þ3:8 (c 0.62, CHCl3), {lit.18
½ ꢂ
a 2D6
m
NMR (CDCl3, 300 MHz): d 5.72 (d, 1H, J = 9.4 Hz), 5.09 (m, 2H),
4.53 (m, 1H), 4.22 (dd, 1H, J = 4.7 and 11.5 Hz), 3.94 (dd, 1H,
J = 3.0 and 11.5 Hz), 2.12 (s, 3H), 2.09 (s, 3H), 2.06 (s, 3H), 1.97 (s,
3H), 1.42–1.66 (m, 2H), 1.18–1.34 (m, 24H), 0.88 (t, 3H,
J = 6.6 Hz); 13C MR (CDCl3, 75 MHz): d 170.8, 170.6, 170.3, 169.6,
71.9, 71.2, 63.1, 47.4, 31.9, 30.9, 29.7, 29.5, 2 ꢃ 29.4, 29.3, 25.2,
23.3, 22.7, 21.0, 20.8, 14.1; ESIMS m/z: 486 [M+H]+; HRMS (ESI):
Calcd for C26H48NO7 [M+H]+ 486.3420, found 486.3441.
ent to afford the diacetate derivative of (ꢀ)-jaspine B 11 (0.08 g,
94%) as a syrup. ½a D26
ꢂ
¼ þ26:8 (c 1.2, CHCl3), {lit.,
½
a 2D6
ꢂ
¼ ꢀ28:4
13e
(c 1.0, CHCl3) for the enantiomer}; IR
m
max: 3298, 2920, 2851,
4.8. tert-Butyl (2R,3R,4R)-1,3,4-trihydroxyoctadecan-2-
ylcarbamate 20
1740, 1658, 1557, 1376, 1232, 1072 cmꢀ1
;
1H NMR (CDCl3,
300 MHz): d 5.56 (d, 1H, J = 8.3 Hz), 5.33 (dd, 1H, J = 3.4 and
5.2 Hz), 4.75 (ddd, 1H, J = 5.6, 7.8 and 8.0 Hz), 4.04 (t, 1H,
J = 8.0 Hz), 3.87 (m, 1H), 3.53 (t, 1H, J = 8.2 Hz), 2.15 (s, 3H), 1.97
(s, 3H), 1.40–1.46 (m, 2H), 1.21–1.33 (m, 24H), 0.88 (t, 3H,
J = 6.8 Hz); 13C NMR (CDCl3, 75 MHz): d 169.8, 169.7, 81.2, 73.6,
70.0, 51.4, 31.9, 29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 26.0, 23.1, 22.6,
20.6, 14.0; ESIMS m/z: 406 [M+H]+; HRMS (ESI): Calcd for
Compound 12 (0.15 g, 0.30 mmol) was taken in dry EtOH (5 mL)
and to it 1:1 Pd/C and Pd(OH)2 (20 mg) were added. The flask was
then purged with hydrogen and hydrogenated at room tempera-
ture for 24 h. The reaction mixture was filtered and the filtrate
was concentrated under reduced pressure to give a syrup, which
was treated with (Boc)2O (0.02 mL, 0.27 mmol), Et3N (0.13 mL,
0.90 mmol) in CH2Cl2 (5 mL) and stirred at 0 °C to rt for 2 h. The
reaction mixture was diluted with CH2Cl2 (10 mL) and washed
with saturated NH4Cl solution, brine, and dried over anhydrous
Na2SO4. The solvent was concentrated in vacuo to give a residue,
which was purified by column chromatography on silica gel by
eluting with ethyl acetate:hexane (3:7) to afford the protected
C
22H41NO4Na [M+Na]+ 406.2933, found 406.2933.
Acknowledgements
G.S.R. and B.C. thank CSIR-New Delhi for research fellowship.
The authors also thank Dr. J.S. Yadav and Dr. G.V.M. Sharma for
their constant support and encouragement.
aminotriol 20 (0.11 g, 86%) (over two steps) as
a syrup.
½
a 2D6
ꢂ
¼ þ6:2 (c 1.5, CHCl3); 1H-NMR (CDCl3, 300 MHz): d 5.21 (d,
References
1H, J = 9.0 Hz), 4.06 (d, 1H, J = 11.0 Hz), 3.76 (dd, 1H, J = 4.0 and
11.0 Hz), 3.62 (m, 1H), 3.52 (m, 1H), 3.39 (d, 1H, J = 8.0 Hz), 1.52–
1.67 (m, 2H), 1.46 (s, 9H), 1.22–1.34 (m, 26H), 0.88 (t, 3H,
J = 7 Hz); 13C NMR (CDCl3, 75 MHz): d 157.2, 80.4, 72.8, 69.6,
62.0, 53.5, 32.8, 31.9, 29.7, 29.6, 29.4, 28.3, 26.1, 22.7, 14.1; ESIMS
m/z: 418 [M+H]+; HRMS (ESI): Calcd for C23H47NO5 [M+H]+
440.3351, found 440.3342.
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4.9. tert-Butyl (3R,4R,5R)-4-hydroxy-5-
tetradecyltetrahydrofuran-3-ylcarbamate 21
To a solution of 20 (0.30 g, 0.58 mmol) in pyridine/CH2Cl2 (4 mL,
1:1 v/v) was added p-toluenesulfonyl chloride (0.12 g, 0.63 mmol).
The mixture was stirred for 18 h at rt. Next, MeOH (0.5 mL) and
EtOH (30 mL) were added to the mixture, and the solution was
extensively washed with an aqueous saturated CuSO4 solution
(3 ꢃ 10 mL) and dried over anhydrous Na2SO4. The solvent was re-
moved on a rotary evaporator and the resulting residue was puri-
fied by column chromatography on silica gel by eluting with ethyl
acetate:hexane (1:4) to give 21 (0.2 g, 86%) as a white solid. mp
82–84 °C; ½a 2D6
ꢂ
¼ ꢀ7:1 (c 1.5, CHCl3) {lit.13e
[a]D = +6.8 (c 1.0,
mmax: 3363, 2919, 2849, 1686,
CHCl3) for the enantiomer}; IR
1543, 1251, 1171 cmꢀ1 1H NMR (300 MHz, CDCl3): d 5.05 (d, 1H,
;
J = 4.5 Hz), 4.26 (m, 1H), 3.96–4.04 (m, 2H), 3.74 (dt, 1H,
J = 3.0 Hz and 6.8 Hz), 3.52 (t, 3H, J = 8.3 Hz); 1.86 (br s, 1H),
1.53–1.61 (m, 2H), 1.44 (s, 9H), 1.21–1.36 (m, 24H), 0.88 (t, 3H,
J = 7 Hz); 13C NMR (CDCl3, 75 MHz): d 155.7, 82.2, 79.9, 71.9,
70.2, 54.3, 31.9, 29.6, 29.5, 29.3, 29.0, 28.3, 26.1, 22.7, 14.1; ESIMS
(m/z): 422 [M+Na]+; HRMS (ESI): Calcd for C23H45NO4Na [M+Na]+
422.3246, found 422.3249.

G. Srinivas Rao et al. / Tetrahedron: Asymmetry 23 (2012) 564–569
569
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