Synthesis and properties of several isomers of the cardioactive steroid ouabain

Article abstract of DOI:10.1016/j.tetlet.2006.02.089

The ouabain isomers 1, 6, 20, 21, and 22 have been synthesized and shown to be readily separable by HPLC, which indicates that they do not correspond to a putative endogenous ouabain-like cardioregulator. 11-epi-Ouabain (1) is of interest as a safer alter

Full text of DOI:10.1016/j.tetlet.2006.02.089

Tetrahedron Letters 47 (2006) 2711–2715
Synthesis and properties of several isomers of the
cardioactive steroid ouabain
Bor-Cherng Hong, Seongkon Kim, Tae-Seong Kim and E. J. Corey*
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
Received 13 February 2006; accepted 15 February 2006
Available online 3 March 2006
Abstract—The ouabain isomers 1, 6, 20, 21, and 22 have been synthesized and shown to be readily separable by HPLC, which indi-
cates that they do not correspond to a putative endogenous ouabain-like cardioregulator. 11-epi-Ouabain (1) is of interest as a safer
alternative to ouabain.
ꢀ 2006 Elsevier Ltd. All rights reserved.
This letter describes synthetic studies on the synthesis of
new cardioactive steroid derivatives aimed at the discov-
ery of molecules that might be safer than ouabain and
digoxin, which are currently among the mainstays for
the medical management of heart disease, including con-
gestive heart failure. These compounds are also relevant
to the existence of an endogenous factor suggested to be
an isomer of ouabain.
lular Na+ levels, which leads to higher Ca+2 levels
and increased muscle contractility in the heart.4,5
The cardioactive steroid glycosides, although valuable
for the treatment of heart failure, have a narrow thera-
peutic window. Their use can lead to death from cardiac
arrhythmia and disturbances of atrio-ventricular con-
traction, as well as other less serious side effects (e.g.,
gastrointestinal disorders, neurological effects, anorex-
ia). Because patients must be monitored very carefully,
there is a great need for safer versions of digoxin or oua-
bain. Fortunately, presently available methods allow
much easier biological evaluation of safety and selectiv-
ity than has been possible previously.
Congestive heart failure is an important cause of death
in elderly humans. It is a progressive disease that is asso-
ciated with reduced cardiac output, excess peripheral
vasoconstriction, and salt and water retention due to im-
paired kidney function.1,2 It is treated by medication
with angiotension receptor blockers, ACE inhibitors,
vasodilators, aldosterone antagonists, and also the
steroidal Na+–K+–ATPase (Na+/K+ pump) inhibitors
digoxin and ouabain.1,2 There are two subunits (a and
b) and multiple isoforms of Na+–K+–ATPase (four iso-
forms on the a-subunit and three isoforms of the b-sub-
unit are now known). Cardiac tissue contains the a1 and
a3 isoforms and there is good evidence that the a1-iso-
form is associated with contractile tissue. Digoxin and
ouabain bind to the intracellular side of the transmem-
brane a1-subunit. The cardioactive natural plant ste-
roids3 increase the force of cardiac muscle contraction
(positive inotropic effect) by maintaining higher intracel-
This study was aimed at the synthesis of isomers of oua-
bain for several reasons. First, ouabain is one of the
most potent and rapidly acting cardioactive steroids
with a satisfactory half-life in vivo (ca. 20 h). Second,
it had been reported that the mammalian hypothalamus
produces an isomer of ouabain that might be an endo-
genous regulator of cardiac function and that is ca. 103
times potent.6,7 Finally, there is a simple and commer-
cially available test (dog arrhythmia model) for deter-
mining the therapeutic index of cardioactive steroids,
allowing a straightforward screen for safety relative to
ouabain or digoxin.
The first isomer of ouabain that we synthesized was the
C-11 diastereomer, 11-epi-ouabain (1). An effective syn-
thesis of 1 is outlined in Scheme 1. A solution of ouabain
octahydrate (Sigma) in acetone (1.25 g/100 mL) was
*
Corresponding author. Tel.: +1 617 495 4033; fax: +1 617 495
0376; e-mail addresses: gorman@chemistry.harvard.edu; corey@
chemistry.harvard.edu
0040-4039/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.02.089

2712
B.-C. Hong et al. / Tetrahedron Letters 47 (2006) 2711–2715
O
O
O
O
O
O
HO
HO
HO
O
O
CH3
CH3
HO
HO
CH3
O
O
Ac2O, Et3N,
DMAP
HO
O
O
O
HO
cat. conc. HCl
O
H
O
O
OH
OH
OH
O
CH2Cl2
acetone
80 - 90%
O
O
HO
O
H
OH
OH
H
OH
OH
O
O
3
ouabain
2
Dess-Martin oxidation
CH2Cl2
O
O
O
O
O
O
HO
O
HO
HO
O
O
CH3
CH3
CH3
O
O
HO
HO
1. NaBH4, MeOH
cat. HCl, MeOH
O
HO
HO
O
O
O
OH
OH
OH
O
2. K2CO3,
MeOH
50% overall
O
O
O
O
O
H
OH
H
OH
H
OH
OH
O
O
1
5
4
Scheme 1.
treated with 12 N hydrochloric acid (0.85 mL/100 mL of
acetone) and allowed to react at 25 ꢁC for 2 h. Neutral-
ization (Et3N), removal of acetone and flash chromato-
graphy on silica gel (5% MeOH–CH2Cl2) gave the
bis-acetonide 2 in 89% yield. Acetylation of 2 (Ac2O),
Et3N, 4-dimethylaminopyridine (DMAP) in CH2Cl2 at
0 ꢁC (using TLC analysis at 5 min intervals to follow
the formation of monoacetate and avoid further acetyl-
ation) gave the monoacetate 3 in 86% yield. Oxidation of
3 with the Dess–Martin periodinane reagent in CH2Cl2
at 25 ꢁC produced the 11-keto steroid 4 in 85% yield.
Reduction of 4 with sodium borohydride in methanol
at 23 ꢁC for 20 min followed by removal of solvent
and chromatography gave the 11b-hydroxy steroid 5.
Finally, removal of the acetonide protecting groups
using 4 N-hydrochloric acid in MeOH (0.8 mL/100 mL
of MeOH) at 25 ꢁC for 2 h, provided after column chro-
matography on silica gel (4:1 EtOH–H2O), 11-epi-oua-
bain (1) in 80% yield.
ketone was very slow and led to a complex mixture of
very stable borate complexes from concurrent deacetyl-
ation and complexation.
Encouraged by the promising biological profile of 11-
epi-ouabain (1), we undertook the synthesis of another
isomer that might be identical to the hypothalamic-
derived compound,6 specifically the regioisomer 11-des-
oxy-7a-hydroxyouabain (6). It was thought that this
structure might explain the CD data measured for ben-
zoylated hypothalamic factor.6c The synthesis of 6 was
accomplished successfully by the multistep pathway
shown in Scheme 2. The C(1)- and C(19)-hydroxyls of
ouabain (dried at 100 ꢁC in vacuo) were selectively pro-
tected by reaction with 1,1-dimethoxycyclopentane
(1.1 equiv) in THF with tosic acid (0.17 equiv) as cata-
lysts at 23 ꢁC for 16 h to give the monoketal 7 (91%).
Selective acetylation of the three rhamnose hydroxyls
occurred at 23 ꢁC in 2 h (reaction monitored by TLC)
using Ac2O, DMAP in CH2Cl2 to generate 8, which
was then chloracetylated to form 9 (23 ꢁC, 30 min) effi-
ciently. The 14b-hydroxyl group of 9 was selectively pro-
tected as the methylthiomethyl (MTM) ether by reaction
with acetic anhydride-dimethylsulfoxide (DMSO)9 at
23 ꢁC for 24 h to afford 10. Activation of the 5b-hydro-
xyl group of 10 using Burgess’s reagent10 in dry THF at
23 ꢁC for 1 h effected elimination to the 5,6-olefin, which
after MTM cleavage led to 11. Acidic hydrolysis of 11,
dechloroacetylation using thiourea and NaHCO3 in
EtOH at 23 ꢁC for 16 h, and epoxidation furnished the
5,6-epoxide 12. The C(1)- and C(19)-hydroxyl groups
were protected as the cyclic carbonate ester 13 and the
C(11)-hydroxyl was removed by Barton deoxygenation
of the C(11)-pentafluorophenylthionocarbonate mixed
ester using Bu3SnH, which provided the 11-deoxy-5,6b-
epoxide 14. Treatment of 14 with dimethylalumino-
phenylselenide11 in CH2Cl2 at ꢀ78 to 0 ꢁC resulted in
selective epoxide cleavage to form a 5b-hydroxy-6a-phen-
11-epi-Ouabain (1) was found to be of comparable
potency to ouabain but to be superior with respect to
therapeutic index (TI) as determined from quadruplicate
in vivo assays with the dog model. The TI for 1 was
found to be at least 4, as compared to 2 for ouabain,
that is an increase of safety by a factor of at least 2.8
It was clear that 1 could be ruled out as a possible struc-
ture for the mammalian hypothalamic isomer of
ouabain6 since it had a much longer retention time on
reverse-phase HPLC analysis (C18-column at 23 ꢁC
using 90% H2O–10% CH3CN–0.1% CF3CO2H) than
ouabain (26.7 min vs 14.7 min).
Another synthesis of 1 from ouabain was briefly exam-
ined to find a simpler route, but without positive results.
Thus, although acetylation of ouabain gave good yields
of a pentaacetate that could be oxidized to an 11-ketone,
sodium borohydride reduction of this pentaacetoxy

B.-C. Hong et al. / Tetrahedron Letters 47 (2006) 2711–2715
2713
O
O
O
O
O
O
OMe
OMe
HO
HO
HO
Ac2O, DMAP
75%
HO
HO
O
O
CH3
CH3
CH3
O
O
HO
HO
HO
HO
AcO
AcO
TsOH, THF
17 h
91%
O
O
O
OH
OH
OH
O
O
O
H
OH
H
OH
H
OH
OH
OH
AcO
ouabain
7
8
chloroacetic anhydride
Et3N, DMAP, 23 ˚C
93%
O
O
O
O
O
O
CA
CA
CA
O
O
O
1. Burgess, THF
1 h
DMSO–Ac2O
O
O
O
CH3
CH3
CH3
O
O
O
23 o
C
76%
AcO
AcO
AcO
AcO
AcO
AcO
2. HgCl2, NaHCO3
H2O–CH3CN
23 oC, 1 h
O
O
O
OH
OMTM
OH
O
O
O
65%
H
H
H
OH
OH
AcO
AcO
AcO
10
11
9, CA = α-chloroacetyl
1. TFA–H2O (2:1), 23 oC, 1 h
2. Thiourea, EtOH
3. m-CPBA, NaHCO3, CH2Cl2
69%
S
F
F
1.
F
F
O
F
Cl
O
O
O
O
O
O
H
H
DMAP, DMF
–5 oC - 5 oC,
64%
O
O
O
O
O
O
COCl2, pyr.
HO
HO
O
CH3
CH3
CH3
O
CH2Cl2, 0 o
93%
C
AcO
AcO
AcO
AcO
AcO
O
H
O
2. n-Bu3SnH, PhH,
reflux
O
OH
OH
OH
100%
O
AcO
O
O
H
H
O
O
O
AcO
AcO
AcO
12
13
14
1. PhSeAlMe2
2. H2O2; Δ
42%
O
O
O
O
O
O
0.5M NaOH
H2O–Dioxane (1:1)
O
1. NBS, THF–H2O
HO
O
CH3
CH3
CH3
AcO
O
HO
O
15 min, 23 oC
85%
AcO
AcO
HO
HO
AcO
AcO
2. Ac2O, DMAP
TEA, CH2Cl2
O
O
O
O
OH
Br
OH
OH
O
O
H
H
H
OH
OH
OH
AcO
HO
AcO
17
16
15
1. AgClO4, DME–H2O
2. Dess-Martin [O]
O
O
O
O
O
O
1. NaBH4, DME,
0
Al–Hg
HO
oC
HO
CH3
CH3
CH3
AcO
AcO
HO
THF–H2O, 0 o
8 h
C
AcO
O
AcO
HO
HO
2. ZnCl2, MeOH,
reflux
O
O
O
OH
O
OH
OH
OH
O
AcO
O
AcO
O
O
H
H
H
OH
OH
OH
OH
AcO
AcO
18
19
6
Scheme 2.
ylselino derivative, which, after oxidation with H2O2–
H2O–CH2Cl2 at 0 ꢁC for 30 min (vigorous stirring), iso-
lation and heating in ClCH2CH2Cl at 80 ꢁC for 1 h
afforded the 6,7-olefinic steroid 15. Deacetylation of 15
gave the heptaol 16, which upon bromoether formation
and reacetylation yielded bromo ether 17. Replacement
of bromine in 17 by hydroxyl was accomplished by the
sequence: (1) Dess–Martin oxidation with periodinane,
which afforded the 7-ketosteroid 18, (2) reductive cleav-
age of the C(6)–O bond, and (3) carbonyl reduction with
sodium borohydride in dimethoxyethane and deacetyl-
ation with zinc chloride in methanol, which provided
the desired 11a-deoxy-7a-hydroxy regioisomer of oua-
bain 6.12 Comparison of C18-reverse-phase HPLC reten-
tion times of 6 and ouabain revealed a substantial
difference using 15:85 CH3CN–H2O as an eluent (oua-
bain, 10.8 min; 6, 12.1 min), clear evidence that the
‘hypothalamic factor’ is not the ouabain regioisomer 6.
Because of this fact and the limited supply of 6 further
biological evaluation of 6 was not pursued.
Three other isomers of ouabain were prepared and eval-
uated, the stereoisomers 20, 21, and 22 (see Scheme 3).
Reaction of ouabain octahydrate with acetone–12 N

2714
B.-C. Hong et al. / Tetrahedron Letters 47 (2006) 2711–2715
O
O
O
O
O
O
HO
HO
HO
HO
HO
HO
HO
HO
HO
OH
OH
OH
3
1'
O
CH3
HO
CH3
HO
OH
O
O
3
1'
O
3
O
CH3
HO
1'
OH
OH
O
HO
HO
OH
OH
HO
OH
20
21
22
O
O
O
O
Br
CH3
AcO
O
1'
HO
HO
O
O
O
O
O
O
O
OH
OH
3
3
HO
HO
OH
OH
23
24
25
Scheme 3.
hydrochloric acid (0.4 mL/100 mL acetone) at 23 ꢁC for
10 days provided a precipitate of the 1,19-acetonide of
the aglycone of ouabain 23. Reaction of 23 with the ace-
tate-cyclic carbonate ester of rhamnosyl-1-bromide
(24)13 (2 equiv) and mercuric cyanide (1.3 equiv) in
CH2Cl2 at reflux for 30 h followed by the addition of
2 more equiv of 24 and 30 h heating at reflux afforded,
after extractive isolation and preparative TLC, two C-
10 diastereomeric glycosides in a ratio of 2.5:1. Methan-
olysis of the major coupling product in MeOH–4 N
hydrochloric acid (1000:1) at 25 ꢁC for 2 h afforded the
10-diastereomer of ouabain (20).14 Methanolysis of the
minor coupling product formed ouabain cleanly.
isomers (1, 6, 20, 21, or 22) match the HPLC data re-
ported6 for the endogenous mammalian hypothalamic
Na+–K+–ATPase inhibitor. In fact, the large differences
in retention time of these isomers lead to skepticism that
an isomer of ouabain would not differ from ouabain in
reverse-phase HPLC analysis. Furthermore, in addition
to the ouabain isomers reported here, we have also syn-
thesized and studied a number of others (to be reported
separately) including the following: (1) the regioisomer
of ouabain in which rhamnose is attached to the
C(19)-hydroxyl, (2) the C(4)-diastereomer of ouabain,
(3) 1-deoxy-2b-hydroxyouabain, and (4) 2b-hydroxy-5-
deoxyouabain. Each of these isomers was readily distin-
guished from ouabain by reversed-phase HPLC analy-
sis, which adds to the doubt that there is an
endogenous inhibitor of Na+–K+–ATPase that is chro-
matographically identical with ouabain. The most recent
studies of ‘endogenous’ ouabain-like inhibitor of Na+–
K+–ATPase18,19 also failed to lend support to the origi-
nal claim.6
The aglycone 23 was transformed into the C(3)-diaste-
reomer 25 by the sequence (1) oxidation with 1.2 equiv
of periodinane in CH2Cl2 at 0 ꢁC for 1 h and 23 ꢁC for
1 h and (2) reduction with NaBH4 at 23 ꢁC. Coupling
of 25 with the protected rhamnosyl bromide 24, as de-
scribed above for 23 + 24, afforded a mixture of C(1)0-
diastereomeric coupling products, which after chro-
matographic separation and acid-catalyzed methanoly-
sis afforded the stereoisomers of ouabain 2115 and 22.16
Another significant result to emerge from this work is
the finding that 11-epi-ouabain is a good inhibitor of
Na+–K+–ATPase with a therapeutic index that is more
than twice as large, and thus is a potentially useful new
cardenolide.
HPLC analysis and comparison of 20, 21, and 22 with
ouabain revealed the following retention times under
identical conditions [C18-ODS reversed-phase column
(250 · 4.6 mm), 90% H2O, 10% CH3CN, 0.1%
CF3CO2H, 23 ꢁC, flow rate 1.5 mL/min]: ouabain,
14.7 min; 20, 19.5 min; 21, 34.2 min; 22, 39.3 min. Thus,
none of the stereoisomers correspond to the chromato-
graphic data reported6 for the hypothalamic factor.
Further, the radio-ouabain displacement assay using
purified kidney Na+–K+–ATPase (Sigma) yielded the
following IC50 values (nM): ouabain 16.1; 20, 278; 21,
220; 22, 446.17
References and notes
1. Eichhorn, E. J.; Bristow, M. R. Circulation 1996, 94,
2285–2296.
2. Rich, M. W.; Brooks, K.; Luther, P. Am. Heart 1998, 135,
367–372.
3. Fieser, L. F.; Fieser, M. Steroids; Reinhold Publishing
Corporation: New York, 1959; pp 727–809.
4. Streyer, L. Biochemistry, 4th ed.; W. H. Freeman: New
York, 1995; pp 310–317.
A number of conclusions can be drawn from the present
investigation of the synthesis and properties of the new
isomers of ouabain reported here. First, none of these
5. The use of foxglove extract, which contains digitalis (a
mixture of cardioactive steroidal glycosides) was intro-
duced by William Withering in 1775 for treatment of heart

B.-C. Hong et al. / Tetrahedron Letters 47 (2006) 2711–2715
2715
failure (dropsy) long before the age of modern therapy or
Na+–K+–ATPase.
relative intensity): 607 (M++Na, 10), 585 (M++H, 16),
553 (12); 461 (10), 369 (27), 299 (20), 277 (90), 207 (100);
exact mass calculated for C29H45O12 (M++H): 585.2911;
found 585.2916.
6. (a) Hallaq, H. A.; Haupert, G. T. Proc. Natl. Acad. Sci.
U.S.A. 1989, 86, 10080–10084; (b) Tymiak, A. A.; Nor-
man, J. A.; Bolgar, M.; DiDonato, G. C.; Lee, H.; Parker,
W. L.; Lo, L.-C.; Berova, N.; Nakanishi, K.; Haber, E.;
Haupert, G. T. Proc. Natl. Acad. Sci. U.S.A. 1993, 90,
8189–8193; (c) Zhao, N.; Lo, L.-C.; Berova, N.; Naka-
nishi, K.; Tymiak, A.; Ludens, J. H.; Haupert, G. T., Jr.
Biochemistry 1995, 34, 9893–9896.
7. This compound could only be obtained in microscopic
amount (reported6 as 1 lg from 5 kg of bovine hypothala-
mus). The chief characterization data were mass spec-
trum, HPLC data, and CD data on a benzoylated sample.
Although the mass spectrum and HPLC retention times
was reported to be the same as for ouabain, the CD
spectrum of a benzoylated sample was reported to be
different.
23
15. Physical data for 21: ½aꢁD ꢀ11.43 (c 0.07, H2O); IR (neat):
1
3100–3500, 2940, 2880, 1739, 1451, 1149, 1047 cmꢀ1; H
NMR (CD3OD–CDCl3 (2:1); 500 MHz): d 1.12 (s, 3H),
1.25 (d, J = 6.2 Hz, 3H), 1.20–1.35 (m, 2H), 1.40–1.60 (m,
3H), 1.68–1.90 (m, 4H), 1.93–2.03 (m, 3H), 2.08–2.20 (m,
4H), 2.74–2.82 (m, 1H), 3.36 (t, J = 9.4 Hz, 1H), 3.70 (dd,
J = 9.5, 3.5 Hz, 1H), 3.72 (d, J = 11.7 Hz, 1H), 3.76 (dd,
J = 3.3, 1.7 Hz, 1H), 4.00 (d, J = 2.0 Hz, 1H), 4.03 (d,
J = 11.7 Hz, 1H), 4.18 (s, 1H), 4.39 (s, 1H), 4.42 (s, 1H),
4.84 (d, J = 1.4 Hz, 1H), 4.87 (dd, J = 18.4, 1.5 Hz, 1H),
5.01 (dd, J = 18.4, 1.5 Hz, 1H), 5.87 (s, 1H); 13C NMR
(CD3OD–CDCl3 (2:1), 100 MHz): d 17.91 (CH3), 19.40
(CH3), 23.79 (CH2), 27.59 (CH2), 33.08 (CH2), 33.24
(CH2), 34.32 (CH2), 34.59 (CH2), 35.99 (CH), 44.65 (CH),
46.78 (CH2), 47.30 (C), 50.32 (C), 52.26 (CH), 58.93
(CH2), 66.37 (CH), 69.00 (CH), 69.62 (CH), 70.76 (CH),
71.97 (two of CH), 73.86 (CH), 75.05 (CH2), 78.36 (C),
86.57 (C), 98.73 (CH), 117.94 (CH), 176.84 (C), 177.50
(C); MS (m/z, relative intensity): 585 (M++H, 10), 553 (6),
461 (9), 369 (27), 277 (100), 207 (27); exact mass calculated
for C29H45O12 (M++H): 585.2911; found 585.2905.
8. These tests were performed by Sierra Biomedical, Inc., San
Diego, CA.
9. See: Yamada, K.; Kato, K.; Nagase, H.; Hirata, Y.
Tetrahedron Lett. 1976, 65–66.
10. Burgess, E. M.; Penton, H. R.; Taylor, E. A. J. Org.
Chem. 1973, 38, 26–31.
11. Prepared from a 1:1 mixture of phenylselenol and tri-
methylaluminum in 1:1 toluene–CH2Cl2.
23
16. Physical data for 22: ½aꢁD +24.17 (c 0.12, H2O); IR (neat):
1
12. Physical data for compound 6 were as follows: H NMR
3100–3500, 2980, 2880, 1733, 1663, 1648, 1633, 1451, 1422,
1
(CD3OD–D2O (v/v 1:1)) d 5.92 (1H, s), 4.93 (1H, d,
J = 18 Hz), 4.86 (1H, dd, J = 18 Hz), 4.71 (1H, s), 4.19
(1H, m), 4.06 (1H, d, J = 12 Hz), 4.05 (1H, m), 3.99 (1H,
d, J = 12 Hz), 3.75 (1H, m), 3.66 (1H, m), 3.63 (1H, m),
3.50 (1H, s), 3.29 (1H, t, J = 10 Hz), 2.76 (1H, m), 1.15
(3H, d, J = 6 Hz), 0.80 (3H, s), 2.6–1.2 (16H, m); MS
(FAB) m/z 585 (M++H), 461, 369, 277; HRMS (FAB) m/z
585.2899 (M++H) (calcd for C29H45O12 585.2911).
1413, 1399, 1335, 1097, 1059, 1019, 1015 cmꢀ1; H NMR
(CD3OD–CDCl3 (2:1), 500 MHz): d 1.12 (s, 3H), 1.29 (d,
J = 6.0 Hz, 3H), 1.20–1.35 (m, 2H), 1.45–1.60 (m, 3H),
1.72–1.90 (m, 5H), 1.95–2.05 (m, 2H), 2.08–2.35 (m, 4H),
2.76–2.82 (m, 1H), 3.20–3.28 (m, 1H), 3.42 (dd, J = 9.2,
3.3 Hz, 1H), 3.87 (d, J = 3.1 Hz, 1H), 3.98 (d, J = 2.1 Hz,
1H), 4.03 (d, J = 11.8 Hz, 1H), 4.29 (s, 1H), 4.35 (s, 1H),
4.40 (d, J = 11.8 Hz, 1H), 4.63 (s, 1H), 4.78 (br s, 1H and
OH), 4.86 (dd, J = 18.6, 1.5 Hz, 1H), 5.00 (dd, J = 18.6,
1.5 Hz, 1H), 5.86 (d, J = 1.5 Hz, 1H); 13C NMR
(CD3OD–CDCl3 (2:1), 100 MHz): d 17.92 (CH3), 19.33
(CH3), 23.87 (CH2), 27.46 (CH2), 30.62 (CH2), 33.19
(CH2), 35.47 (CH2), 35.88 (CH), 36.72 (CH2), 44.68 (CH),
46.70 (CH2), 47.30 (C), 50.21 (C), 52.18 (CH), 58.73
(CH2), 66.14 (CH), 68.88 (CH), 71.98 (CH), 73.20 (CH),
73.29 (CH), 74.38 (CH), 74.76 (C), 74.93 (CH2), 78.80
(CH), 86.45 (C), 99.10 (CH), 117.93 (C), 176.71 (C),
177.19 (CH).
13. Backinowski, L. V.; Balan, N. F.; Shashkov, A. S.;
Kochetkov, N. K. Carbohydr. Res. 1980, 84, 225–235.
23
14. Physical data for 20: ½aꢁD +13.2 (c 0.50, H2O); IR (neat):
3100–3500, 2933, 2887, 1740, 1623, 1446, 1442, 1438, 1419,
1399, 1374, 1346, 1326, 1321, 1178, 1120, 1061, 1024 cmꢀ1
;
1H NMR (CD3OD–CDCl3 (2:1), 500 MHz): d 0.93 (s,
3H), 1.30 (d, J = 6.0 Hz, 3H), 1.15–1.40 (m, 4H), 1.42–
2.20 (m, 12H), 2.85–2.92 (m, 1H), 3.18–3.25 (m, 1H), 3.41
(dd, J = 9.2, 3.3 Hz, 1H), 3.85 (d, J = 3.3 Hz, 1H), 4.07 (d,
J = 11.8 Hz, 1H), 4.16 (br s, 1H), 4.22 (s, 1H), 4.40 (d,
J = 11.8 Hz, 1H), 4.62 (s, 1H), 4.73 (br s, 2H and OH),
4.87 (dd, J = 18.4, 1.5 Hz, 1H), 5.00 (dd, J = 18.4, 1.5 Hz,
1H), 5.88 (s, 1H); 13C NMR (CD3OD–CDCl3 (2:1),
100 MHz): d 17.51 (CH3), 17.96 (CH3), 24.02 (CH2),
24.57 (CH2), 31.46 (CH2), 33.43 (CH2), 37.05 (CH2), 38.30
(CH2), 40.90 (CH), 48.06 (CH), 48.36 (C), 49.85 (CH2),
50.59 (C), 51.36 (CH), 61.28 (CH2), 68.69 (CH), 71.33
(CH), 72.22 (CH), 73.24 (CH), 73.43 (CH), 73.58 (C),
74.51 (CH), 74.91 (CH2), 75.85 (CH), 85.16 (C), 99.17
(CH), 117.88 (CH), 176.74 (C), 176.86 (C); MS (m/z,
17. We are grateful to Dr. Albert L. Rauch of Pfizer Inc.,
Groton, MA for carrying out the assays and for these
data.
18. Murrell, J. R.; Randall, J. D.; Rosoff, J.; Zhao, J.; Jensen,
R. V.; Gullans, S. R.; Haupert, G. T. Circulation 2005,
112, 1301–1308.
19. Kawamura, A.; Guo, J.; Itagaki, Y.; Bell, C.; Wang, Y.;
Haupert, G. T., Jr.; Magil, S.; Gallagher, R. T.; Berova,
N.; Nakanishi, K. Proc. Natl. Acad. Sci. U.S.A. 1999, 96,
6654–6659.