Determination of the relative configuration of the C-2-C-1′-fragment of cytostatin

Article abstract of DOI:10.1055/s-2002-34379

Four diastereomers of a simple subtructure of cytostatin containing the α,β-unsaturated lactone subunit were synthesized and their NMR-spectroscopical data were compared with values recorded for the natural product in order to unravel the relative stereoc

Full text of DOI:10.1055/s-2002-34379

2096
PAPER
Determination of the Relative Configuration of the C-2-C-1 -Fragment of
Cytostatin
D
etermination o
a
f
the Relat
u
ive Configur
r
a
tion of
t
he C-2-C-1
n
-Fragment
o
t
f
C
ytostatinBialy,a Meritxell Lopez-Canet,a Herbert Waldmann*a,b
a
Max-Planck-Institut für molekulare Physiologie, Abteilung Chemische Biologie, Otto-Hahn-Str. 11, 44227 Dortmund
b
Universität Dortmund, Fachbereich 3, Organische Chemie, 44221 Dortmund
Fax +49(231)1332499; E-mail: herbert.waldmann@mpi-dortmund.mpg.de
Received 6 June 2002
Dedicated to Prof. D. Seebach on the occasion of his 65th birthday.
Na+-
O
O
Abstract: Four diastereomers of a simple subtructure of cytostatin
containing the , -unsaturated lactone subunit were synthesized
and their NMR-spectroscopical data were compared with values re-
corded for the natural product in order to unravel the relative stere-
ochemistry in cytostatin.
O
P
HO
O
O
OH
Cytostatin
antimetastatic activity
Key words: natural products, lactones, aldol reactions, asymmetric
synthesis, phosphatases
1
OH
O
O
The 6-subtituted- , -unsaturated -lactone is an impor-
tant structural element of various biologically active natu-
ral products including for instance compounds with
cytotoxic, antiviral, antibiotic or anticancer activity.1
OH
O
Leptomycin B
inhibitor of nuclear
export
In the natural products the 6-substituted lactone often does
not carry a further subtituent or it embodies a second sub-
tituent in the 5-position, i. e. mainly a hydroxyl, a methyl
or an ethyl group, with the subtituents being in syn or anti-
configuration. While the presence of an additional adja-
cent double bond in the 6-substituent is a very common
motif, a methyl branching at the first exocyclic carbon has
been described in the case of cytostatin 1 (Figure 1). Cy-
tostatin is a member of the phoslactomycin family of nat-
ural products isolated from Streptomyces spec. It shows
potent antimetastatic activity in vivo and highly selective
inhibition of the serine/threonine phosphatase 2A in vit-
ro.2 In particular, the latter activity is of interest since pro-
tein phophatases are considered to be a new class of
potential targets for drug development and natural prod-
ucts able to inhibit these enzymes might serve as biologi-
cally validated starting points in structural space for the
development of new and selective phosphatase inhibi-
tors.3
O
2
O
O
OH
O
Pironetin
immunosuppressant
Et
3
O
5
2
3
O
4'
2'
6
1'
4
3'
4
Due to the potent biological activity and the unique struc-
tural features of cytostatin, we embarked on a total synthe-
sis of this natural product.4 However, this synthetic
endeavour was hampered by the fact that although the
NMR spectroscopic data of cytostatin 1 were reported, its
absolute and relative configuration were not. Thus we
sought to determine the relative configuration of the C5-
C1 stereotriad of this potent phosphatase inhibitor. It was
felt that for this purpose, examination of the reported
Figure 1 Structures of biologically active natural compounds with
the , -unsaturated lactone moiety and targeted substructure 4.
NMR coupling constants alone might not be sufficient. A
comparison of the 1H and 13C NMR spectroscopic data of
cytostatin with the corresponding data for all relative
stereoisomers of a partial structure 4 containing the lac-
tone should allow for a better conclusion. This appeared
to be justified since only weak interactions between the
lactone moiety and the phosphate moiety in the natural
compound due to the unbranched alkyl tether between
them could be expected. Although there have been a few
reports on the synthesis of similar structures including a
Synthesis 2002, No. 14, Print: 07 10 2002.
Art Id.1437-210X,E;2002,0,14,2096,2104,ftx,en;C02402SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

PAPER
Determination of the Relative Configuration of the C-2-C-1 -Fragment of Cytostatin
2097
related stereotriad in the literature,5 no systematic varia-
tion of the stereochemistry was carried out. Also, some of
the reported structures carried a bulky subtituent in the vi-
cinity of the lactone, which might influence its conforma-
tion, leading to NMR data, which may not be useful for
our purpose.5
OH
O
a
5
6
O
O
OH
OH
The synthesis plan was based on the aldol strategy, giving
access to compounds with syn (Evans procedure)6 or anti
configuration (Heathcock procedure)7 of the subtituents at
C-5 and C-6. The configuration of the adjacent methyl
group at C-1 would be installed by the well-established
Evans asymmetric alkylation procedure.8 This strategy
has the advantage of giving access to all possible diatere-
omers, it guarantees easy separation of diastereomers and
relies on intermediates which could also be used in the
synthesis of cytostatin.4
N
O
O
O
Ph
b
8a
N
O
O
O
Ph
N
O
7
Ph
8b
The synthesis started from the chiral alcohol 5,8 which
was oxidized by the Swern procedure to yield aldehyde 6
(Scheme 1). This intermediate had to be used immediately
without any purification due to its pronounced volatility.
Aqueous workup followed by drying the organic layer
over activated molecular sieves yielded a solution of the
crude aldehyde 6 which could be used directly for the next
reaction. The Lewis-acid mediated modification of the al-
dol reaction according to Heathcock starting from the
chiral norephedrine-derived N-propionyl-oxazolidinone 7
as nucleophile yielded the expected anti-aldol 8a with
modest yield and selectivity, which is in accordance with
previous observations.9 The side product 8b turned out to
be the non Evans-syn aldol.9 Both products could be easily
separated and purified by flash chromatography. A boron
mediated aldol reaction starting from 7 yielded the syn-
product 8c in high selectivity and yield. The second anti-
diatereomer 8d was synthesized in moderate yield by the
Heathcock procedure starting from the valine-derived N-
propionyl-oxazolidinone 9.
O
O
O
O
OH
c
N
N
O
O
Ph
Ph
7
8c
O
O
O
O
OH
d
N
N
O
O
9
8d
Scheme 1 Synthesis of four diastereomers by the aldol methodolo-
gy; Reagents and conditions: (a) (COCl)2, DMSO, 78 °C, 2.5 h;
Et3N, CH2Cl2, 78 °C to rt (b) Bu2BOTf, iPr2NEt, CH2Cl2, 0 °C, 45
min; 6, Et2AlCl, 78 °C, 2.6 h; H2O2, MeOH, 0 °C, 30 min, 34% 8a
and 21% 8b (from 5 (c) Bu2BOTf, iPr2NEt, CH2Cl2, 0 °C, 45 min; 6,
78 °C, 90 min, r.t., 90 min; H2O2, MeOH, r.t., 1 h, 68% (from 5) (d)
Bu2BOTf, iPr2NEt, CH2Cl2, 0 °C, 45 min; 6, Et2AlCl, 78 °C, 2.6 h;
H2O2, MeOH, 0 °C, 30 min.
For 8a as a representative in Scheme 2 the reaction se-
quence is shown that was employed to convert the diaste-
reomers 8a d into the desired , -unsaturated lactones
4a d. After protection as methoxymethyl(MOM) ethers
10a d the chiral auxiliary was removed by reduction to
the alcohols 11a d employing in situ generated
LiBH3OH.10 Subsequent oxidation to the corresponding
aldehydes with the Dess Martin periodinane11 was fol-
lowed by completely Z-selective Still Gennari
olefination12 to yield the , –unsaturated esters 12a d.
These were subjected to acid-mediated lactonization by
heating in 2-propanol with tetrabromomethane, a proce-
dure which probably generates HBr in situ.13 The desired
lactone-diastereomers 4a d were obtained in satisfying
overall yields (Schemes 2 and 3).
CH-5 and CH3-5, the 13C-shifts of CH3-5 and CH-6, as
well as the coupling constants between CH-4 and CH-5 of
lactones 4a and 4d do not fit the data of cytostatin. A more
careful comparison is required to determine the (CH-6,
CH-1 )-configuration. While the 13C-shift at CH3-1 and
the 1H-shifts at CH-5 and CH3-1 in compound 4b clearly
differ from the corresponding signals of cytostatin, all sig-
nals of syn,anti-lactone 4c are in good agreement with
them, the maximal deviations beeing 0.8 ppm in the 13C
and 0.11 ppm in the 1H-spectrum for signals C-6 and CH-
1 , respectively.
Interestingly, the coupling constants of the proton at C-6
are nearly identical for all lactones 4a d, the only differ-
ence being that the small coupling constant (ca. 3 Hz) re-
flects the coupling constant between CH-5 and CH-6 for
syn-lactones 4b and 4c, and the coupling constant be-
tween CH-6 and CH-1 for anti-lactones 4a and 4d. This
can be rationalized by the preferred conformations of the
The NMR-spectroscopical data of the lactones 4a d and
the corresponding data for cytostatin 1 are shown in
Tables 1 and 2.
Examination of the 1H NMR spectroscopic data suggests
that the configuration at CH-5 and CH-6 is syn in the nat-
1
ural product. Most significantly, the H shifts of CH-4,
Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

2098
L. Bialy et al.
PAPER
O
O
OH
O
O
OMOM
a
N
O
N
O
Ph
Ph
8a
10a
b
OMOM
OH OMOM
c, d
MeO
O
12a
11a
e
O
O
Scheme 3 Overall yields of the syntheses of the lactones 4b d.
4a
Scheme 2 Synthesis of the lactone 4a; Reagents and conditions: (a)
MOMCl, iPr2NEt, CH2Cl2, 0 °C, 1 h, r.t., 18 h, 91% (b) LiBH4, H2O,
Et2O, 0 °C to r.t., 110 min, 63% (c) Dess Martin periodinane,
CH-6) and (CH-6, CH-1 ) are around 180° and 60° for
anti-lactones 4a and 4d, as well as 50° and 180° for syn-
CH2Cl2, NaHCO3,1 h (d) (CF3CH2O)2P(O)CH2C(O)OMe, 18-crown- lactones 4b and 4c. Thus, a close examination of the cou-
6, KHMDS, THF, 78 °C, 2.75 h, 77% (from 11a) (e) CBr4, i-PrOH,
82 °C, 15 h, 97%.
pling constants alone would not have allowed a clear de-
termination of the relative stereochemistry of the lactone
triad of cytostatin. In contrast, additional inspection of the
chemical shifts strongly suggest that syn, anti is the con-
figuration of the natural product at CH-5 to CH-1 .
lactones depicted in Figure 2 (determined by MM-2 cal-
culations). In all cases, the smallest subtituent at C-1 ,
In conclusion we have determined the most probable con-
figuration of the stereochemical triad at C-5 to C-1 in the
lactone moiety of cytostatin by comparing the chemical
shifts and the coupling constants of four diastereomers of
namely CH-1 , is nearly in ecliptic orientation to the CH3-
5 methyl group, thereby minimizing steric interaction. As
a consequence, the values of the dihedral angles (CH-5,
Table 1 1H NMR Data of Lactones 4a d and of Cytostatin 1a [ (ppm), coupling constants (Hz)]
O
2
3
4
O
4'
2'
6
5
1'
3'
4
Compound Cytostatin
Atom
Anti-anti 4a
Syn-syn 4b
Syn-anti 4c
Anti-syn 4d
=CH-3
=CH-4
CH-5
5.92 (dd, 9.6, 0.6 Hz)
5.92 (dd, 9.8, 2.3 Hz)
6.86 (dd, 9.8, 2.9 Hz)
2.76 (m)
5.94 (dd, 9.6, 0.8 Hz)
7.15 (dd, 9.6, 6.5 Hz)
5.94 (dd, 9.6, 0.8 Hz)
7.17 (dd, 9.6, 6.5 Hz)
5.92 (dd, 9.8, 2.7 Hz)
6.84 (dd, 9.8, 2.2 Hz)
2.70 (m)
7.15 (dd, 9.6, 6.5 Hz)
2.58 (m)
2.66 (ddquint, 0.8, 3.1, 2.58 (m)
7.0 Hz)
CH3-5
CH-6
CH-1
CH3-1
1.00 (d, 7.0 Hz)
4.11 (dd, 10.2, 2.7 Hz)
1.81 (m)
1.15 (d, 7.2 Hz)
4.07 (dd, 9.0, 3.3 Hz)
1.92 2.00 (m)
1.03 (d, 7.0 Hz)
4.09 (dd, 9.8, 3.1 Hz)
1.89 1.98 (m)
1.02 (d, 7.2 Hz)
1.11 (d, 7.2 Hz)
4.09 (dd, 10.6, 3.1 Hz) 4.11 (dd, 10.8, 2.4 Hz)
1.92 (m)
1.92 (dsext, 2.4, 7.0 Hz)
0.98 (d, 7.0 Hz)
0.98 (d, 6.8 Hz)
1.05 (d, 6.7 Hz)
1.10 (d, 6.3 Hz)
0.93 (d, 6.6 Hz)
a All spectra were recorded in MeOH-d4 with the same spectrometer (see Experimental Section)
Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Determination of the Relative Configuration of the C-2-C-1 -Fragment of Cytostatin
2099
Table 2 13C NMR Data of Lactones 4a d and of Cytostatin 1.a
(ppm)
tet), sept (septet). FAB and EI measurements were taken with a Jeol
SX 102A using a 3-nitrobenzyl alcohol (3-NBA) matrix. Optical ro-
tations were measured with a Perkin-Elmer Polarimeter 341. Flash
chromatography was performed using silica gel from Merck (Silica
gel 60). TLC was performed with aluminium-backed silica gel 60
F254 plates (Merck). Melting points were recorded on a Büchi B-540
apparatus and are uncorrected. MM2 calculations were performed
wih CS Chem3D Std® (CambridgeSoft Corporation).
Compound Cytostatin Anti-anti Syn-syn Syn-anti Anti-syn
atom
4a
4b
4c
4d
C=O
167.5
120.1
155.0
31.6
166.5
120.1
154.6
31.9
16.8
89.2
35.3
17.0
167.3
120.0
154.8
31.5
11.2
85.6
34.9
16.0
167.2
120.0
155.0
31.5
10.9
84.8
34.8
14.4
166.9
120.1
155.2
32.1
16.0
87.0
34.9
13.3
=CH-3
=CH-4
CH-5
CH3-5
CH-6
CH-1
CH3-1
(4R,5S)-3-[(2S,3S,4S)-3-Hydroxy-2,4-dimethylhept-6-enoyl]-4-
methyl-5-phenyl-1,3-oxazolidin-2-one (8a) and (4R,5S)-3-
[(2S,3R,4S)-3-Hydroxy-2,4-dimethylhept-6-enoyl]-4-methyl-5-
phenyl-1,3-oxazolidin-2-one (8b)
11.0
To a soln of oxalyl chloride (2.0 mL, 23.3 mmol) in CH2Cl2 (25 ml)
at –78 °C, a soln of DMSO (2.1 mL, 29.3 mmol) in CH2Cl2 (5 mL)
was added dropwise. The soln was stirred for 1 h at –78 °C. A soln
of the alcohol 5 (1.83 g, 18.3 mmol) in CH2Cl2 (5 mL) was added
dropwise and the soln was stirred for 2.5 h at –78 °C. Et3N (12.7
mL, 91.5 mmol) was added at –78 °C, the mixture was warmed to
r. t. and washed with a 1 M KH2PO4 soln (100 mL). The aq phase
was extracted with CH2Cl2 (10 mL). The organic phase was washed
with brine (5 mL), dried over Na2SO4, followed by activated molec-
ular sieves (4 Å). The soln of crude aldehyde 6 was used directly
without further purification.
85.6
35.6
14.9
a All spectra were recorded in MeOH-d4 with the same spectrometer
(see Experimental Section)
To a soln of the N-propionyloxazolidinone 7 (2.84 g, 12.2 mmol) in
CH2Cl2 (24 mL) at 0 °C freshly distilled Bu2BOTf (2.4 mL, 14.0
mmol) was added, immediately followed by iPr2NEt (2.4 mL, 14.0
mmol). The soln was stirred for 45 min at 0 °C, then cooled to
–78 °C. In a separate flask, the soln of crude aldehyde 6 precooled
to –78 °C was added via canula to a –78 °C cold 1 M soln of Et2AlCl
in hexanes (36.6 mL, 36.6 mmol). The resulting yellow soln was
stirred for 5 min at –78 °C, followed by the addition of –78 °C eno-
late soln via canula. The mixture was stirred for 2.6 h at –78 °C and
a soln of 30% aq H2O2 (9 mL) in MeOH (45 mL) was added slowly.
The resulting mixture was stirred 30 min at 0 °C, diluted with H2O
(100 mL) and extracted with Et2O (2 250 mL). The combined or-
ganic layers were washed with sat. NaHCO3 (50 mL), brine (50 mL)
and dried over Na2SO4. After evaporation of the solvent, the crude
product was purified by column chromatography on silica gel (cy-
clohexane–EtOAc, 3:1 to 2:1) to yield 1.37 g (34%) of the anti,anti-
aldol 8a as a white solid and 0.86 g (21%) of the syn,syn-aldol 8b as
a sticky white solid.
a relevant model compound with the values recorded for
the natural product. These results could not have been pre-
dicted from a thorough examination of the coupling con-
stants determined for cytostatin alone, since the side chain
attached to the lactone can rotate freely around the C6-C1
bond to adopt an optimal conformation.
All reactions were carried out under an argon atmosphere. All sol-
vents were distilled using standard procedures before use. THF was
distilled under argon from molten potassium. Et2O was distilled un-
der argon from molten Na/K alloy. CH2Cl2 was distilled under ar-
gon from CaH2. Dibutylboryltriflate was synthesized as previously
described.14 All other chemicals were purchased from commercial
sources and used without further purification. Yields refer to isolat-
ed and pure compounds. 1H and 13C NMR data were recorded on a
Varian Mercury 400 spectrometer. Signal multiplicities are abbre-
viated: d (doublet), t (triplet), q (quartet), quint (quintet), sext (sex-
Figure 2 Calculated conformations and dihedral angles of lactones 4a d (MM-2 calculations).
Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

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8a
L. Bialy et al.
PAPER
Rf 0.37 (cyclohexane–EtOAc, 3:1); [ ]D20 +40 (c 0.25, CHCl3); mp
Rf 0.45 (cyclohexane–EtOAc, 2:1); [ ]D 20 +47.6 (c 0.25, CHCl3);
115 °C (EtOAc–cyclohexane).
mp 75.2 °C.
1H NMR (400 MHz, CDCl3): = 7.36–7.45 (m, 3 H, Ph-H), 7.29–
1H NMR (400 MHz, CDCl3): = 7.36–7.45 (m, 3 H, Ph-H), 7.29–
7.32 (m, 2 H, Ph-H), 5.80 (dddd, 1 H, 2J = 16.8, 2J = 10.2, 2J = 8.0,
2J = 6.3 Hz, =CH), 5.68 (d, 1 H, 2J = 7.2 Hz, PhCHO), 5.00–5.10
(m, 2 H, =CH2), 4.78 (quint, 1 H, 2J = 6.6 Hz, NCH), 4.16 (quint, 1
H, 2J = 6.5 Hz, CH-2 ), 3.47 (t, 1 H, 2J = 5.9 Hz, CHOH), 2.41–2.48
(m, 1 H, CHH-5 ), 1.91–2.00 (m, 1 H, CHH-5 ), 1.65–1.75 (m, 1
H,CH-4 ), 1.29 (d, 3 H, 2J = 7.0 Hz, CH3-2 ), 0.95 (d, 3 H, 2J = 6.8
Hz, CH3-4 ), 0.92 (d, 3 H, 2J = 6.5 Hz, CH3-4).
7.32 (m, 2 H, Ph-H), 5.83 (dddd, 1 H, 2J = 16.8, 2J = 10.0, 2J = 8.0,
2
2J = 6.3 Hz, =CH), 5.68 (d, 1 H, J = 7.2 Hz, PhCHO), 5.02–5.10
(m, 2 H, =CH2), 4.79 (quint, 1 H, 2J = 6.6 Hz, NCH), 3.97 (dq, 1 H,
2
2
2J = 2.2, 2J = 7.0 Hz, CH-2 ), 3.66 (ddd, 1 H, J = 9.0, J = 3.0,
2J = 2.2 Hz, CHOH), 3.03 (d, 1 H, 2J = 3.0 Hz, OH), 2.50–2.57 (m,
1 H,CHH-5 ), 1.94–2.02 (m, 1 H, CHH-5 ), 1.64–1.74 (m, 1 H, CH-
2
2
4 ), 1.23 (d, 3 H, J = 7.0 Hz, CH3-2 ), 0.90 (d, 3 H, J = 6.5 Hz,
CH3-4 ), 0.90 (d, 3 H, 2J = 6.6 Hz, CH3-4).
13C NMR (100 MHz, CDCl3): = 177.5 (O=C-1), 153.1 (O=C-1 ),
137.2 (=CH), 133.1 (Ph-C), 129.0 (Ph-CH), 128.9 (Ph-C), 125.8
(Ph-CH), 116.4 (=CH2), 79.2 (CHOH), 79.0 (CHOPh), 55.1 (CHN),
39.8 (CH-2 ), 36.6 (CH-4 ), 35.6 (CH2-5 ), 16.5 (CH3-4 ), 15.6
(CH3-2 ), 14.6 (CH3-4).
13C NMR (100 MHz, CDCl3): = 177.9 (O=C-1), 152.6 (O=C-1 ),
137.2 (=CH), 133.2 (Ph-C), 129.0 (Ph-CH), 128.9 (Ph-CH), 125.7
(Ph-CH), 116.6 (=CH2), 79.1 (CHOPh), 75.0 (CHOPh), 54.9
(CHN), 39.6 (CH-2 ), 37.5 (CH2-5 ), 35.6 (CH-4 ), 15.3 (CH3-4),
14.5 (CH3-4 ), 9.6 (CH3-2 ).
MS (FAB): m/z (%) = 354.1 (53) [M + Na+], 332.1 (100) [MH+].
MS (FAB): m/z (%) = 332.2 (100) [MH+].
HRMS: m/z calcd for C19H26NO4 [MH+], 332.1862; found,
HRMS: m/z calcd for C19H26NO4 [MH+], 332.1862; found,
332.1848.
332.1872.
8b
(4S)-3-[(2R,3R,4S)-3-Hydroxy-2,4-dimethylhept-6-enoyl]-4-
Isopropyl-1,3-oxazolidin-2-one (8d)
Rf 0.37 (cyclohexane–EtOAc, 2:1); [ ]D 20 +39 (c 0.52, CHCl3).
The aldol adduct 8d was synthesized as described above for 8a
starting from N-propionyloxazolidinone 9 (537 mg, 2.9 mmol) and
was isolated as a colorless oil; yield: 317 mg. The product was con-
taminated by N-propionyloxazolidinone 9 which could not be sepa-
rated by column chromatography and was used without further
purification.
1H NMR (400 MHz, CDCl3): = 7.37–7.44 (m, 3 H, Ph-H), 7.28–
7.32 (m, 2 H, Ph-H), 5.78 (dddd, 1 H, 2J = 16.8, 2J = 10.0, 2J = 7.4,
2
2J = 6.5 Hz, =CH), 5.68 (d, 1 H, J = 7.2 Hz, PhCHO), 5.00–5.10
(m, 2 H, =CH2), 4.78 (quint, 1 H, 2J = 6.6 Hz, NCH), 4.10 (dq, 1 H,
2
2
2
2J = 4.3, J = 6.8 Hz, CH-2 ), 3.74 (dd, 1 H, J = 6.8, J = 4.3 Hz,
CHOH), 2.19–2.26 (m, 1 H,CHH-5 ), 1.91–2.00 (m, 1 H, CHH-5 ),
1.63–1.78 (m, 1 H, CH-4 ), 1.25 (d, 3 H, 2J = 6.8 Hz, CH3-2 ), 1.00
(d, 3 H, 2J = 6.6 Hz, CH3-4 ), 0.90 (d, 3 H, 2J = 6.6 Hz, CH3-4).
Rf 0.59 (cyclohexane–EtOAc, 2:1).
1H NMR (400 MHz, CDCl3): = 5.73–5.88 (m, 1 H, =CH), 4.99–
5.07 (m, 2 H, =CH2), 4.40–4.45 (m, 1 H, NCH), 4.20–4.29 (m, 2 H,
CH2O), 4.04 (dq, 1 H, 2J = 8.6, 2J = 6.8 Hz, CH-2 ), 3.63 (dd, 1 H,
2J = 8.6,2J = 3.3 Hz, CHOH), 2.41 (dsept, 1 H, 2J = 3.9,2J = 7.0 Hz,
CHCH3), 2.16–2.23 (m, 1 H, CHH-5 ), 1.99–2.07 (m, 1 H, CHH-5 ),
1.73 (dsext, 1 H, 2J = 3.3,2J = 6.8 Hz, CH-4 ), 1.11 (d, 3 H, 2J = 6.8
Hz, CH3-2 ), 0.93 (d, 3 H, 2J = 6.8 Hz, CH3-4 ), 0.91 (d, 3 H, 2J = 7.0
Hz, CHCH3), 0.89 (d, 3 H, 2J = 7.0 Hz, CHCH3).
13C NMR (100 MHz, CDCl3): = 177.2 (O=C-1), 152.7 (O=C-1 ),
136.7 (=CH), 133.3 (Ph-C), 129.0 (Ph-CH), 128.9 (Ph-CH), 125.8
(Ph-CH), 116.5 (=CH2), 79.0 (CHOPh), 75.0 (CHOH), 55.0 (CHN),
40.1 (CH-2 ), 37.9 (CH2-5 ), 35.6 (CH-4 ), 15.1 (CH3-4 ), 14.7
(CH3-4), 11.7 (CH3-2 ).
MS (FAB): m/z (%) = 354.1 (100) [M + Na+], 332.1 (86) [MH+].
HRMS: m/z calcd for C19H26NO4 [MH+], 332.1862; found,
MS (FAB): m/z (%) = 307.0 (100) [M + Na+], 284.1 (33) [MH]+.
HRMS: m/z calcd for C15H26NO4 [MH+], 284.1862; found,
332.1857.
(4R,5S)-3-[(2R,3S,4S)-3-Hydroxy-2,4-dimethylhept-6-enoyl]-4-
methyl-5-phenyl-1,3-oxazolidin-2-one (8c)
284.1841.
The crude aldehyde soln was synthesized as described above for 8a
starting from alcohol 5 (5.35 g, 53.5 mmol).
(4R,5S)-3-[(2S,3S,4S)-3-(Methoxymethoxy)-2,4-dimethylhept-
6-enoyl]-4-methyl-5-phenyl 1,3-oxazolidin-2-one (10a)
To a soln of the aldol 8a (1.30 g, 3.92 mmol) in CH2Cl2 (9.4 mL)
and iPr2NEt (8.7 mL, 51 mmol) at 0 °C (chloromethyl)methylether
(3.0 mL, 39 mmol) was added dropwise. After stirring for 1 h at
0 °C, the soln was stirred for another 18 h at r.t., a 1 M KH2PO4 soln
(50 mL) was added, the mixture was extracted with Et2O (3 100
mL), the combined organic layers were washed with brine (50 mL)
and dried over Na2SO4. After evaporation of the solvent, the crude
product was purified by column chromatography on silica gel (cy-
clohexane–EtOAc, 5:1). The product was isolated as a colorless oil;
yield: 1.34 g (91%).
To a soln of N-propionyloxazolidinone 7 (12.5 g, 53.5 mmol) and
iPr2NEt (12.3 mL, 72.2 mmol) in CH2Cl2 (180 mL) at 0 °C a 1 M
soln of Bu2BOTf in CH2Cl2 (64.2 mL, 64.2 mmol) was added drop-
wise. The soln was stirred for 45 min at 0 °C, then cooled to –78 °C.
The raw aldehyde soln was added dropwise, the soln was stirred for
90 min at –78 °C and then for 90 min at r.t. The reaction was
quenched by addition of a 1 M KH2PO4 soln (450 mL), extracted
with CH2Cl2 (2 500 mL). After evaporation of the solvent, the
crude product was redissolved in MeOH (100 mL), cooled to 0 °C
and 30% aq H2O2 (150 mL) was added dropwise. The mixture was
stirred for 1 h at r.t., diluted with brine (300 mL) and extracted with
CH2Cl2 (3 300 mL). The combined organic layers were washed
with brine (100 mL) and dried over Na2SO4. After evaporation of
the solvent, the crude product was purified by column chromatog-
raphy on silica gel (cyclohexane–EtOAc, 9:2). The product (15.41
g) was dissolved in a minimum of hot EtOAc (4–5 mL), diluted with
cyclohexane (60 mL), and the crystals were collected after 24 h. The
mother liquor contained material suitable for another recrystalliza-
tion. The product was isolated as colourless needles; yield: 12.0 g
(68%).
Rf 0.47 (cyclohexane–EtOAc, 3:1); [ ]D20 +52 (c 0.505, CHCl3).
1H NMR (400 MHz, CDCl3): = 7.34–7.43 (m, 3 H, Ph-H), 7.28–
7.31 (m, 2 H, Ph-H), 5.80 (dddd, 1 H, 2J = 17.0, 2J = 10.2, 2J = 7.6,
2
2J = 6.5 Hz, =CH), 5.65 (d, 1 H, J = 7.4 Hz, PhCHO), 4.98–5.08
(m, 2 H, =CH2), 4.78 (quint, 1 H, 2J = 7.0 Hz, NCH), 4.65 [d, 1 H,
1J = 6.5 Hz, MOM-CHHO], 4.52 [d, 1 H, 1J = 6.5 Hz, MOM-
CHHO], 4.33 (dq, 1 H, 2J = 8.9, 2J = 7.0 Hz, CH-2 ), 3.76 (dd, 1 H,
2J = 8.9, 2J = 2.5 Hz, CHOMOM), 3.33 (s, 3 H, MOM-CH3O),
2.34–2.42 (m, 1 H, CHH-5 ), 1.90–1.99 (m, 1 H, CHH-5 ), 1.78–
Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Determination of the Relative Configuration of the C-2-C-1 -Fragment of Cytostatin
2101
1.87 (m, 1 H, CH-4 ), 1.16 (d, 3 H, 2J = 7.0 Hz, CH3-2 ), 1.02 (d, 3
H, 2J = 7.0 Hz, CH3-4 ), 0.88 (d, 3 H, 2J = 6.5 Hz, CH3-4).
HRMS: m/z calcd for C21H30NO5 [MH+], 376.2124; found,
376.2113.
13C NMR (100 MHz, CDCl3): = 176.0 (O=C-1), 152.8 (O=C-1 ),
137.8 (=CH), 133.6 (Ph-C), 128.9 (Ph-CH), 128.8 (Ph-CH), 125.8
(Ph-CH), 116.0 (=CH2), 98.5 (MOM-CH2O), 85.7 (CHOMOM),
78.7 (CHOPh), 56.2 (MOM-CH3O), 54.9 (CHN), 40.9 (CH-2 ),
35.5 (CH2-5 ), 34.8 (CH-4 ), 17.1 (CH3-4 ), 15.0 (CH3-2 ), 14.7
(CH3-4).
(4S)-4-Isopropyl-3-[(2R,3R,4S)-3-(methoxymethoxy)-2,4-dime-
thylhept-6-enoyl]-1,3-oxazolidin-2-one (10d)
The oxazolidinone 10d was synthesized as described above for 10a
starting from N-propionyloxazolidinone 8d and was isolated as a
white, waxy solid; yield: 313 mg (36% over 2 steps).
Rf 0.48 (cyclohexane–EtOAc, 3:1); [ ]D20 +65 (c 0.3, CHCl3).
MS (FAB): m/z (%) = 398.1 (20) [M + Na+], 376.1 (27) [MH]+,
344.1 (100) [M – CH3O]+.
1H NMR (400 MHz, CDCl3): = 5.73–5.84 (m, 1 H, =CH), 5.00–
5.08 (m, 2 H, =CH2), 4.63 (d, 1 H, 1J = 6.5 Hz, MOM-CHHO ), 4.49
HRMS: m/z calcd for C21H30NO5 [MH+], 376.2124; found,
376.2115.
1
[d, 1 H, J = 6.5 Hz, MOM-CHHO], 4.40–4.47 (m, 1 H, NCH),
4.17–4.27 (m, 3 H, CH-2 , CH2-5), 3.81 (dd, 1 H, 2J = 9.4, 2J = 1.8
Hz, CHOMOM), 3.33 (s, 3 H, MOM-CH3O), 2.23–2.40 [m, 2 H,
CHCH3, CH2-5 (1)], 2.00–2.09 (m, 1 H, CH2-5 ), 1.67–1.77 (m, 1
H, CH-4 ), 1.08 (d, 3 H, 2J = 7.0 Hz, CH3-2 ), 0.95 (d, 3 H, 2J = 6.8
(4R,5S)-3-[(2S,3R,4S)-3-(Methoxymethoxy)-2,4-dimethylhept-
6-enoyl]-4-methyl-5-phenyl 1,3-oxazolidin-2-one (10b)
The oxazolidinone 10b was synthesized as described above for 10a
starting from N-propionyloxazolidinone 8b (331 mg, 1.00 mmol)
and was isolated as a colorless oil; yield: 332 mg (88%).
2
Hz, CH3-4 ), 0.91 (d, 3 H, J = 7.0 Hz, CHCH3), 0.88 (d, 3 H,
2J = 7.0 Hz, CHCH3).
13C NMR (100 MHz, CDCl3): = 176.3 (O=C-1), 153.8 (O=C-1 ),
137.7 (=CH), 116.3 (=CH2), 98.6 (MOM-CH2O), 84.0 (CHO-
MOM), 62.8 (CH2-5), 58.7 (CHN), 56.0 (MOM-CH3O), 41.1 (CH-
2 ), 38.8 (CH2-5 ), 34.6 (CH-4 ), 28.2 (CHCH3), 18.2 (CHCH3),
15.0 (CH3-2 ), 14.4 (CHCH3), 13.6 (CH3-4 ).
Rf 0.4 (cyclohexane–EtOAc, 4:1); [ ]D 20 +57.6 (c 0.205, CHCl3).
1H NMR (400 MHz, CDCl3): = 7.36–7.44 (m, 3 H, Ph-H), 7.28–
7.32 (m, 2 H, Ph-H), 5.70–5.80 (m, 1 H, =CH), 5.66 (d, 1 H, 2J = 7.4
2
Hz, PhCHO), 4.98–5.06 (m, 2 H, =CH2), 4.79 (dq, 1 H, J = 7.4,
2J = 6.6 Hz, NCH), 4.66 (s, 2 H, MOM-CH2O), 4.11 (quint, 1 H,
MS (FAB): m/z (%) = 350.1 (30) [M + Na+], 328.1 (42) [MH+],
2
2
2J = 7.0 Hz, CH-2 ), 3.83 (dd, 1 H, J = 7.0, J = 3.7 Hz, CHO-
MOM), 3.39 (s, 3 H, MOM-CH3O), 2.24–2.32 (m, 1 H, CHH-5 ),
1.94–2.03 (m, 1 H, CHH-5 ), 1.60–1.70 (m, 1 H, CH-4 ), 1.27 (d, 3
H, 2J = 7.0 Hz, CH3-2 ), 0.95 (d, 2J = 6.8 Hz, 3 H, CH3-4 ), 0.88 (d,
3 H, 2J = 6.6 Hz, CH3-4).
296.1 (100) [M – OCH3]+, 266.1 (66) [M – C2H5O2]+.
HRMS: m/z calcd for C17H30NO5 [MH+], 328.2124; found,
328.2146.
(2R,3S,4S)-3-(Methoxymethoxy)-2,4-dimethylhept-6-en-1-ol
(11a)
13C NMR (100 MHz, CDCl3): = 175.7 (O=C-1), 152.8 (O=C-1 ),
137.6 (=CH), 133.5 (Ph-C), 128.9 (Ph-CH), 128.8 (Ph-CH), 125.8
(Ph-CH), 116.2 (=CH2), 98.6 (MOM-CH2O), 83.4 (CHOMOM),
79.0 (CHOPh), 56.2 (MOM-CH3O), 54.9 (CHN), 41.0 (CH-2 ),
38.4 (CH2-5 ), 37.1 (CH-4 ), 14.7 (CH3-4), 14.6 (CH3-4 ), 14.1
(CH3-2 ).
To a soln of the oxazolidinone 10a (1.30 g, 3.45 mmol) in Et2O (70
mL) and H2O (68 L, 3.8 mmol) at 0 °C a 2 M soln of LiBH4 (1.9
mL, 3.8 mmol) was added dropwise over 10 min. The soln was
stirred for 110 min at r.t. and a 1 M soln of NaOH (7 mL) and H2O
(12 mL) were added carefully. The mixture was stirred for 15 min,
extracted with Et2O (3 50 mL), the organic phase was washed
with brine (50 mL) and dried over Na2SO4. After evaporation of the
solvent, the crude product was purified by column chromatography
on silica gel (pentane–Et2O, 1:1 to 1:2). The product was isolated as
a colorless oil; yield: 439 mg (63%).
MS (FAB): m/z (%) = 398.1 (92) [M + Na+], 376.1 (13) [MH+],
344.1 (86) [M – CH3O]+, 314.1 (100) [M–C2H5O2]+.
HRMS: m/z calcd for C21H30NO5 [MH+], 376.2124; found,
376.2140.
Rf 0.36 (cyclohexane–EtOAc, 2:1); [ ]D20 +51.6 (c 0.5, CHCl3).
(4R,5S)-3-[(2R,3S,4S)-3-(Methoxymethoxy)-2,4-dimethylhept-
6-enoyl]-4-methyl-5-phenyl 1,3-oxazolidin-2-one (10c)
The oxazolidinone 10c was synthesized as described above for 10a
starting from N-propionyloxazolidinone 8c (9.35 g, 28.2 mmol) and
was isolated as a colorless oil; yield: 10.1 g (95%).
1H NMR (400 MHz, CDCl3): = 5.77 (dddd, 1 H, 2J = 16.8,
2J = 10.2, 2J = 7.4, 2J = 6.1 Hz, =CH), 4.98–5.05 (m, 2 H, =CH2),
1
2
4.68 (s, 2 H, MOM-CH2O), 3.83 (dd, 1 H, J = 11.3, J = 3.5 Hz,
CHHOH), 3.53 (dd, 1 H, 1J = 11.3, 2J = 4.3 Hz, CHHOH), 3.43 (s,
Rf 0.71 (cyclohexane–EtOAc, 2:1); [ ]D20 +16.4 (c 0.44, CHCl3).
2
3 H, MOM-CH3O), 3.33 (dd, 1 H, J = 7.4, 2J = 3.7 Hz, CHO-
1H NMR (400 MHz, CDCl3): = 7.34–7.44 (m, 3 H, Ph-H), 7.29–
MOM), 2.5–3.0 (br s, 1 H, OH), 2.24–2.32 (m, 1 H, CHH2-5), 1.76–
1.91 (m, 3 H, CHH-5, CH-2, CH-4), 1.01 (d, 3 H, 2J = 7.0 Hz, CH3-
2), 0.95 (d, 3 H, 2J = 6.8 Hz, CH3-4).
13C NMR (100 MHz, CDCl3): = 137.7 (=CH), 116.1 (=CH2), 99.1
(MOM-CH2O), 87.7 (CHOMOM), 65.4 (CH2OH), 56.4 (MOM-
CH3O), 37.1 (CH-2), 35.8 (CH2-5), 35.7 (CH-4), 17.0 (CH3-4), 15.6
(CH3-2).
7.33 (m, 2 H, Ph-H), 5.79 (dddd, 1 H, 2J = 16.8, 2J = 10.2, 2J = 7.8,
2
2J = 6.1 Hz, =CH), 5.65 (d, 1 H, J = 6.8 Hz, PhCHO), 5.00–5.07
2
(m, 2 H, =CH2), 4.66 (quint, 1 H, J = 6.8, NCH), 4.64 (d, 1 H,
1
1J = 7.1 Hz, MOM-CHHO), 4.63 (d, 1 H, J = 7.1 Hz, MOM-
CHHO), 4.00 (dq, 1 H, 2J = 4.1, 2J = 6.8 Hz CH-2 ), 3.68 (dd, 1 H,
2J = 7.2, 2J = 4.1 Hz, CHOMOM), 3.36 (s, 3 H, MOM-CH3O),
2.35–2.42 (m, 1 H, CHH-5 ), 1.82–1.90 (m, 1 H, CHH2-5 ), 1.70–
MS (FAB): m/z (%) = 225.1 (31) [M + Na+], 203.2 (69) [MH+],
2
1.80 (m, 1 H, CH-4 ), 1.21 (d, 3 H, J = 6.8 Hz, CH3-2 ), 0.99 (d,
171.1 (100) [M – OCH3]+.
2J = 6.8 Hz, 3 H, CH3-4 ), 0.92 (d, 3 H, 2J = 6.6 Hz, CH3-4).
HRMS: m/z calcd for C11H23NaO3 [M + Na+], 225.1467; found,
225.1469.
13C NMR (100 MHz, CDCl3): = 175.1 (O=C-1), 153.1 (O=C-1 ),
137.4 (=CH), 133.4 (Ph-C), 128.8 (Ph-CH), 128.8 (Ph-CH), 125.8
(Ph-CH), 116.4 (=CH2), 99.0 (MOM-CH2O), 85.2 (CHOMOM),
79.3 (CHOPh), 56.8 (MOM-CH3O), 55.8 (CHN), 41.2 (CH-2 ),
37.1 (CH2-5 ), 36.9 (CH-4 ), 15.6 (CH3-4 ), 14.4 (CH3-4), 10.6
(CH3-2 ).
(2R,3R,4S)-3-(Methoxymethoxy)-2,4-dimethylhept-6-en-1-ol
(11b)
The alcohol 11b was synthesized as described above for 11a start-
ing from N-propionyloxazolidinone 10b (305 mg, 0.812 mmol) and
was isolated as a colorless oil; yield: 118 mg (72%).
MS (FAB): m/z (%) = 376.3 (100) [MH+], 344.3 (98) [M – CH3O]+.
Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

2102
L. Bialy et al.
PAPER
Rf 0.19 (cyclohexane–EtOAc, 2:1); [ ]D20 – 74 (c 0.535, CHCl3).
periodinane in CH2Cl2 (0.92 mL, 0.43 mmol) was added dropwise.
The mixture was stirred for 70 min and then poured into a well-
stirred mixture of a sat. NaS2O3 soln (20 mL), a sat. NaHCO3 soln
(20 mL) and Et2O (50 mL). The mixture was stirred for 1 h, extract-
ed with Et2O (2 50 mL), the organic phase was washed with brine
(50 mL) and dried over Na2SO4, yielding 56 mg of the crude alde-
hyde as a colorless oil, which was directly used in the next step
without purification.
1H NMR (400 MHz, CDCl3): = 5.70–5.80 (m, 1 H, =CH), 4.99–
5.05 (m, 2 H, =CH2), 4.67 (s, 2 H, MOM-CH2O), 3.42–3.56 (m, 3
H, CH2OH, CHOMOM), 3.42 (s, 3 H, MOM-CH3O), 2.6–2.8 (br s,
1 H, OH), 2.15–2.22 (m, 1 H, CHH-5), 1.94–2.03 (m, 1 H, CH-2),
1.75–1.91(m, 2 H, CHH-5, CH-4), 0.96 (d, 3 H, 2J = 6.6 Hz, CH3-
4), 0.82 (d, 3 H, 2J = 7.0 Hz, CH3-2).
13C NMR (100 MHz, CDCl3): = 136.7 (=CH), 116.5 (=CH2), 98.8
(MOM-CH2O), 87.5 (CHOMOM), 65.3 (CH2OH), 56.3 (MOM-
CH3O), 37.9 (CH2-5), 37.1 (CH-2), 33.7 (CH-4), 16.1 (CH3-4), 10.6
(CH3-2).
Rf 0.63 (cyclohexane–EtOAc, 2:1).
To a soln of 18-crown-6 (357 mg, 1.35 mmol) and bis(2,2,2-triflu-
oroethyl)(methoxy-carbonylmethyl)phosphonate (0.14 mL, 0.66
mmol) in THF (8 mL) at –78 °C a 0.5 M soln of potassium hexam-
ethyldisilazide in toluene (1.0 mL, 0.5 mmol) was added dropwise
over 15 min. The soln was stirred for 35 min at –78 °C and a soln of
the crude aldehyde in THF (1 mL) was added dropwise over 45 min.
The soln was stirred for 2 h, 45 min at –78 °C, quenched with a sat.
NH4Cl soln (12 mL) at –78 °C, warmed to r.t. and extracted with
Et2O (3 40 mL). The combined organic layers were washed with
brine (20 mL) and dried over Na2SO4. After evaporation of the sol-
vent, the crude product was purified by column chromatography on
silica gel (pentane–Et2O, 20:1 to 10:1). The product was isolated as
a colorless oil; yield: 57 mg (77% over 2 steps).
MS (FAB): m/z (%) = 225.1 (21) [M + Na+], 171.1 (100) [M –
OCH3]+.
HRMS: m/z calcd for C11H23O3 [MH+], 203.1647; found, 203.1627.
(2S,3S,4S)-3-(Methoxymethoxy)-2,4-dimethylhept-6-en-1-ol
(11c)
The alcohol 11c was synthesized as described above for 11a starting
from N-propionyloxazolidinone 10c (10.0 g, 26.6 mmol) and was
isolated as a colorless oil; yield: 4.19 g (78%).
Rf 0.22 (cyclohexane–EtOAc, 3:1); [ ]D20 +113 (c 0.356, CHCl3)
Rf 0.54 (cyclohexane–EtOAc, 5:1); [ ]D20 – 25.3 (c 0.265, CHCl3).
1H NMR (400 MHz, CDCl3): = 6.41 (dd, 1 H, 2J = 11.5, 2J = 10.2
1H NMR (400 MHz, CDCl3): = 5.77 (dddd, 2J = 17.2, 2J = 10.5,
2J = 7.9,2J = 5.9 Hz, 1 H, =CH), 5.05–5.08 (m, 2 H, =CH2), 4.68 (s,
2 H, MOM-CH2O), 3.51–3.47 (m, 2 H, CH2OH), 3.43 (s, 3 H,
2
Hz, =CH-3), 5.77 (d, 1 H, J = 11.5 Hz, =CH-2), 5.69–5.80 (m, 1
2
MOM-CH3O), 3.41 (dd, J = 8.6, 2J = 2.5 Hz, 1 H, CHOMOM),
H, =CH-8), 4.97–5.05 (m, 2 H, =CH2), 4.68 (s, 2 H, MOM-CH2O),
3.89 (qdd, 1 H, 2J = 6.8, 2J = 3.3, 2J = 10.2 Hz, CH-4), 3.70 (s, 3 H,
OCH3-1), 3.40 (s, 3 H, MOM-CH3O), 3.26 (dd, 1 H, 2J = 6.6,
2J = 3.3 Hz, CHOMOM), 2.28–2.36 (m, 1 H, CHH-7), 1.82–1.91
(m, 1 H, CHH-7), 1.63–1.74 (m, 1 H, CH-6), 1.09 (d, 3 H, 2J = 6.8
Hz, CH3-4), 0.85 (d, 3 H, 2J = 6.8 Hz, CH3-6).
13C NMR (100 MHz, CDCl3): = 166.8 (C=O), 152.8 (=CH-3),
137.5 (=CH-8), 118.4 (=CH-2), 116.1 (=CH2), 98.2 (MOM-CH2O),
86.9 (CHOMOM), 56.2 (MOM-CH3O), 51.2 (OCH3-1), 37.3 (CH2-
7), 36.9 (CH-6), 34.8 (CH-4), 18.6 (CH3-4), 15.8 (CH3-6).
2.79 (br s,1 H, OH), 2.37–2.41 (m, 1 H, CHH-5), 1.92–1.99 (m, 1
H, CH-2), 1.74–1.86 (m, 2 H, CHH-5), CH-4), 0.84 (d, 2J = 6.5 Hz,
3 H, CH3-4), 0.79 (d, 2J = 6.9 Hz, 3 H, CH3-2).
13C NMR (100 MHz, CDCl3): = 137.3 (=CH), 116.3 (=CH2), 99.2
(MOM-CH2O), 83.9 (CHOMOM), 65.1 (CH2OH), 56.3 (MOM-
CH3O), 37.7 (CH2-5), 36.8 (CH-4), 36.0 (CH-2), 15.7 (CH3-4), 9.8
(CH3-2).
MS (FAB): m/z (%) = 203.1 (16) [MH+], 171.1 (100) [M – OCH3]+.
HRMS: m/z calcd for C11H23O3 [MH+], 203.1647; found, 203.1660.
MS (FAB, glycerine): m/z (%) = 279.1 (43) [M + Na+], 257.1 (37)
[M + H+], 225.1 (100) [M – CH3O]+, 195.1 (62) [M – C2H5O2]+.
(2S,3R,4S)-3-(Methoxymethoxy)-2,4-dimethylhept-6-en-1-ol
(11d)
The alcohol 11d was synthesized as described above for 11a start-
ing from N-propionyloxazolidinone 10d (293 mg, 0.895 mmol) and
was isolated as a colorless oil; yield: 84 mg (46%).
Rf 0.2 (cyclohexane–EtOAc, 2:1); [ ]D20 – 66 (c 0.485, CHCl3)
1H NMR (400 MHz, CDCl3): = 5.71–5.81 (m, 1 H, =CH), 5.00–
5.06 (m, 2 H, =CH2), 4.66–4.70 (m, 2 H, MOM-CH2), 3.81 (ddd, 1
HRMS: m/z calcd for C14H24NaO4 [M + Na+], 279.1572; found,
279.1588.
Methyl (2Z,4R,5R,6S)-5-(methoxymethyl)-4,6-dimethylnona-
2,8-dienoate (12b)
The ester 12b was synthesized as described above for 12a starting
from alcohol 11b (58 mg, 0.287 mmol) and was isolated as a color-
less oil; yield: 48 mg (65% over 2 steps).
2
2
H, 1J = 11.1, J = 6.1, J = 3.5 Hz, CHHOH), 3.51 (ddd, 1 H,
Rf 0.56 (cyclohexane–EtOAc, 5:1); [ ]D20 –48 (c 0.12, CHCl3)
1J = 11.1,2J = 7.0,2J = 4.1 Hz, CHHOH), 3.42 (s, 3 H, MOM-CH3),
3.38 (dd, 1 H, J = 8.8, 2J = 2.5 Hz, CHOMOM), 2.90 (t, 1 H,
2
1H NMR (400 MHz, CDCl3): = 6.05 (dd, 1 H, 2J = 11.5, 2J = 10.4
Hz, =CH-3), 5.70–5.80 (m, 2 H, =CH-2, =CH-8), 4.98–5.06 (m, 2
H, =CH2), 4.65 (s, 2 H, MOM-CH2O), 3.77–3.87 (m, 1 H, CH-4),
3.70 (s, 3 H, OCH3-1), 3.40 (s, 3 H, MOM-CH3O), 3.24 (dd, 1 H,
2J = 6.5 Hz, OH), 2.12–2.20 (m, 1 H, CHH-5), 1.96–2.05 (m, 1 H,
CHH-5), 1.71–1.86 (m, 2 H, CH-2, CH-4), 0.95 (d, 3 H, 2J = 7.0 Hz,
CH3-4), 0.88 (d, 3 H, 2J = 6.8 Hz, CH3-2).
2
2J = 7.0, J = 3.5 Hz, CHOMOM), 2.17–2.25 (m, 1 H, CHH-7),
13C NMR (100 MHz, CDCl3): = 137.5 (=CH), 116.4 (=CH2), 99.1
(MOM-CH2O), 87.6 (CHOMOM), 65.5 (CH2OH), 56.4 (MOM-
CH3O), 39.0 (CH2-5), 37.7 (CH-2), 35.6 (CH-4), 15.2 (CH3-4), 13.4
(CH3-2).
1.92–2.00 (m, 1 H, CHH-7), 1.61–1.68 (m, 1 H, CH-6), 1.06 (d, 3
H, 2J = 6.6 Hz, CH3-4), 0.91 (d, 3 H, 2J = 6.8 Hz, CH3-6).
13C NMR (100 MHz, CDCl3): = 166.8 (C=O), 152.9 (=CH-3),
137.6 (=CH-8), 118.5 (=CH-2), 116.3 (=CH2), 98.6 (MOM-CH2O),
86.9 (CHOMOM), 56.2 (MOM-CH3O), 51.3 (OCH3-1), 38.7 (CH2-
7), 36.6 (CH-6), 36.0 (CH-4), 16.4 (CH3-4), 14.4 (CH3-6).
MS (FAB): m/z (%) = 225.1 (32) [M + Na+], 171.1 (100) [M –
OCH3]+.
HRMS: m/z calcd for C11H23O3 [MH+], 203.1647; found, 203.1654.
MS (FAB): m/z (%) = 279.1 (17) [M + Na+], 257.1 (24) [M + H+],
225.1 (70) [M – CH3O]+, 195.1 (100) [M–C2H5O2]+.
Methyl (2Z,4R,5S,6S)-5-(methoxymethyl)-4,6-dimethylnona-
2,8-dienoate (12a)
To a slurry of alcohol 11a (58 mg, 0.287 mmol) and NaHCO3 (277
mg, 3.30 mmol) in CH2Cl2 (5.6 mL) a 15% soln of Dess–Martin
HRMS: m/z calcd for C14H24NaO4 [M + Na+], 279.1572; found,
279.1567.
Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Determination of the Relative Configuration of the C-2-C-1 -Fragment of Cytostatin
2103
Methyl (2Z,4S,5S,6S)-5-(methoxymethyl)-4,6-dimethylnona-
2,8-dienoate (12d)
The ester 12d was synthesized as described above for 12a starting
from alcohol 11d (58 mg, 0.287 mmol) and was isolated as a color-
less oil; yield: 45 mg (61% over 2 steps).
13C NMR (100 MHz, MeOH-d4): = 166.5 (C=O), 154.6 (=CH-4),
138.0 (=CH-3 ), 120.1 (=CH-3), 119.9 (=CH2), 89.2 (CHO), 35.9
(CH2-2 ), 35.3 (CH-1 ), 31.9 (CH-5), 17.0 (CH3-1 ), 16.8 (CH3-5).
MS (FAB): m/z (%) = 203.0 (25) [M + Na+], 181.1 (100) [M + H+].
HRMS: m/z calcd for C11H17O2 [MH+], 181.1229; found, 181.1230.
Rf 0.56 (cyclohexane–EtOAc, 5:1); [ ]D20 +43.9 (c 0.28, CHCl3).
1H NMR (400 MHz, CDCl3): = 6.36 (dd, 1 H, 2J = 11.6, 2J = 10.2
(5R,6R)-5-Methyl-6-[(1S)-1-methylbut-3-enyl)]-5,6-dihydro-
2H-pyran-2-one (4b)
2
Hz, =CH-3), 5.77 (dd, 1 H, J = 11.6, 3J = 1.0 Hz, =CH-2), 5.68–
5.78 (m, 1 H, =CH-8), 4.97–5.04 (m, 2 H, =CH2), 4.63–4.67 (m, 2
H, MOM-CH2O), 3.84–3.92 (m, 1 H, CH-4), 3.70 (s, 3 H, OCH3-1),
3.38 (s, 3 H, MOM-CH3O), 3.31 (t, 1 H, 2J = 4.9 Hz, CHOMOM),
2.16–2.24 (m, 1 H, CHH-7), 1.84–1.93 (m, 1 H, CHH-7), 1.67–1.75
The lactone 4b was synthesized as described above for 4a starting
from ester 12b (31 mg, 121 mol) and was isolated as a colorless
oil; yield: 19 mg (87%).
20
Rf 0.5 (cyclohexane–EtOAc, 2:1); [ ]D
168 (c 0.415, CHCl3).
2
(m, 1 H, CH-6), 1.06 (d, 3 H, J = 6.8 Hz, CH3-4), 0.93 (d, 3 H,
1H NMR (400 MHz, MeOH-d4): = 7.15 (dd, 1 H, 2J = 9.6, 2J = 6.5
2J = 6.8 Hz, CH3-6).
2
3
Hz, =CH-4), 5.94 (dd, 1 H, J = 9.6, J = 0.8 Hz, =CH-3), 5.78
5.89 (m, 1 H, =CH-3 ), 5.04 5.12 (m, 2 H, =CH2), 4.09 (dd, 1 H,
2J = 9.8, 2J = 3.1 Hz, CH-O), 2.66 (ddquint, 1 H, 3J = 0.8, 2J = 3.1,
2J = 7.0 Hz, CH-5), 2.22 2.29 (m, 1 H, CHH-2 ), 1.89 1.98 (m, 2
H, CH-1 , CHH-2 ), 1.10 (d, 3 H, 2J = 6.3 Hz, CH3-1 ), 1.03 (d, 3 H,
2J = 7.0 Hz, CH3-5).
13C NMR (100 MHz, CDCl3): = 166.8 (C=O), 153.2 (=CH-3),
137.4 (=CH-8), 118.5 (=CH-2), 116.2 (=CH2), 98.2 (MOM-CH2O),
86.4 (CHOMOM), 56.2 (MOM-CH3O), 51.2 (OCH3-1), 38.0 (CH2-
7), 36.6 (CH-6), 35.4 (CH-4), 18.4 (CH3-4), 15.0 (CH3-6).
MS (FAB): m/z (%) = 279.1 (15) [M + Na+], 257.1 (41) [MH+],
225.1 (100) [M – CH3O]+, 195.1 (70) [M–C2H5O2]+.
13C NMR (100 MHz, MeOH-d4): = 167.3 (C=O), 154.8 (=CH-4),
136.6 (=CH-3 ), 120.0 (=CH-3), 117.6 (=CH2), 85.6 (CHO), 37.2
(CH2-2 ), 34.9 (CH-1 ), 31.5 (CH-5), 16.0 (CH3-1 ), 11.2 (CH3-5).
HRMS: m/z calcd for C14H24NaO4 [M + Na+], 279.1572; found,
279.1591.
MS (FAB): m/z (%) = 203.1 (12) [M + Na+], 181.1 (100) [MH+].
HRMS: m/z calcd for C11H17O2 [MH+], 181.1229; found, 181.1237.
Methyl (2Z,4S,5R,6S)-5-(methoxymethyl)-4,6-dimethylnona-
2,8-dienoate (12c)
The ester 12c was synthesized as described above for 12a starting
from alcohol 11c (108 mg, 0.535 mmol) and was isolated as a col-
orless oil; yield: 60 mg (44% over 2 steps).
Rf 0.38 (cyclohexane–EtOAc, 10:1); [ ]D20 +72.6 (c 1.15, CHCl3)
(5S,6S)-5-Methyl-6-[(1S)-1-methylbut-3-enyl)]-5,6-dihydro-
2H-pyran-2-one (4c)
The lactone 4c was synthesized as described above for 4a starting
from ester 12c (32 mg, 0.125 mmol) and was isolated as a colorless
oil; yield: 16 mg (71%).
1H NMR (400 MHz, CDCl3): = 6.17 (dd, 1 H, 2J = 11.5, 2J = 10.4
Hz, =CH-3), 5.75 (dd, 1 H, 2J = 11.5, 3J = 1.0 Hz, =CH-2), 5.70–
5.80 (m, 1 H, =CH-8), 4.96–5.03 (m, 2 H, =CH2), 4.65 [d, 1 H,
1J = 6.6 Hz, MOMCHHO], 4.62 [d, 1 H, 1J = 6.6 Hz, MOM-
CHHO], 3.78–3.88 (m, 1 H, CH-4), 3.70 (s, 3 H, OCH3-1), 3.40 (s,
Rf 0.25 (cyclohexane–EtOAc, 10:1); [ ]D20 +139.3 (c 0.4, CHCl3).
1H NMR (400 MHz, MeOH-d4): = 7.17 (dd, 1 H, 2J = 9.6, 2J = 6.5
Hz, CH-4), 5.94 (dd, 1 H, 2J = 9.6, 3J = 0.8 Hz, =CH-3), 5.83 (dddd,
1 H, 2J = 16.8, 2J = 10.4, 2J = 8.2, 2J = 6.1 Hz, =CH-3 ), 5.04 5.11
(m, 2 H, =CH2), 4.09 (dd, 1 H, 2J = 10.6, 2J = 3.1 Hz, CH-O), 2.54
2.62 (m, 2 H, CH-5, CHH-2 ), 1.98 2.06 (m, 1 H, CHH-2 ), 1.86
1.97 (m, 1 H, CH-1 ), 1.02 (d, 3 H, 2J = 7.2 Hz, CH3-5), 0.93 (d, 3
H, 2J = 6.6 Hz, CH3-1 ).
13C NMR (100 MHz, MeOH-d4): = 167.2 (C=O), 155.0 (=CH-4),
137.0 (=CH-3 ), 120.0 (=CH-3), 117.5 (=CH2), 84.8 (CHO), 37.6
(CH2-2 ), 34.8 (CH-1 ), 31.5 (CH-5), 14.4 (CH3-1 ), 10.9 (CH3-5).
2
3 H, MOM-CH3O), 3.22 (t, 1 H, J = 5.7 Hz, CHOMOM), 2.31–
2.40 [m, 1 H, CHH-7], 1.80–1.88 [m, 1 H, CHH-7], 1.66–1.76 (m,
1 H, CH-6), 1.05 (d, 2J = 6.8 Hz, 3 H, CH3-4), 0.94 (d, 2J = 6.8 Hz,
3 H, CH3-6).
13C NMR (100 MHz, CDCl3): = 166.7 (C=O), 153.8 (=CH-3),
137.8 (=CH-8), 118.2 (=CH-2), 116.0 (=CH2), 98.6 (MOM-CH2O),
87.2 (CHOMOM), 56.2 (MOM-CH3O), 51.3 (OCH3-1), 36.8 (CH2-
7), 36.4 (CH-6), 35.1 (CH-4), 16.3 (CH3-4), 15.1 (CH3-6).
MS (FAB): m/z (%) = 181.1 (100) [MH+].
HRMS: m/z calcd for C11H17O2 [MH+], 181.1229; found, 181.1220.
MS (FAB): m/z (%) = 279.1 (16) [M + Na+], 257.1 (47) [MH+],
225.1 (100) [M – CH3O]+.
HRMS: m/z calcd for C14H25O4 [MH+], 257.1753; found, 257.1769.
(5S,6R)-5-Methyl-6-[(1S)-1-methylbut-3-enyl)]-5,6-dihydro-
2H-pyran-2-one (4d)
The lactone 4d was synthesized as described above for 4a starting
from ester 12d (30 mg, 0.117 mmol) and was isolated as a colorless
oil; yield: 15 mg (71%).
(5R,6S)-5-Methyl-6-[(1S)-1-methylbut-3-enyl)]-5,6-dihydro-
2H-pyran-2-one (4a)
A soln of ester 12a (37 mg, 144 mol) and CBr4 (24 mg, 72 mol)
in i-PrOH (6.4 mL) was heated at 82 °C for 15 h. After evaporation
of the solvent, the crude product was purified by column chroma-
tography on silica gel (pentane–Et2O, 5:1 to 2:1). The product was
isolated as white needles; yield: 25 mg (97%).
Rf 0.33 (cyclohexane–EtOAc, 5:1); [ ]D20 –66.7 (c 0.54, CHCl3),
mp 44.1 °C.
1H NMR (400 MHz, MeOH-d4): = 6.86 (dd, 1 H, 2J = 9.8, 2J = 2.9
Hz, =CH-4), 5.92 (dd, 1 H, 2J = 9.8, 3J = 2.3 Hz, =CH-3), 5.78–5.88
(m, 1 H, =CH-3 ), 5.01–5.10 (m, 2 H, =CH2), 4.07 (dd, 1 H,
2J = 9.0, 2J = 3.3 Hz, CH–O), 2.72 2.80 (m, 1 H, CH-5), 2.32–2.39
(m, 1 H, CHH-2 ), 1.92–2.00 (m, 2 H, CH-1 , CHH-2 ), 1.15 (d, 3
H, 2J = 7.2 Hz, CH3-5), 1.05 (d, 3 H, 2J = 6.7 Hz, CH3-1 ).
Rf 0.5 (cyclohexane–EtOAc, 2:1); [ ]D20 +75.3 (c 0.275, CHCl3).
1H NMR (400 MHz, MeOH-d4): = 6.84 (dd, 1 H, 2J = 9.8, 2J = 2.2
Hz, =CH-4), 5.92 (dd, 1 H, 2J = 9.8, 3J = 2.7 Hz, =CH-3), 5.81 (ddt,
2
2
1 H; J = 7.2, 2J = 14.2, J = 10.2 Hz, =CH-3 ), 5.03 5.10 (m, 2
H, =CH2), 4.11 (dd, 1 H, 2J = 10.8, 2J = 2.4 Hz, CH-O), 2.65 2.75
(m, 1 H, CH-5), 2.23 2.32 (m, 1 H, CHH-2 ), 2.12-2.20 (m, 1 H,
CHH-2 ), 1.92 (dsext, 1 H, 2J = 2.4, 2J = 7.0 Hz, CH-1 ), 1.11 (d, 3
H, 2J = 7.2 Hz, CH3-5), 0.98 (d, 3 H, 2J = 7.0 Hz, CH3-1 ).
13C NMR (100 MHz, MeOH-d4): = 166.9 (C=O), 155.2 (=CH-4),
137.9 (=CH-3 ), 120.1 (=CH-3), 117.2 (=CH2), 87.0 (CHO), 39.1
(CH2-2 ), 34.9 (CH-1 ), 32.1 (CH-5), 16.0 (CH3-5), 13.3 (CH3-1 ).
MS (FAB): m/z (%) = 181.1 (100) [MH+].
Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York

2104
L. Bialy et al.
PAPER
HRMS: m/z calcd for C11H17O2 [MH+], 181.1229; found, 181.1261.
(4) Bialy, L.; Waldmann, H. Angew. Chem., Int. Ed. Engl. 2002,
41, 1748.
(5) See for example: (a) Entzeroth, M.; Blackman Mynderse, A.
J.; Moore, R. E. J. Org. Chem. 1985, 50, 1255. (b) Diez-
Martin, D.; Kotecha, N. R.; Ley, S. V.; Mantegani, S.;
Menendez, C. J.; Organ, H. M.; White, A. D.; Banks, B. J.
Tetrahedron 1992, 37, 7899. (c) Jung, M. E.; Lee, C. P. Org.
Lett. 2001, 3, 333. (d) Bluet, G.; Bazán-Tejeda, B.;
Campagne, J.-M. Org. Lett. 2001, 3, 3807.
Acknowledgement
We are grateful to Prof. Masaaki Ishizuka for kindly providing a
sample of isolated cytostatin. This research was supported by the
Fonds der Chemischen Industrie.
(6) Evans, D. A.; Bartroli, J. A.; Shih, T. L. J. Am. Chem. Soc.
1981, 103, 2127.
(7) Walker, M.; Heathcock, C. H. J. Org. Chem. 1990, 55, 173.
(8) Evans, D. A.; Bender, S. L.; Morris, J. J. Am. Chem. Soc.
1988, 110, 2506.
(9) (a) Raimundo, B. C.; Heathcock, C. H. Synlett 1995, 12,
1213. (b) Paterson, I.; Hulme, A. N. J. Org. Chem. 1995, 60,
3288.
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Synthesis 2002, No. 14, 2096–2104 ISSN 0039-7881 © Thieme Stuttgart · New York