An acid-catalyzed ring-switch reaction of lactams to lactones: concise synthesis of 2,4-dialkyl-3-hydroxybutanolides

Article abstract of DOI:10.1016/j.tet.2008.01.107

A novel approach for the synthesis of 2,4-dialkyl-3-hydroxybutanolides, having three successive stereogenic centers, by an acid-catalyzed ring-switch reaction of 2-(2-hydroxyalkyl)lactams is described. This transformation was applied to the synthesis of the key intermediates of teromerase inhibitor UCS1025A.

Full text of DOI:10.1016/j.tet.2008.01.107

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 3133e3140
www.elsevier.com/locate/tet
An acid-catalyzed ring-switch reaction of lactams to lactones:
concise synthesis of 2,4-dialkyl-3-hydroxybutanolides
Chiaki Yamauchi a, Masami Kuriyama b, Rumiko Shimazawa b, Tsumoru Morimoto a,
Kiyomi Kakiuchi a, Ryuichi Shirai a,b,
*
a Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Takayama, Ikoma, Nara 630-0192, Japan
b Faculty of Pharmaceutical Science, Doshisha Women’s College of Liberal Arts, Kodo, Kyotanabe, Kyoto 610-0395, Japan
Received 18 December 2007; received in revised form 26 January 2008; accepted 29 January 2008
Available online 1 February 2008
Abstract
A novel approach for the synthesis of 2,4-dialkyl-3-hydroxybutanolides, having three successive stereogenic centers, by an acid-catalyzed
ring-switch reaction of 2-(2-hydroxyalkyl)lactams is described. This transformation was applied to the synthesis of the key intermediates of
teromerase inhibitor UCS1025A.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
stereogenic centers, by an acid-catalyzed ring-switch reaction
of the 2-(2-hydroxyalkyl)lactams (outlined in Scheme 1).
Syntheses of functionalized g-butyrolactones are an impor-
tant subject in organic and bioorganic chemistry.1 The synthesis
of 2,4-dialkyl-3-hydroxybutanolides has been of continuous
interest due to their utility as chiral synthons and their biological
activity.2 Several biologically interesting 2,4-dialkyl-3-
hydroxybutanolides, such as (þ)-blastmycinone,3 (ꢀ)-3-epi-
blastmycinone,3c Laetianolide A,4 NFX-2,5 and UCS1025A,6
are shown in Figure 1. Polyketide metabolites, blastmycinone
and NFX-2, include butyl and hexyl carbon chains at the
C-2 position, respectively. Laetianolide A was isolated from
Laetia procera (Flacourtiaceae), and UCS1025A was isolated
from the fermentation broth of Acremonium sp. KY4917
fungus.
O
H
O
Me
H
OH
H
N
H
H
O
O
UCS1025A
O
O
( )4
( )6
O
O
O
Me
OH
Me
OH
NFX-2
R1
OH
Laetianolide A
O
R2
O
O
O
2,4-dialkyl-3-hydroxy
butanolide
The three contiguous chiral centers arranged precisely in
these molecules provide a reasonable challenge for the devel-
opment of new methodologies.
Here, we report on a novel tactic for the synthesis of 2,4-
dialkyl-3-hydroxybutanolides, which have three successive
O
O
O
O
Me
Me
O
O
O
Me
O
O
(+)-Blastmycinone
(+)-Blastmycinone analog
(-)-3-epi-Blastmycinone
Figure 1. 2,4-Dialkyl-3-hydroxybutanolide natural products and derivatives.
* Corresponding author. Tel./fax: þ81 774 65 8510.
E-mail address: rshirai@dwc.doshisha.ac.jp (R. Shirai).
0040-4020/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.01.107

3134
C. Yamauchi et al. / Tetrahedron 64 (2008) 3133e3140
O
O
being converted into corresponding exocyclic b,g-unsaturated
valerolactam 3b in good yields (Scheme 3).
OH
H+
( )n NHBoc
OH
R
BocN
O
OH
( )n
O
O
1. KHMDS (1.1 eq.)
THF, -78 °C
2. AcOH (2.2 eq.) in THF
-78 °C
R
n=1,2
Me
Me
BocN
BocN
Scheme 1. Acid-catalyzed ring-switch reaction of 2-(2-hydroxyalkyl)lactams
to 2,4-dialkyl-3-hydroxybutanolides.
2b
3b 80%
Scheme 3. Kinetic isomerization of 2b to 3b.
2. Results and discussion
The hydroxyl group, which would be incorporated into the
lactone ring, was introduced by dihydroxylation reaction cata-
lyzed by osmium tetroxide (Scheme 4). Treatment of butyro-
lactam 3a with a catalytic amount of osmium tetroxide in
the presence of NMO as a co-oxidant in CH2Cl2 gave a diaste-
reomixture of two diols: anti-4a and syn-4a (73:27). Similarly,
dihydroxylation of valerolactam 3b also took place in similar
stereoselectivity to give the diols anti-4b and syn-4b (82:18).
The observed preference of anti-4 over syn-4 can be ratio-
nalized as shown in Figure 2. Because of the A(1,3) strain
between the side chain and the lactam ring, conformer 3a-B
would be more stable than 3a-A. Thus, osmium tetroxide ap-
proaches the C]C bond preferentially from the less hindered
methylene side, the opposite face of the carbonyl group.
Young and co-workers reported the ring-switch reaction of
optically active amino acid derivatives as shown in Scheme
5.10 N-Boc protected butyrolactam 7 and valerolactam 10
with a hydroxyl group generated by reduction of the aldehyde
or the carboxylic acid residue were transformed to mono-
substituted butanolides 8 and 11, respectively, under the con-
dition of borane reduction.
The application of this conversion from the above synthe-
sized 2-(2-hydroxyalkyl)lactam 4 would produce 2,4-dialkyl-
3-hydroxybutanolides efficiently. Because the hydroxylated
lactams 4 were isolated as stable compounds that survived
during the dihydroxylation in the presence of basic amines,
we tried to employ mild acidic condition for a ring-switch
reaction from lactams to lactones.
The mixture of diastereoisomers of 4a and 4b were dis-
solved in benzene and a catalytic amount of TsOH was added
and stirred for 30 min at rt to give 2,4-dialkyl-3-hydroxybuta-
nolide in quantitative yields from dihydroxylated lactams 4a
and 4b (Scheme 4). The isolated yield of 5a from deconju-
gated alkene (two steps) was 51 (anti-5a) and 19% (syn-5a),
and 5b from 3b was 50 (anti-5b) and 11% (syn-5b).
2.1. Acid-catalyzed ring-switch reaction
The introduction of the 2-substituent having three succes-
sive stereogenic centers was performed as follows. Deprotona-
tion of N-Boc-butyrolactam 1a and N-Boc-valerolactam 1b7
by LDA followed by an aldol reaction produced the corre-
sponding aldol adducts, which were directly converted to the
exocyclic a,b-unsaturated lactams 2a and 2b via methanesul-
fonates, respectively (Scheme 2).8
O
O
1. LDA, propionaldehyde
THF, -78 °C
Me
BocN
( )n
BocN
( )n
2. MsCl, Et3N, 0 °C;
then Et3N, reflux
n=1 1a
n=2 1b
n=1 2a 49%, E:Z=7:1
n=2 2b 79%, E:Z=17:1
Scheme 2. Syntheses of 2-propylidenelactams by aldol condensation.
According to the reported procedures9 on deconjugation of
a,b-unsaturated esters to the corresponding unsaturated b,g-
esters, deprotonation of 2a by different bases followed by
kinetic protonation was examined. The results are summarized
in Table 1.
By use of potassium tert-butoxide as the base for deproto-
nation and water as the proton source for kinetic deconjuga-
tion, trace amounts of the desired product and starting
materials were recovered. When LDA was employed as the
base, the starting exocyclic a,b-unsaturated lactam was recov-
ered quantitatively, and the result indicates that deprotonation
did not take place under this condition. Gratifyingly, use of po-
tassium bis(trimethylsilyl)amide (KHMDS) and subsequent
kinetic protonation with acetic acid in THF gave the desired
deconjugated butyrolactam 3a as the sole product in 87% yield
(Table 1, entry 3). The same reaction condition resulted in 2b
The relative stereochemistry of Ha, Hb, and Hc of the ring-
switched compounds syn-5a/anti-5a and syn-5b/anti-5b was
determined by NOE-difference experiments as shown in
Figure 3. Enhancement was observed between Ha and Hb
and between Ha and Hc in syn-5. A small enhancement
between Ha and Hb and no enhancement between Ha and
Hc were observed in anti-5.
Table 1
Kinetic isomerization of 2a to 3a
Entry Base
Temperaturea (ꢁC) Proton source
2a (%) 3a (%)
1
2
3
KOtBu
LDA
ꢀ20
ꢀ78
H2O
Trace
Trace
Trace
87
2.2. Synthetic approach to the 2,4-dialkyl-3-
hydroxybutanolide core of UCS1025A
AcOH in THFb >99
KHMDS ꢀ78
AcOH in THFb Trace
a
For each entry, deprotonation and subsequent protonation were conducted
at the same temperature indicated.
As an application of acid-catalyzed ring-switch reaction,
we planned to synthesize the trisubstituted butanolide, a key
b
Amount: 2.2 equiv.

C. Yamauchi et al. / Tetrahedron 64 (2008) 3133e3140
3135
O
O
O
O
O
OH
OH
cat. OsO4, NMO
quinuclidine
H
H
TsOH•H2O
NHBoc
NHBoc
Me
Me
Me
O
O
+
:
BocN
BocN
BocN
+
CH2Cl2, 0 °C
C6H6, r.t.
OH
OH
Me
OH
anti-5a
Me
OH
syn-5a
3a
anti-4a
syn-4a
73
27
51%
19%
(from 3a)
(from 3a)
O
O
O
O
OH
O
OH
O
cat. OsO4, NMO
quinuclidine
H
H
TsOH•H2O
Me
Me
Me
+
NHBoc
O
NHBoc
+
:
BocN
BocN
BocN
CH2Cl2, 0 °C
C6H6, r.t.
OH
OH
Me
OH
anti-5b
Me
OH
3b
anti-4b
syn-4b
syn-5b
82
18
50%
11%
(from 3b)
(from 3b)
Scheme 4. Acid-catalyzed ring-switch reaction of 3a and 3b.
Favored
anti-4a
OsO4
O
O
Hb
OH
Hb
Me
Hc
Ha
Hc
Ha
O
O
CH3
H
CH3
H
H
Me
OH
NHBoc
NHBoc
H
BocN
H
BocN
O
anti-5a
noe : Ha/Hb = 1.0%
Ha/Hc = not observed
syn-5a
O
noe : Ha/Hb = 4.0%
Ha/Hc = 3.3%
3a-A
3a-B
OsO4
Unfavored
O
O
Hb
OH
Hb
Figure 2. Stereoselective osmylation of 3a.
Me
Hc
Ha
Hc
Ha
O
O
intermediate of UCS1025A having all carbon, oxygen, and
nitrogen atoms in its lactone core and substituents at C-2
and C-4 centers with correct stereochemistry (Scheme 6).
Based on the kinetic deconjugationedihydroxylation proto-
col described above, trisubstituted butanolide 14 was syn-
thesized from b,g-unsaturated butyrolactam 12, which was
prepared from 1a and 4-tert-butyldimethylsiloxy-1-butyralde-
hyde11 via (i) aldol reaction, (ii) methanesulfonylation followed
by triethylamine-catalyzed b-elimination, and (iii) kinetic de-
conjugation of the dienolate (Scheme 7). Dihydroxylation of
12 with OsO4 afforded anti-13 and syn-13 in 60 and 22% yields,
respectively. Subsequently, a ring-switch reaction of anti-13 and
syn-13 took place efficiently to yield anti-14 and syn-14.
The relative stereochemistry of Ha, Hb, and Hc of the ring-
switched compounds syn-14/anti-14 were determined by
NOE-difference experiments, as shown in Figure 4. The en-
hancement was observed between Ha and Hb and between
Ha and Hc in syn-14. A small enhancement between Ha and
Me
OH
syn-5b
NHBoc
NHBoc
anti-5b
noe : Ha/Hb = 1.0%
Ha/Hc = not observed
noe : Ha/Hb = 4.7%
Ha/Hc = 4.0%
Figure 3. Determination of relative stereochemistry of 5 by NOE-difference
experiment.
Hb and no enhancement between Ha and Hc were observed
in anti-14.
Kinetic resolution of Sharpless asymmetric dihydroxylation
on 12 with AD-mix a and b was attempted,12 although no di-
hydroxylated products were produced. Therefore, we turned
our tactics to the diastereoselective aldol reaction of 1a with
chiral a-hydroxyaldehyde 15 leading to the direct production
of a dihydroxylactam derivative (Scheme 8).
The aldol reaction of 1a with (S)-4-(tert-butyldiphenyl-
siloxy)-2-triethylsiloxybutanal 15 prepared from (S)-malic
NaBH3CN-MeOH
O
O
O
pH 4
H
t
CO2 Bu
BocN
BocN
O
OH
O
t
t
NHBoc
BuO2C
BuO2C
6
7
8
O
O
O
NHBoc
CO2Me
BH3•SMe2
BocN
BocN
CO2H
O
OH
MeO2C
MeO2C
9
10
11
Scheme 5. Reported ring-switch reaction by Young and co-workers.10

3136
C. Yamauchi et al. / Tetrahedron 64 (2008) 3133e3140
TBSO
O
O
OH
Hb
Hb
Ha
Hc
Ha
O
O
Hc
OH
TBSO
NHBoc
NHBoc
anti-14
syn-14
noe : Ha/Hb = 5.0%
Ha/Hc = not observed
noe : Ha/Hb = 7.1%
Ha/Hc = 4.0%
Scheme 6. Synthetic approach to the key intermediate of UCS1025A.
acid13 afforded aldol adducts as a mixture of four diastereo-
mers (16a, 17a, 18a, and 19a) in the ratio of 27:60:6.5:6.5
by 1H NMR analysis. We were able to separate the two major
diastereomeric products 16a and 17a from the mixture, how-
ever, 18a and 19a could not be separated. Treatment of the
separated aldol adducts 16a and 17a with TsOH at rt for 3 h
resulted in a deprotection of the TES group to afford corre-
sponding diols, which were directly subjected to in situ ring-
switch lactonization to give chiral butanolides 20a and 21a,
respectively.
The absolute configuration of 20a and 21a was determined
by NOE-difference experiments (Fig. 5). The enhancements
between Ha and Hc and between Ha and Hb in 20a demon-
strated that they are cis oriented. On the other hand, the ab-
sence of enhancement between Ha and Hc in 21a revealed
that they are trans oriented, while trans orientation between
Ha and Hb was assigned by the enhancement of Hb and Hd.
Figure 4. Determination of relative stereochemistry of 14 by NOE-difference
experiment.
Wako chemicals. The products were isolated by flash silica
gel column chromatography (MERCK Silica Gel 60). 1H
NMR was recorded on a JEOL JNM-ECP500 (500 MHz) spec-
trometer. Chemical shifts (d) are reported in parts per million
downfield from internal TMS. 13C NMR spectra were recorded
on a JEOL JNM-ECP500 (125.8 MHz) spectrometer. IR spectra
were obtained from a Hitachi 270-30 Infrared Spectrophotome-
ter and a JASCO FT/IR-420 spectrometer. High-resolution mass
spectra were measured with a JEOL JMS-700. Elemental anal-
yses were performed by a PerkineElmer 2400II CHNS/O.
4.2. Syntheses of 2-propylidenelactams
4.2.1. tert-Butyl 2-oxo-3-propylidenepyrrolidine-1-
carboxylate (2a)
Compound 1a7 (3.37 g, 18.2 mmol) was added to a solution
of LDA (20.0 mmol) in THF (55 mL) at ꢀ78 ꢁC. The reaction
mixture was allowed to warm to ꢀ20 ꢁC, stirred at this tem-
perature for 1 h, and cooled to ꢀ78 ꢁC. Propionaldehyde
(1.30 mL, 18.2 mmol) in THF (45 mL) was added dropwise,
and the mixture was stirred at this temperature for 1 h and
quenched with saturated aqueous NH4Cl solution. Extractive
workup with ethyl acetate yielded the crude alcohol, which
was dissolved in a mixture of dry toluene (24 mL) and triethyl-
amine (3.8 mL, 27.3 mmol). Methanesulfonyl chloride
(1.6 mL, 20.5 mmol) was added dropwise at 0 ꢁC and the mix-
ture was allowed to warm to rt. Additional triethylamine
(6.4 mL, 45.5 mmol) was added and the mixture was refluxed
for 13 h. After addition of a saturated aqueous NH4Cl solution,
the organic layer was extracted with ethyl acetate, and the
combined organic layers were dried over anhydrous Na2SO4
and concentrated in vacuo after filtration. Purification by flash
chromatography (ethyl acetate/hexane¼1:1) gave impure 2a
3. Conclusion
We have demonstrated the synthesis of 2,4-dialkyl-3-
hydroxybutanolides from the lactams via an acid-catalyzed
ring-switch reaction to lactone. The relative and absolute
stereochemistries of 2,4-dialkyl-3-hydroxybutanolides were
assigned using NOE-difference experiments. The butanolides
provided by this synthetic tactic can be utilized for the synthe-
ses of more complicated natural products.
4. Experimental
4.1. General
All nonaqueous operations were carried out in dried glass-
ware under an N2 atmosphere. Anhydrous dichloromethane,
benzene, and tetrahydrofuran (THF) were purchased from
O
O
OH
H
NHBoc
TsOH•H2O
C6H6, r.t.
OTBS
O
BocN
OH
OH
anti-14 90%
O
cat. OsO4, NMO
quinuclidine
TBSO
anti-13 60%
OTBS
BocN
CH2Cl2, 0 °C
O
O
O
OH
H
NHBoc
12
TsOH•H2O
C6H6, r.t.
OTBS
BocN
OH
syn-13 22%
OH
TBSO
syn-14 90%
Scheme 7. Synthesis of 2,4-dialkyl-3-hydroxybutanolide 14.

C. Yamauchi et al. / Tetrahedron 64 (2008) 3133e3140
3137
O
O
OH
H
NHBoc
NHBoc
TsOH•H2O
H2O, THF
OTBDPS
OTBDPS
O
BocN
BocN
OTES
OH
O
TBDPSO
TBDPSO
1. 1.0M LiHMDS
THF, -78 °C
16a 21%
20a 90%
BocN
2.
O
O
O
OH
H
OTBDPS
TsOH•H2O
H2O, THF
H
O
1a
15
OTES
OTES
OH
17a 47%
21a 84%
+
18a/19a 10%
Scheme 8. Syntheses of chiral 2,4-dialkyl-3-hydroxybutanolides.
4.3. Syntheses of b,g-unsaturated lactams
Hd
NHBoc
Hd
O
O
Hb
Hb
Hc
4.3.1. (E)-tert-Butyl 2-oxo-3-(prop-1-enyl)pyrrolidine-1-
carboxylate (3a)
Hc
Ha
O
O
Ha
OH
OH
20a
To a THF (20 mL) solution of 2a (623.6 mg, 2.77 mmol) was
added a toluene solution of KHMDS (0.5 M, 6.1 mL,
3.04 mmol) at ꢀ78 ꢁC, and the reaction mixture was stirred
for 3 h. To the mixture was added a solution of acetic acid
(1.6 mL, 27.7 mmol) in THF (15 mL) at ꢀ78 ꢁC, and the reac-
tion mixture was stirred for 30 min. After addition of a saturated
aqueous NaHCO3 solution, the organic layer was extracted with
ethyl acetate, and the organic layers were dried over anhydrous
MgSO4 and concentrated in vacuo after filtration. Purification
by flash chromatography (ethyl acetate/hexane¼1:1) gave
539.7 mg (87%) of b,g-unsaturated lactam 3a as a pale yellow
needle. Compound 3a: mp 36e37 ꢁC. 1H NMR (CDCl3):
d 5.61 (1H, J¼15.4, 6.1 Hz, dq), 5.48 (1H, J¼15.4, 6.6,
1.7 Hz, ddd), 3.78e3.73 (1H, m), 3.58 (1H, J¼11.0, 9.2,
7.3 Hz, ddd), 3.13 (1H, J¼8.3, 8.3, 8.0 Hz, ddd), 2.21e2.14
(1H, m), 1.84 (1H, J¼18.3, 12.8, 8.6 Hz, ddd), 1.69 (3H,
J¼6.1 Hz, d), 1.50 (9H, s). 13C NMR (CDCl3): d 174.3, 150.3,
129.0, 126.4, 82.7, 46.9, 44.3, 27.9, 24.6, 17.9. IR (KBr):
3400, 3000, 1740, 1640 cmꢀ1. Anal. Calcd for C12H19NO3: C,
63.98; H, 8.50; N, 6.22. Found: C, 64.12; H, 8.65; N, 6.21.
TBDPSO
NHBoc
TBDPSO
21a
noe : Ha/Hb = 5.0%
Ha/Hc = not observed
Hb/Hd = 2.7%
noe : Ha/Hb = 7.0%
Ha/Hc = 5.0%
Figure 5. Determination of relative stereochemistry of 20a and 21a by NOE-
difference experiment.
(Z-isomer; 0.22 g, 5%) and 2a (E-isomer; 1.77 g, 44%) of 2-pro-
pylidenelactam 2a as a yellow needle. Compound 2a (Z-isomer):
1H NMR (CDCl3): d 5.99 (1H, J¼7.6, 2.2 Hz, tt). Compound 2a
1
(E-isomer): mp 39e41 ꢁC. H NMR (CDCl3): d 6.56 (1H, tt,
J¼7.5 Hz, 2.8 Hz), 3.65 (2H, dd, J¼3.9 Hz, 10.7 Hz), 2.51e
2.59 (2H, m), 2.02e2.13 (2H, m), 1.45 (9H, s), 0.97 (3H, t,
J¼7.5 Hz). 13C NMR (CDCl3): d 12.6, 20.4, 22.4, 27.8, 27.8,
28.2, 43.0, 82.4, 103.7, 130.1, 139.2, 150.7, 166.8. IR (KBr):
3000, 1740, 1640 cmꢀ1. Anal. Calcd for C12H19NO3: C, 63.98;
H, 8.50; N, 6.22. Found: C, 63.68; H, 8.72; N, 6.11.
4.2.2. tert-Butyl 2-oxo-3-propylidenepiperidine-1-
carboxylate (2b)
Operating as above with 1b7 (2.32 g), 2-propylidenelactam
2b (Z-isomer; 0.12 g, 4%), and 2b (E-isomer; 2.11 g, 75%)
were isolated both as a pale yellow oil. Compound 2b (Z-iso-
4.3.2. (E)-tert-Butyl 2-oxo-3-(prop-1-enyl)piperidine-1-
carboxylate (3b)
Operating as above with 2b (732.3 mg), b,g-unsaturated lac-
1
mer): H NMR (CDCl3): d 5.87 (1H, J¼7.6 Hz, t), 3.64 (2H,
1
tam 3b (588.3 mg, 80%) was isolated as a pale yellow oil. H
J¼6.1 Hz, t), 2.58 (2H, J¼7.6, 7.9 Hz, dq), 2.45 (2H,
J¼6.7 Hz, t), 1.86 (2H, J¼6.7, 6.1 Hz, tt), 1.54 (9H, s), 1.03
(3H, J¼7.9 Hz, t). 13C NMR (CDCl3): d 166.0, 152.7, 146.1,
128.8, 82.4, 45.5, 30.4, 27.9, 22.8, 22.6, 13.8. IR (neat):
2970, 1764, 1713, 1294, 1148 cmꢀ1. HRMS (FAB): calcd
for [C13H21NO3þNa]þ, 262.1414; found, 262.1425. Com-
NMR (CDCl3): d 5.62 (1H, J¼15.3, 6.0, 1.2 Hz, ddd), 5.55
(1H, J¼15.3, 5.5 Hz, dq), 3.74 (1H, J¼13.3, 6.9, 4.4 Hz, ddd),
3.60 (1H, J¼13.3, 6.9, 4.4 Hz, ddd), 3.09 (1H, J¼9.5, 6.0,
5.8 Hz, ddd), 2.03e1.67 (4H, m), 1.71 (3H, J¼5.5 Hz, d),
1.52 (9H, s). 13C NMR (CDCl3): d 172.84, 153.16, 128.49,
127.68, 82.78, 47.16, 45.71, 27.94, 27.16, 21.27, 18.02. IR
(neat): 2977, 1770, 1714, 1293, 1151 cmꢀ1. HRMS (EI): calcd
for C13H21NO3, 239.1521; found, 239.1519.
1
pound 2b (E-isomer): H NMR (CDCl3): d 6.94 (1H, J¼7.3,
2.1 Hz, tt), 3.69 (2H, J¼5.8 Hz, t), 2.46 (2H, J¼6.9, 1.2 Hz,
td), 2.15 (2H, J¼7.6, 7.3, 1.2 Hz, ttt), 1.87 (2H, J¼6.9,
5.8 Hz, tt), 1.54 (9H, s), 1.05 (3H, J¼7.6 Hz, t). 13C NMR
(CDCl3): d 165.3, 152.9, 143.9, 129.1, 82.4, 45.6, 27.8, 23.9,
22.0, 21.4, 12.6. IR (neat): 2970, 1765, 1713, 1303,
1149 cmꢀ1. HRMS (EI): calcd for [C13H21NO3þNa]þ,
239.1521; found, 239.1518.
4.4. Syntheses of g-butyrolactones
4.4.1. (R*)-tert-Butyl 3-((1R*,2R*)-1,2-dihydroxypropyl)-2-
oxopyrrolidine-1-carboxylate (anti-4a) and (R*)-tert-butyl

3138
C. Yamauchi et al. / Tetrahedron 64 (2008) 3133e3140
3-((1S*,2S*)-1,2-dihydroxypropyl)-2-oxopyrrolidine-1-
carboxylate (syn-4a)
(CDCl3): d 4.98 (1H, br s, eNH), 4.50 (1H, J¼3.2, 6.7 Hz,
dq), 4.45 (1H, J¼9.8, 3.2 Hz, dd), 3.26e3.22 (2H, m), 2.62
(1H, J¼9.8, 4.9 Hz, dt), 2.08e1.99 (1H, m), 1.94e1.87 (1H,
m), 1.46 (3H, J¼6.7 Hz, d), 1.43 (9H, s). 13C NMR (CDCl3):
d 177.5, 156.8, 80.0, 79.3, 70.6, 45.5, 38.4, 28.3, 24.4, 13.7.
IR (neat): 3384, 2978, 2933, 1768, 1694, 1524, 1174,
1052 cmꢀ1; HRMS (FAB): calcd for [C12H21NO5þNa]þ,
282.1312; found, 282.1312. anti-5a: 1H NMR (CDCl3): d 4.69
(1H, J¼6.7, 6.5 Hz, dq), 4.32 (1H, J¼6.7, 6.1 Hz, dd), 3.56e
3.47 (1H, m), 3.23e3.19 (1H, m), 2.58 (1H, J¼10.4, 4.9 Hz,
dt), 2.03e1.96 (1H, m), 1.71e1.65 (1H, m), 1.44 (9H, s), 1.39
(3H, J¼6.5 Hz, d). 13C NMR (CDCl3): d 177.4, 157.3, 80.4,
78.2, 73.3, 44.8, 37.7, 30.3, 28.3, 14. IR (neat): 3378, 2978,
2933, 1768, 1693, 1530, 1169, 1054 cmꢀ1. HRMS (FAB): calcd
for [C12H21NO5þNa]þ, 282.1312; found, 282.1314.
To a solution of b,g-unsaturated lactam 3a (470.9 mg,
2.09 mmol) in CH2Cl2 (7 mL) were added a quinuclidine
(11.8 mg, 0.10 mmol), NMO (734.4 mg, 6.27 mmol), and
2% aqueous OsO4 (1.3 mL, 0.10 mmol) at 0 ꢁC, and the reac-
tion mixture was stirred for 1 h. After addition of a saturated
aqueous Na2S2O3 solution, the organic layer was extracted
with ethyl acetate, and the combined organic layers were dried
over anhydrous MgSO4, and concentrated in vacuo after filtra-
tion to give the crude diol 4a (564.6 mg), which was used in
next reaction without further purification.
4.4.2. (R*)-tert-Butyl 3-((1R*,2R*)-1, 2-dihydroxypropyl)-
2-oxopiperidine-1-carboxylate (anti-4b) and (R*)-tert-butyl
3-((1S*,2S*)-1,2-dihydroxypropyl)-2-oxopiperidine-1-
carboxylate (syn-4b)
Operating as above with 3b (105.0 mg) afforded the crude
diol 4b (120.5 mg), which was used in next reaction without
further purification.
4.4.5. tert-Butyl 3-((3R*,4R*,5R*)-4-hydroxy-5-methyl-2-
oxotetrahydrofuran-3-yl)propylcarbamate (anti-5b) and
tert-butyl 3-((3R*,4S*,5S*)-4-hydroxy-5-methyl-2-
oxotetrahydrofuran-3-yl)propylcarbamate (syn-5b)
Operating as above with crude 4b (120.5 mg), g-butyrolac-
tone anti-5b (59.7 mg, 50%) and syn-5b (13.1 mg, 11%) were
4.4.3. (R*)-tert-Butyl 3-((1R*,2R*)-4-(tert-
butyldimethylsilyloxy)-1,2-dihydroxybutyl)-2-
1
isolated as a colorless oil. anti-5b: mp 100e101 ꢁC. H NMR
(CDCl3): d 4.66 (1H, J¼6.5, 6.7 Hz, dq), 4.24 (1H, J¼6.5,
5.5 Hz, dd), 3.23e3.08 (2H, m), 2.60 (1H, J¼5.5, 7.5 Hz, dt),
1.83e1.58 (4H, m), 1.43 (9H, s), 1.40 (3H, J¼6.7 Hz, d). 13C
NMR (CDCl3): d 177.7, 156.5, 79.6, 78.3, 73.4, 47.1, 39.6,
28.3, 27.5, 25.1, 14.1. IR (KBr): 3440, 2979, 2938, 1742,
1684, 1522, 1175, 1038 cmꢀ1. Anal. Calcd for C13H23NO5: C,
57.13; H, 8.48; N, 5.12. Found: C, 57.09; H, 8.64; N, 5.05.
oxopyrrolidine-1-carboxylate (anti-13) and (R*)-tert-Butyl
3-((1S*,2S*)-4-(tert-butyldimethylsilyloxy)-1,2-
dihydroxybutyl)-2-oxopyrrolidine-1-carboxylate (syn-13)
Operatingasabovewith12 (236.5 mg), diolanti-13 (154.4 mg,
60%) and syn-13 (57.9 mg, 22%) were isolated both as a colorless
needle. anti-13: mp 91e93 ꢁC. 1H NMR (CDCl3): d 3.96e3.76
(5H, m), 3.62e3.53 (1H, m), 2.74 (1H, td, J¼9.5, 3.4 Hz),
2.24e1.99 (2H, m), 1.85e1.67 (2H, m), 1.53 (9H, s), 0.90 (9H,
s), 0.09 (6H, s). 13C NMR (CDCl3): d 174.7, 150.1, 82.7, 72.2,
71.9, 61.3, 46.8, 44.8, 35.2, 27.9, 25.8, 18.6, 18.0, ꢀ5.6, ꢀ5.6.
IR (CHCl3): 3400, 2900, 1720, 1400, 1300 cmꢀ1. Anal. Calcd
for C19H37NO6Si: C, 56.54; H, 9.24; N, 3.47. Found: C, 56.73;
1
syn-5b: H NMR (CDCl3): d 4.47 (1H, J¼3.0, 6.4 Hz, dq),
4.37 (1H, J¼4.9, 3.0 Hz, dd), 3.27e3.08 (2H, m), 2.56 (1H,
J¼9.8, 4.9 Hz, dt), 1.92e1.64 (4H, m), 1.45 (3H, J¼6.4 Hz,
d), 1.44 (9H, s). 13C NMR (CDCl3): d 177.5, 156.6, 81.6,
79.0, 71.0, 48.1, 39.9, 28.7, 28.4, 19.9, 13.8. IR (neat): 3376,
2936, 1768, 1681, 1530, 1170 cmꢀ1. HRMS (FAB): calcd for
[C13H23NO5þNa]þ, 296.1468; found, 296.1480.
1
H, 9.48; N, 3.46. syn-13: mp 96e98 ꢁC. H NMR (CDCl3):
d 3.89e3.76 (4H, m), 3.69e3.55 (2H, m), 2.84 (1H, dt, J¼11.4,
8.6 Hz), 2.21e2.16 (1H, m), 1.94e1.70 (3H, m), 1.54 (9H, s),
0.89 (9H, s), 0.07 (6H, s). 13C NMR (CDCl3): d 177.5, 149.8,
83.4, 74.4, 70.2, 61.1, 46.0, 44.9, 36.1, 28.0, 25.9, 21.3, 18.2,
4.4.6. tert-Butyl 3-((3R*,4R*,5R*)-5-(2-(tert-
butyldimethylsilyloxy)ethyl)-4-hydroxy-2-
oxotetrahydrofuran-3-yl)propylcarbamate (anti-14)
Operating as abovewith anti-13(1.01 g), g-butyrolactone anti-
14 (908 mg, 90%) was isolated as a colorless needle. Mp 102e
ꢀ5.4, ꢀ5.4. IR (CHCl3): 3400, 2900, 1720, 1400, 1300 cmꢀ1
;
Anal. Calcd for C19H37NO6Si: C, 56.54; H, 9.24; N, 3.47. Found:
C, 56.78; H, 9.52; N, 3.45.
1
103 ꢁC. H NMR (CDCl3): d 5.07 (1H, br s), 4.61 (1H, J¼7.5,
5.7 Hz, dt), 4.25 (1H, J¼5.7, 3.5 Hz, dd), 3.90e3.82 (1H, m),
3.72 (1H, J¼10.1, 2.9 Hz, td), 3.43e3.20 (2H, m), 2.60 (1H,
J¼8.7, 7.2, 3.5 Hz, ddd), 2.24e2.12 (1H, m), 2.07e1.97 (1H,
m), 1.92e1.78 (2H, m), 1.44 (9H, s), 0.91 (9H, s), 0.10 (6H, s).
13C NMR (CDCl3): d 177.6, 156.5, 81.0, 79.8, 73.2, 59.3, 46.4,
38.1, 31.1, 29.4, 28.4, 25.9, 18.8, ꢀ5.5, ꢀ5.6. IR (KBr): 3600,
3400, 3000, 1760, 1680 cmꢀ1. Anal. Calcd for C19H37NO6Si: C,
56.54; H, 9.24; N, 3.47. Found: C, 56.64; H, 9.42; N 3.48.
4.4.4. tert-Butyl 2-((3R*,4R*,5R*)-4-hydroxy-5-methyl-2-
oxotetrahydrofuran-3-yl)ethylcarbamate (anti-5a) and tert-
butyl 2-((3R*,4S*,5S*)-4-hydroxy-5-methyl-2-
oxotetrahydrofuran-3-yl)ethylcarbamate (syn-5a)
To the crude 4a (564.6 mg) were added benzene (1.0 mL)
and TsOH$H2O (one crystal) at rt, and the mixture was stirred
for 30 min. After addition of a saturated aqueous NaHCO3 so-
lution, the organic layer was extracted with ethyl acetate, and
the combined organic layers were dried over anhydrous
MgSO4 and concentrated in vacuo after filtration. Purification
by flash chromatography (ethyl acetate/hexane¼3:1) gave
100.7 mg (19%) of g-butyrolactone syn-5a and 275.3 mg
4.4.7. tert-Butyl 3-((3R*,4S*,5S*)-5-(2-(tert-
butyldimethylsilyloxy)ethyl)-4-hydroxy-2-
oxotetrahydrofuran-3-yl)propylcarbamate (syn-14)
Operating as above with syn-13 (323.4 mg), g-butyrolac-
tone syn-14 (290.8 mg, 90%) was isolated as a colorless
1
(51%) of anti-5a both as a colorless oil. syn-5a: H NMR

C. Yamauchi et al. / Tetrahedron 64 (2008) 3133e3140
3139
needle. Mp 107e109 ꢁC. 1H NMR (CDCl3): d 4.40e4.37 (2H,
m), 3.88 (1H, J¼10.5, 4.1 Hz, dt), 3.78e3.64 (1H, m), 3.33e
3.21 (2H, m), 2.69e2.63 (1H, m), 2.17e2.11 (2H, m), 2.01e
1.92 (2H, m), 1.44 (9H, s), 0.91 (9H, s), 0.11 (6H, s). 13C
NMR (CDCl3): d 177.32, 156.40, 81.86, 79.46, 69.86, 59.30,
44.77, 38.93, 31.06, 28.41, 25.85, 24.12, 18.21, ꢀ5.53,
ꢀ5.62. IR (KBr): 3600, 3400, 3000, 1720 cmꢀ1. Anal. Calcd
for C19H37NO6Si: C, 56.54; H, 9.24; N, 3.47. Found: C,
56.55; H, 9.51; N, 3.44.
a saturated aqueous NaHCO3 solution, the organic layer was
extracted with ethyl acetate, and the organic layers were dried
over anhydrous Na2SO4 and concentrated in vacuo after filtra-
tion. Purification by flash chromatography (ethyl acetate/
hexane¼1:1) gave 352.4 mg (90%) of g-butyrolactone 20a
as a oil. [a]2D4 ꢀ22.9 (c 1.0, CHCl3). 1H NMR (CDCl3):
d 7.67e7.63 (4H, m), 7.47e7.40 (6H, m), 4.88 (1H, br s, e
NH), 4.53e4.51 (1H, m), 4.48e4.44 (1H, m), 3.86 (1H,
J¼10.6, 4.4 Hz, dt), 3.75 (1H, J¼10.2, 2.6 Hz, td), 3.34e
3.22 (2H, m), 2.66 (1H, J¼9.6, 5.0 Hz, dt), 2.22e2.08 (2H,
m), 2.05e1.91 (2H, m), 1.44 (9H, s), 1.06 (9H, s). 13C
NMR (CDCl3): d 177.2, 156.5, 135.5, 132.5, 130.0, 127.9,
81.3, 79.6, 70.0, 60.2, 44.8, 38.7, 31.0, 28.4, 26.8, 24.3,
19.0. IR (neat): 3408, 2932, 1733, 1686, 1521, 1172,
1111 cmꢀ1. HRMS (FAB): calcd for [C29H41NO6SiþNa]þ,
550.2601; found, 550.2604.
4.5. Syntheses of chiral trisubstituted g-butyrolactones
4.5.1. (R)-tert-Butyl 3-((1S,2S)-4-(tert-
butyldiphenylsilyloxy)-1-hydroxy-2-(triethylsilyloxy)butyl)-
2-oxopyrrolidine-1-carboxylate (16a) and (S)-tert-butyl 3-
((1S,2S)-4-(tert-butyldiphenylsilyloxy)-1-hydroxy-2-
(triethylsilyloxy)butyl)-2-oxopyrrolidine-1-carboxylate
(17a)
4.5.3. tert-Butyl 2-((3S,4S,5S)-5-(2-(tert-butyl-
diphenylsilyloxy)ethyl)-4-hydroxy-2-oxo-
To a solution of 1a (106.7 mg, 0.58 mmol) in THF (4 mL)
was added a LiHMDS (0.63 mL, 1.0 M in THF) at ꢀ78 ꢁC. To
the mixture was added a solution of 1513 (182.7 mg,
0.40 mmol) in THF (2 mL), and the reaction mixture was
stirred for 2 h at ꢀ78 ꢁC. After addition of a saturated aqueous
NH4Cl solution, the organic layer was extracted with ethyl
acetate, and the combined organic layers were dried with
Na2SO4 and concentrated in vacuo after filtration. Purification
by flash chromatography (ethyl acetate/hexane¼1:4) gave
53.0 mg (21%) of 16a as a colorless oil and 121.5 mg (47%)
of 17a as a colorless oil. Compound 16a: [a]2D4 ꢀ12.4 (c
0.7, CHCl3). 1H NMR (CDCl3): d 7.66e7.64 (4H, m),
7.43e7.35 (6H, m), 4.26 (1H, J¼1.8 Hz, d), 4.02 (1H,
J¼6.3, 3.3 Hz, td), 3.80e3.71 (4H, m), 3.54 (1H, J¼10.2,
7.1 Hz, td), 2.72 (1H, J¼11.0, 9.2 Hz, td), 2.09e1.96 (2H,
m), 1.78e1.72 (2H, m), 1.54 (9H, s), 1.05 (9H, s), 0.92 (9H,
J¼7.7 Hz, t), 0.58 (6H, J¼7.7 Hz, q). 13C NMR (CDCl3):
d 177.2, 149.9, 135.6, 133.7, 129.6, 127.6, 83.2, 73.9, 70.2,
60.6, 44.9, 44.6, 35.4, 28.0, 26.8, 21.5, 19.1, 6.9, 5.1. IR
(neat): 3472, 3071, 2955, 1779, 1718 cmꢀ1; HRMS (FAB):
calcd for [C35H55NO6Si2þNa]þ, 664.3460; found, 664.3458.
Compound 17a: [a]2D4 ꢀ3.5 (c 1.2, CHCl3). 1H NMR
(CDCl3): d 7.67e7.65 (4H, m), 7.45e7.37 (6H, m), 4.21
(1H, J¼4.3, 6.7 Hz, td), 3.89e3.70 (4H, m), 3.56 (1H,
J¼9.3, 7.5 Hz, td), 2.73 (1H, J¼9.8, 6.7 Hz, td), 2.12e2.06
(1H, m), 1.94e1.61 (3H, m), 1.53 (5H, s), 1.05 (9H, s), 0.91
(9H, J¼7.6 Hz, t), 0.60 (4H, J¼7.6 Hz, q). 13C NMR
(CDCl3): d 176.0, 150.0, 135.5, 133.3, 129.7, 127.7, 82.9,
76.3, 70.5, 60.2, 44.9, 44.4, 35.4, 28.0, 26.8, 22.1, 19.0, 6.9,
5.0. IR (neat): 3482, 3071, 2956, 1779, 1720 cmꢀ1. HRMS
(FAB): calcd for [C35H55NO6Si2þNa]þ, 664.3460; found,
664.3463.
tetrahydrofuran-3-yl)ethylcarbamate (21a)
Operating as above with 17a (1.00 g, 1.56 mmol), g-butyro-
lactone 21a (691.5 mg, 84%) was isolated as a colorless oil.
[a]2D4 ꢀ17.3 (c 1.0, CHCl3). H NMR (CDCl3): d 7.67e7.65
1
(4H, m), 7.44e7.37 (6H, m), 5.03 (1H, J¼5.8 Hz, t, eNH),
4.62 (1H, J¼6.3, 0.8 Hz, td), 4.39e4.36 (1H, m), 3.86e3.73
(2H, m), 3.28e3.16 (2H, m), 2.58 (1H, J¼10.4, 4.9 Hz, dt),
2.00e1.83 (3H, m), 1.78e1.71 (1H, m), 1.42 (9H, s), 1.05 (9H,
s). 13C NMR (CDCl3): d 177.3, 156.8, 135.5, 133.1, 129.8,
127.7, 83.6, 79.9, 72.4, 59.8, 42.0, 38.5, 35.3, 28.3, 26.8, 24.5,
19.1. IR (neat): 3410, 2932, 1733, 1695, 1509, 1165,
1111 cmꢀ1. HRMS (FAB): calcd for [C29H41NO6SiþNa]þ,
550.2601; found, 550.2597.
Acknowledgements
This work was supported in part by Grant-in-Aid for Scien-
tific Research (C) (No. 18590023) from the Japan Society for
the Promotion of Science and Kyoto-Advanced Nanotechnol-
ogy Network. We also thank Mr. Asanoma for elemental anal-
ysis and Ms. Nishikawa for measurement of HRMS.
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3140
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