Synthesis of both enantiomers of brevioxime and determination of its absolute configuration

Article abstract of DOI:10.3987/com-03-s64

Brevioxime is an inhibitor of juvenile hormone biosynthesis, isolated from Penicillium brevicompactum. We synthesized both enantiomers of brevioxime and determined the absolute configuration of natural product as S.

Full text of DOI:10.3987/com-03-s64

HETEROCYCLES, Vol. 61, 2003
481
HETEROCYCLES, Vol. 61, 2003, pp. 481 - 491
Received, 29th August, 2003, Accepted, 8th October, 2003, Published online, 20th October, 2003
SYNTHESIS OF BOTH ENANTIOMERS OF BREVIOXIME AND
DETERMINATION OF ITS ABSOLUTE CONFIGURATION
Yutaka Nishimura, Ken Ishigami, and Takeshi Kitahara*
Department of Applied Biological Chemistry, Graduate School of Agricultural
and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo
113-8657, Japan
Abstract – Brevioxime is an inhibitor of juvenile hormone biosynthesis, isolated
from Penicillium brevicompactum. We synthesized both enantiomers of
brevioxime and determined the absolute configuration of natural product as S.
INTRODUCTION
Brevioxime (1) was isolated from Penicillium brevicompactum as anti-juvenile hormone (JH) agent by
Primo- YÚfera and coworkers in 1997. 1 It is known that the enzymes involved in the final steps of JH
biosynthesis are specific for insects. Brevioxime is thought to inhibit the final steps of JH biosynthesis, so,
it is very attractive compound as a potential and selective insecticide. Racemic syntheses of brevioxime
have already been reported by three groups including us.2 Although Clark reported (-)-brevioxime, they
couldn’t determine its absolute configuration.3 Now, we report the synthesis of both enantiomers of
brevioxime and the determination of the absolute configurations of natural compound in this paper.
HO
N
H
N
O
O
(-)-1 : (-)-Brevioxime
Figure 1

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RESULTS AND DISCUSSION
Our synthetic approach is based on its probable biosynthetic route as shown in Figure 2. We had already
synthesized racemic brevioxime in similar approach successfully.2 The heterocyclic skeleton of
brevioxime (1) will be constructed by intramolecular aminalization of 2 under acid condition. We
considered that it is possible to control occurring stereochemistry by introduction of chiral center at the
adjacent carbon. Even if the selectivity is not desirable, it will be no matter to separate those
diastereomers.
H+
PGO
selective
aminal cyclization
H
CHO
PGO
O
O
*
O
O
C7H13
Both enantiomers
of
*
*
H
N
N
or
Brevioxime (1)
sepalation of
occurring diastereomer
2
3
# PG:protective group
Figure 2
Synthesis of the amine moiety of the key intermediate (2) was achieved as shown in Scheme 1. We
employed alcohol (4) as starting material prepared from (S)-malic acid in 4 steps easily by Moriwake’s
procedure.4 Alcohol (4) was converted to azide (5), which was treated with hydrochloric acid to afford
diol. Then primary and secondly hydroxy groups were selectively protected using tert-butyldimethylsilyl
chloride (TBDMSCl) and tert-butyldiphenylsilyl chloride (TBDPSCl) respectively in 2 steps to give 6.
Finally the desired amine (7) was obtained by hydrogenatin of the azide (6).
c, d, e
a, b
O
O
O
O
OH
N3
4
5
OTBDPS
OTBDPS
NH2
f
TBDMSO
TBDMSO
N3
6
7
Scheme 1. a) MsCl, pyridine, CH2Cl2. b) NaN3, DMF, 100 oC, 87% in 2 steps. c) conc.HCl,
MeOH, quant. d) TBDMSCl, imidazole, DMF, 93%. e) TBDPSCl, imidazole, DMF, 92%. f) H2,
10% Pd-C, EtOAc, quant.
The carboxylic acid moiety of 2 was prepared from 2-octenal (8)5 as shown in Scheme 2. The aldehyde
(8) was reacted with ethyl a-bromopropionate under Reformatsky’s condition to give corresponding
hydroxy ester, whose hydroxyl group was protected as TBDMS ether (9). Hydrolysis of this ester

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483
followed by the coupling reaction with the amine (7) gave amide (10). TBDMS groups were removed to
afford 11, which was oxidized by Swern’s method to give corresponding hemiaminal. Concerning to
this oxdation, we tried other conditions, but no better result was obtained than that by Swern oxdation.2
Treatment of the resulting hemiaminal substrate with p-toluenesulfonic acid promoted cyclization which
afforded a mixture of oxazinones (12 and 13, ca. 1:1 ratio) with bicyclic. These diastereomers were
separated easily by flash colum chromatography.
a, b
c, d, e
CHO
CO2Et
OTBDMS
8
9
OH
H
TBDPSO
HO
C7H13
f
N
H13C7
OTBDMS
OTBDPS
H
N
TBDMSO
O
O
11
10
TBDPSO
TBDPSO
H
N
H
O
C7H13
O
C7H13
g, h
+
N
O
O
12
13
Scheme 2. a) ethyl a-bromopropionate, Zn, benzene, 91%. b) TBDMSCl, imidazole,
84%. c) LiOH, H2O, THF, MeOH, 92%. d) (COCl)2, benzene. e) 7, Et3N, CH2Cl2, 97%
in 2 steps. f) TsOH, MeOH, 86%. g) DMSO, (COCl)2, Et3N, CH2Cl2. h) TsOH, CH2Cl2,
12:32% in 2 steps, 13:30% in 2 steps.
s
4.45
H
w
HO
2.18
C7H13
Me
H
N
H
O
3.52
H
O
O
O
H
N
1.88 H
O
H5.20
H 3.48
m
s : strong
m: middle
w: week
NOEs of 14
Figure 3
In order to determine the relative stereochemistry of 12 and 13, the alcohol (14) derived from 13 was
subjected to NOE experiments. Its stereochemistry was unambiguously assigned by NOE observations as
shown in Figure 3. Then, these diastereoisomers (12 and 13) were comverted to (+)- and (-)-brevioxime
respectively as follows (Scheme 3). After the removal of silyl group of 12, hydroxyl group was oxidized
with Dess-Martin periodinane to yield ketone. Finally, this ketone was reacted with hydroxylamine6 to

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afford (-)-brevioxime ((-)-1) as colorless crystal ([a]D22 = -209° ( c 0.26, CHCl3)). Although this reaction
gave both geometrical isomers in a ratio of ca. 2:1, these were easily separable by flash column
chromatography. The Z-isomer was convertible to E-isomer according to the reported procedure.2 In the
same manner as above, 13 was converted to (+)-1 ([a]D22 = +214° ( c 0.26, CHCl3)). IR, 1H NMR and 13C-
NMR spectra of synthetic (-)-1 and (+)-1 were identical with those of natural brevioxime.
Thus, the stereochemistry of natural brevioxime was determined to be S. However [a]D values described
in previous reports were –39 (natural product) and –129, respectively,1,3 which were much different from
that of the present study. So, we examined the enantiomeric purity of our synthesized brevioximes. Both
(-)-1 and (+)-1 were converted to the corresponding (R)-MTPA ester and analyzed by HPLC. It was
found that the optical purity of (-)-1 was 96% e.e. and that of (+)-1 was 97% e.e. We suppose that the
reported natural and synthetic brevioxime were not optically or chemically pure.
HO
N
H
N
TBDPSO
H
N
O
O
O
O
C7H13
a, b, c
(-)-1 : (-)-Brevioxime
12
[a]D22 = -209° ( c 0.26, CHCl3)
96% e.e.
TBDPSO
H
N
O
O
C7H13
d, e, f
(+)-1 : (+)-Brevioxime
[a]D22 = +214° ( c 0.24, CHCl3)
97% e.e.
13
Scheme 3. a) TBAF, THF, 91%. b) Dess-Martin ox., 59%. c) HONH2·HCl, NaOAc, MeOH, E-
isomer 46%, Z-isomer 24%. d) TBAF, THF, 89%. e) Dess-Martin ox., 94%. f) HONH2HCl,
NaOAc, MeOH, E-isomer 49%, Z-isomer 27%. .
In conclusion, we have accomplished the synthesis of both enantiomers of brevioxime and determined the
absolute configuration of natural (-)-brevioxime to be S as shown in Scheme 3. It seems that natural
brevioxime is not optically pure and its enantiomeric excess is estimated at 17%, if chemically pure.
Biological study of these enantiomers and related analogs was conducted and the results will be reported
elsewhere.
EXPERIMENTAL
Optical rotations were recorded with a JASCO DIP-1000 polarimeter. IR spectra were measured with a

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JASCO FT/IR-230 spectrophotometer. 1H and 13C NMR and NOESY were recorded on JEOL JNM EX90,
AL300 and A500. MS spectra were recorded on JEOL JMS SX102. Column chromatography was
performed using Merck silica gel 60 (0.060-0.200 mm) and Kanto Silica gel 60N (40-100 mm). TLC was
carried out on Merck glass plates precoated with silica gel 60 F254 (0.25 mm). HPLC was performed using
Senshu Pak Silica-1301-N (4.6ø x 300 mm).
(S)-4-(2-Azidoethyl)-2,2-dimethyl-1,3-dioxolane (5)
To an ice-cooled solution of 4 (34.2 g, 234 mmol) and pyridine (57 mL, 36.6 mmol) in CH2Cl2 (300 mL)
was added MsCl (32.6 mL, 421 mmol) and stirred at 4 °C for 8 h. The reaction mixture was poured into
ice-cooled water and extracted with Et2O. The organic layer was washed with saturated cupric sulfate
solution, water, saturated NaHCO3 and brine, dried over MgSO4 and concentrated in vacuo. The residue
was employed in the next step without further purification.
To a solution of crude mesylate in DMF (350 mL) was added NaN3 (22.8 g, 351 mmol) and stirred at
100 °C for 2.5 h. After dilution with H2O at 0 °C the reaction mixture was extracted with hexane and
combined organic layers were washed with H2O, brine, dried over MgSO4 and concentrated in vacuo. The
residue was purified by column chromatography on silica gel (EtOAc:hexane = 1:20) to afford 5 (34.8 g,
87% in 2 steps) as a colorless oil: [a]D19 = –16.1° (c 0.82, CHCl3); IR (film, cm–1) n 2100 (N3); H NMR
1
(90 MHz, CDCl3) d = 1.40 (3H, s), 1.35 (3H, s), 1.7-1.9 (2H, m), 3.3-3.7 (1H, m), 3.34 (2H, t, J = 7.1 Hz),
4.0-4.3 (2H, m).
(S)-4-Azido-1-tert-butyldimethylsilyloxy-2-tert-butyldiphenylsilyloxybutane (6)
To a solution of 5 (22.3 g, 118 mmol) in MeOH (150 mL) was added 3 N HCl (20 mL) and the mixture
was stirred at rt for 3 days. Then the reaction mixture was concentrated in vacuo and purified by column
chromatography on silica gel (EtOAc only) to afford (S)-4-azidobutane-1,2-diol (15.6 g, quant.) as a
1
colorless oil: IR (film, cm–1) n 3440 (OH), 2100 (N3); H NMR (90 MHz, CDCl3) d = 1.5-1.8 (2H, m),
2.4-4.0 (7H, m).
To an ice-cooled solution of (S)-4-azidobutane-1,2-diol (21.1 g, 157 mmol) and imidazole (16.1 g, 236
mmol) in DMF (200 mL) was added tert-butyldimethylsilyl chloride (28.4 g, 188 mmol) carefully and the
reaction mixture was stirred at 4 °C for 10 h. After the addition of water, the reaction mixture was
stirred 30 min and then extracted with EtOAc. The organic layer was washed with water and brine, dried
over MgSO4 and concentrated in vacuo. The residue was purified by column chromatography on silica gel
(EtOAc:hexane = 1:10) to afford (S)-4-azido-1-tert-butyldimethylsilyloxybutane-2-ol (36.0 g, 93%) as a
colorless oil: [a]D21 = –10.6° (c 1.37, CHCl3); IR (film, cm–1) n 3420 (OH), 2100 (N3), 1260 (SiMe); H
1
NMR (90 MHz, CDCl3) d = 0.08 (6H, s), 0.90 (9H, s), 1.67 (2H, q, J = 6.6 Hz), 3.47 (2H, t, J = 6.6 Hz),

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3.3-3.9 (3H, m).
To an ice-cooled solution of (S)-4-azido-1-tert-butyldimethylsilyloxybutane-2-ol (1.99 g, 8.11 mmol),
imidazole (1.38 g, 20.3 mmol) and N,N-dimethylaminopyridine (10 mg) in DMF (20 mL) was added tert-
butyldiphenylsilyl chloride (3.2 mL, 12 mmol) and the reaction mixture was stirred at rt for 10 h. After
the addition of water, the reaction mixture was stirred 30 min and then extracted with EtOAc. The organic
layer was washed with water and brine, dried over MgSO4 and concentrated in vacuo. The residue was
purified by column chromatography on silica gel (EtOAc:hexane = 1:50) to afford 6 (3.77 g, 92%) as a
colorless oil: [a]D21 = –9.63° (c 0.50, CHCl3); IR (film, cm–1) n 2100 (N3), 1260 (SiMe); H NMR (300
1
MHz, CDCl3) d = –0.16 (3H, s), 0.12 (3H, s), 0.78 (9H, s), 1.03 (9H, s), 1.7-1.9 (2H, m), 3.2-3.5 (4H, m),
3.79 (1H, qui, J = 5.4 Hz).
(S)-4-tert-Butyldimethylsilyloxy-3-tert-butyldiphenylsilyloxybutylamine (7)
Under hydrogen, a suspension of the azide (6) (10.4 g, 20.5 mmol) and 10% Pd-C (350 mg) in EtOAc (50
mL) was stirred at rt for 3 h. The reaction mixture was filtered through Celite and concentrated in vacuo
to afford crude 7 (9.35 g, quant.) as a colorless oil: IR (film, cm–1) n 3380 and 3310 and 1600 (NH2), 1260
(SiMe). This amine (7) was employed in the next reaction without further purification.
(E)-3-tert-Butyldimethylsilyloxy-2-methyldec-8-enoic acid ethyl ester (9)
Under argon, to the suspension of activated zinc (168 mg, 4.10 mmol) in benzene (1 mL) was added
dropwise a solution of ethyl a-bromopropionate (706 mg, 3.90 mmol) and aldehyde (8) (500 mg, 3.90
mmol) in benzene (10 mL) at 60 °C and the suspension was refluxed for 2 h. To the reaction mixture was
added 20% sulfuric acid and the reaction mixture was stirred at rt for 10 min and then poured into water.
The mixture was extracted with EtOAc and the organic layer was washed with diluted sulfuric acid, water,
saturated NaHCO3 and brine, dried over MgSO4 and concentrated in vacuo. The residue was purified by
column chromatography on silica gel (EtOAc:hexane = 1:50) to afford hydroxyester (813 mg, 91%) as a
colorless oil: IR (film, cm–1) n 3480 (OH), 1730 and 1710 (CO2Et); 1H NMR (300 MHz, CDCl3) d = 1.1-
1.7 (15H, m), 1.9-2.1 (2H, m), 2.5-2.7 (1H, m), 3.65 and 3.89 (1H, m), 4.1-4.3 (2H, m), 5.3-5.5 (2H, m).
To an ice-cooled solution of hydroxy ester (813 mg, 3.56 mmol) and imidazole (363 mg, 5.43 mmol) in
DMF (6 mL) was added tert-butyldimethylsilyl chloride (968 mg, 4.63 mmol) and the reaction mixture
was stirred at rt for 10 h. After the addition of water, the reaction mixture was stirred for 30 min and then
extracted with EtOAc. The organic layer was washed with water and brine, dried over MgSO4 and
concentrated in vacuo. The residue was purified by column chromatography on silica gel (EtOAc:hexane
= 1:100) to afford 9 (1.03 g, 85%) as a colorless oil: IR (film, cm–1) n = 1740 (CO2Et), 1260 (SiMe); 1H
NMR (300 MHz, CDCl3) d = 0.0-0.5 (6H, m), 0.86 (9H, s), 1.07 and 1.10 (3H, d, J = 7.0), 1.25 and 1.25

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(3H, t, J = 7.1), 1.2-1.5 (6H, m), 1.6-1.65 (3H, m), 1.9-2.0 (2H, m), 2.45-2.7 (1H, m), 3.9-4.0 (1H, m),
4.05-4.15 (2H, m), 5.3-5.5 (2H, m).
(E)-N-[(S)-4-tert-Butyldimethylsilyloxy-3-trert-butyldiphenylsilyloxybutyl]-3-tert-butyldimethylsilyloxy-
2-methyldec-8-enamide (10)
To an ice-cooled solution of 9 (5.83 g, 17.0 mmol) in THF (70 mL), MeOH (30 mL) and water (10 mL)
was added a solution of 3 N lithium hydroxide (35 mL, 105 mmol) and the reaction mixture was stirred at
rt for 3 days. The resulting solution was quenched with 1 N hydrochloric acid carefully at 0 °C and
extracted with EtOAc. The organic layer was washed with water and brine, dried over MgSO4 and
concentrated in vacuo. The residue was purified by column chromatography on silica gel (EtOAc:hexane
= 1:50) to afford corresponding carboxylic acid (4.92 g, 92%) as a colorless oil: IR (film, cm–1) n 3100
(CO2H), 1260 (SiMe).
A solution of carboxylic acid (1.38 g, 4.39 mmol) in benzene (18 mL) was treated with oxalyl chloride (5
mL, 57 mmol) at 0 °C and stirred at rt for 2 h. After concentration, the residue was solved in CH2Cl2 (30
mL). This solution was added dropwise to a solution of amine (7) (3.01 g, 6.57 mmol) and triethylamine
(3 mL, 32 mmol) in CH2Cl2 (30 mL) at 0 °C and the reaction mixture was stirred at rt for 3 h. Then the
reaction mixture was poured into water and extracted with EtOAc. The organic layer was washed with
water and brine, dried over MgSO4 and concentrated in vacuo. The residue was purified by column
20
chromatography on silica gel (EtOAc:hexane = 1:20) to afford 10 (3.21 g, 97%) as a colorless oil: [a]D
=
1
–8.40° (c 1.11, CHCl3); IR (film, cm–1) n 3550 and 1660 (NHCO), 1260 (SiMe); H NMR (300 MHz,
CDCl3) d = –0.2-0.7 (12H, m), 0.79 (9H, s), 0.88 (9H, s), 1.05 (9H, s), 1.2-1.5 (7H, m), 1.6-1.8 (7H, m),
1.9-2.0 (2H, m), 2.2 (1H, m), 3.1-3.5 (4H, m), 3.7-3.8 (2H, m), 5.3-5.5 (2H, m), 6.13, 6.24 and 6.40 (1H,
m), 7.3-7.5 (6H, m), 7.60 (4H, d, J=7.4 Hz). Anal. Calcd for C43H75NO4Si3: C, 68.47; H, 10.02; N, 1.86.
Found: C, 67.70; H, 9.99; N 1.83.
(E)-N-[(S)-4-Hydroxy-3-tert-butyldiphenylsilyloxybutyl]-3-hydroxy-2-methyldec-8-enamide (11)
A solution of 10 (2.10 g, 2.78 mmol) and p-TsOH (600 mg) in CH2Cl2 (150 mL) was stirred at 40 °C for 1
day. Then the reaction mixture was poured into saturated NaHCO3 and extracted with CH2Cl2. The
organic layer was washed with water, saturated NaHCO3 and brine, dried over MgSO4 and concentrated
in vacuo. The residue was purified by column chromatography on silica gel (EtOAc:hexane = 2:1- EtOAc
only) to afford 11 (1.26 g, 86%) as a colorless oil: [a]D21 = –0.69° (c 0.35, CHCl3); IR (film, cm–1) n 3550
(OH), 1660-1630 (NCO); 1H NMR (300 MHz, CDCl3) d = 1.08 (9H, s), 1.2-1.5 (7H, m), 1.6-1.8 (7H, m),
1.9-2.0 (2H, m), 2.5 (1H, m), 3.0-3.9 (6H, m), 5.3-5.6 (2H, m), 7.3-7.5 (6H, m), 7.6-7.7 (4H, m); HRMS
m/z [MH+] 526.3353 (calcd for C31H48NO4Si 525.3340).

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(E)-2-Hept-5-enyl-8-hydroxy-3-methyl-6,7,8,8a-tetrahydro-8-tert-butyldiphenylsilyloxy-3-methyl-4H-
pyrrolo[2,1-b][1,3]oxazin-4-one [(8S,8aS)-12 and (8S, 8aR)-13]
To a solution of oxalyl chloride (1.99 mL, 22.8 mmol) in CH2Cl2 (180 mL) was added DMSO (1.78 mL,
25.1 mmol) at –78 °C. After 5 min, a solution of diol (11) (3.00 g, 5.71 mmol) in CH2Cl2 (20 mL) was
added to the reaction mixture and it was stirred at –40 °C for 1 h. After addition of triethyl amine (20 mL,
143 mmol), the reaction mixture was poured into water and extracted with Et2O. The organic layer was
washed with water, saturated NH4Cl and brine, dried over MgSO4 and concentrated in vacuo. The residue
was filtered through silica gel (EtOAc only) to afford hemiaminal as a colorless oil: IR (film, cm–1) n
3550 (OH), 1660-1630 (NCO). This compound was employed in the next step without further
purification.
A solution of hemiaminal and p-TsOH (300 mg) in CH2Cl2 (180 mL) was stirred at 0 °C for 3 h. Then the
reaction mixture was poured into saturated NaHCO3 and extracted with CH2Cl2. The organic layer was
washed with water, saturated NaHCO3 and brine, dried over MgSO4 and concentrated in vacuo. The
residue was purified by flash column chromatography on silica gel (EtOAc:hexane = 1:4-1:3) to afford 12
(943 mg, 32%) and 13 (865 mg, 30%) as a colorless oil:
28
12: [a]D = –115° (c 1.08, CHCl3); IR (film, cm–1) n 3450, 1670, 1660 and 1650 (NCO); 1H NMR (300
MHz, CDCl3) d = 1.07 (9H, s), 1.3-1.5 (4H, m), 1.63 (3H, d, J = 4.2 Hz), 1.79 (3H, s), 1.8-2.1 (5H, m),
2.23 (1H, m), 3.45 (1H, dt, J = 3.8, 7.5 Hz), 3.78 (1H, dt, J = 7.9, 10.8 Hz), 4.43 (1H, dd, J = 3.8, 7.5 Hz),
4.94 (1H, d, J = 3.8 Hz), 5.3-5.5 (2H, m), 7.3-7.5 (6H, m), 7.6-7.8 (4H, m); HRMS m/z [MH+] 504.2947
(calcd for C31H42NO3Si 504.2934).
13: [a]D19 = +28.9° (c 0.22, CHCl3); IR (film, cm–1) n 3450, 1660 (NCO); 1H NMR (300 MHz, CDCl3) d =
1.08 (9H, s), 1.3-1.5 (4H, m), 1.64 (3H, d, J = 4.2 Hz), 1.76 (3H, s), 1.8-2.0 (4H, m), 2.1-2.3 (2H, m),
3.45-3.65 (2H, m), 4.42 (1H, dd, J = 3.7, 6.8 Hz), 5.09 (1H, d, J = 3.7 Hz), 5.3-5.5 (2H, m), 7.3-7.5 (6H,
m), 7.6-7.8 (4H, m); HRMS m/z [MH+] 504.2948 (calcd for C31H42NO3Si 504.2934).
(S)-[(E,E) and (E,Z)]-2-(5-Heptenyl)-6,7-dihydro-3-methyl-4H-pyrrolo[2,1-b][1,3]oxazine-4,8(8aH)-
dione 8-oxime [(–)-Brevioxime (1) and Z-Isomer of (–)-Brevioxime]
To an ice-cooled solution of 12 (325 mg, 0.65 mmol) in THF (7 mL) was added TBAF-hydrate (350 mg)
and the reaction mixture was stirred at rt for 1 h and concentrated in vacuo. The residue was purified by
flash column chromatography on silica gel (EtOAc:hexane = 1:1-2:1) to afford corresponding alcohol
(156 mg, 91%) as a colorless oil: [a]D19 = –60.8° (c 1.04, CHCl3); IR (film, cm–1) n 3400 and 1650
1
(NCO); H NMR (300 MHz, CDCl3) d = 1.3-1.45 (2H, m), 1.4-1.45 (2H, m), 1.64 (3H, d, J = 4.6 Hz),
1.80 (3H, s), 1.9-2.15 (4H, m), 2.15-2.4 (2H, m), 3.57 (1H, ddd, J = 2.7, 8.4, 11.1 Hz ), 3.73 (1H, ddd, J =
7.2, 9.3, 11.1 Hz ), 4.45 (1H, dd, J = 3.8, 6.0 Hz), 5.21 (1H, d, J = 3.5 Hz), 5.35-5.5 (2H, m).

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To an ice-cooled solution of alcohol (400 mg, 1.50 mmol) in CH2Cl2 (15 mL) was added Dess-Martin
periodinane (1.91 g, 4.49 mmol) and the mixture was stirred at rt for 6 h. The reaction mixture was
poured into saturated Na2SO3 and extracted with CH2Cl2. The organic layer was washed with water,
saturated NaHCO3 and brine, dried over MgSO4 and concentrated in vacuo. The residue was purified by
flash column chromatography on silica gel (EtOAc:hexane = 1:1) to afford ketone (236 mg, 60%) as a
colorless oil: [a]D28 = –203° (c = 1.37, CHCl3); IR (film, cm-1) n 1780 (s, C=O), 1630-1680 (s, NCO); 1H
NMR (300 MHz, CDCl3) d = 1.3-1.45 (2H, m), 1.5-1.7 (2H, m), 1.64 (3H, d, J = 4.8 Hz), 1.84 (3H, s),
1.95-2.05 (2H, m), 2.2-2.4 (2H, m), 2.65-2.8 (2H, m), 3.61 (1H, ddd, J = 7.2, 8.7, 11.4 Hz), 4.12 (1H, m),
5.03 (1H, s), 5.3-5.5 (2H, m).
To an ice-cooled solution of the corresponding ketone (165 mg, 0.63 mmol) in MeOH (10 mL) were
added NaOAc (129 mg, 1.57 mmol) and NH2OH•HCl (87.1 mg, 1.25 mmol) and the mixture was stirred
at rt for 3 h. Then the reaction mixture was poured into water and extracted with CH2Cl2. The organic
layer was washed with water, saturated NaHCO3 and brine, dried over MgSO4 and concentrated in vacuo.
The residue was purified by flash column chromatography on silica gel (EtOAc:hexane = 1:1) to afford
(–)-1 [E:Z = 46% (81 mg) : 24% (42 mg)] as colorless crystal.
(–)-Brevioxime (1): mp 147-149ºC; [a]D22 = –209° (c 0.26, CHCl3); 1H NMR (300 MHz, CDCl3) d = 1.3-
1.4 (2H, m), 1.5-1.6 (2H, m), 1.63 (3H, d, J = 4.5 Hz), 1.83 (3H, s), 1.85-2.0 (2H, m), 2.2-2.4 (2H, m),
2.8-3.0 (2H, m), 3.48 (1H, dt, J = 8.1, 11.4 Hz), 4.07 (1H, ddd, J = 3.6, 9.3, 11.4 Hz), 5.3-5.4 (2H, m),
13
5.56 (1H, s), 8.79 (1H, s); C-NMR (75 MHz, CDCl3) d =10.1, 17.9, 23.8, 26.2, 29.1, 30.6, 32.2, 41.7,
84.1, 107.0, 125.2, 130.8, 157.7, 163.4, 163.9; HRMS m/z [MH+] 279.1669 (calcd for C15H23N2O3
279.1708).
1
Z-Isomer of (–)-Brevioxime: H NMR (300 MHz, CDCl3) d = 1.35-1.4 (2H, m), 1.5-1.6 (2H, m), 1.6-
1.65 (3H, m), 1.83 (3H, s), 1.9-2.0 (3H, m), 2.15-2.45 (2H, m), 2.70 (1H, ddd, J = 1.8, 7.5, 9.6 Hz), 2.84
(1H, m), 3.34 (1H, ddd, J = 7.5, 9.6, 11.1 Hz), 5.3-5.5 (2H, m), 5.82 and 5.83 (1H, s), 9.0 (1H, brs); 13C-
NMR (75 MHz, CDCl3) d = 10.0, 17.9, 26.3, 27.1, 29.0, 30.5, 32.2, 41.5, 79.8, 106.7, 125.1, 130.9, 156.2,
163.3, 164.2.
(R)-[(E,E) and (E,Z)]-2-(5-Heptenyl)6,7-dihydro-3-methyl-4H-pyrrolo[2,1-b][1,3]oxazine-4,8(8aH)-
dione 8-oxime [(+)-Brevioxime (1) and Z-Isomer of (+)-Brevioxime]
In the same manner as above, 13 (3.30 g, 6.53 mmol) was treated with TBAF to afford alcohol (14, 1.54 g,
89%) as colorless oil: [a]D23 = +110° (c 1.06, CHCl3); IR (film, cm-1) n = 1780 (s, C=O), 1630-1680 (s,
1
NCO); H NMR (300 MHz, CDCl3) d = 1.5-1.6 (2H, m), 1.25-1.4 (2H, m), 1.65 (3H, m), 1.79 (3H, s),
1.5-2.0 (3H, m), 2.15-2.35 (3H, m), 3.6 (2H, m), 4.48 (1H, m), 5.03 (1H, d, J = 3.6 Hz), 5.3-5.5 (2H, m).
In the same manner as above, 14 (175 mg, 0.67 mmol) was oxidized to afford ketone (233 mg, 94%) as

490
HETEROCYCLES, Vol. 61, 2003
colorless oil: [a]D25 = +225° (c 1.06, CHCl3); IR (film, cm-1) n = 1780 (s, C=O), 1630-1680 (s, NCO); 1H
NMR (300 MHz, CDCl3) d = 1.3-1.45 (2H, m), 1.5-1.7 (2H, m), 1.64 (3H, d, J = 4.8 Hz), 1.84 (3H, s),
1.95-2.05 (2H, m), 2.2-2.4 (2H, m), 2.65-2.8 (2H, m), 3.61 (1H, ddd, J = 7.2, 8.7, 11.4 Hz), 4.12 (1H, m),
5.03 (1H, s), 5.3-5.5 (2H, m).
In the same manner as above, ketone (250 mg, 0.94 mmol) was treated with NH2OH•HCl to afford (+)-1
[E:Z = 49% (92 mg) : 27% (51 mg)] as colorless crystal.
22
1
13
(+)-Brevioxime: mp 149-152ºC; [a]D = +214° (c 0.26, CHCl3); H NMR and C-NMR spectra are
identical with those of (–)-brevioxime (1); HRMS m/z [MH+] 279.1695 (calcd for C15H23N2O3 279.1708).
1 13
Z-Isomer of (+)-Brevioxim: H NMR and C-NMR spectra are identical with those of Z-isomer of (–)-
Brevioxime.
Determination of enantiomeric purity of (–)-1 and (+)-1
Both enantiomers of Brevioxime were converted to the corresponding (R)-MTPA esters and their
enantiomeric purities were determined by HPLC analysis on a Senshu Pak® [Silica-1301-N 4.6X300 mm
hexane/THF (10:1), 1.0 mL/min]: tR = 12 min [(R)-MTPA ester of (+)-Brevioxime (+)-1] ]: tR = 15 min
[(R)-MTPA ester of (–)-brevioxime (–)-1].
(R)-MTPA ester of (–)-brevioxime (–)-1-----[(–)-1:(+)-1 = 98.2:1.8]-----96% e.e.
(R)-MTPA ester of (+)-brevioxime (+)-1-----[(–)-1:(+)-1 = 1.4:98.6]-----97% e.e.
ACKNOWLEDGEMENTS
We sincerely thank Dr. K. Furihata, The University of Tokyo, for NOE experiment and Ms. H. Naito, The
University of Tokyo, for elemental analyses.
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