New type of mono-tetrahydrofuran ring acetogenins from Goniothalamus donnaiensis

Article abstract of DOI:10.1021/np9605448

A new type of Annonaceous acetogenin was isolated from the roots of Goniothalamus donnaiensis. The structures of two epimeric pairs, donnaienin A (1) and 34-epi-donnaienin A (1'), and donnaienin B (2) and 34-epi-donnaienin B (2'), characterized by the presence of a γ-(hydroxymethyl) γ-lactone moiety, were elucidated by spectroscopic analysis and chemical derivatization. Four known mono-THF acetogenins-murisolin, isoannonacin, and a mixture of annonacin and goniothalamicin-were also isolated.

Full text of DOI:10.1021/np9605448

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122
J . Nat. Prod. 1997, 60, 122-125
Notes
New Typ e of Mon o-tetr a h yd r ofu r a n Rin g Acetogen in s fr om Gon ioth a la m u s
d on n a ien sis
Zhong J iang and De-Quan Yu*
Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100 050,
People’s Republic of China
Received J uly 9, 1996X
A new type of Annonaceous acetogenin was isolated from the roots of Goniothalamus
donnaiensis. The structures of two epimeric pairs, donnaienin A (1) and 34-epi-donnaienin A
(1′), and donnaienin B (2) and 34-epi-donnaienin B (2′), characterized by the presence of a
γ-(hydroxymethyl) γ-lactone moiety, were elucidated by spectroscopic analysis and chemical
derivatization. Four known mono-THF acetogeninssmurisolin, isoannonacin, and a mixture
of annonacin and goniothalamicinswere also isolated.
In recent years, nearly 200 acetogenins have been
isolated from several genera of the Annonaceae.1 Five
types of terminal lactones have been reported.2-4 From
the roots of Goniothalamus donnaiensis Finet et Gag-
nep, we have isolated two novel epimeric pairs belonging
to a new subclass of the acetogenins, characterized by
the presence of a γ-(hydroxymethyl) γ-lactone, namely,
donnaienin A (1) and 34-epi-donnaienin A (1′) and
donnaienin B (2) and 34-epi-donnaienin B (2′).
Donnaienin A (1) and 34-epi-donnaienin A (1′), like
some similar lactol compounds,5 were isolated as an
epimeric pair. High-performance TLC (Si gel), devel-
oped with different solvents, always afforded one spot,
and repeated reversed-phase and normal-phase HPLC
similarly gave a sharp single peak. MS and elemental
analysis indicated a molecular formula of C35H64O7 and
an identical carbon skeleton for 1 and 1′ (Figure 1).
However, the 13C-NMR spectrum revealed a duplication
of several signals that appeared at δ 69.3/71.2, 104.9/
105.2, 131.8/132.5, 150.5/149.4, and 171.9/172.8, with
a relative intensity of 55/45 for all of these, suggesting
the presence of two epimeric compounds. 1H-NMR, 1H-
F igu r e 1. Diagnostic EIMS fragment ions (m/ z) of compounds
1 and 1′.
NMR spectrum, the signals at δ 104.9/105.2 (C-34)
replaced the signal around δ 77.9 (or 82.5). These data
indicated that for 1 and 1′, H-34 was substituted by a
hydroxy group, and this was confirmed by a DEPT
experiment that indicated that C-34 of 1 (1′) was a
quaternary carbon.
In order to confirm that 1 and 1′ were epimeric at
C-34, a phenylhydrazone derivative (3) was prepared.6
In the 13C-NMR spectrum of 3, all the signals appeared
to be singlets, suggesting it was one compound. In its
1H-NMR spectrum, the signals of H-4, H-3a, and H-3b
appeared at δ 3.90 (m), 2.70 (dq), 2.86 (dd), respectively
(Table 1). The EIMS of 3 and of its TMSi derivative
(3a ) further confirmed the structures of 1 and 1′ (Figure
2).
The relative configurations of the tetrahydrofuran
(THF) system of 1 and 1′ were assigned as threo/ trans/
threo by 1H- and 13C-NMR.7,8 The absolute stereochem-
istry of C-4, C-15, and C-20 was assigned by studying
the per-Mosher ester derivatives (3s and 3r ) of 3.9 The
1H-NMR chemical shift data of 3s and 3r showed that
the signs for ∆δS-R of H-3, H-33, and H-35 were
negative, indicating the C-4R configuration in 1 and 1′.
This result is identical to all acetogenins examined so
far that possess an OH at C-4. Similarly, the Mosher
ester data showed that the optical signs for ∆δS-R of
H-16, H-17, H-18, and H-19 were negative. These
allowed the absolute stereochemical assignment of the
carbinol centers adjacent to the mono-THF ring in 1 and
1′ as C-15R and C-20R (Table 2).
1
1H COSY, and H-13C COSY indicated that the chemi-
cal shifts of protons H-3 and H-4 were obviously
different for 1 and 1′. H-3a and H-3b of 1 were observed
at δ 2.26 (dq) and 2.52 (dd), respectively, correlating
with the 13C-NMR signal at δ 33.0; H-4 of 1 was at δ
3.91 (m) and correlated with the 13C-NMR signal at δ
69.3. In the case of 1′, H-3a and H-3b resonated at δ
2.42 (m), correlating with the carbon at δ 32.0; H-4
appeared at δ 3.77 (m), correlating with the carbon at
δ 71.2. In the HMBC spectrum, the carbon chemical
shift at δ 69.3 correlated with the protons resonating
at δ 2.26 and 2.52, while the carbon that appeared at δ
71.2 correlated with the protons at δ 2.42. Accordingly,
it was possible to assign the NMR spectra for 1 and 1′
(Table 1). Several spectral characteristics in the γ-lac-
tone moiety of 1 and 1′ clearly distinguished them from
any previously known acetogenins. First, in the 1H-
NMR spectrum, the H-34 signal (ca. δ 5.04 or 4.50)
disappeared, and the H-35 protons exhibited a signal
at δ 1.66 (s) instead of δ 1.42 (d). Second, in the 13C-
Donnaienin B (2) and 34-epi-donnaienin B (2′) were
also obtained as an epimeric pair, and they gave only
X Abstract published in Advance ACS Abstracts, J anuary 15, 1997.
S0163-3864(96)00544-7 CCC: $14.00
© 1997 American Chemical Society and American Society of Pharmacognogy

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Notes
Ta ble 1. 1H- (500 MHz) and 13C- (125 MHz) NMR Resonances (δ) for Compounds 1, 1′, and 3
1′
J ournal of Natural Products, 1997, Vol. 60, No. 2 123
1
3
position
δ 1H (J in Hz)
δ
13C
δ 1H (J in Hz)
δ
13C
δ 1H (J in Hz)a
δ
13Cb
1
2
3a
3b
171.9
131.8
33.0
172.8
132.5
32.0
161.5
131.9
33.4
2.26, dq (14.1, 9.3)
2.52, dd (14.1, 4.2)
3.91, m
1.2-1.6, m
3.41, m
3.77, m
1.97, m
1.62, m
1.97, m
1.62, m
3.77, m
3.41, m
1.2-1.6, m
0.88, t (6.8)
6.96, s
2.42, m
2.42, m
3.77, m
1.2-1.6, m
3.41, m
3.77, m
1.97, m
1.62, m
1.97, m
1.62, m
3.77, m
3.41, m
1.2-1.6, m
0.88, t (6.8)
6.96, s
2.70, dq (13.9, 8.2)
2.86, dd (13.9, 4.0)
3.90, m
1.2-1.6, m
3.40, m
3.80, m
1.97, m
1.62, m
1.97, m
1.62, m
3.80, m
3.40, m
1.2-1.6, m
0.88, t (6.8)
7.07, s
4
69.3
71.2
70.8
5-14
15
16
17a,b
22-38
74.4c
82.6
22-38
74.4d
82.6
22-40
74.0e
82.7
28.8
28.8
28.7
18a,b
28.8
28.8
28.7
19
20
21-31
32
33
34
35
82.6
74.3c
22-38
14.0
150.5
104.9
24.2
82.6
74.3d
22-38
14.0
149.4
105.2
24.2
82.7
74.3e
22-40
14.0
141.7
145.3
20.9
1.66, s
1.66, s
2.37, s
a
b
Aromatic signals: δ 7.37 (1H, t), 7.46 (2H, t), 7.56 (2H, d). Aromatic signals: δ 125.6 (2C), 128.2 (1C), 128.8 (2C), 142.0 (1C).
c-e Assignments with same superscript may be interchangeable.
THF ring and the OH groups were established by EIMS
of 2 and 2′ (Figure 3), and further confirmed by the
analogous EIMS fragmentations of 4 and its per-TMSi
derivative (4a ) (Figure 4).
The relative stereochemistry between C-13 and C-14
of 2 and 2′ was determined as threo by comparing the
13C-NMR signal of the hydroxylated carbon C-14 (δ 74.7)
1
and the H-NMR signals of H-13 (δ 3.80) and H-14 (δ
3.40) with those of model compounds of known relative
stereochemistry.7 The ether proton H-13 of 2 and 2′
resonated at δ 3.80, also suggesting the existence of a
trans-THF ring in 2 and 2′.11 The formation of an
acetonide 4b from 4 provided further evidence that a
1,2-diol was present in 2 and 2′. The acetonyl methyls
appeared at δ 1.367, and the dioxolane ring protons
appeared at δ 3.60, indicating that the 1, 2-diol has a
threo configuration.12,13
F igu r e 2. Diagnostic EIMS fragment ions (m/ z) of compounds
3 and 3a .
Ta ble 2. 1H-NMR Chemical Shift Data (δ) for the
Determination of the Absolute Configuration of Compound 3
from Its (S)- and (R)-MTPA Mosher Ester Derivatives
The absolute stereochemistry of C-4 and C-14 in 2 and
2′ was assigned by the preparation of the per-Mosher
ester derivatives (4bs and 4br ) of 4b. The 1H-NMR
data of 4bs and 4br (Table 4) indicated C-4R and C-14S
configurations. Consequently, C-13 and C-10 were
concluded to have the respective S and R configurations
in both 2 and 2′. The H-14 signal in 4b showed a
quartet pattern at δ 3.40, indicating that the threo diol
at C-17, C-18 has the S,S configuration.11,14
The mixture of epimers of 1 and 1′ showed potent
cytotoxcity against KB (human nasopharyngeal carci-
noma) (IC50 < 1 µg/mL) and HCT-8 (human colon
adenocarcinoma) cells (IC50 < 10 µg/mL); the mixture
of epimers of 2 and 2′ was also cytotoxic to KB cells
(53.8% inhibition, 10 µg/mL).
carbinol
confign
proton chemical shifts (∆δ ) δs-δr)
MTPA MTPA
deriv
confign H-4
H-3
H-33
H-35
at C-4
3
S
5.53
5.53
2.69, 3.05
2.76, 3.09
6.76
6.92
2.19
2.23
R
∆δ
R
-(0.07, 0.04) -(0.16) -(0.04)
proton chemical shifts (∆δ ) δs-δr)
MTPA MTPA
deriv confign H-20 H-19
at C-15
H-16 H-15 and C-20
H-18, H-17
3
S
4.96
5.02
3.92
4.00
1.78, 1.40
1.92, 1.49
3.92 4.96
4.00 5.02
R
∆δ
R
-(0.08) -(0.14, 0.09) -(0.08)
one spot by high-performance TLC with different sol-
vents. Repeated reversed-phase and normal-phase
HPLC also gave one sharp peak in each case. MS and
elemental analysis indicated a molecular formula of
C35H64O8 and an identical carbon skeleton. Similar to
Exp er im en ta l Section
Gen er a l Exp er im en ta l P r oced u r es. Melting point
determinations were made on a Boetius micromelting
point apparatus and are uncorrected. Optical rotation
determinations were made on a Perkin-Elmer 241
polarimeter. UV spectra were measured on a Shimadzu
UV-240 spectrometer. IR spectra were measured on a
Perkin-Elmer 683 spectrometer. 1H-NMR, COSY, and
13C-NMR spectra were obtained on a Bruker AM-500
spectrometer. MS spectra were obtained on a ZAB-2F
1 and 1′, the H- and 13C-NMR spectra of 2 and 2′ also
1
showed the duplication of several signals with a ratio
of 55/45, suggesting they were epimeric at C-34. This
suggestion was confirmed by the formation of a phenyl-
hydrazone derivative (4). The NMR spectra of the
mixture of 2 and 2′ and 4 (Table 3) indicated that 2 and
2′ are mono-THF acetogenins with a single hydroxyl
group adjacent to the THF ring.10 The positions of the

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124 J ournal of Natural Products, 1997, Vol. 60, No. 2
Ta ble 3. 1H- (500 MHz) and 13C- (125 MHz) NMR Resonances (δ) for Compounds 2, 2′, 4, and 4b
Notes
2
2′
4
4b
position
δ 1H (J in Hz)
δ
13C
δ 1H (J in Hz)
δ
13C
δ 1H (J in Hz)a
δ
13Cb
δ 1H (J in Hz)c
1
2
3a
3b
4
171.8
131.9
33.0
172.5
132.4
32.1
161.5
132.0
33.2
2.26, dq (14.1, 9.3)
2.52, dd (14.1, 4.2)
3.91, m
2.41, m
2.41, m
3.80, m
2.69, dq (13.9, 8.2)
2.85, dd (13.9, 4.0)
3.91, m
2.69, dq (13.9, 8.2)
2.85, dd (13.9, 4.0)
3.89, m
68.9
70.8
70.7
5-9
10
11a,b
1.2-1.6, m
22-38
1.2-1.6, m
22-38
1.2-1.6, m
22-40
1.2-1.6, m
3.91, m
79.6
3.91, m
79.4
3.91, m
79.3
3.89, m
2.00, m
32.4
2.00, m
32.4
2.00, m
32.4
2.00, m
1.60, m
1.60, m
1.60, m
1.60, m
12a,b
2.00, m
28.5
2.00, m
28.5
2.00, m
28.4
2.00, m
1.60, m
1.60, m
1.60, m
1.60, m
13
14
15-16
17
18
19-31
32
33
34
35
3.80, m
3.41, m
1.2-1.6, m
3.41, m
82.0
7.47d
33-35
74.3d
74.2d
22-38
14.0
150.6
105.0
24.2
3.80, m
3.41, m
1.2-1.6, m
3.41, m
82.0
74.7e
33-35
74.3e
74.2e
22-38
14.0
149.5
105.2
24.2
3.78, m
3.40, m
1.2-1.6, m
3.40, m
8.18
74.7f
3.80, m
3.42, m
1.2-1.6, m
3.60, m
33-38
74.4f
3.41, m
3.41, m
3.40, m
74.3f
3.60, m
1.2-1.6, m
0.88, t (6.8)
6.97, s
1.2-1.6, m
0.88, t (6.8)
6.95, s
1.2-1.6, m
0.87, t (6.8)
7.07, s
22-40
14.1
141.6
145.3
20.9
1.2-1.6, m
0.87, t (6.8)
7.07, s
1.66, s
1.66, s
2.37, s
2.37, s
a
b
Aromatic signals: δ 7.37 (1H, t), 7.46 (2H, t), 7.56 (2H, d). Aromatic signals: δ 125.6 (2C), 128.2 (1C), 128.8 (2C), 142.0 (1C) c Aromatic
signals: δ 7.37 (1H, t), 7.46 (2H, t), 7.56 (2H, d); acetonyl methyl signal: δ 1.37 (6H, s). d-f Assignments with same superscript may be
interchangeable.
Marine Chemical Factory (Qingdao City, Shangdong
Province, People’s Republic of China), was used for
column chromatography. Si gel GF254 (40-µm diameter)
was used for preparative and analytical TLC. TLC
plates were visualized by spraying with 5% H2SO4 in
EtOH, followed by heating. Normal-phase analytical
HPLC runs were obtained using a Dupont column
packed with Zorbaxsil 7-µm Si gel. Reversed-phase
HPLC was performed on a column packed with Nucleo-
sil 7-µm C18 Si gel.
F igu r e 3. Diagnostic EIMS fragment ions (m/ z) of compounds
2 and 2′.
P la n t Ma ter ia l. The dried roots (9.5 kg) of G.
donnaiensis Finet et Gagnep (Annonaceae) were col-
lected from Long J in County, Guangxi Province, People’s
Republic of China, in August 1994, and a voucher
specimen of the plant has been deposited at the Depart-
ment of Medicinal Plants, Guangxi College of Tradi-
tional Chinese Medicine. The plant material was
pulverized using an electric mill.
Biologica l Eva lu a tion . Five-day cytotoxicity tests
of the isolated compounds against human solid tumor
cell lines were performed at the Department of Phar-
macology, Institute of Materia Medica, Chinese Acad-
emy of Medical Sciences, using the KB nasopharyngeal
carcinoma and HCT-8 colon adenocarcinoma cell lines.
Extr a ction a n d Isola tion . The pulverized roots of
G. donnaiensis (9.5 kg) were exhaustively extracted with
95% EtOH to yield extract F001 (2.05 kg), which was
partitioned between H2O and CHCl3 (1:1), giving the
H2O-soluble fraction F002 (448 g) and the CHCl3-soluble
fraction F003 (820 g). F003 was then partitioned
between 90% aqueous MeOH and petroleum ether (1:
1) to yield the petroleum ether-soluble fraction F006 (42
g) and the aqueous MeOH-soluble fraction F005 (638
g). F005 (91 g) was applied to a column of Si gel (120-
180 mesh), eluted with CHCl3 containing gradually
increasing proportions of MeOH. Impure components
were combined according to their similar appearance
on TLC analysis, and these were again subjected to
repeated chromatography to yield the crude compounds
1 (1′) and 2 (2′). These were then purified by prepara-
tive TLC, developed with CHCl3-MeOH (93:7) and
F igu r e 4. Diagnostic EIMS fragment ions (m/ z) of compounds
4 and 4a .
F igu r e 5. Structure of compound 4b.
spectrometer. Elemental analysis was performed on a
MOD1106 elemental analyzer. Gilson Model 303 pumps
and a Gilson Model 116 ultraviolet detector were used
in HPLC detection.
Si gel (120-180 mesh), purchased from Qing-dao

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Notes
J ournal of Natural Products, 1997, Vol. 60, No. 2 125
Ta ble 4. 1H-NMR Chemical Shift Data (δ) for the Determination of the Absolute Configuration of Compound 4b from Its (S)- and
(R)-MTPA Mosher Ester Derivatives
proton chemical shifts (∆δ ) δs-δr)
carbinol confign
at C-4
MTPA deriv
MTPA confign
H-4
H-3
H-33
H-35
4b
S
R
5.53
5.53
2.68, 3.03
2.75, 3.08
6.76
6.91
2.19
2.23
R
∆δ
-(0.07, 0.05)
-(0.15)
-(0.04)
proton chemical shifts (∆δ ) δs-δr)
carbinol confign
at C-14
MTPA
deriv
MTPA
confign
Acetonyl Methyls
H-18, H-17
H-14
H-13
H-12
H-11
H-10
4b
S
R
1.33, 1.34
1.37, 1.39
3.44, 3.48
3.57, 3.59
5.07
5.09
4.02
4.01
2.00, 1.69
1.86, 1.67
2.00, 1.75
1.92, 1.74
3.87
3.76
S
∆δ
-(0.04, 0.05)
-(0.13, 0.11)
+(0.01)
+(0.14, 0.02)
+(0.08, 0.01)
+(0.11)
hexane-EtOAc-MeOH (6:3:1), respectively, to afford
the two amorphous powders 1 (1′) and 2 (2′). Using the
same methods, four known compounds (murisolin, iso-
annonacin, and a mixture of annonacin and goniothal-
amicin) were also obtained. The two epimers 1 (1′) and
2 (2′), when run on reversed-phase and normal-phase
HPLC with different solvent systems, gave a sharp
single peak in all cases.
purified by preparative TLC. Compound 4b: colorless
oil; H-NMR (500 MHz, CDCl3) data, see Table 3.
1
MTP A Der iva t ives of 3 a n d 4b . (R)-(+)- or (S)-
(-)-Methyl-R-(trifluoromethyl)phenylacetic acid (MTPA,
35 mg) and N,N′-dicyclohexylcarbodiimide (DCC, 30 mg)
were added to a 5-mg sample of 3 or 4b dissolved in
dry CH2Cl2 with a few crystals of (dimethylamino)-
pyridine (DMAP). Each mixture was stirred at room
temperature for 6 h, and the products (3r , 3s, 4br , and
4bs) were purified by preparative TLC. 3r and 3s:
Don n a ien in A (1) a n d 34-epi-d on n a ien in A (1′):
white, amorphous powder from hexane-EtOAc (1:4), 88
mg; mp 96-98 °C, [R]18 -7.6° (c 0.07, CHCl3); UV
1
D
colorless oil; H-NMR (500 MHz, CDCl3 referenced to
(MeOH) λ max 205 (ꢀ 6831), 248 sh (ꢀ 1192) nm; IR ν
max 3390 (OH), 2920 and 2850 (CH), 1762 (lactone
CdO), 1467 (CH) cm-1; 1H-NMR data, see Table 1; 13C-
NMR data, see Table 1; FABMS m/ z [M + Na]+ 619
(40); EIMS m/ z [MH]+ 597 (0.2), 579 (2), 561 (2), 543
(3), 525 (2), 379 (3), 361 (28), 343 (12), 309 (100), 291
(15); anal. C 70.53%, H 10.97%, calcd for C35H64O7, C
70.47%, H 10.74%.
TMS) data, for characteristic resonances see Table 2.
4br and 4bs: colorless oil; H NMR (500 MHz, CDCl3
reference to TMS) data, for characteristic resonances
see Table 4.
1
Ack n ow led gm en t. This work was supported by the
Science Foundation of Chinese Academy of Medical
Sciences. The authors are grateful to Prof. Shou-Yang
Liu of Guangxi College of Traditional Chinese Medicine,
for the collection and identification of the plant material,
and to Yu-Mei Ye, Department of Pharmacology, Insti-
tute of Materia Medica, Chinese Academy of Medical
Sciences, for the cytotoxicity testing.
Don n a ien in B (2) a n d 34-epi-d on n a ien in B (2′):
white, amorphous powder from EtOAc, 76 mg; mp 70-
72 °C, [R]30 -19.0° (c 0.09, MeOH); UV (MeOH) λ max
D
208 (ꢀ 6815), 250 sh (ꢀ 1180) nm; IR ν max 3395 (OH),
2923 and 2852 (CH), 1752 (lactone CdO), 1465 (CH);
1H-NMR data, see Table 3; 13C-NMR data, see Table 3;
FABMS m/ z [M + Na]+ 635 (35); CIMS m/ z [MH -
H2O]+ 595 (8), 577 (23), 559 (100), 541 (38), 523 (25);
EIMS m/ z 367 (2), 349 (50), 331 (30), 313 (8), 297 (20),
297 (82), 261 (10); anal. C 68.58%, H 10.42%, calcd for
C35H64O8, C 68.63%, H 10.46%.
Refer en ces a n d Notes
(1) Hopp, D. C.; Zeng, L.; Gu, Z.-M.; McLaughlin, J . L. J . Nat. Prod.
1996, 59, 97-99.
(2) Rupprecht, J . K.; Hui, Y.-H.; McLaughlin, J . L. J . Nat. Prod.
1990, 53, 237-278.
(3) Fang, X.-P.; Rieser, M. J .; Gu, Z.-M.; Zhao, G.-X.; McLaughlin,
J . L. Phytochem. Anal. 1993, 4, 27-67.
P h en ylh yd r a zon e Der iva tives of 1 (1′) a n d 2 (2′).
In each case, a mixture of a 20-mg sample and 5 mg of
phenylhydrazine in 10 mL of EtOH was refluxed for 2
h. The viscous mass (3 or 4) which was produced after
removal of solvent in vacuo was purified by preparative
TLC. Compound 3 was obtained as a white powder: 1H-
NMR (500MHz, CDCl3) and 13C-NMR (125 MHz, CDCl3)
data, see Table 1; EIMS m/ z 469 (30), 451 (25), 433 (10),
399 (90), 381 (35), 363 (5). Compound 4 was also
obtained as a white powder: 1H-NMR (500 MHz, CDCl3)
and 13C-NMR (125 MHz, CDCl3) data, see Table 3;
EIMS m/ z 457 (2), 439 (15), 421 (10), 403 (8), 369 (85),
351 (38).
TMSi Der iva tives of 3 a n d 4. Samples of no more
than 1 mg were treated with 20 µL of N,O-bis(trimeth-
ylsilyl)-acetamide and 2 µL of pyridine and heated at
70 °C for 30 min to yield trimethylsilyl (TMSi) ethers
(3a and 4a ) that were analyzed by EIMS.
Aceton id e Der iva tive of 4. To 4 (12 mg in 5 mL of
CH2Cl2) was added 0.3 mL of 2,2-dimethoxypropane and
a few of crystals of p-toluenesulfonic acid, and stirred
at room temperature for 2 h. The product (4b) was
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