Stereoselective synthesis of a promising flower-inducing KODA analog, (9R,12S,13R,15Z)-9-hydroxy-12,13-methylene-10-oxooctadec-15-enoic acid

Article abstract of DOI:10.1271/bbb.130243

Stereoselective synthesis of a promising flower-inducing 9,10-ketol octadecadienoic acid (KODA) analog, (9R,12S,13R,15Z)-9-hydroxy-12,13-methylene- 10-oxooctadec-15-enoic acid, was designed to obtain the desired stereoisomer via coupling between chiral sulfone and aldehyde segments. A known chiral cyclopropane derivative was converted to the sulfone segment via carbon-chain elongation and sulfonylation. Dec-9-en-1-ol was converted to the aldehyde segment, whose C-9 configuration was introduced by Sharpless asymmetric dihydroxylation. Coupling of the both segments and subsequent assembly gave the desired (9R,12S,13R,15Z)-analog. The (9S,12S,13R,15Z)-analog was also synthesized by using the enatiomeric aldehyde segment. This strategy made it possible to synthesize the remaining stereoisomeric analogs.

Full text of DOI:10.1271/bbb.130243

Biosci. Biotechnol. Biochem., 77 (6), 1354–1357, 2013
Communication
Stereoselective Synthesis of a Promising Flower-Inducing KODA Analog,
(9R,12S,13R,15Z)-9-Hydroxy-12,13-methylene-10-oxooctadec-15-enoic Acid
y
Shin SHIMOMURA, Shuho OYAMA, Kyohei NAKANO, Morifumi HASEGAWA, and Hiroaki TOSHIMA
Department of Bioresource Science, College of Agriculture, Ibaraki University,
3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan
Received March 22, 2013; Accepted April 16, 2013; Online Publication, June 7, 2013
[doi:10.1271/bbb.130243]
Stereoselective synthesis of a promising flower-induc-
ing 9,10-ketol octadecadienoic acid (KODA) analog,
(9R,12S,13R,15Z)-9-hydroxy-12,13-methylene-10-oxooc-
tadec-15-enoic acid, was designed to obtain the desired
stereoisomer via coupling between chiral sulfone and
aldehyde segments. A known chiral cyclopropane de-
rivative was converted to the sulfone segment via
carbon-chain elongation and sulfonylation. Dec-9-en-1-
ol was converted to the aldehyde segment, whose C-9
configuration was introduced by Sharpless asymmetric
dihydroxylation. Coupling of the both segments and
subsequent assembly gave the desired (9R,12S,13R,15Z)-
analog. The (9S,12S,13R,15Z)-analog was also synthe-
sized by using the enatiomeric aldehyde segment. This
strategy made it possible to synthesize the remaining
stereoisomeric analogs.
test the flowering of L. paucicostata, two artifacts, FN1
(2) and FN2 (3), were formed from KODA and
noradolenochrome, an autoxidation product of norepi-
nephrine.9) Potent flower-inducing activity was observed
only in 2, possessing the (9R)-configuration, derived
from 1R. In another example, it was found that
endogenous KODA levels were closely related to
flower-inducing activity in Pharbitis nil.10) Synthetic
(ꢀ)-KODA and (R)-KODA (1R) at a concentration of
100 mM remarkably promoted flower induction at 129%
and 215% (water control, 100%) respectively.11) In many
other studies of various garden plants, crops, and trees,
KODA participated in flowering and dormancy.12–14)
To study the mechanism of flowering as regulated by
KODA, new KODA analogs and their probes having
chemical stability and potent activity are needed. In
view of the production of cycloadduct 2 and 3, the
C-12,13 double bond of KODA might be rather reactive.
Moreover, KODA might isomerize to conjugated enone
or diene. To avoid such reactivity and to maintain the
cis-configuration of 2 derived from (12Z)-geometry in
1R, we designed a KODA derivative (4R) possessing a
cyclopropane ring at the C-12,13 position. Because 1R
and 4R have similar molecular sizes and the same (9R)-
configuration, 4R is an appropriate analog to study the
flower-inducing activity of KODA. Here we report the
stereoselective synthesis of 4R, and a strategy that can
be applied to 4S and the remaining stereoisomeric
analogs. We have synthesized racemic mixtures of 4R
and 4S containing 9-keto-10-hydoxy isomers via a linear
synthetic strategy, and each mixture was confirmed to
exhibit about twice higher flower-inducing activity than
KODA in Pharbitis nil (unpublished results). Thus 4R
is a promising KODA analog to study the mechanism
of flowering.
Key words: 9,10-ꢀ-ketol octadecadienoic acid; flower-
inducing activity; cyclopropane derivative;
lipase hydrolysis; Sharpless asymmetric
dihydroxylation
Chailakhyan proposed the existence of florigen in
1936.1) Florigen is defined as a mobile substance
induced initially in leaves under photoperiodic control
that moves from the leaves to the shoot apex and
promotes flowering. Recently, the FT protein of Arabi-
dopsis thaliana,2–4) the Hd3a protein of rice, and
homologous proteins5,6) were identified by the molecular-
genetic approach, and they are recognized widely as
florigen. Furthermore, the study of the molecular
mechanisms of flowering is progressing and has pro-
vided the result that 14-3-3 proteins act as intracellular
receptors for florigen.7) In contrast to flowering regu-
lation by proteins homologous to FT/Hd3a, other
processes of regulation by low molecular compounds
are plausible based on results using KODA and related
compounds (Fig. 1).8–11) KODA, (12Z,15Z)-9-hydroxy-
10-oxooctadec-15-enoic acid, possessing a 9,10-ketol
octadecadienoic acid structure, was isolated as a stress-
released compound in a search for the flower-inducing
factor (FIF) from Lemna paucicostata (Fig. 1).8)
Although KODA exists as a mixture of (R)-KODA
(1R, 70%) and (S)-KODA (1S, 30%), the (R)-configu-
ration of 1R is considered to be important in exhibiting
flower-inducing activity based on the fact that when
KODA was incubated with norepinephrine in water to
The improved convergent synthetic strategy for 4R
consists of the following three operations: (i) preparation
of
a chiral sulfone segment (9) possessing the
(12S,13R,15Z)-configuration, (ii) preparation of a chiral
aldehyde segment (13) possessing the (9R)-configura-
tion, and (iii) coupling between 9 and 13 and subsequent
assembly to 4R. Because the antipodes of 9 and 13 can
be prepared easily, three stereoisomeric KODA analogs
of 4R can theoretically be synthesized.
Preparation of 9 was started from a known chiral
24
cyclopropane derivative (5) (>99% e.e., ½ꢀꢁ
þ18.7
D
22
(c 1.58, CH2Cl2), lit. ½ꢀꢁ
þ18.2 (c 1.58, CH2Cl2)15)
)
D
y
To whom correspondence should be addressed. Fax: +81-29-888-8525; E-mail: toshima@mx.ibaraki.ac.jp
Abbreviations: KODA, 9,10-ketol octadecadienoic acid; AD, asymmetric dihydroxylation

Synthesis of a Promising Flower-Inducing KODA Analog
1355
R1 R2
1
COOH
10
9
18
15
13
12
(R)-KODA (1R): R1 = H, R2 = OH
(S)-KODA (1S): R1 = OH, R2 = H
O
R1 R2
H
H
10
COOH
HO
HN
9
O
O
FN1 (2): R1 = H, R2 = OH
FN2 (3): R1 = OH, R2 = H
OH
O
R1 R2
10
COOH
13 12
9
H
H
O
(9R,12S,13R,15Z)-9-Hydroxy-12,13-methylene-10-oxooctadec-15-enoic acid (4R):R1 = H, R2 = OH
(9S,12S,13R,15Z)-9-Hydroxy-12,13-methylene-10-oxooctadec-15-enoic acid (4S):R1 = OH, R2 = H
Fig. 1. Structures of KODA and Related Compounds.
Sulfone segment
a, b, c, d
e, f
OTBDPS
HO
OCOPr
5 (>99% e.e.)
HO
OTBDPS
7
6
C6H4(p-CH3)
g, h
i, j, k
OTBDPS
S
O
O
8
9
Aldehyde segment
OH
l, m
HO
OH
OBz
then recrystallizaton
from EtOAc-Hexane
10
11 (>99% e.e.)
C6H4(4-OMe)
O
OMPM
OMPM
n, o, p
q, r
O
OHC
OTBS
OTBS
13
12
l, s, n-r
10
OHC
OTBS
ent-13
Scheme 1. Synthesis of the Sulfone Segment (9) and the Aldehyde Segment (13).
Reagents and conditions: (a) DHP, PPTS, CH2Cl2, r.t., 2 h, 100%; (b) K2CO3, MeOH, r.t., 2 h, 98%; (c) TBDPSCl, imidazole, DMF, 0 ꢃC-r.t.,
overnight, 93%; (d) PPTS, EtOH, 60 ꢃC, overnight, 91%; (e) CBr4, Ph3P, CH2Cl2, 0 ꢃC-r.t., 20 min, 99%; (f) lithium acetylide ethylenediamine
complex, DMSO-THF, 0 ꢃC-r.t., 1.5 h, 82%; (g) n-BuLi, HMPA-THF, ꢄ78 ꢃC, 1 h, then CH3CH2I, ꢄ78 ꢃC-r.t., overnight, 89%; (h) H2, Lindlar
cat., hexane, r.t., 1 h, 98%; (i) TBAF, THF, 0 ꢃC-r.t., 3.5 h, 100%; (j) CBr4, Ph3P, CH2Cl2, 0 ꢃC-r.t., 20 min, 72%; (k) 4-CH3C6H4SO2Na, DMF,
0 ꢃC-r.t., overnight, 70%; (l) BzCl, pyridine, CH2Cl2, 0 ꢃC-r.t., 2 h, 100%; (m) AD-mix-ꢂ, t-BuOH-H2O, 0–4 ꢃC, overnight, 98%; (n) 4-
MeOC6H4CH(OMe)2, PPTS, CH2Cl2, r.t., 3 h, 100%; (o) K2CO3, MeOH, r.t., 2 h, 98%; (p) TBSCl, imidazole, DMF, 0 ꢃC-r.t., 2 h, 93%; (q)
DIBAL-H, CH2Cl2, ꢄ78 ꢃC-r.t., 96%; (r) (COCl)2, DMSO, Et3N, CH2Cl2, ꢄ78 ꢃC-r.t., 30 min, 96%; (s) AD-mix-ꢀ, t-BuOH-H2O, 0–4 ꢃC,
overnight, 99%.
23
obtained via lipase hydrolysis of the corresponding
meso-dibutyrate (Scheme 1). The optical purity of 5 was
determined by HPLC analysis (DAICEL CHIRALCELꢀ
OD-H ꢁ 4:6 ꢂ 250 mm, solvent hexane:IPA ¼ 200:1,
eluent 0.8 mL/min, temperature 30 ꢃC, UV 210 nm, RT
66.1 min for 5, 70.4 min for ent-5). Sequential protection
and deprotection of 5 was carried out to give 6 as
follows: (i) protection of the hydroxy group as tetrahy-
dropyranyl (THP) acetal (100%), (ii) deprotection of the
butyryl group by methanolysis (98%), (iii) protection of
the resulting hydroxyl group as tert-butyldiphenylsilyl
(TBDPS) ether (93%), and (iv) deprotection of the THP
group by transacetalization (91%). Optical rotation of 6
was measured as ½ꢀꢁ
þ10.6 (c 0.73, CH2Cl2), the
D
absolute value of which was identical to that measured
22
as ½ꢀꢁ
ꢄ10.3 (c 0.73, CH2Cl2) for ent-6.15) All new
D
compounds from 6 were characterized by 1H-NMR, 13C-
NMR, IR, HRMS, and optical rotation. Bromination of 6
with carbon tetrabromide and triphenylphosphine gave
the corresponding bromide (99%), and this was treated
with lithium acetylide ethylenediamine complex to give
terminal alkyne (7) (82%). The lithium salt of 7,
obtained by treatment with n-butyl lithium, was alky-
lated with iodoethane to give internal alkyne (89%).
Partial hydrogenation of the alkyne in the presence of
Lindlar catalyst gave (Z)-alkene (8) (98%). Sulfone

1356
S. SHIMOMURA et al.
SO2Tol OMPM
a, 13
9
OTBS
OTBS
OH
O
14
OMPM
b, c
15
OH
d e, f, g
COOH
O
4R
OH
a, ent-13
COOH
9
b-g
O
4S
Scheme 2. Synthesis of 4R and 4S.
Reagents and conditions: (a) n-BuLi, THF, ꢄ78 ꢃC, 20 min, then 13 (or ent-13), ꢄ78 ꢃC-r.t., 1 h; (b) DMP, CH2Cl2, 0 ꢃC-r.t., 15 min, 76%
(2 steps); (c) Al–Hg, Na2HPO4, MeOH, 0 ꢃC-r.t., 3 h, 93%; (d) TBAF, THF, 0 ꢃC-r.t., 6 h, 98%; (e) DMP, CH2Cl2, 0 ꢃC-r.t., 5 h, 75%;
(f) NaClO2, NaH2PO4, 2-methyl-2-butene, t-BuOH–H2O, 0 ꢃC-r.t., 1 h, 79%; (g) DDQ, CH2Cl2–H2O, 0 ꢃC-r.t., 3 h, 71%.
segment 9 was finally obtained as follows: (i) depro-
tection of the TBDPS group with tetra-n-butylammoni-
um fluoride (TBAF) (100%), (ii) bromination with
carbontetrabromide and triphenylphosphine (72%), (iii)
sulfonylation of the resulting bromide with sodium p-
toluenesulfinate (70%).
gave 15 as a single stereoisomer, and this was clearly
determined to have the desired structure by spectral data
at this stage. The formation of carboxyl group and final
deprotection were completed to give 4R as follows: (i)
deprotection of the TBS ether of 11 with TBAF (98%),
(ii) oxidation with Dess-Martin periodinane (DMP) to an
aldehyde (75%), (iii) oxidation with sodium chlorite to a
carboxylic acid (79%), and (iv) oxidative deprotection
of the (4-methoxyphenyl)methyl (MPM) group with
2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) (71%).
Coupling between 9 and ent-13 and the same patterns of
assembly used for 4R gave 4S in a similar yield. Both 4R
and 4S were obtained as single diastereomers, whose H-9
and H-11 signals in 1H-NMR spectra are clearly
distinguishable from each other.23) Thus it was confirmed
that no epimerization was present in our synthesis.
In conclusion, stereoselective synthesis of a KODA
derivative, (9R,12S,13R,15Z)-9-hydroxy-12,13-methyl-
ene-10-oxooctadec-15-enoic acid (4R), considered to
be a promising KODA analog to study the mechanism of
flowering, was accomplished from chiral segments 9 and
13. (9S,12S,13R,15Z)-Analog (4S) was also synthesized
from chiral segments 9 and ent-13. Since preparation of
ent-6 has been reported, ent-9 can be prepared via the
same route as used here for 9. Thus our strategy makes it
possible to synthesize the remaining stereoisomeric
analogs. Scale-up synthesis of all four stereoisomeric
analogs is now in progress. The structure-activity
relationships of flower-inducing activity in Pharbitis
nil and other plants will be reported elsewhere.
Preparation of 13 was started from 9-decen-1-ol (10),
the hydroxyl group of which was protected as a benzoyl
group (100%). To introduce the required (9R)-config-
uration, the terminal alkene was subjected to Sharpless
asymmetric dihydroxylation (AD) with AD-mix-ꢂ16)
to give 11 (98%, 86% e.e.). With AD-mix-ꢀ, ent-11
(99%, 84% e.e.) was obtained. The optical purity
of 11/ent-11 was determined by HPLC analysis
(DAICEL CHIRALCELꢀ OD-H ꢁ 4:6 ꢂ 250 mm,
solvent hexane:IPA ¼ 95:5, eluent 1.0 mL/min, temper-
ature 30 ꢃC, UV 254 nm, RT 31.9 min for 11, 41.5 min
for ent-11). The optical purities of 11 and ent-11 were
increased up to >99% e.e. by two rounds of recrystal-
lization from ethyl acetate-hexane: 11 [mp 40–42 ꢃC,
25
½ꢀꢁ
½ꢀꢁ
þ6.6 (c 5.07, MeOH)] and ent-11 [mp 40–42 ꢃC,
D
D
24
ꢄ6.9 (c 5.01, MeOH)]. The introduction of
protecting groups of 12 was carried out as follows:
(i) acetalization of 11 with p-methoxybenzaldehyde
dimethyl acetal (100%), (ii) deprotection of the benzoyl
group by methanolysis (98%), (iii) protection of the
resulting hydroxyl group as tert-butyldimethylsilyl
(TBS) ether (93%). Reductive cleavage of the acetal in
12 with diisobutylaluminum hydride (DIBAL-H) gave
selectively a primary alcohol (96%). Swern oxidation17)
of the alcohol gave the aldehyde segment 13 (96%). By
the same route, ent-11 was converted to ent-13, the
segment for 4S.
Acknowledgment
Since both segments were obtained, we tried for
coupling and subsequent assembly to 4R. The ꢀ-
lithiosulfone generated by treatment of 9 with n-
butyllithium18) was coupled with 13 to give 14 as an
inseparable mixture of diastereomers (Scheme 2). Oxi-
dation of 14 with Dess-Martin periodinane (DMP)19,20)
(76%, 2 steps from 9) and successive reductive
desulfonylation with aluminum amalgam21,22) (93%)
This work was supported by Japan Society for the
Promotion of Science (JSPS) KAKENHI, Grant-in-Aid
for Scientific Research (C), Grant no. 22580114.
References and Notes
1) Chailakhyan MK, C. R. Acad. Sci. URSS, 13, 79–83 (1936).
2) Abe M, Kobayashi Y, Yamamoto S, Daimon Y, Yamaguchi A,

Synthesis of a Promising Flower-Inducing KODA Analog
1357
Ikeda Y, Ichinoki H, Notaguchi M, Goto K, and Araki T,
Science, 309, 1052–1056 (2005).
18) Julia M and Paris J-M, Tetrahedron Lett., 14, 4833–4836
(1973).
3) Wigge PA, Kim MC, Jaeger KE, Busch W, Schmid M,
Lohmann JU, and Weigel D, Science, 309, 1056–1059 (2005).
4) Corbesier L, Vincent C, Jang S, Fornara F, Fan Q, Searle I,
Giakountis A, Farrona S, Gissot L, Turnbull C, and Coupland G,
Science, 316, 1030–1033 (2007).
19) Dess DB and Martin JC, J. Org. Chem., 48, 4155–4156 (1983).
20) Dess DB and Martin JC, J. Am. Chem. Soc., 113, 7277–7287
(1991).
21) Trost BM, Arndt HC, Strege PE, and Verhoeven TR, Tetrahe-
dron Lett., 17, 3477–3478 (1976).
22) Paquette LA, Lin H-S, Gunn BP, and Coghlan MJ, J. Am. Chem.
5) Tamaki S, Matsuo S, Wong HL, Yokoi S, and Shimamoto K,
Science, 316, 1033–1036 (2007).
ˆ
6) Tamaki S and Shimamoto K, Nippon Nogeikagaku Kaishi
(in Japanese), 46, 123–127 (2008).
Soc., 110, 5818–5826 (1988).
25
23) Data for 4R. ½ꢀꢁ
ꢄ40.0 (c 0.60, CH2Cl2); 1H-NMR (CDCl3,
D
400 MHz) ꢃ: ꢄ0.09 (1H, q, J ¼ 5:3 Hz, H-19a), 0.80 (1H, td,
J ¼ 8:4, 5.3 Hz, H-19b), 0.90 (1H, m, H-13), 0.96 (3H, t,
J ¼ 7:5 Hz, H-18), 1.10 (1H, m, H-12), 1.25–1.39 (7H, m),
1.40–1.56 (2H, m), 1.58–1.68 (2H, m), 1.80 (1H, m), 1.90–2.07
(4H, m, H-14 and H-17), 2.35 (2H, t, J ¼ 7:4 Hz, H-2), 2.39
(1H, dd, J ¼ 17:2, 7.6 Hz, H-11a), 2.59 (1H, dd, J ¼ 17:2,
6.4 Hz, H-11b), 3.45 (1H, broadening OH), 4.25 (1H, dd,
J ¼ 7:3, 3.6 Hz, H-9), 5.39 (2H, m, H-15 and H-16), COOH
proton was not detected; 13C-NMR (CDCl3, 100 MHz) ꢃ: 10.6,
11.0, 14.3, 15.5, 20.7, 24.6, 24.8, 26.5, 28.9, 29.0, 29.2, 33.6,
7) Taoka K, Ohki I, Tsuji H, Furuita K, Hayashi K, Yanase T,
Yamaguchi M, Nakashima C, Purwestri YA, Tamaki S, Ogaki
Y, Shimada C, Nakagawa A, Kojima C, and Shimamoto K,
Nature, 476, 332–335 (2011).
8) Yokoyama M, Yamaguchi S, Inomata S, Komatsu K, Yoshida
S, Iida T, Yokokawa Y, Yamaguchi M, Kaihara S, and
Takimoto A, Plant Cell Physiol., 41, 110–113 (2000).
9) Yamaguchi S, Yokoyama M, Iida T, Okai M, Tanaka O, and
Takimoto A, Plant Cell Physiol., 42, 1201–1209 (2001).
[Erratum] Plant Cell Physiol., 43, 141 (2002).
33.8, 37.7, 76.1, 127.8, 132.0, 178.0, 212.2; IR ꢄmax (film) cmꢄ1
:
3426, 3065, 3007, 2933, 2858, 1711, 1247; HR-EI-MS calcd for
10) Suzuki M, Yamaguchi S, Iida T, Hashimoto I, Teranishi H,
Mizoguchi M, Yano F, Todoroki Y, Watanabe N, and
Yokoyama M, Plant Cell Physiol., 44, 35–43 (2003).
11) Yokokawa Y, Kobayashi K, Yokoyama M, and Yamamura S,
Chem. Lett., 32, 844–845 (2003).
C19H32O4 (Mþ) m=z: 324.2301; found, 324.2300. Data for 4S.
26
½ꢀꢁ
þ30.8 (c 0.20, CH2Cl2); 1H-NMR (CDCl3, 400 MHz) ꢃ:
D
ꢄ0.10 (1H, q, J ¼ 5:3 Hz, H-19a), 0.79 (1H, td, J ¼ 8:4, 5.3 Hz,
H-19b), 0.90 (1H, m, H-13), 0.96 (3H, t, J ¼ 7:5 Hz, H-18),
1.14 (1H, m, H-12), 1.25–1.70 (11H, m), 1.81 (1H, m), 1.95–
2.07 (4H, m, H-14 and H-17), 2.35 (2H, t, J ¼ 7:5 Hz, H-2),
2.43 (1H, dd, J ¼ 17:2, 7.5 Hz, H-11a), 2.54 (1H, dd, J ¼ 17:2,
6.7 Hz, H-11b), 3.50 (1H, broadening OH), 4.22 (1H, dd,
J ¼ 7:2, 3.6 Hz, H-9), 5.38 (2H, m, H-15 and H-16), COOH
proton was not detected; 13C-NMR (CDCl3, 100 MHz) ꢃ: 10.5,
10.8, 14.3, 15.4, 20.7, 24.6, 24.8, 26.6, 28.9, 29.1, 29.2, 33.7
(duplicate signal), 37.4, 76.1, 127.8, 132.0, 178.1, 212.3; IR
ꢄmax (film) cmꢄ1: 3426, 3065, 3007, 2933, 2858, 1711, 1247;
HR-EI-MS calcd for C19H32O4 (Mþ) m=z: 324.2301; found,
324.2303.
12) Yokoyama M, Regul. Plant Growth Dev. (in Japanese), 40, 90–
100 (2005).
ˆ
13) Yoshida S, Nippon Nogeikagaku Kaishi (in Japanese), 46, 306–
308 (2008).
14) Shiseido Co., Ltd., Japan Kokai Tokkyo Koho, 2012-46458
(Mar. 8, 2012).
15) Grandjean D, Pale P, and Chuche J, Tetrahedron, 47, 1215–
1230 (1991).
16) Kolb HC, VanNieuwenhze MS, and Sharpless KB, Chem. Rev.,
94, 2483–2547 (1994).
17) Omura K and Swern D, Tetrahedron, 34, 1651–1660 (1978).