Syntheses of lambertellols and their stable analogues; investigation of the real active species in the mycoparasitism by Lambertella species

Article abstract of DOI:10.1021/jo8005478

(Chemical Equation Presented) Lambertellols A (1) and B (2), isolated from mycoparasites Lambertella species, were synthesized. The synthesis features intramolecular aldol-type cyclizations of aldehydes 12 and 14 and site specific oxidations of 1-hydroxylambertellols as key steps. The synthesis also provided all diastereomers of 1-hydrolambertellols 17-19 and 25. Chiral resolution made the optically active forms available, which enabled the investigation of the real active species in the mycoparasitism by Lambertella species against Monilinia fructigena. These experiments suggested that lambertellin (3) is responsible for this phenomenon. Chemically labile 1 and 2 should be converted to 3 during the bioassay. The parasite may excrete 1 and 2 as readily diffusible forms, which are then transformed into 3 to inhibit the host M. fructigena. The parasite may have acquired this drug delivery system mechanism as an evolutionary enhancement.

Full text of DOI:10.1021/jo8005478

Syntheses of Lambertellols and Their Stable Analogues;
Investigation of the Real Active Species in the Mycoparasitism by
Lambertella Species
Masahiro Nomiya, Takanori Murakami, Noboru Takada, Toshikatsu Okuno, Yukio Harada,
and Masaru Hashimoto*
Faculty of Agriculture and Life Science, Hirosaki UniVersity, 3-Bunkyo-cho, Hirosaki, 036-8561, Japan
hmasaru@cc.hirosaki-u.ac.jp
ReceiVed March 22, 2008
Lambertellols A (1) and B (2), isolated from mycoparasites Lambertella species, were synthesized. The
synthesis features intramolecular aldol-type cyclizations of aldehydes 12 and 14 and site specific oxidations
of 1-hydroxylambertellols as key steps. The synthesis also provided all diastereomers of 1-hydrolam-
bertellols 17-19 and 25. Chiral resolution made the optically active forms available, which enabled the
investigation of the real active species in the mycoparasitism by Lambertella species against Monilinia
fructigena. These experiments suggested that lambertellin (3) is responsible for this phenomenon.
Chemically labile 1 and 2 should be converted to 3 during the bioassay. The parasite may excrete 1 and
2 as readily diffusible forms, which are then transformed into 3 to inhibit the host M. fructigena. The
parasite may have acquired this “drug delivery system” mechanism as an evolutionary enhancement.
Introduction
isolated spirobutenolides, lambertellols A (1) and B (2),4 along
with known lambertellin (3)5 from the culture broth of a
congeneric fungus Lambertella sp. 1346 which also causes
similar mycoparasitism on apple fruits.1 These compounds were
thought be responsible for the onset of the mycoparasitism,
because these compounds potently inhibited the growth of the
host hyphae.6 The parasite L. corni-maris did not produce these
metabolites when it was cultured alone. Recently we revealed
that L. corni-maris exuded 1-3 in considerable amounts only
when the host M. fructigena is also present. Our further
investigations suggested that a particular stimulant does not exist,
but “high acidity” stimulates the productions of 1-3. The host
remarkably acidified the environment. Since the spreading rate
of the acidic area on PSA medium is almost identical to the
Filamentous fungus Lambertella corni-maris invades the other
pathogenic fungus Monilinia fructigena on PSA (potato-sucrose-
agar) medium. Harada, one of the present authors, reported that
neither L. corni-maris nor M. fructigena inhibited each other
to be intermixed together after a month of simultaneous culture
on PSA medium; however only L. corni-maris was isolated from
anywhere on the medium.1 The same behavior sometimes occurs
on apple fruits in the field.2 It was also found that only L. corni-
maris could be detected from rotten apples which had been
seeded with M. fructigena as a pretreatment and stored under
ambient atmosphere for a couple of months.1 This phenomenon
is recognized as mycoparasitism.1,3 In our study exploring
chemical substances responsible for the phenomenon, we have
(4) Murakami, T.; Morikawa, Y.; Hashimoto, M.; Okuno, T.; Harada, Y.
Org. Lett. 2004, 6, 157.
(1) Harada, Y.; Sasaki, M. Rep. Tottori Mycol. Inst. 1990, 28, 275.
(2) Hori, S. ENGEINO TOMO (in Japanese) 1912, 8, 949.
(3) Jeffries, P.; Young, T. W. K. Interfungal Parasitic Relationships; CABI
International: Wallingford, 1994.
(5) Armstrong, J. J.; Turner, W. B. J. Chem. Soc. 1965, 5927.
(6) Murakami, T.; Takahashi, Y.; Fukushi, E.; Kawabata, J.; Hashimoto, M.;
Okuno, T.; Harada, Y. J. Am. Chem. Soc. 2004, 126, 9214.
10.1021/jo8005478 CCC: $40.75
Published on Web 06/04/2008
2008 American Chemical Society
J. Org. Chem. 2008, 73, 5039–5047 5039

Nomiya et al.
SCHEME 2. Synthesis of Intermediates 12 and 14
SCHEME 1. Isomerization and Decomposition of
Lambertellols
growth rate of the host hyphae, the parasite L. corni-maris
detects the high acidity only in the case where the host inhabits
very close to the parasite. Accordingly, the host can grow freely
until its hyphae reach the parasite. On reaching the host, L.
corni-maris begins to produce these antibiotics to deteriorate
the host. We proposed these might be the reason why only L.
corni-maris was isolated after simultaneous cultivation with M.
fructigena without remarkable inhibition at a glance.7
During the course of structural studies, we observed isomer-
ization between 1 and 2 under mild conditions such as on silica
gel or in methanol. This interconversion can be explained by
retro-Michael type opening of the butenolide ring to the
carboxylic acid 4, followed by Michael type ring closure to
deliver the epimer as shown in Scheme 1.8 Conversion of 1
and 2 into 3 also occurred under the isomerization conditions
probably by the sequential (i) oxidation of semiquinone moiety
of 4 into quinone 5, (ii) intramolecular Michael type ring closure
at the C2 position to furnish the pyrone, and finally (iii) oxidative
aromatization. Accordingly, 4 and/or 5 might also be responsible
for the observed mycoparasitism, although these have not been
isolated from growing cultures thus far. We further investigated
this subject by studying the activities employing 1, 2, and their
congeners including their enantiomers. This paper reports the
first syntheses of 1, 2, and stable analogues 17-19 and 25. The
syntheses involved chiral resolutions which enabled us to obtain
the metabolites and their analogues in optically active forms.
These studies suggest 3 is the active substance responsible for
the mycoparasitism.
C5 aromatic proton located as pseudo-peri position.10,11 Ac-
cordingly, we expected that this alcohol function would remain
unaffected under oxidation conditions. Thus, we arrived at
17-19 and 25 as the synthetic precursors for the conversion to
the final products. Since these triols were expected to be stable
because of the absence of C1 carbonyl, these were to be
employed as stable mimics of lambertellols in the biological
studies.
The synthesis commenced with 2,3-bis(hydroxymethyl)phenol
derivative 6 prepared from 2,3-dimethylphenol (5 steps, 40%
overall yield) according to the published procedures (Scheme
2).12,13 The alcohol moiety in 6 was protected as a MPM (p-
methoxyphenylmethyl) ether, and the acetonide group was
removed by p-TsOH in aqueous acetonitrile, yielding diol 7 in
76% yield over two steps. Oxidation of 7 with MnO2 followed
by treatment of the resultant aldehyde with allylmagnesium
bromide furnished diol 8 in good overall yield. The diol moiety
of 8 was then protected as an acetonide, and the terminal double
bond was oxidatively cleaved to aldehyde 9 in 82% yield over
two steps.
Results and Discussions
1. Total Synthesis of Lambertellols. The total synthesis of
1 and 2 is described below. Since, the C1 carbonyl function of
each compound facilitates the retro-Michael type ring opening
of the butenolide ring, causing the interconversion and decom-
position as discussed above, the C1 carbonyl group was to be
introduced in the final step of the synthesis. We have also
observed that the C4-OH group in both 1 and 2 is chemically
inert, for example, toward acetylation,9 due to the steric effect
of the neighboring butenolide ring as well as the overhanging
(9) Lambertellol A (1) is slightly less stable than lambertellol B (2). So, 2
was mainly used for derivatizations. When 1 was subjected to acetylation
conditions, polar materials were only observed by the TLC analysis.
(10) Murakami, T.; Sasaki, A.; Fukushi, E.; Kawabata, J.; Hashimoto, M.;
Okuno, T. Bioorg. Med. Chem. Lett. 2005, 15, 2587.
(11) Murakami, T.; Hashimoto, M.; Okuno, T. Bioorg. Med. Chem. Lett.
2005, 15, 4185.
(12) Suzuki, M.; Sugiyama, T.; Watanabe, M.; Murayama, T.; Yamashita,
K. Agric. Biol. Chem. 1987, 51, 2161.
(7) Murakami, T.; Takada, N.; Harada, Y.; Okuno, T.; Hashimoto, M. Biosci.
Biotechnol. Biochem. 2007, 71, 1230.
(13) Nicolau, K. C.; Vassilikogiannakis, G.; Montagnon, T. Angew. Chem.,
Int. Ed. 2002, 41, 3276.
(8) Lee, S.; Zhao, Z. Tetrahedron Lett. 1999, 40, 7921.
5040 J. Org. Chem. Vol. 73, No. 13, 2008

Synthesis of Lambertellols
SCHEME 3. Synthesis of 1-Hydrolambertellols rac-17, rac-18, rac-19, and rac-25
Addition of vinyl Grignard reagent to 9 produced adduct 10
in 87% as a 1:1 mixture of diastereomers. The butenolide ring14
was constructed in 60% yield via a two-step reaction, meth-
acrylation and ring-closing metathesis using Grubbs II catalyst.15
Compound 11 was then converted into the aldehyde 12 in 88%
by cleavage of the MPM group ether16 followed by PCC
oxidation of the liberated alcohol. Disiloxanilydene derivative
14 was also prepared from 11 by (i) deprotection of the
acetonide group, (ii) tetraisopropyldisiloxanylidene formation,17
(iii) removal of the MPM group, and (iv) PCC oxidation.18 We
expected that a replacement of the acetonide group (six-
membered ring) in 12 to a disiloxanylidene group (eight-
membered ring) would alter the geometrical relationship between
the aldehyde and the γ-carbon of the butenolide to give different
stereoselectivity in the next cyclization.
Construction of the central cyclohexane ring was attempted
next (Scheme 3). Treatment of the diastereomeric mixture 12
with NaHMDS in DMF at -40 °C led to the cyclization of the
intermediate enolate to provide tetracyclic 15 and its diastere-
omer 16 in 13% and 77% yield, respectively. Other isomers
were not observed. However, acidic removal of the acetonide
group in 15 was accompanied by isomerization at the C1
position to give a 8:2 mixture of triols rac-17 and rac-18. These
structures were confirmed after HPLC separation. The stabilized
cation 20 may contribute to the epimerization. Interestingly,
similar treatment of 16 gave triol rac-19 in quantitative yield
without isomerization.
The reaction employing disiloxanylidene 14 exhibited dif-
ferent stereoselectivity. Triols rac-18 and rac-25 were obtained
in 67% and 31% yield, respectively, after deprotection by
TBAF-AcOH in THF.19 The cyclization involved incomplete
deprotection of the disiloxanilydene group, and silanols 23 and
24 were isolated as minor products along with 21 and 22. These
were stable enough to be isolated by silica gel. The FDMS of
both 23 and 24 provided pseudomolecular ion signals at m/z )
522, which is 18 larger than the molecular weights of 21 and
22. Fragment patterns in the EIMS were quite similar between
23 and 24. Both of them showed exchangeable phenolic protons
1
[δ 8.00 ppm (23), 7.92 ppm (24)] in their H NMR spectra,
which led to their proposed structures as depicted. Independent
treatments of pure 23 and 24 with TBAF-AcOH system provided
rac-25 and rac-18, respectively, both in quantitative yields.
Needless to say, disiloxanilidenes 21 and 22 could be isolated,
and these also gave rac-25 and rac-18 in quantitative yields
under the same conditions.
It is notable that remarkable line broadenings were observed
1
for some signals of the precursors 13 and 14 in the H NMR
spectra (see Supporting Information). These might be caused
by slow conformational movement around their 1,3,5,2,4-
trioxadisilocine moieties. Interestingly, these broadenings were
not observed in those of 21 and 22. The NMR spectra of rac-
17, rac-18, rac-19, and rac-25 resembled each other but were
not identical. Their relative stereochemistries were established
based on observed NOEs as shown in Figure 1.
The C1-OH group was selectively oxidized to complete the
synthesis as shown in Scheme 4. Treatment of rac-17 with PCC
in CH2Cl2 provided lambertelol A (rac-1) in a racemic form.
As anticipated, the sterically hindered C4-OH was not oxidized.
However, the substrate was less soluble in CH2Cl2 and the
reaction required a long reaction time (more than 12 h). Use of
(14) Albrecht, U.; Langer, P. Tetrahedon 2007, 63, 4648.
(15) Chatterjee, A. K.; Grubbs, R. H. Org. Lett. 1999, 1, 1751.
(16) Oikawa, Y.; Yoshioka, T.; Yonemitsu, O. Tetrahedron Lett. 1982, 23,
885.
(17) Ohtsuka, E.; Ohkubo, M.; Yamane, A.; Ikehara, M. Chem. Pharm. Bull.
1983, 31, 1983.
(18) We succeeded in preparing 13 on a small scale by another route including
a disiloxanylidene formation of diol 8 and the following similar reactions to
those described in the text. We have not met difficulties in this scheme. However,
this needs 14 steps of reactions for preparing 12 and 14 from 8. The scheme in
the manuscript requires totally 11 steps for preparing both of them from 8. Taking
the total efficiency into account, we adopted the route in the manuscript.
(19) Plfeiderer, W.; Pfister, M.; Farkas, S.; Schirmeister, H.; Charubala, R.;
Stengele, K. P.; Mohr, M.; Bergmann, F.; Gokhale, S. Nucleoside Nucleotide
1991, 10, 377.
J. Org. Chem. Vol. 73, No. 13, 2008 5041

Nomiya et al.
SCHEME 5. Optical Resolution with Chiral HPLC
FIGURE 1. Characteristic NOEs and stereochemistries of rac-17, rac-
18, rac-19, and rac-25
mixed solvent (1:1 CH2Cl2-acetone) led to complete dissolution
of the substrates, which shortened the reaction time, yielding
the best results without significant decomposition of the
products. Decomposition to 3 during purification could be
minimized by employing rapid silica gel column chromatog-
raphy (loaded with 20:80 EtOAc-hexane and then eluted with
100% EtOAc) to provide rac-1 (35% yield) in satisfactory
purity. Other conditions such as MnO2 or Dess-Martin perio-
dinane20 oxidations also gave rac-1 but in lower yield. In the
same manner, diastereomers rac-18 and rac-25 were converted
into rac-1 and lambertellol B (rac-2) in 33% and 25% yield,
respectively. Interestingly, rac-19 was soluble in CH2Cl2 and
oxidation with MnO2 in CH2Cl2 gave the best results to afford
rac-2 in 55% yield after purification. The ODS HPLC retention
1
time, the UV-vis profile, the H NMR, and the IR spectra of
synthetic rac-1 and rac-2 were identical to those of natural 1
and 2.
SCHEME 4. Oxidation To Complete the Synthesis of 1 and
2
oxidation of the resolved 18 and ent-18, respectively. The CD
spectra of 1 and 2 were identical with those obtained for the
natural products. Absolute configurations of the resolved triols
were established by conversion into 1 or 2 followed by
comparison of the CD spectra with those of the natural
products.4 Interestingly, all enantiomers with (4S)-configurations
eluted faster than their corresponding antipodes in the HPLC
resolutions.
3. Biological Study and Discovery of the Active Species.
Having in hand the enantiomeric pairs of 1, 2 and all possible
stereoisomers of triols (17-19, 25), their inhibitory activities
against the host fungus M. fructigena were investigated. Since
host M. fructigena makes the spores only under specific
conditions and it was technically difficult to prepare the host
spores in the laboratory, the assays were performed by the paper
disk method.
2. Optical Resolution for the Bioassay. We envisoned triols
17-19 and 25 as the stable mimics of 1 and 2 for biological
experiments because the triols are not capable of retro-Michael
type butenolide ring opening. Thus, enantiomeric pairs of
lambertellols 1, 2, and analogous triols 17-19 and 25 were
prepared by chiral resolution. Chiral HPLC using CHIRAL PAK
AS-H (DAICEL Co. Ltd.)21 was found to be effective for their
resolutions (Scheme 5).
Only rac-1 could not be separated by this system. However,
an enantiomeric pair of 1 and ent-1 was provided by independent
(20) Dess, D. B.; Martin, J. C. J. Org. Chem. 1983, 48, 4155.
(21) Kennedy, J. H. J. Chromatogr. A 1996, 725, 219.
5042 J. Org. Chem. Vol. 73, No. 13, 2008

Synthesis of Lambertellols
FIGURE 2. Structure-activity relationship of lambertellols and the related compounds.
After culturing the host M. fructigena on the PSA medium
for 5 days, paper disks (8 mm diameter) containing the samples
(20 µg/disk ) 40 µg/cm2) were placed on the media, ca. 2 cm
apart from the end of the growing hyphae. Within 3 days post-
treatment, remarkable inhibition was observed around the disks
containing 1 and 2 at the same concentration as the natural
products. The results for other compounds are summarized in
Figure 2.
Interestingly, the enantiomers ent-1 and ent-2 as well as
natural lambertellol C (26, racemate)10 inhibited the growth by
the same level. These results might suggest that the enzyme or
other substrate responsible for the observed activity has some
tolerance with regards to the structure of the inhibitor. This
suggested that the structurally similar triols 17-19 or 25 might
FIGURE 3. Precipitations of lambertellin (3, the reddish particles)
exhibit activity, but none of them did so. Their enantiomers
found in PSA medium. (A) The PSA medium at 36 h at 20 °C after
aqueous lambertellol B solution (2, 40 µg/cm2) was added. The HPLC
analysis detected only 3 from this medium. (B) The culture medium at
40 days at 20 °C after Lambertella sp. 1346 was seeded. The dark
right part in B is the hyphae.
22
ent-17, ent-19, or ent-25 were also not active.
In an early stage of these studies, we thought that 3 was not
a candidate for the observed activity, because the zone of
inhibition exhibited by 3 was smaller than those observed for 1
and 2. However we now propose that 3 but not 1 nor 2 is the
true active species in the mycoparasitism between Lambertella
spp. and M. fructigena for the following reasons:
(iii) We found that PSA medium completely decomposed
lambertellols within 36 h to precipitate 3 (Figure 3A), as
confirmed by HPLC after extraction. The assays took 3
days. Lambertellols could not survive through these experi-
ments. Since neither 4 nor 5 have been detected, theie
lifetimes should be shorter than that of 3. Accordingly, none
of 4, its enantiomer, and 5 must be present when the hyphae
reached to the samples as a result of running out of their
source lambertellols. These ruled out the possibility of
undetected 4 and 5 being the active factors.23
(i)
If 4 was the responsible compound, the activity of ent-1
and ent-2 cannot be explained. Compound 4 is chiral and
can be generated from 1 and 2, but not from their
enantiomers.
(ii) Lambertellin (3) is a planar compound, and all the
lambertellols 1, 2 and enantiomers can provide 3; the
activity of 3 is consistent with both enantiomers exhibit-
ing activity.
(iv) Lambertellin (3) is sparingly soluble and readily precipi-
tates in PSA under the conditions employed for the assay.
This suggests that the concentration of 3 around the paper
(22) Antibiotic assays against another pathogenic fungus, Cochlibolus
miyabeanus, were also examined and showed similar results. Compounds 1, 2,
3, ent-1, and ent-2 inhibited the growth of C. miyabeanus similarly (EC50 ) ca.
1.0 µg/mL). On the other hand, the EC50 values for the triols (17, 18, 19, and
25) and their enantiomers (ent-17, ent-18, ent-19, and ent-25) were estimated
to be more than 100 µg/mL in each case.
(23) It is hard to discuss the biological activities of the intact 1, 2, and 4 and
their enantiomers because of their instabilities in these experiments.
J. Org. Chem. Vol. 73, No. 13, 2008 5043

Nomiya et al.
m/z ) 424 (0.2, M+), 366 (0.9, [M - acetone]+), 286 (3.9, [M -
CH3OC6H4CH2OH]+), 121 (100, CH3OC6H4CH2+); EIHRMS found
m/z 424.1878 calcd for C25H28O6, M+ 424.1886.
disks can not become high, and 3 does not diffuse readily,
which can explain why the zone of inhibition observed
for 3 is smaller than that observed for 1 and 2.
Lambertellol C (26)10 exhibited inhibition at a level
similar to that of 1 and 2. However, it can readily provide
3, but not 4. This is also evidence that 3 is the active
agent.
2,2-Dimethyl-4-((4-methyl-5-oxo-2,5-dihydrofuran-2-yl)methyl)-
4H-benzo[d][1,3]dioxine-5-carbaldehyde (12). A solution of 11
(180 mg, 424 µmol) in a mixture of CH2Cl2 (1.0 mL) and H2O
(0.1 mL) was stirred with 2,3-dichloro-5,6-dicyano-1,4-benzo-
quinone (154 mg, 639 µmol) at room temperature for 1.5 h. The
mixture was poured into saturated aqueous NaHCO3 solution (25
mL) and extracted with AcOEt (15 mL × 3). The combined organic
extracts were washed with brine (20 mL), dried over MgSO4 and
then concentrated in vacuo. Silica gel column chromatography of
the residue (AcOEt-hexane ) 26:74) gave 5-((5-(hydroxymethyl)-
2,2-dimethyl-4H-benzo[d][1,3]dioxin-4-yl)methyl)-3-methylfuran-
2(5H)-one (115 mg, 89%) as an oil. The 1H NMR spectrum
indicated that the sample thus obtained was a 42:38 diatereomeric
(v)
Conclusion
As described, we have achieved the first synthesis of 1, 2, and
their enantiomers. These studies also enabled us to utilize triols
(17-19, 25) and their enantiomers as congeners. Our synthesis
provided all of them in one protocol. Biological investigations using
these synthetic samples have clarified the role of lambertellols with
regards to the onset of mycoparasitism between Lambertella spp.
and M. fructigena. More specifically lambertellin (3), the degrada-
tion product of 1 and 2, is responsible for the observed activity.
The parasite may excrete 1 and 2 as the diffusible forms, which
are later converted into 3 to exhibit hyphal inhibition against the
host M. fructigena. In fact, precipitation of 3 was observed
considerably detached from the hyphae in the PSA medium
culturing Lambertella sp. 1346 (Figure 3, B). These Lambertella
species might have acquired this “drug delivery system” mechanism
in the course of their evolution.
1
mixture. H NMR (400 MHz, CDCl3, a ) 0.42, b ) 0.38) δ 1.39
(3H × b, s), 1.42 (3H × a, s), 1.595 (3H × b, s), 1.603 (3H × a),
1.890 (3H × b, dd, J ) 1.5, 2.9 Hz), 1.895 (3H × a, dd, J ) 1.9,
2.9 Hz), 2.06 (1H × a, ddd, J ) 3.9, 8.8, 14.2 Hz), 2.21 (1H × a,
ddd, J ) 2.4, 8.8, 14.2 Hz), 2.23 (1H × b, ddd, J ) 2.9, 8.3, 14.6
Hz), 2.56 (1H × b, ddd, J ) 4.8, 6.3, 14.6 Hz), 4.52 (1H × a, d,
J ) 12.2 Hz), 4.58 (1H × b, d, J ) 12.7 Hz), 4.65 (1H × a, d, J
) 12.2 Hz), 4.72 (1H × b, d, J ) 12.7 Hz), 4.85 (1H × b, m),
5.26 (1H × a, m), 5.28 (1H × b, dd, J ) 2.9, 6.3 Hz), 5.38 (1H ×
a, dd, J ) 2.4, 8.8 Hz), 6.79 (1H × a, dd, J ) 1.0, 8.3 Hz), 6.80
(1H × b, dd, J ) 1.0, 7.8 Hz), 6.95 (1H × a, quint, J ) 2.9 Hz),
7.00 (1H × b, dd, J ) 1.0, 7.3 Hz), 7.02 (1H × a, dd, J ) 1.0, 7.3
Hz), 7.20 (1H + 1H × b).
Experimental Section
A solution of the alcohol (69.0 mg, 227 µmol) in CH2Cl2 (1.5
mL) was stirred with pyridinium chlorochromate (PCC, 140 mg,
651 µmol) at room temperature for 1 h. After Celite (ca. 200 mg)
and diethyl ether (10 mL) were added, the resulting suspension
was stirred for additional 10 min, and then it was filtered through
Celite pad. After concentration in vacuo, the residue was quickly
purified with short silica gel column chromatography (AcOEt-hexane
) 25:75) gave 12 (99%) as an oil. The 1H NMR spectrum indicated
that the sample thus obtained was a 55:45 diatereomeric mixture.
5-((5-((4-Methoxybenzyloxy)methyl)-2,2-dimethyl-4H-
benzo[d][1,3]dioxin-4-yl)methyl)-3-methylfuran-2(5H)-one (11).
Preparation of 10 is described in Supporting Information. A solution
of the starting 10 (29 mg, 75.4 µmol) in CH2Cl2 (1.0 mL) was
stirred with methacryloylchloride (23.5 mg, 223 µmol) and Et3N
(30.5 mg, 301 µmol) at room temperature for 2 h. The mixture
was poured into H2O (25 mL) and extracted with AcOEt (25 mL
× 3). The combined extracts were washed with brine, dried over
MgSO4 and concentrated in vacuo. The polar material was removed
by passing through a short silica gel column to give the crude 1-(5-
((4-methoxybenzyloxy)methyl)-2,2-dimethyl-4H-benzo[d][1,3]dioxin-
4-yl)but-3-en-2-yl methacrylate (21.0 mg, 62%) as oil. This sample
was immediately used for the next step.
IR (film) 2990, 1755, 1695, 1460, 1275, 1210, 1145, 1055 cm-1
;
1H NMR (400 MHz, CDCl3, a ) 0.55, b ) 0.45) δ 1.44, 1.62
(each 3H, s), 1.87 (3H × a, t, J ) 1.9 Hz), 1.91 (3H × b, t, J )
1.7 Hz), 1.97 (1H × a, ddd, J ) 5.4, 8.3, 14.2 Hz), 2.01 (1H × b,
ddd, J ) 2.9, 8.3, 14.2 Hz), 2.24 (1H × a, ddd, J ) 2.4, 7.3, 14.2
Hz), 2.33 (1H × b, ddd, J ) 5.4, 6.3, 14.2 Hz), 4.94 (1H × b, m),
5.21 (1H × a, m), 5.72 (1H × b, dd, J ) 2.9, 6.3 Hz), 5.75 (1H ×
a, dd, J ) 2.4, 8.3 Hz), 6.98 (1H × a, quint, J ) 1.5 Hz), 7.08 (1H
× a, dd, J ) 1.5, 7.8 Hz), 7.10 (1H × b, dd, J ) 1.5, 7.8 Hz), 7.25
(1H × b, quint, J ) 1.5 Hz), 7.39 (1H × a, t, J ) 7.8 Hz), 7.42
(1H × b, t, J ) 7.8 Hz), 7.45 (1H × b, dd, J ) 1.5, 7.8 Hz), 7.47
(1H × a, dd, J ) 1.5, 7.8 Hz), 9.94 (1H × b, s), 9.98 (1H × a, s);
EIMS (rel int %) m/z ) 302 (9.7, M+), 284 (25.4, [M - H2O]+),
244 (2.1, [M - acetone]+), 147 (100, not assigned); EIHRMS found
m/z 302.1158 calcd for C17H18O5, M+ 302.1154.
The crude ester in toluene (500 µL) was refluxed with Grubbs
second catalyst15 (2.0 mg, 2.4 µmol) for 1 h. After cooling, the
mixture was directly subjected to silica gel column. Elution with
AcOEt-hexane (18:82) gave 11 (19 mg, 97%, 60% in 2 steps) as
an oil. The 1H NMR spectrum indicated that the sample thus
obtained was a 7:3 diatereomeric mixture. IR (film) 2990, 2935,
1
2860, 1760, 1510, 1460, 1275, 1250, 1060, 1040 cm-1; H NMR
(400 MHz, CDCl3) δ 1.39 (3H × 0.7, s), 1.41 (3H × 0.3, s) 1.58
(3H × 0.7, s), 1.59 (3H × 0.3, s), 1.86 (3H × 0.3, dd, J ) 1.5, 2.9
Hz), 1.87 (3H × 0.7, dd, J ) 1.5, 2.9 Hz), 1.98 (1H × 0.3, ddd, J
) 4.4, 9.3, 14.6 Hz), 2.12 (1H × 0.7, ddd, J ) 2.9, 9.3, 14.6 Hz),
2.23 (1H × 0.3, ddd, J ) 2.0, 8.8, 14.6 Hz), 2.51 (1H × 0.7, ddd,
J ) 4.4, 6.3, 14.6 Hz), 3.807 (3H × 0.3, s), 3.815 (3H × 0.7, s),
4.33 (1H × 0.3, d, J ) 11.2 Hz), 4.37 (1H × 0.7, d, J ) 12.0 Hz),
4.429 (1H × 0.3, d, J ) 11.2 Hz), 4.430 (1H × 0.3, d, J ) 11.2
Hz), 4.455 (1H × 0.7, d, J ) 11.7 Hz), 4.470 (1H × 0.3, d, J )
11.2 Hz), 4.486 (1H × 0.7, d, J ) 11.7 Hz), 4.57 (1H × 0.7, d, J
) 12.0 Hz), 4.81 (1H × 0.7, m), 5.22 (1H × 0.3, m), 5.24 (1H ×
0.7, dd, J ) 2.4, 6.3 Hz), 5.36 (1H × 0.3, dd, J ) 2.9, 9.3 Hz),
6.78 (1H × 0.3, dd, J ) 1.0, 8.3 Hz), 6.79 (1H × 0.7, dd, J ) 1.0,
8.3 Hz), 6.87 (2H × 0.3, brd, J ) 8.8 Hz), 6.88 (1H × 0.3, quint,
J ) 1.2 Hz), 6.89 (2H × 0.7, brd, J ) 8.8 Hz), 6.95 (1H × 0.7,
dd, J ) 1.0, 7.3 Hz), 6.97 (1H × 0.3, dd, J ) 1.0, 7.3 Hz), 7.13
(1H × 0.7, quint, J ) 1.5 Hz), 7.161 (1H × 0.3, dd, J ) 7.3, 8.3
Hz), 7.167 (1H × 0.7, dd, J ) 7.3, 8.3 Hz), 7.23 (2H × 0.3, brd,
J ) 8.8 Hz), 7.26 (2H × 0.7, brd, J ) 8.8 Hz); EIMS (rel int %)
5-((7-((4-Methoxybenzyloxy)methyl)-2,2,4,4-tetraisopropyl-
6H-benzo[f][1,3,5,2,4]trioxadisilocin-6-yl)methyl)-3-methylfuran-
2(5H)-one (13). A solution of 11 (119 mg, 280 mmol) in 80%
aqueous acetic acid (10 mL) was stirred at 55 °C for 5 h. After
concentration in vacuo below 30 °C, the residue was purified with
silica gel column chromatography (AcOEt-hexane ) 30:70) to
give 5-(2-(2-((4-methoxybenzyloxy)methyl)-6-hydroxyphenyl)-2-
hydroxyethyl)-3-methylfuran-2(5H)-one (101 mg, 94%) as needles.
The 1H NMR spectrum indicated that the sample thus obtained was
1
a 60:40 diatereomeric mixture. H NMR (400 MHz, CDCl3 a )
0.60, b ) 0.40) δ 1.857 (3Η × a, t, J ) 2.0 Hz), δ 1.862 (3Η ×
b, t, J ) 2.2 Hz), 2.10 (2H × a + 1H × b, m), 2.36 (1H × b, ddd,
J ) 3.4, 11.0, 14.5 Hz), 3.78 (3H × b, s), 3.79 (3H × a, s), 4.33,
4.38 (each 1H × b, d, J ) 11.1 Hz), 4.431 (2H × a, s), 4.431 (1H
× b, d, J ) 11.5 Hz), 4.432 (1H × a, d, J ) 11.4 Hz), 4.47 (1H
× b, d, J ) 11.5 Hz), 4.58 (1H × a, d, J ) 11.4 Hz), 4.77 (1H ×
5044 J. Org. Chem. Vol. 73, No. 13, 2008

Synthesis of Lambertellols
a, m), 5.19 (1H × b, m), 5.37 (1H × a, m), 5.46 (1H × b, m), 6.72
(1H × a, quint, J ) 1.6 Hz), 6.77 (1H × b, brd, J ) 7.6 Hz), 6.79
(1H × a, brd, J ) 7.6 Hz), 6.82-6.88 (4H × a + 4H × b, m),
6.99 (1H × b, quint J ) 1.6 Hz), 7.10 (1H × b, brt, J ) 7.8 Hz),
7.10 (1H × a, brt, J ) 7.8 Hz), 6.82-6.88 (2H, m), 8.51 (1H × a,
br), 8.68 (1H × b, br).
washed with brine, dried over MgSO4, and then concentrated in vacuo.
Silica gel column chromatography of the residue eluted successively
with AcOEt-hexane ) 22:78 and 28:72 gave 15 (58.1 mg, 77%) and
16 (10.0 mg, 13%), respectively, both as needles.
Physical Properties of (1S*,3S*,4S*)-1-Hydrolambertellol
1,8-O-Isopropylidene Acetal (15). Mp 210-212 °C (from AcOEt-
hexane ) 4:6). IR (KBr) 3410, 3000, 2870, 1740, 1590, 1470, 1270,
A solution of the diol (576 mg, 1.50 mmol) in DMF (15.0 mL)
was stirred with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (493
mg, 1.56 mmol) and imidazol (273 mg, 4.54 mmol) at room
temperature for 2 h. The mixture was poured into aqueous NH4Cl
solution (50 mL) and extracted with ether (30 mL × 3). The ethereal
extracts were combined, dried over MgSO4, and concentrated in
vacuo. Silica gel column chromatography (AcOEt-hexane ) 5:95)
of the residue gave 13 (882 mg, 94%) as a solid. Mp 106-109 °C
(from MeOH-H2O ) 7:3); IR (KBr) 2945, 2865, 1760, 1465, 1250,
1040, 885, 835, 700 cm-1. The 1H NMR spectrum showed broaden
1
1140, 1015, 870, 750 cm-1; H NMR (400 MHz, CDCl3, lamber-
tellol numbering) δ 1.57, 1.60 (each 3H, s, C(CH3)2), 1.97 (3H, d,
J ) 1.1 Hz, C3′CH3), 2.30 (1H, dd, J ) 6.8, 12.8 Hz, C2HH),
2.51 (1H, dd, J ) 10.6, 12.8 Hz, C2HH), 4.57 (1H, brs, C4H),
4.85 (1H, dd, J ) 6.8, 10.6 Hz, C1H), 6.83 (1H, d, J ) 8.4 Hz,
C7H), 6.99 (1H, d, J ) 7.4 Hz, C5H), 7.04 (1H, q, J ) 1.1 Hz,
C4′H), 7.27 (1H, dd, J ) 7.4, 8.4 Hz, C6H), NOE C1H T C2Hꢀ,
C2Hꢀ T C4′H, C4′H T C1H, C4′H T C4H, C4H T C5H; 13C
NMR (100 MHz, CDCl3) δ 10.7, 23.9, 28.2, 34.2, 63.3, 70.6, 86.5,
101.7, 116.3, 118.9, 119.1, 129.3, 131.3, 133.6, 148.9, 150.6, 172.5;
EIMS (rel int %), m/z ) 302 (15.0, M+), 244 (89.2, [M -
acetone]+), 192 (100); EIHRMS found m/z 302.1156 calcd for
C17H18O5, M+ 302.1154.
1
signals. Thus, only characteristic signals are described. H NMR
(400 MHz, CDCl3) δ 0.28-0.73 (7H, m), 0.96-1.25 (21H, m),
1.78 (3H, t, J ) 1.7 Hz), 2.03, 2.21, 2.47, 2.72 (each 1H × 0.5,
br), 3.81 (3H, s), 4.96 (1H, brt, J ) ca. 8 Hz), 6.62 (1H × 0.5, br);
ESIMS (rel int %) m/z ) 649 (100, [M + Na]+), 645 (6.2, [M +
H3O]+), 644 (12.8, [M + H2O]+), 627 (4.9, [M + H]+); ESI-HRMS
found m/z 649.2997 calcd for C34H50O7Si2Na, [M + Na]+ 649.2993.
2,2,4,4-Tetraisopropyl-6-((4-methyl-5-oxo-2,5-dihydrofuran-
2-yl)methyl)-6H-benzo[f][1,3,5,2,4]trioxadisilocine-7-carbalde-
hyde (14). A solution of 13 (97.0 mg, 155 µmol) in a mixture of
CH2Cl2 (4.0 mL) and water (0.4 mL) was stirred with 2,3-dichloro-
5,6-dicyano-1,4-benzoquinone (44.2 mg, 194 µmol) at room tem-
perature for 2 h. The mixture was poured into saturated aqueous
NaHCO3 solution (30 mL) and extracted with AcOEt (20 mL ×
3). The combined extracts were washed with brine, dried over
MgSO4, and concentrated in vacuo. The residue was purified with
silica gel column chromatography (AcOEt-hexane ) 20:80) gave
5-((7-(hydroxymethyl)-2,2,4,4-tetraisopropyl-6H-benzo-
Physical Properties of (1S*,3R*,4S*)-Isomer (16). Mp 165-167
°C (from AcOEt-hexane ) 3:7). IR (KBr) 3390, 2990, 2850, 1760,
1595, 1470, 1285, 1140, 870, 750 cm-1 1H NMR (400 MHz,
;
CDCl3, lambertellol numbering) δ 1.58, 1.59 (each 3H, s, C(CH3)2),
1.95 (3H, d, J ) 1.6 Hz, C3′CH3), 2.16 (1H, dd, J ) 5.8, 13.0 Hz,
C2HH), 2.22 (1H, brd, J ) 4.8 Hz, OH, exchangeable with D2O),
2.24 (1H, dd, J ) 10.8, 13.0 Hz, C2HH), 4.52 (1H, d, J ) 4.8 Hz,
C4H), 5.11 (1H, dd, J ) 5.8, 10.3 Hz, C1H), 6.78 (1H, d, J ) 8.2
Hz, C7H), 6.94 (1H, d, J ) 7.6 Hz, C5H), 7.15 (1H, q, J ) 1.6
Hz, C4′H), 7.23 (1H, dd, J ) 7.6, 8.2 Hz, C6H), NOE C2HR T
C1H, C4H T C1H, C4H T C5H, C4′H T C2Hꢀ; 13C NMR (100
MHz, CDCl3) δ 10.7, 23.8, 28.4, 33.2, 63.3, 71.8, 86.7, 101.6, 116.1,
118.6, 118.9, 129.4, 123.0, 134.8, 150.5, 151.6, 173.3; EIMS (rel
int %), m/z ) 302 (7.6, M+), 244 (100, [M - acetone]+), 134 (95.3);
EIHRMS found m/z 302.1146 calcd for C17H18O5, M+ 302.1154.
(1S*,3S*,4S*)-1-HydrolambertellolA(rac-17)and(1R*,3S*,4S*)-
Isomer (rac-18). A solution of 15 (15.0 mg, 49.6 µmol) in 80:20
mixture of acetonitrile and H2O (1.0 mL) was stirred with p-TsOH
(ca. 0.5 mg) at room temperature for 6 h. The mixture was poured
into H2O (15 mL) and extracted with AcOEt (15 mL × 3). The
combined organic solution was washed with brine, dried over
MgSO4, and then concentrated in vacuo. Silica gel column chro-
matography of the residue (AcOEt-hexane ) 50:50) gave a 80:20
mixture of rac-17 and rac-18 (13.0 mg, 100%) as white solid.
Analytical samples were obtained by HPLC (column, Merck LiChro-
CART RP 18e (φ 4 mm × 125 mm); eluent, CH3CN-H2O 1.0 mL/
min flow, detected at 210 nm) to give pure rac-17 and rac-18.
Physical Properties of (1S*,3S*,4S*)-1-Hydrolambertellol
A (rac-17). Amorphous powder, HPLC retention time tR ) 16.4
min (above conditions); IR (KBr) 3450, 3235, 2925, 1750, 1595,
[f][1,3,5,2,4]trioxadisilocin-6-yl)methyl)-3-methylfuran-2(5H)-
1
one (74.6 mg, 95%) as an oil. The H NMR spectrum showed
broaden signals. Thus, only characteristic signals are described. 1H
NMR (400 MHz, CDCl3) δ 0.30-0.75 (7H, m), 1.01-1.26 (21H,
m), 1.82 (3H, brs), 2.15-2.70 (2H), 3.30 (1H × 0.5, brd, J ) 7.0
Hz, exchangeable with D2O), 3.40 (1H × 0.5, brd, J ) 8.2 Hz,
exchangeable with D2O), 4.67-5.07 (3H, Br), 5.67 (1H, brt, J )
7.7 Hz), 5.75 (1H, brdd, J ) 5.0, 8.5 Hz), 6.89-7.23 (4H, m);
ESIMS (rel int %) m/z ) 529 (100, [M + Na]+), 524 (8.6, [M +
H2O]+), 507 (30.9, [M + H]+), 489 (27.9, [M + H - H2O]+).
A solution of the alcohol (74.6 mg, 147 µmol) in CH2Cl2 (3.0
mL) was stirred with PCC (74.7 mg, 347 µmol) at room temperature
for 1 h. Ether (10 mL) and Celite (ca. 500 mg) was added and the
resulting suspension was further stirred at the same temperature
for 30 min. After filtration through Celite pad, the filtrate was
concentrated in vacuo to give 14 (73.2 mg, 99%) as almost pure
state. IR (film) 2945, 2870, 1765, 1695, 1460, 1260, 1060, 885,
1475, 1290, 1260, 1065 cm-1 1H NMR (400 MHz, CD3OD,
;
1
830, 700 cm-1. The H NMR spectrum showed broaden signals.
lambertellol numbering) δ 1.88 (3H, d, J ) 1.5 Hz, C3′CH3), 2.26,
2.51 (each 1H, dd, J ) 6.5, 14.0 Hz, C2H2), 4.51 (1H, s, C4H),
5.10 (1H, t, J ) 6.5 Hz, C1H), 6.80 (1H, d, J ) 7.7 Hz, C7H),
6.94 (1H, d, J ) 7.7 Hz, C5H), 7.08 (1H, q, J ) 1.5 Hz, C4′H),
7.19 (1H, t, J ) 7.7 Hz, C6H). NOE C1H T C2Hꢀ, C1H T C4′H,
C4H T C4′H, C4H T C5H; 13C NMR (100 MHz, CD3OD) δ 10.6,
37.1, 65.2, 72.1, 88.2, 116.3, 120.7, 124.6, 130.4, 132.0, 138.1,
152.1, 157.6, 175.4; EIMS (rel int %), m/z ) 262 (7.4, M+), 244
(49.3, [M - H2O]+), 226 (56.9, [M - H2O × 2]+) 134 (100);
EIHRMS found m/z 262.0865 calcd for C14H14O5, M+ 262.0841.
Physical Properties of (1R*,3R*,4S*)-Isomer (rac-18). Rf )
0.21 (AcOEt-hexane ) 60:40), mp 186 °C (prism, from hexane-
AcOEt ) 50:50); HPLC retention time tR ) 11.4 min (above
conditions); IR (KBr) 3400, 2905, 1745, 1590, 1470, 1285, 1265,
Thus, only characteristic signals are described. 1H NMR (400 MHz,
CDCl3) δ 0.62-1.25 (28H, m), 1.85, 1.88 (each 3H × 0.5, brs),
2.01-2.51 (2H, m), 4.68 (1H × 0.5, br), 5.17 (1H × 0.5, brd, J )
5.5 Hz), 5.69 (1H, br), 6.87-7.61 (4H, m), 10.79 (1H, br); ESIMS
(rel int %) m/z ) 1031 (25.6, [2M + Na]+), 543 (16.6, [M + K]+),
527 (100, [M + Na]+), 522 (11.6, [M + H2O]+), 505 (27.8, [M +
H]+); ESI-HRMS found m/z 527.2265 calcd for C26H40O6Si2Na,
[M + Na]+ 527.2261.
(1S*,3S*,4S*)-1-Hydrolambertellol 1,8-O-Isopropylidene Ac-
etal (15) and Its (3R*)-Isomer (16). To a solution of 12 (75.0
mg, 248 µmol) in DMF (2.0 mL) was added sodium bis(trimeth-
ylsilyl)amide (1.0 M in THF solution, 250 µL) was added at -40
°C under Ar atmosphere. Upon addition of sodium bis(trimethylsilyl)-
amide, the clear solution turned to green and changed to orange solution
after 2 min. After stirring for 5 min, saturated aqueous NH4Cl solution
(ca. 3 mL) was added. The mixture was poured into H2O (30 mL)
and extracted with AcOEt (20 mL × 3). The combined extracts were
1060, 770 cm-1 1H NMR (400 MHz, CD3OD, lambertellol
;
numbering) δ 1.89 (3H, d, J ) 1.5 Hz, C3′CH3), 2.05 (1H, dd, J
) 6.6, 13.6 Hz, C2HH), 2.56 (1H, dd, J ) 6.0, 13.6 Hz, C2HH),
4.68 (1H, s, C4H), 5.25 (1H, dd, J ) 6.0, 6.6 Hz, C1H), 6.79 (1H,
J. Org. Chem. Vol. 73, No. 13, 2008 5045

Nomiya et al.
d, J ) 7.7 Hz, C7H), 6.96 (1H, d, J ) 7.7 Hz, C5H), 7.18 (1H, t,
J ) 7.7 Hz, C6H), 7.29 (1H, q, J ) 1.3 Hz, C4′H), NOE C1H T
C2Hꢀ, C4H T C4′H, C4H T C2HR, C4H T C5H, C4′H T C2HR;
13C NMR (100 MHz, CD3OD) δ 10.6, 38.1, 65.6, 71.2, 89.5, 116.0,
120.2, 124.6, 130.3, 130.7, 138.7, 153.0, 157.1, 175.8; ESIMS (rel
int %) m/z ) 263 (29.7, [M + H]+), 262 (16.3, M+), 245 (51.8,
[M + H - H2O]+), 227 (100, [M + H - 2H2O]+); ESI-HRMS
found m/z 263.0926 calcd for C14H15O5, [M + H]+ 263.0919.
(1S*,3R*,4S*)-1-Hydrolambertellol B (rac-19). In a similar
manner to that described above, solution of 16 (9.8 mg, 32.5 µmol)
was treated with p-TsOH (ca. 0.5 mg) for 3 h and the successive
similar work up gave rac-19. (8.5 mg, 100%) as white solid after
silica gel column chromatography (AcOEt-hexane ) 40:60). Mp
192 °C (decompose, prism); IR (KBr) 3400, 2925, 1740, 1630,
1385, 1275, 1040 cm-1; 1H NMR (400 MHz, CD3OD, lambertellol
numbering) δ 1.88 (3H, d, J ) 1.6 Hz, C3′CH3), 2.18 (1H, dd, J
) 4.4, 13.7 Hz, C2HH), 2.42 (1H, dd, J ) 5.4, 13.7 Hz, C2HH),
4.68 (1H, s, C4H), 5.23 (1H, dd, J ) 4.4, 5.4 Hz, C1H), 6.78 (1H,
d, J ) 8.2 Hz. C7H), 6.99 (1H, d, J ) 7.6 Hz, C5H), 7.18 (1H, dd,
J ) 7.6, 8.2 Hz, C6H), 7.38 (1H, q, J ) 1.6 Hz, C4′H), NOE C1H
T C2Hꢀ, C4H T C2Hꢀ, C4′H T C2HR, C4H T C5H; 13C NMR
(100 MHz, CDCl3) δ 10.6, 39.2, 64.6, 73.3, 89.1, 115.6, 119.4,
124.3, 130.4, 130.8, 139.0, 152.7, 157.2, 175.7; EIMS (rel int) m/z
) 262 (3.6, M+), 244 (42.5, [M - H2O]+), 226 (37.9, [M -
2H2O]+), 134 (100); EIHRMS found m/z 262.0819 calcd for
C14H14O5, M+ 262.0841.
numbering) δ 0.68-1.18 (28H, SiCH(CH3)2 × 2), 1.88 (3H, d, J
) 1.5 Hz, C3′CH3), 2.40 (1H, dd, J ) 6.4, 15.0 Hz, C2HH), 2.53
(1H, dd, J ) 3.4, 15.0 Hz, C2HH), 2.54 (1H, br, OH), 5.36 (1H,
dd, J ) 3.4, 6.4 Hz, C1H), 5.40 (1H, s, C4H), 6.57 (1H, q, J ) 1.5
Hz, C4′H), 6.89 (1H, brd, J ) 7.6 Hz, C7H), 7.24 (1H, brd, J )
7.6 Hz, C5H), 7.28 (1H, t, J ) 7.6 Hz, C6H), NOE C2Hꢀ T C4′H,
C4′H T C1H, C4H T C2HR, C4H T C5H; 13C NMR (100 MHz,
CDCl3) δ 10.6, 12.6, 12.79, 12.81, 13.3, 16.6, 16.8, 17.05, 17.07,
17.16, 17.25, 17.31, 39.4, 62.5, 70.5, 89.0, 118.6, 120.8, 127.7,
129.7, 130.5, 138.7, 149.4, 151.7, 173.7; EIMS (rel int) m/z ) 461
(100, [M - isopropyl]+), 443 (22.1, [M - isopropyl - H2O]+),
425 (23.3, [M - isopropyl - 2H2O]+); EIHRMS found m/z
461.1808 calcd for C23H33O6Si2, [M - isopropyl]+ 461.1816.
Physical Properties of (1R*,3S*,4S*)-1-Hydrolambertellol
A 1,8-O-Disiloxanylidene Acetal (22). Rf ) 0.57 (AcOEt-hexane
) 40:60); IR (KBr) 3435, 2495, 2870, 1765, 1460, 1275, 1050,
1
1015, 885, 695 cm-1; H NMR (400 MHz, CDCl3 lambertellol
numbering) δ 0.84-1.16 (28H, SiCH(CH3)2 × 2), 1.90 (3H, d, J
) 1.5 Hz, C3′CH3), 1.95 (1H, brd, J ) 13.4 Hz, C2HH), 2.60 (1H,
d, J ) 3.0 Hz, OH exchangeable with D2O), 2.95 (1H, dd, J )
4.3, 13.4 Hz, C2HH), 4.53 (1H, br, C4H), 5.42 (1H, dd, J ) 2.1,
4.3 Hz, C1H), 6.92 (1H, d, J ) 7.9 Hz, C7H), 7.03 (1H, d, J ) 7.9
Hz, C5H), 7.28 (1H, t, J ) 7.9 Hz, C6H), 7.43 (1H, br, C4′ H),
NOE C1H T C2Hꢀ, C4H T C4′H, C4H T C5H; 13C NMR (100
MHz, CDCl3) δ 10.5, 12.2, 12.75, 12.78, 13.1, 16.8, 16.9, 17.1,
17.20, 17.21, 17.27, 17.6, 17.7), 37.0, 63.3, 71.7, 86.8, 121.9, 123.6,
127.5, 128.3, 129.9, 135.7, 152.5, 153.4, 173.2; EIMS (rel int) m/z
) 461 (100, [M - isopropyl]+), 443 (22.8, [M - isopropyl -
H2O]+), 425 (20.9, [M - isopropyl-2×H2O]+); EIHRMS found
m/z 461.1813 calcd for C23H33O6Si2, [M - isopropyl]+ 461.1816.
Physical Properties of (1R*,3R*,4S*)-1-O-(Hydroxydiisopro-
pylsilyloxy)diisopropylsilyloxy-1-hydrolambertellol B (23). Rf )
0.36 (AcOEt-hexane ) 40:60); IR (KBr) 3370, 2945, 2865, 1745,
(1R*,3S*,4S*)-1-HydrolambertellolA(rac-18)and(1R*,3R*,4S*)-
1-Hydrolambertellol B (rac-25) from 14. To a solution of 14 (46.0
mg, 91.1 µmol) in DMF (1.0 mL) was added sodium bis(trimeth-
ylsilyl)amide (1.0 M in THF solution, 95 µL) at -40 °C under Ar
atmosphere. Upon addition of sodium bis(trimethylsilyl)amide, the
clear solution turned to green and changed to orange solution after
several seconds. After stirring for 5 min, saturated aqueous NH4Cl
solution (ca. 3 mL) was added. The mixture was poured into H2O
(30 mL) and extracted with AcOEt (20 mL × 3). The combined
extracts were washed with brine, dried over MgSO4, and then
concentrated in vacuo to give a crude mixture of 19, 20, 21, and
22 (ca. 48 mg). After the crude mixture was dissolved in THF (1.0
mL), acetic acid (200 µL) and TBAF (1.0 M in THF, 200 µL)
were successively added at room temperature. The mixture was
stirred for 30 min. The mixture was poured into H2O (20 mL) and
extracted with AcOEt (20 mL × 3). Silica gel column chromatog-
raphy of the residue eluted successively with AcOEt-hexane )
35:65 gave rac-18 (16.1 mg, 67%) and rac-25 (7.5 mg, 31%) both
1
1465, 1285, 1050, 880, 690 cm-1; H NMR (400 MHz, CDCl3,
lambertellol numbering) 0.90-1.10 (28H, m, SiCH(CH3)2 × 2),
1.91 (3H, d, J ) 1.5 Hz, C3′CH3), 2.48 (1H, dd, J ) 6.4, 12.5 Hz,
C2HH), 2.60 (1H, dd, J ) 9.8, 15.0 Hz, C2HH), 3.26 (1H, br, OH
exchangeable with D2O), 5.19 (1H, s, C4H), 5.57 (1H, dd, J )
6.4, 9.8 Hz, C1H), 6.81 (1H, q, J ) 1.5 Hz, C4′H), 6.88 (1H, brd,
J ) 7.9 Hz, C7H), 7.17 (1H, brd, J ) 7.9 Hz, C5H), 7.27 (1H, t,
J ) 7.9 Hz, C6H), 8.00 (1H, br, phenolic proton), NOE C1H T
C4′H, C4H T C2HR, C4H T C5H; 13C NMR (100 MHz, CDCl3)
δ 10.8, 13.28, 13.31, 13.6, 14.1, 16.8, 17.09, 17.13, 17.15, 17.16,
17.18, 17.22, 17.3, 40.9, 68.8, 71.7, 88.2, 116.5, 118.0, 121.4, 130.1,
132.7, 136.6, 147.2, 155.6, 173.4; FDMS (rel int) m/z ) 523 (37.0,
[M + H]+), 522 (38.1, [M]+), 374 (100, [M - (i-Pr)2Si(OH)2]+);
FD-HRMS found m/z 522.2474 calcd for C26H42O7Si2, M+ 522.2469.
Physical Properties of (1R*,3S*,4S*)-1-O-(Hydroxydiisopro-
pylsilyloxy)diisopropylsilyloxy-1-hydrolambertellol A (24). Rf )
0.29 (AcOEt-hexane ) 40:60); IR (KBr) 3370, 2945, 2865, 1745,
1
as solids. The H NMR, 13C NMR, IR, spectra as well as TLC
behavior of rac-18 were identical those of the sample provided
from 15.
Physical Properties of (1R*,3R*,4S*)-1-Hydrolambertellol
B (rac-25). Rf ) 0.33 (AcOEt-hexane ) 60:40); IR (KBr) 3455,
3235, 2940, 1735, 1595, 1475, 1280, 1040, 985, 815 cm-1; 1H NMR
(400 MHz, CD3OD, lambertellol numbering) δ 1.88 (3H, d, J )
1.6 Hz, C3′CH3), 2.27 (1H, dd, J ) 8.5, 13.1 Hz, C2HH), 2.39
(1H, dd, J ) 6.7, 13.1 Hz, C2HH), 4.86 (1H, s, C4H), 5.20 (1H,
dd, J ) 6.7, 8.5 Hz, C1H), 6.78 (1H, brd, J ) 8.0 Hz. C7H), 7.01
(1H, brd, J ) 8.0 Hz, C5H), 7.02 (1H, q, J ) 1.5 Hz, C4′H), 7.20
(1H, t, J ) 8.0 Hz, C6H), NOE C1H T C2HR T C1H T C4′H T
C4H T C2Hꢀ, C4H T C5H; 13C NMR (100 MHz, CDCl3) T
10.7, 40.0, 66.4, 72.8, 89.4, 116.0, 119.2, 124.0, 130.4, 132.9, 139.0,
152.3, 157.3, 175.2; ESIMS (rel int %) m/z ) 285 (23.9, [M +
Na]+), 280 (47.4, [M + H2O]+), 263 (17.6, [M + H]+), 262 (30.3,
M+), 245 (100, [M + H - H2O]+), 227 (98.0, [M + H - 2H2O]+);
ESI-HRMS found m/z 285.0737 calcd for C14H14O5Na, [M + Na]+
285.0739. Analytical samples of the intermediates 21, 22, 23, and
22 were isolated preparative silica gel TLC before treatment with
TBAF .
1460, 1290, 1250, 1050, 885, 690 cm-1 1H NMR (400 MHz,
,
CDCl3, lambertellol numbering) δ 0.90-1.07 (28H, SiCH(CH3)2
× 2), 1.92 (3H, d, J ) 1.5 Hz, C3′CH3), 2.13 (1H, dd, J ) 5.8,
13.4 Hz, C2HH), 2.75 (1H, dd, J ) 5.2, 13.4 Hz, C2HH), 2.76
(1H, br, OH exchangeable with D2O), 4.66 (1H, br, C4H), 5.63
(1H, dd, J ) 5.2, 5.8 Hz, C1H), 6.86 (1H, br, J ) 8.2 Hz, C7H),
7.01 (1H, brd, J ) 7.9 Hz, C5H), 7.19 (1H, q, J ) 1.5 Hz, C4′H),
7.28 (1H, brt, J ) 8.0 Hz, C6H), 7.92 (1H, br, phenolic proton),
NOE C4H T C4′H, C4H T C5H; 13C NMR (100 MHz, CDCl3) δ
10.5, 13.26, 13.29, 13.6, 13.8, 17.02, 17.04, 17.10, 17.11, 17.16,
17.23, 17.25, 17.4, 37.9, 66.2, 70.9, 87.1, 117.1, 120.4, 122.9, 128.2,
129.6, 136.1, 151.3, 155.1, 173.7; FDMS (rel int) m/z ) 523 (72.7,
[M + H]+), 522 (100, [M]+), 479 (82.7, [M - isopropyl]+), 374
(100, [M - (i-Pr)2Si(OH)2]+); FD-HRMS found m/z 522.2474 calcd
for C26H42O7Si2, M+ 522.2469.
Physical Properties of (1R*,3R*,4S*)-1-Hydrolambertellol
B 1,8-O-Disiloxanylidene Acetal (21). Rf ) 0.62 (AcOEt-hexane
) 40:60); IR (KBr) 3445, 2495, 2870, 1745, 1470, 1275, 1060,
1040, 995, 885, 670 cm-1; 1H NMR (400 MHz, CDCl3, lambertellol
rac-Lambertellol B (2) from rac-19. A suspension of a mixture
of the starting 18 (5.5 mg, 21.0 µmol) and manganese(IV) oxide
(15.0 mg) in CH2Cl2 (2.0 mL) was stirred at room temperature for
4 h. The mixture was filtered through Celite and the filtrate was
5046 J. Org. Chem. Vol. 73, No. 13, 2008

Synthesis of Lambertellols
concentrated in vacuo. After dissolving with a mixture of CH3CN
and H2O (10:90) the sample was loaded on Sep-pak ODS (5 g).
Elution with CH3CN:H2O (10:90) gave rac-2 (3.0 mg, 55%) as
needles. IR (KBr) 3500, 2925, 1760, 1635, 1340, 1245, 1040, 730
(22.4, [M + H2O]+), 261 (100, [M + H]+); ESI-HRMS found m/z
261.0770 calcd for C14H13O5; [M + H]+ 261.0763. The IR, and
1H NMR spectra of this sample was identical with that of the natural
lambertellol A (1) except for the chemical shift for exchangeable
4
1
1
cm-1; H NMR (400 MHz, CDCl3) δ 1.96 (3H, d, J ) 1.5 Hz),
OH signals in the H NMR spectrum.
2.51 (1H, br, exchangeable with D2O), 2.95 (1H, d, J ) 17.5 Hz),
3.20 (1H, d, J ) 17.5 Hz), 4.88 (1H. s), 7.01 (1H, d, J ) 8.5 Hz),
7.06 (1H, d, J ) 7.5 Hz), 7.09 (1H, d, J ) 1.5 Hz), 7.56 (1H, dd,
J ) 7.5, 8.5 Hz), 12.10 (1H, s, exchangeable with D2O); EIHRMS
found m/z 260.0678 calcd for C14H12O5; M+ 260.0685. The IR and
1H NMR spectra of this sample were identical with that of the
natural lambertellol B (2) except for the chemical shift for
Acknowledgment. Part of this work was supported by Grant-
in-Aid for Scientific Research (no. 17580090) from the Ministry
of Education, Science, Sports, and Culture of Japan. The authors
would like to thank Professor Jun Kawabata and Dr. Eri Fukushi
of Hokkaido University for measurements of mass spectra. The
authors are grateful to Professor Hiromasa Kiyota of Tohoku
University for fruitful discussions about deprotection of the
acetonide 15. The authors thank to Professor Babak Borhan of
Michigan State University for his kind reviewing of the
manuscript before submission.
4
1
exchangeable OH signals in the H NMR spectrum.
rac-Lambertellol A (1) from rac-17. A suspension rac-17 (8.1
mg, 30.9 µmol) was treated with PCC (50.3 mg, 233.3 µmol) in
CH2Cl2 (0.5 mL) acetone (0.5 mL). Ether (15 mL) was added and
the resulting mixture was stirred for an additional 5 min. After
filtration through Celite, concentration of the filtrate gave rac-1
containing small amount of lambertellin (3) being generated during
work up. After filtration through Celite, the eluent was passed
through short silica gel filter (AcOEt-hexane ) 20:80, then AcOEt
100%) gave rac-1 (2.8 mg, 35%) as needles. IR (KBr) 3420, 2925,
Supporting Information Available: Experimental proce-
dures, compounds 7-10, rac-lambertellol A (1) from rac-18,
rac-lambertellol B (2) from rac-25, optical resolutions of rac-
17, rac-18, rac-19, rac-25, rac-2, preparation of 1 and ent-1,
antifungal assay against Monilinia fructigena, germination inhibi-
tion assay against Cochlibolus miyabeanus, physical data and
spectra of 1, 2, 7-19, and 21-25. This material is available free
of charge via the Internet at http://pubs.acs.org.
1
1735, 1640, 1460, 1260, 1125, 1055, 745 cm-1; H NMR (400
MHz, CDCl3) δ 1.97 (3H, d, J ) 1.5 Hz), 2.93 (1H, d, J ) 17.5
Hz), 3.23 (1H, d, J ) 17.5 Hz), 4.88 (1H. br), 6.97 (1H, br), 7.01
(1H, d, J ) 8.5 Hz), 7.10 (1H, d, J ) 7.5 Hz), 7.56 (1H, dd, J )
7.5, 8.5 Hz), 12.08 (1H, s, exchangeable with D2O); ESIMS (rel
int %) m/z ) 283 (6.6, [M + Na]+), 279 (13.6, [M + H3O]+), 278
JO8005478
J. Org. Chem. Vol. 73, No. 13, 2008 5047