Studies directed towards the preparation of probes for the photoaffinity labelling of gibberellin receptors

Article abstract of DOI:10.1071/CH10441

Model studies for the preparation of photoaffinity probes designed to explore the nature of gibberellin receptor sites have provided a wide range of gibberellin derivatives that should afford useful scaffolds incorporating auxiliary groups attached to C-2

Full text of DOI:10.1071/CH10441

RESEARCH FRONT
Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2011, 64, 471–488
Studies Directed Towards the Preparation of Probes for the
Photoaffinity Labelling of Gibberellin Receptors-
A
B
A C
,
James R. Crow, Peter M. Chandler, and Lewis N. Mander
A
Research School of Chemistry, Australian National University, Canberra,
ACT 0200, Australia.
B
CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
C
Corresponding author. Email: mander@rsc.anu.edu.au
Model studies for the preparation of photoaffinity probes designed to explore the nature of gibberellin receptor sites have
provided a wide range of gibberellin derivatives that should afford useful scaffolds incorporating auxiliary groups attached
to C-2 and C-12. Methodology features the stereocontrolled opening of 2b,3b-epoxy gibberellins by attack on the lower
face at C-2, while functionalization of C-12 was effected by the rhodium acetate-catalyzed CH insertion reaction of a
17-diazo ketone. Compounds were screened for bioactivity in growth and barley endosperm-based bioassays.
Manuscript received: 3 December 2010.
Manuscript accepted: 17 February 2011.
Introduction
12
11
Until the landmark studies by Matsuoka et al.,[1,2] our under-
standing of the molecular basis of gibberellin signalling in plants
was almost non-existent. In the early 1990s, it had been reported
that protoplasts prepared from aleurone cells were capable of
responding to gibberellin (GA), e.g. GA4 (Fig. 1), even when the
GA molecule was bound to a matrix that was external to the
cell.[3–5] It was inferred that the GA receptor would be localized
to the plasma membrane, allowing external GA to be perceived
at the outer surface of the membrane. Since 2005, there has been
much stronger support for a GA receptor (GID1) that is nuclear-
localized, and in several plant species, mutants in this protein
have been identified that are defective in their ability to respond
to either applied or endogenous GA. In vitro studies using
purified GID1 protein have shown specific, saturable binding of
labelled GAs, followed by binding of DELLA proteins to the
GA–receptor complex that initiates GA signalling.[1,2,6] How-
ever, it remains uncertain whether there is another GA receptor
located in the plasma membrane of aleurone cells. Accordingly,
we have undertaken the construction of a series of modified GAs
with a view to preparing photoaffinity probes[7] designed to
provide further insight into the nature of these hormone recog-
nition processes.
O
1
13
9
2
3
8
10 H
17
CO
16
15
6
HO
H 5
4
CO2H
7
GA4 (1)
O
O
S
I
O
CO
H
HO
N3
HO
H
CO2H
2
Fig. 1.
N
N
CF3
Br
I
The construction of an effective photoaffinity probe involves
several major considerations: the choice of a suitable photo-
phore, location on the GA molecule with or without a linker,
and a method for detecting cross-linked protein. The azide-
based probe 2 (Fig. 1) was employed by Beale et al.[8] but its
bioactivity was poor. Crosslinking was nevertheless attempted,
but with limited success.[9] Among the wide range of potential
photophores, we were attracted to the use of phenyl trifluoro-
methyl diazirines[10–12] because they appeared to offer signifi-
cant advantages, namely chemical robustness, activation at
OH
OH
3
N
CF3
N
N
CF3
I125
OR
SnBu3
OR
N
Scheme 1.
yDedicated to the memory of Professor Athel Beckwith, an outstanding chemist and wonderful colleague.
Ó CSIRO 2011
10.1071/CH10441
0004-9425/11/040471

RESEARCH FRONT
472
J. R. Crow, P. M. Chandler, and L. N. Mander
O
H
longer wavelengths (4300 nm) to minimize damage to plant
tissue, effective cross-linking via CH-insertion and the option to
incorporate a radioactive label at a late stage of the synthetic
sequence. A nine-step synthesis of a suitable precursor, namely 3,
has been described by Weber and Brunner,[13] who have also
demonstrated that the iodine substituent may be replaced by
tributylstannyl, which in turn may be displaced by radioactive
iodine (Scheme 1).
O
CO
H
CO2R
O
H
HO
CO2R
RO
HO
A downside of using phenyl trifluoromethyl diazirines,
however, is their relative steric bulk and we were concerned to
establish whether their incorporation might interfere with bind-
ing. So, before embarking on the assembly of actual candidates,
we elected to incorporate benzyloxy functions at various loca-
tions on the GA molecule as surrogates for the diazirine group
and check whether bioactivity was being maintained. This
strategy would also allow us to conserve supplies of 3. Location
on the GA molecule is obviously critical and constrained by
the need to preserve functionality that is essential for biolo-
gical activity, namely the 7-carboxyl, a 3b-hydroxyl and the
g-lactone function.[14] The D-ring double bond and the 13-
hydroxyl may also be important for some plant species. A
preliminary screen[15] of GAs substituted by a benzyloxy group
attached to C-1a, C-1b, C-2b, C-13 and C-18 showed dimin-
ished bioactivity (less than 5% of the parent GA) in two
bioassays.[16] The C-11b analogue was the most promising
(growth assay, 33%) but the parent GA is prepared with
considerable difficulty.[14] The investigation of two further
sites, namely C-2a and C-12, is the subject of this paper.
CO
H
O
RO
CO2R
O
Scheme 2.
O
O
CF3COCH3
O
R
CO
O
CO
H
H
Oxone
(78%)
H
H
CO2Me
CO2Me
4
5
6
R ϭ O
Ph3PϭCH2
(77%)
R ϭ CH2
Scheme 3.
6
ROH, B(C6F5)3
Discussion
O
O
H
RO
HO
RO
An attractive strategy for the stereocontrolled installation of
functionality at the 2a position appeared to be through the trans-
diaxial opening of a 2b,3b-epoxide as outlined in Scheme 2.
Previous experience with the epoxidation of gibberellin D2-
enes, however, had shown that direct methods using peroxy-
carboxylic acids required forcing conditions, and resulted in
modest yields of 2:3 mixtures of the desired 2b,3b epoxide and
its 2a,3a-diastereomer. Although a route had been developed
beginning with osmium tetroxide dihydroxylation, as described
previously,[17] we sought a more direct approach, which led to
the discovery that treatment of the 2,3-ene 4 with in situ-
generated methyl trifluoromethyl dioxirane[18] gave the desired
2b,3b-epoxide 5 in 78% yield. A small amount (6%) of the
known 2a,3a-stereoisomer was also obtained[19] (Scheme 3).
The next step was to re-establish the 16,17-ene functionality,
and was achieved using a Wittig methylenation, performed
under salt-free conditions, affording alkene 6 in 77% yield.
For the epoxide-opening reaction, we were attracted to the
methodology developed by Chandrasekhar that highlights the
use of the non-traditional Lewis-acid catalyst tris(pentafluoro-
phenyl)borane, B(C6F5)3, in the opening of epoxides with
various nucleophiles including alcohols, amines and thiols.[20]
Reaction with methanol using dichloromethane (DCM) as the
solvent to give 7 was found not to proceed until heated to reflux,
and to require 25 mol-% of the Lewis acid. Reaction yields were
rather variable, the best yield being 36%. However, allyl alcohol
and benzyl alcohol were found to couple more smoothly, giving
8 in 77% yield at 40% conversion and 9 in 65% yield (Scheme 4).
An important aspect of these conversions is the stability of the
D16 ene functionality, which is somewhat acid-labile (isomeri-
zation to the 16-ene is quite facile). The series of products were
then subjected to thiolate-mediated cleavage of the methyl ester
nPrSNa
CO
H
CO
H
HMPA
HO
H
CO2H
CO2Me
10 R ϭ Me (95%)
11 R ϭ CH2CH=CH2 (75%)
12 R ϭ CH2Ph (83%)
7 R ϭ Me (36%)
8 R ϭ CH2CH=CH2 (60%)
9 R ϭ CH2Ph (65%)
Scheme 4.
Table 1. Gibberellin A4 (GA4) derivatives
Approximate activity (% relative to parent GA)
Compound
Growth assay
Aleurone assay
2a-Methoxy GA4 (10)
2a-Allyloxy GA4 (11)
2a-Benzyloxy GA4 (12)
400
150
10
100
300
100
function,[21] which made the free acids 10, 11 and 12 available
for bioassay.
The bioactivity of the model photoaffinity probes was tested
in barley (Hordeum vulgare) Himalaya, in which two bioassay
systems have been developed.[16] Hormone-biosynthetic mutant
strains of barley have been developed in which natural GA
biosynthesis is blocked, resulting in dwarf plants. The applica-
tion of bioactive GAs restores normal growth in these plants, and
the amount of GA required to normalize growth provides a
measure of the relative bioactivity of a GA. The growth assay
used entails the measurement of the maximal rate of first-leaf

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
473
O
OH
O
H
OH
Table 2. Gibberellin A1 (GA1) derivatives
CO
H
CO
H
Compound
Approximate activity
HO
HO
H
(% relative to parent GA)
CO2H
CO2H
14
Growth assay
Aleurone assay
13
cf. ref. [22]
2a-Benzyloxy GA1 (22)
2a-Phenethyloxy GA1 (23)
2a-Phenylpropanoxy GA1 (24)
o5
o1
o5
o5
o1
o1
O
O
H
OAc
O
OAc
O
CF3COCH3
Oxone
O
CO
CO
H
H
O
OAc
OH
O
H
(82%)
OAc
H
16
CO2MOM
CO2MOM
CO
H
15
CO
H
5 steps
Br
AcO
AcO
1. K2CO3, MeOH
2. TMSCl, iPrNEt2
3. Ph3P=CH2, Hϩ
H
1. K2CO3, EtOH
CO2Me
CO2Me
75% yield
OH
2. TMSCl, iPrNEt2
25
26
O
O
OTMS
Pb(OAc)4, I2 hν
OH
O
O
O
CO
O
CO
H
H
Ph3P=CH2, Hϩ
O
H
O
H
OAc
Zn, HOAc
OAc
Br
H
17
H
CO2MOM
(28%)
CO2Me
CO
18
CO
H
H
1. ROH, B(C6F5)3
2. DHP, Hϩ
AcO
AcO
CO2Me
CO2Me
27
28
OH
O
OTHP
O
1. nPrNa
HMPA
RO
HO
RO
Scheme 6.
CO
CO
H
H
2. H3Oϩ
THPO
H
H
If the MOM ester was deliberately converted to the methoxy
analogue first, the sequence of silylation and Wittig processes
produced superior results (75% yield). After opening the epox-
ide 18 with a selection of alcohols, the possibility of epimeriza-
tion at C-3 during ester hydrolysis[23] was avoided by masking
as tetrahydropyranyl (THP) ethers 19–21.
CO2H
CO2Me
19 R ϭ CH2Ph (70%)
22 R ϭ CH2Ph (84%)
23 R ϭ CH2CH2Ph (69%)
24 R ϭ CH2CH2CH2Ph (70%)
20 R ϭ CH2CH2Ph (98%)
21 R ϭ CH2CH2CH2Ph (86%)
Scheme 5.
Hydrolysis was then effected with thiolate and the resulting
acids submitted for bioassay, but disappointingly, bioactivity
(Table 2) was greatly reduced relative to the parent GA1 (o5% in
the growth assay ando1% in the aleurone test), so we transferred
our focus to 12-substituted derivatives.
elongation of seeds germinated and grown in contact with a
solution of the GA in question. This assay had been found to be
the most precise of several possible growth assays.[13] As well,
bioactivity was measured in aleurone tissue.
We were pleased to find that the methanol and allyl alcohol
adducts (10 and 11 respectively) were more potent than the
parent GA4 (Table 1) in both assays, but disappointed to find that
the benzyloxy derivative 12, though as potent as GA4 in the
aleurone assay, showed only 10% activity in the growth assay.
In an attempt to retain acceptable levels of bioactivity, we then
turned to the use of 13-hydroxy GAs, such as GA1 (13), that on
the whole are more bioactive than their 13-desoxy analogues.
We also elected to vary the length of the attachment linker.
Beginning with GA3 (14), we assembled 15 by previously
established methodology,[22] choosing to mask the 7-carboxyl
with a methoxymethyl (MOM) group, which could be more
easily removed than the more usual methoxy at the end of the
sequence. The epoxide 16 was smoothly prepared with trifluoro-
dioxirane as for 5 and the sequence completed as summarized in
Scheme 5. The 16-ene methylene was re-introduced by first
removing the 13-acetate function from 16, replacing it by a
trimethylsilyl group, which has been shown to favour Wittig
reactions with this type of substrate.[17] The conversion pro-
ceeded in poor yield (28% after desilylation), however, and
moreover, the MOM ester group had undergone transesterifica-
tion to afford methyl ester 18, an outcome that could be
rationalized by initiation with adventitious base leading to
liberation of methoxide from the MOM function, maintaining
the conversion by autocatalysis.
Past efforts towards the functionalization of C-12 have
allowed the confirmation of the structures of almost 32 naturally
occurring 12-hydroxylated GAs.[24] Access to C-12 was gained
by transannular functionalization of bromohydrin 26 followed
by reductive fission of the resulting ether 27 to give 28
(Scheme 6). Manipulation of these products was not straight-
forward because of the proximity of the 16-ene and oxygen
functions, and so in the current study, we saw an advantage in
taking an alternative approach as outlined in Scheme 7.
The key reaction utilized a transannular CH insertion[25]
mediated by diazoketone 31 to give 32 followed by oxidative
ring fission, thereby affording aldehyde 34. Starting from
GA4 (1), the 7-carboxyl and the 3b-hydroxyl were protected as
the methyl ester and the MOM ether respectively, then hydro-
boration of the 16,17-ene followed by Jones oxidation gave acid
30, possessingthedesiredendoconfiguration. Transformationto
diazoketone 31 was straightforward and CH insertion catalyzed
by Rh2(OAc)4 proceeded with remarkable efficiency, producing
the desired cyclized product 32 in 88% yield. It was envisaged
that a-hydroxylation of the ketone function, followed by cleav-
age with Pb(OAc)4, would open the newly formed ring while
generating functionality to allow both elaboration at C-12 and
the restoration of the 16,17-double bond.
Hydroxylation was best achieved (88% yield) by treatment of
the derived t-butyldimethylsilyl (TBS) enol ether with dimethyl

RESEARCH FRONT
474
J. R. Crow, P. M. Chandler, and L. N. Mander
N2
O
H
O
O
CO
1. BH3·SMe2; H2O2
2. Jones’ oxidation
1. (COCl)2, DMF
2. CH2ϭN2
CO2H
CO
CO
H
H
H
MOMO
MOMO
O
MOMO
(83%)
(88%)
H
H
CO2Me
CO2Me
CO2Me
29
30
31
Rh2(OAc)4
(88%)
OH
CH=O
O
O
O
O
H
O
1. TBSOTf, Et3N
2. Dimethyl dioxirane
Pb(OAc)4,
MeOH
CO
CO
CO2Me
CO
H
H
H
MOMO
MOMO
MOMO
HO
MOMO
H
H
(88%)
CO2Me
CO2Me
(86%)
CO2Me
34
32
33
NaOH, MeOH
(97%)
CH2OAc
CH=O
CH2OAc
O
O
H
O
1. BH3·SMe2; H2O2
2. ArSeCN, nBu3P
CO2H
1. NaBH4
2. Ac2O, Py, DMAP
CO
CO
NO2
CO2H
CO
H
H
H
MOMO
(73%)
Se
MOMO
H
(74%)
H
CO2Me
CO2Me
CO2Me
35
36
37
1. K2CO3
2. PHCH2OC(=NH)CCl3,
CF3SO3H
(77%)
CH2OCH2Ph
CH2OCH2Ph
CH2OCH2Ph
1. DHP, Hϩ
2. nPrSNa, HMPA
3. H3Oϩ
i
O
O
O
1. CBr4 PrOH
2. H2O2
CO
CO
NO2
CO
H
H
H
(69%)
(72%)
MOMO
Se
HO
H
H
H
CO2Me
CO2H
CO2Me
40
39
38
Scheme 7.
N
N
CF3
dioxirane, then Pb(OAc)4 in methanol to give aldehyde 34 in
good yield. It was of interest to note that as a consequence of
steric buttressing between the 12b-carboxaldehyde substituent
and the 17-carboxyl, the GA skeleton is distorted, as evidenced
by the reduced coupling constant between H-5 and H-6 of
6.9 Hz compared with the normal value of 10–11 Hz. Treatment
of aldehyde 34 with NaOH in aqueous methanol induced
epimerization at C-12 as expected (J5,6 reverted to 11 Hz) and
also resulted in hydrolysis of the 17-ester group. Given the
mildness of the procedure (20 min at room temperature), we
suspected that the hydrolysis was assisted by the aldehyde
function before undergoing isomerization. With the desired
stereochemistry of the C-12 side chain established, aldehyde
35 was reduced to the corresponding alcohol, which was then
protected as the acetate 36. The 17-carboxy group was subjected
to reduction with borane–dimethylsulfide complex, giving the
17-ol from which we planned to restore the 16,17-ene function
via the 17-selenide 37.[26] The oxidation step to generate the
16-alkene was delayed until the rest of the functionality had
been elaborated, however. Thus, the acetate group was removed
from 37 and the 12a-benzyloxymethyl functionality introduced
by treatment with benzyl trichloroacetimidate and catalytic
triflic acid to afford 38. The 3-MOM group was then removed
I
CH2OAc
O
O
Steps as in
Scheme 7
CO
NO2
H
RO
Se
H
O
CO2Me
37 R ϭ MOM
41 R ϭ H
CO
H
CBr4
MeOH
HO
H
CO2H
42
Scheme 8.
by heating 38 in isopropyl alcohol in the presence of CBr4
(generating HBr in situ).[27] Oxidation of the selenenyl ether
with H2O2 then gave the 16,17-ene 39.[26] The free alcohol
function at C-3 was temporarily protected as a THP ether, in
order to prevent epimerization when converting the methyl ester
to the carboxylic acid, which was performed using propane
thiolate. The removal of the THP group then afforded 12a-
benzyloxymethyl GA4 40. We were greatly encouraged to find
that the growth bioassay assay showed 40 to be essentially
identical in activity to the parent GA4 (1), indicating that the

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
475
12a-position would make an excellent point of attachment for
the photoaffinity moiety and prompted testing of 40 in the
aleurone bioassay. Disappointingly, bioactivity in the aleurone
assay was found to be one fifth that of GA4 (1). Nevertheless,
given the bioactivity of 40, we elected to prepare the fully
decorated probe including the diazirine function, namely 43,
from 37 (Scheme 8). In the event, the methyl ester of 43 was
prepared successfully, but our efforts to hydrolyze the ester
group resulted in destruction of the diazirine moiety.
ultraviolet detector set at either 210 or 254 nm. Alltima C18
columns were supplied by Alltech.
ent-2a,3a-Epoxy-10b-hydroxy-16-oxo-17,20-
dinorgibberellane-7,19-dioic Acid 7-Methyl
Ester 19,10-Lactone 5
To a stirred solution of ketone 4 (0.50 g, 1.52 mmol) in MeCN
(25 mL) at 08C was added 4 ꢀ 10ꢁ4 M Na2EDTA(aq) (0.45 mL),
then a mixture of NaHCO3 (1.27 g, 15.15 mmol) and oxone
(9.31 g, 15.15 mmol), followed by trifluoroacetone (3.40 mL,
37.88 mmol). After 16 h, the reaction was allowed to warm to
room temperature (rt) and the solvent then removed under
vacuum. The resulting residue was taken up in water (40 mL)
and DCM (40 mL), and the aqueous layer was then separated
and extracted with DCM (2 ꢀ 25 mL). The combined organic
extracts were washed with water (2 ꢀ 20 mL), and the combined
aqueous layers were then back-extracted with DCM (10 mL).
The combined organic layers were washed with brine (50 mL)
and dried (MgSO4). Concentration under vacuum and column
chromatography on silica (EtOAc/hexane 1:1, increasing to 2:1)
afforded 5 (0.407 g, 78%) as a white foam, followed by 2,3-epi-5
(0.083 g, 6%) as a white foam.
Conclusion
The aim of this research has been to establish methods for the
design and synthesis of a GA photoaffinity probe in order to shed
further light on GA receptors. Previous work had highlighted the
importance of designing a photoprobe that retained strong bio-
activity, based on the presumption that activity would imply
binding affinity for the GA receptor. Considerable progress has
been made towards this ultimate goal and in particular provided
a range of gibberellin scaffolds that should assist in further
studies. Inter alia, by extending the GA skeleton at C-12, the
resulting primary alcohol derived from aldehyde 35 allows
easy differentiation from the 3b-hydroxyl, thereby reducing the
number of protecting groups.
Epoxide 5 crystallized from EtOAc/hexane, mp 177–1788C.
max/cmꢁ1 2952, 2878, 1777, 1740, 1437, 1381, 1346, 1283,
n
1259, 1198, 1175, 1158, 1108, 1056, 1028, 990, 920, 882, 871,
832, 752, 733. dH (300 MHz, CDCl3) 1.31 (3 H, s, H-18), 1.57–
2.13 (10 H, m), 2.29 (1 H, dd, J 4.1, 15.8, H-1), 2.41 (1 H, m,
H-13), 2.69 (1 H, d, J 10.6, H-6), 3.09 (1 H, d, J 10.4, H-5), 3.13–
3.18 (2 H, m, H-2 and H-3), 3.71 (3 H, s, ꢁCO2CH3). dC
(75 MHz, CDCl3) 14.7 (C-18), 16.9 (C-11), 24.9 (C-12), 31.8
(C-1), 34.7 (C-14), 44.6 (C-13), 48.1 (C-2 or C-3), 48.4 (C-8),
49.3 (C-2 or C-3), 49.9 (C-4), 50.2 (C-15), 51.9 (C-6), 52.3
(ꢁCO2CH3), 54.5 (C-9), 56.5 (C-5), 91.1 (C-10), 171.7 (C-7),
175.6 (C-19), 219.5 (C-16). m/z (EI) 346 (Mþ, 3%), 318 (100),
300 (2), 286 (32), 274 (17), 258 (19), 243 (23), 227 (10), 215
(35), 197 (47), 181 (51), 155 (46), 129 (24), 117 (16), 105 (21),
91 (44), 77 (27). m/z (HRMS) Calc. for Mþ, C19H22O6:
346.1416. Found: 346.1419. Anal. Calc. for C19H22O6:
C 65.9, H 6.4. Found: C 66.0, H 6.1%.
Epoxide 2,3-epi-5: Crystallized from EtOAc/hexane, mp
2358C (lit. 2488C[19]). nmax/cmꢁ1 2952, 1782, 1739, 1437,
1382, 1351, 1275, 1256, 1195, 1161, 1139, 1108, 1041, 991,
938, 888, 840, 806, 752. dH (300 MHz, CDCl3) 1.36 (3 H, s,
H-18), 1.58–2.17 (11 H, m), 2.42 (1 H, m, H-13), 2.63 (1 H, d, J
10.1, H-6), 2.99 (1 H, d, J 10.1, H-5), 3.20 (1 H, d, J 3.2, H-3),
3.32 (1 H, t, J 3.7, H-2), 3.74 (3 H, s, –CO2CH3). dC (75 MHz,
CDCl3) 16.0 (C-18), 16.8 (C-11), 25.0 (C-12), 31.7 (C-1), 34.9
(C-14), 44.7 (C-13), 49.8 (C-8), 50.3 (C-15), 51.4 (C-4), 51.6,
51.9, 54.6, 57.7 (C-2, C-3, C-5, C-6 and C-9), 52.5 (–CO2CH3),
92.6 (C-10), 172.1 (C-7), 173.9 (C-19), 220.3 (C-16). m/z (EI)
346 (Mþ, 3%), 318 (61), 302 (11), 286 (22), 270 (11), 258 (40),
242 (100), 227 (25), 215 (24), 197 (47), 181 (51), 155 (30),
129 (34), 105 (31), 91 (62), 77 (36). m/z (HRMS) Calc. for
Mþ, C19H22O6: 346.1416. Found: 346.1420. Anal. Calc. for
C19H22O6: C 65.9, H 6.4. Found: C 65.6, H 6.7%.
Experimental
Melting points (mp) were recorded on a Gallenkamp melting
point apparatus and are uncorrected. Infrared spectra (nmax) were
recorded on a Perkin-Elmer 1800 Fourier-transform infrared
spectrophotometer as a thin film on KBr discs. Proton nuclear
magnetic resonance (1H NMR) spectra were recorded on a
Varian Mercury 300 spectrometer at 300 MHz. Carbon-13 nu-
clear magnetic resonance (13C NMR) spectra were recorded on a
Varian Mercury 300 spectrometer at 75.5 MHz. Chemical shifts
are reported as d values in parts per million (ppm) relative to
tetramethylsilane for all recorded NMR spectra. For proton
spectra recorded in deuterated chloroform, the residual CHCl3
peak was used as the internal reference (7.26 ppm), whereas the
central peak of CDCl3 (77.0 ppm) was used as the reference
for carbon spectra. For proton spectra recorded in deuterated
methanol, the residual HCD2OD peak was used as the internal
reference (3.31 ppm), whereas the central peak of CD3OD
(49.0 ppm) was used as the reference for carbon spectra. Dis-
tortionless enhancement by polarization transfer (DEPT) and
attached proton test (APT) experiments were used in the as-
signment of carbon spectra. Where THP protecting groups have
been used, integrations relate to individual diastereomers; where
peaks are superimposed, integrations indicate the sum of both
diastereomers. Thus, a single methyl peak integrates to 6 H.
Assignment of the anomeric protons of the diastereomers
has been made where possible, and designated as THP-H1 and
THP-H10 in the proton NMR; similarly, where possible, the
anomeric carbon is assigned as THP-C1 and THP-C10 in the
carbon NMR. The balance of protons associated with the THP
group have been designated THP where possible. Low-
resolution (LRMS) and high-resolution (HRMS) EI mass
spectra (70 eV) were recorded on a Fisons VG Autospec double-
focussing mass spectrometer, and electrospray ionization (ESI)
mass spectra were recorded on a Micromass single quadrupole
mass spectrometer. Microanalyses were carried out by the
Australian National University Analytical Services Unit. High-
performance liquid chromatography (HPLC) was carried out
using Waters 510 HPLC pumps, and a Waters Lambda-Max 481
ent-2a,3a-Epoxy-10b-hydroxy-20-norgibberell-16-ene-
7,19-dioic Acid 7-Methyl Ester 19,10-Lactone 6
To a stirred suspension of triphenylmethylphosphonium iodide
(2.72 g, 6.76 mmol) in THF (25 mL) at ꢁ788C was added 1.0 M
sodium hexamethyldisilazide (NaHMDS) in THF (5.41 mL,
5.41 mmol). This mixture was allowed to warm to rt and stirred
for 1 h, forming a bright yellow solution.

RESEARCH FRONT
476
J. R. Crow, P. M. Chandler, and L. N. Mander
To a stirred solution of 5 (648 mg, 1.35 mmol) in THF
(25 mL) at ꢁ788C was added slowly via gas-tight syringe the
ylide solution (8.13 mL, 1.76 mmol) prepared above. After 1 h,
the reaction was allowed to warm to rt over 1 h. After a further
1 h, the reaction was poured into saturated aqueous NH4Cl
solution (60 mL) and EtOAc (60 mL). The aqueous layer
was separated and extracted with EtOAc (2 ꢀ 40 mL), and
the combined organic layers were then washed with water
(2 ꢀ 40 mL). The combined aqueous layers were back-extracted
with EtOAc (2 ꢀ 30 mL), and the combined organic layers were
then washed with brine (20 mL) and dried (MgSO4). Concentra-
tion under vacuum and column chromatography on silica
(EtOAc/hexane 1:3) afforded 6 (357 mg, 77%) as a white solid.
(5 mL), acidified to pH 3 with cold 2.0 M HCl, and then
extracted with 20% 2-butanol in EtOAc (3 ꢀ 4 mL). The com-
bined organic layers were washed to pH 4.5 with saturated
aqueous KH2PO4, then washed with copper(II) chloride solution
(2.5 mL), back-extracting each time with 20% 2-butanol in
EtOAc. The combined organic layers were washed with brine
(7 mL) and dried (MgSO4). Concentration under vacuum and
column chromatography on silica (EtOAc/hexane/AcOH
2:1:0.001) afforded 10 (19 mg, 95%) as a white solid, which was
further purified by reverse-phase HPLC on C-18 stationary
phase (65% methanol and 35% water containing 0.1% acetic
acid). Crystallization from EtOAc/hexane afforded crystals, mp
137–1398C. nmax/cmꢁ1 3435, 2927, 2880, 1756, 1657, 1454,
1379, 1320, 1281, 1204, 1163, 1105, 1071, 969, 932, 878, 819.
dH (300 MHz, CDCl3) 1.23 (3 H, s, H-18), 1.34–2.11 (10 H, m),
2.21 (1 H, d, J 15.1, H-1), 2.63 (1 H, m, H-13), 2.78 (1 H, d, J
10.8, H-6), 3.15 (1 H, d, J 10.8, H-5), 3.33 (3 H, s, –OCH3), 3.52
(1 H, m, H-2), 3.87 (1 H, s, H-3), 4.86 (1 H, s, H-17), 4.98 (1 H, s,
H0-17). dC (75 MHz, CDCl3) 15.4 (C-18), 17.2 (C-11), 32.6 (C-
12), 33.9 (C-1), 37.9 (C-14), 40.3 (C-13), 45.5 (C-15), 52.4 and
52.8 (C-5 and C-6), 53.7 (C-4), 54.7 (C-9), 57.2 (–OCH3), 73.1
(C-3), 81.6 (C-2), 95.1 (C-10), 107.6 (C-17), 158.6 (C-16), 177.4
(C-7), 180.2 (C-19). m/z (EI) 362 (Mþ, 11%), 344 (86), 326 (16),
316 (47), 300 (62), 286 (46), 268 (75), 255 (79), 240 (35), 230
(53), 223 (71), 215 (74), 202 (36), 185 (31), 183 (24), 173 (22),
155 (44), 153 (54), 143 (38), 129 (48), 117 (35), 105 (60), 91
(100), 79 (66), 71 (44), 57 (56). m/z (HRMS) Calc. for Mþ,
C20H26O6: 362.1729. Found: 362.1729.
n
max/cmꢁ1 2974, 2938, 1777, 1734, 1658, 1436, 1381, 1343,
1280, 1259, 1197, 1174, 1160, 1115, 1098, 1058, 1030, 993,
916, 873, 833, 822, 753, 733. dH (300 MHz, CDCl3) 1.29 (3 H, s,
H-18), 1.22–2.05 (10 H, m), 2.27 (1 H, dd, J 4.0, 15.8, H-1), 2.60
(1 H, m, H-13), 2.65 (1 H, d, J 10.4, H-6), 3.06 (1 H, d, J 10.4,
H-5), 3.10–3.15 (2 H, m, H-2 and H-3), 3.68 (3 H, s, ꢁCO2CH3),
4.82 (1H, s, H-17), 4.93 (1H, s, H0-17). dC (75 MHz, CDCl3) 14.6
(C-18), 16.3 (C-11), 31.3 (C-12), 32.0 (C-1), 37.0 (C-14), 38.8
(C-13), 44.3 (C-15), 48.2 (C-8), 48.3 and 49.3 (C-2 and C-3),
50.8 (C-6), 51.5 (C-4), 52.0 (ꢁCO2CH3), 54.2 (C-9), 56.6 (C-5),
91.5 (C-10), 107.4 (C-17), 156.0 (C-16), 172.4 (C-7), 176.0 (C-
19). m/z (EI) 344 (Mþ, 3%), 312 (100), 283 (5), 268 (7), 257 (8),
240 (84), 222 (53), 207 (21), 193 (24), 181 (29), 169 (18), 155
(58), 143 (22), 131 (17), 115 (26), 91 (52), 77 (28). m/z (HRMS)
Calc. for Mþ, C20H24O5: 344.1624. Found: 344.1621.
ent-3a,10b-Dihydroxy-2b-methoxy-20-norgibberell-16-
ene-7,19-dioic Acid 7-Methyl Ester 19,10-Lactone 7
ent-2b-Allyloxy-3a,10b-dihydroxy-20-norgibberell-16-
ene-7,19-dioic Acid 7-Methyl Ester 19,10-Lactone 8
To a stirred solution of epoxide 6 (50 mg, 0.145 mmol) in DCM
(2 mL) was added (C6F5)3B (37 mg, 0.073 mmol) in DCM
(1 mL), followed by MeOH (12 mL, 0.291 mmol), and the
resulting mixture was heated to reflux. After 18 h, reaction
was allowed to cool to rt and the solvent then removed under
vacuum. Column chromatography on silica (EtOAc/hexane 2:3,
increasing to 2:1) then afforded 7 (20 mg, 36%) as an oil.
To a stirred solution of 6 (25 mg, 0.073 mmol) in DCM (1 mL)
was added (C6F5)3B (9.3 mg, 0.018 mmol) in DCM (0.5 mL),
followed by allyl alcohol (10 mL, 0.15 mmol), and the resulting
mixture was heated to reflux. After 18 h, reaction was allowed to
cool to rt and the solvent then removed under vacuum. Column
chromatography on silica (EtOAc/hexane 2:3, increasing to 2:1)
then afforded starting material (15 mg, 60%) followed by 8
(9 mg, 31%) as an oil. nmax/cmꢁ1 3469, 2935, 1778, 1757, 1736,
1656, 1455, 1436, 1379, 1323, 1283, 1198, 1168, 1100, 1058,
995, 927, 876, 758. dH (300 MHz, CDCl3) 1.17 (3 H, s, H-18),
1.24–2.11 (10 H, m), 2.27 (1 H, d, J 14.8, H-1), 2.62 (1 H, m,
H-13), 2.75 (1 H, d, J 10.8, H-6), 3.18 (1 H, d, J 10.8, H-5), 3.68
(1 H, m, H-2), 3.70 (3 H, s, ꢁCO2CH3), 3.82 (1 H, s, H-3), 3.98
(2 H, ddd, J 1.5, 3.3, 6.8, H-10), 4.84 (1 H, s, H-17), 4.97 (1 H, s,
H0-17), 5.16 (1 H, tdd, J 1.3, 2.7, 10.3, H-30), 5.26 (1 H, tdd, J 1.5,
3.2, 17.2, H0-30), 5.83 (1 H, m, H-20). dC (75 MHz, CDCl3) 14.9
(C-18), 16.2 (C-11), 31.4 (C-12), 33.4 (C-1), 36.7 (C-14), 38.8
(C-13), 44.5 (C-15), 51.1 and 51.2 (C-5 and C-6), 51.6 (C-8),
51.9 (ꢁCO2CH3), 52.0 (C-4), 53.6 (C-9), 70.3 (C-10), 76.6 (C-2
and C-3), 92.8 (C-10), 107.3 (C-17), 117.2 (C-30), 134.3 (C-20),
156.9 (C-16), 173.3 (C-7), 176.9 (C-19). m/z (EI) 402 (Mþ,
46%), 384 (16), 370 (94), 356 (16), 342 (37), 329 (18), 312 (51),
300 (55), 284 (77), 259 (49), 240 (75), 223 (68), 211 (45), 199
(92), 179 (67), 155 (46), 143 (54), 129 (58), 105 (63), 91 (100),
79 (53). m/z (HRMS) Calc. for Mþ, C23H30O6: 402.2042.
Found: 402.2046.
n
max/cmꢁ1 3468, 2936, 1758, 1736, 1658, 1455, 1436, 1379,
1319, 1284, 1196, 1162, 1101, 1072, 1052, 997, 968, 929, 879,
757. dH (300 MHz, CDCl3) 1.17 (3 H, s, H-18), 1.29–2.13 (10 H,
m), 2.29 (1 H, d, J 14.9, H-1), 2.62 (1 H, m, H-13), 2.74 (1 H, d, J
10.7, H-6), 3.19 (1 H, d, J 10.7, H-5), 3.32 (3 H, s, ꢁOCH3), 3.53
(1 H, m, H-2), 3.70 (3 H, s, ꢁCO2CH3), 3.85 (1H, s, H-3), 4.84
(1 H, s, H-17), 4.96 (1 H, s, H0-17). dC (75 MHz, CDCl3) 14.9 (C-
18), 16.1 (C-11), 31.4 (C-12), 33.1 (C-1), 36.6 (C-14), 38.8 (C-
13), 44.5 (C-15), 51.1 and 51.1 (C-5 and C-6), 51.6 (C-8), 52.0
(ꢁCO2CH3 and C-4), 53.5 (C-9), 57.6 (ꢁOCH3), 72.5 (C-3),
79.6 (C-2), 92.9 (C-10), 107.4 (C-17), 156.9 (C-16), 173.3 (C-7),
177.0 (C-19). m/z (EI) 376 (Mþ, 9%), 344 (67), 300 (12), 282
(15), 258(11), 240 (27), 180 (19), 130 (32), 91 (16), 68 (100). m/z
(HRMS) Calc. for Mþ, C21H28O6: 376.1886. Found: 376.1882.
ent-3a,10b-Dihydroxy-2b-methoxy-20-norgibberell-
16-ene-7,19-dioic Acid 19,10-Lactone 10
To a stirred, degassed suspension of NaH (240 mg, 10 mmol)
in hexamethylphosphoramide (HMPA) (5 mL) was added
dropwise freshly distilled propanethiol (0.7 mL, 7.72 mmol),
and the mixture stirred for 2 h, then left to stand for 1 h. To a
stirred solution of 7 (21 mg, 0.056 mmol) in HMPA (0.5 mL)
was added the thiolate solution (0.13 mL, 0.195 mmol) prepared
above. After 18 h, the reaction mixture was diluted with water
ent-2b-Allyloxy-3a,10b-dihydroxy-20-norgibberell-
16-ene-7,19-dioic Acid 19,10-Lactone 11
To a stirred, degassed suspension of NaH (240 mg, 10 mmol)
in HMPA (5 mL) was added dropwise freshly distilled

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
477
propanethiol (0.7 mL, 7.72 mmol), and the mixture stirred for
2 h, then left to stand for 1 h.
ent-3a,10b-Dihydroxy-2b-phenylmethoxy-20-
norgibberell-16-ene-7,19-dioic Acid 19,10-Lactone 12
To a stirred solution of 8 (52 mg, 0.13 mmol) in HMPA
(0.75 mL) was added the thiolate solution (0.3 mL, 0.45 mmol)
prepared above. After 18 h, the reaction mixture was diluted
with water (5 mL), acidified to pH 3 with cold 2.0 M HCl, and
then extracted with 20% 2-butanol in EtOAc (3 ꢀ 4 mL). The
combined organic layers were washed to pH 4.5 with saturated
aqueous KH2PO4, then washed with copper(II) chloride solution
(3 mL), back-extracting each time with 20% 2-butanol in
EtOAc. The combined organic layers were washed with brine
(15 mL) and dried (MgSO4). Concentration under vacuum
and column chromatography on silica (EtOAc/hexane/AcOH
1:1:0.001) afforded 11 (36 mg, 75%) as a white solid, which was
further purified by reverse-phase HPLC on C-18 stationary
phase (60% methanol and 40% water containing 0.1% acetic
acid). nmax/cmꢁ1 3436, 2935, 2878, 1753, 1656, 1454, 1424,
1380, 1319, 1280, 1202, 1168, 1102, 1058, 970, 924, 876. dH
(300 MHz, CDCl3) 1.22 (3 H, s, H-18), 1.34–2.07 (10 H, m),
2.28 (1 H, d, J 14.7, H-1), 2.64 (1 H, m, H-13), 2.78 (1 H, d, J
10.7, H-6), 3.14 (1 H, d, J 10.8, H-5), 3.68 (1 H, d, J 5.7, H-2),
3.84 (1 H, s, H-3), 3.98 (2 H, ddd, J 1.5, 3.3, 6.8, H-10), 4.86 (1 H,
s, H-17), 4.98 (1 H, s, H0-17), 5.16 (1 H, tdd, J 1.3, 2.7, 10.3,
H-30), 5.26 (1 H, tdd, J 1.5, 3.2, 17.2, H0-30), 5.83 (1 H, m, H-20).
dC (75 MHz, CDCl3) 15.1 (C-18), 16.2 (C-11), 31.4 (C-12), 33.5
(C-1), 36.6 (C-14), 38.7 (C-13), 44.3 (C-15), 50.8, 51.1 and 51.5
(C-5, C-6 and C-8), 52.0 (C-4), 53.6 (C-9), 70.3 (C-3), 73.4
(C-10), 77.2 (C-2), 92.8 (C-10), 107.6 (C-17), 117.3 (C-30), 134.2
(C-20), 156.6 (C-16), 176.8 (C-19), 177.2 (C-7). m/z (EI) 388
(Mþ, 16%), 371 (14), 352 (6), 342 (9), 329 (15), 313 (31), 301
(15), 286 (36), 268 (24), 258 (26), 241 (23), 229 (22), 214 (14),
201 (23), 199 (48), 179 (33), 157 (24), 145 (24), 131 (20), 129
(26), 119 (17), 105 (30), 91 (48), 79 (28). m/z (EI) Calc. for Mþ,
C22H28O6: 388.1886. Found: 388.1882.
To a degassed suspension of NaH (166 mg, 6.92 mmol) in
HMPA (3.5 mL) was added dropwise freshly distilledpropane
thiol (0.48 mL, 5.34 mmol), and the mixture stirred for 2 h
then left to stand for 1 h. To a stirred solution of 9 (55 mg,
0.122 mmol) in HMPA (0.5 mL) was added the thiolate solution
(0.28 mL, 0.426 mmol) prepared above. After 18 h, the reaction
mixture was diluted with water (5 mL), acidified to pH 3 with
cold 2.0 M HCl, and then extracted with 20% 2-butanol in
EtOAc (3 ꢀ 4 mL). The combined organic layers were washed
to pH 4.5 with saturated aqueous KH2PO4, then washed with
copper(II) chloride solution (2 ꢀ 3 mL), back-extracting each
time with 20% 2-butanol in EtOAc. The combined organic
layers were washed with brine (15 mL) and dried (MgSO4).
Concentration under vacuum and column chromatography on
silica (EtOAc/hexane/AcOH 2:1:0.001) afforded 12 (44 mg,
83%) as a white solid, which was further purified by reverse-
phase HPLC on C-18 stationary phase (70% methanol and
30% water containing 0.05% acetic acid). nmax/cmꢁ1 3401,
2930, 2876, 1752, 1709, 1657, 1453, 1378, 1318, 1278, 1201,
1166, 1100, 1059, 926, 878. dH (300 MHz, CDCl3) 1.17 (3 H, s,
H-18), 1.29–2.14 (10 H, m), 2.28 (1 H, d, J 15.1, H-1), 2.62 (1 H,
m, H-13), 2.62 (1 H, d, J 10.6, H-6), 3.19 (1 H, d, J 10.7, H-5),
3.71 (1 H, d, J 5.1, H-2), 3.76 (1 H, s, H-3), 4.47 (1 H, d, J 12.0,
H-10), 4.54 (1 H, d, J 12.0, H0-10), 4.85 (1 H, s, H-17), 4.97 (1 H,
s, H0-17), 7.22–7.31 (5 H, m, H-200-H-600). dC (75 MHz, CDCl3)
15.6 (C-18), 17.2 (C-11), 32.7 (C-12), 34.2 (C-1), 37.9 (C-14),
40.3 (C-13), 45.5 (C-15), 52.4 (C-8), 52.8 and 53.0 (C-5 and
C-6), 53.8 (C-4), 54.7 (C-9), 72.0 (C-10), 73.7 (C-3), 79.0 (C-2),
94.9 (C-10), 107.5 (C-17), 127.3 (C-400), 128.3 (C-200 and C-600),
129.1 (C-300 and C-500), 139.4 (C-100), 158.3 (C-16), 175.7 (C-7),
179.9 (C-19). m/z (EI) 438 (Mþ, 6%), 420 (4), 406 (1), 392 (3),
374 (1), 347 (2), 329 (10), 314 (43), 301 (9), 286 (27), 268 (35),
245 (16), 227 (20), 199 (49), 185 (6), 171 (16), 143 (15), 129
(16), 105 (19), 91 (100). m/z (HRMS) Calc. for Mþ, C26H30O6:
438.2042. Found: 438.2041.
ent-3a,10b-Dihydroxy-2b-phenylmethoxy-20-
norgibberell-16-ene-7,19-dioic Acid 7-Methyl
Ester 19,10-Lactone 9
To a stirred solution of 6 (64 mg, 0.145 mmol) in DCM (2.6 mL)
was added (C6F5)3B (24 mg, 0.047 mmol), followed by benzyl
alcohol (39 mL, 0.372 mmol), and the resulting mixture was
heated to reflux. After 5 h 30 min, the reaction was allowed to
cool to rt and the solvent was removed under vacuum. Column
chromatography on silica (EtOAc/hexane 1:8, increasing to 1:4)
then afforded 9 (55 mg, 65%) as an oil. nmax/cmꢁ1 3473, 2936,
2879, 1775, 1757, 1737, 1657, 1454, 1436, 1379, 1322, 1284,
1200, 1168, 1100, 1060, 996, 975, 955, 929, 914, 880, 734. dH
(300 MHz, CDCl3) 1.15 (3 H, s, H-18), 1.22–2.07 (10 H, m),
2.27 (1 H, d, J 14.8, H-1), 2.58 (1 H, m, H-13), 2.73 (1 H, d, J
10.8, H-6), 3.15 (1 H, d, J 10.7, H-5), 3.66 (3 H, s, ꢁCO2CH3),
3.68 (1 H, m, H-2), 3.84 (1 H, s, H-3), 4.46 (1 H, d, J 12.5, H-10),
4.53 (1 H, d, J 12.5, H0-10), 4.80 (1 H, s, H-17), 4.93 (1 H, d, J 1.3,
H0-17), 7.21–7.28 (5 H, m, H-200–H-600). dC (75 MHz, CDCl3)
15.1 (C-18), 16.3 (C-11), 31.5 (C-12), 33.3 (C-1), 36.7 (C-14),
38.9 (C-13), 44.6 (C-15), 51.1 and 51.2 (C-5 and C-6), 51.6
(C-8), 52.0 (ꢁCO2CH3), 52.1 (C-4), 53.6 (C-9), 71.0 (C-10),
73.2 (C-3), 76.6 (C-2), 92.8 (C-10), 107.3 (C-17), 127.3 (C-400),
127.5 (C-200 and C-600), 128.3 (C-300 and C-500), 137.7 (C-100),
156.7 (C-16), 173.1 (C-7), 177.2 (C-19). m/z (EI) 452 (Mþ, 2%),
434 (2), 421 (4), 406 (1), 392 (2), 361 (3), 343 (4), 328 (23), 314
(8), 296 (16), 268 (16), 239 (10), 223 (15), 199 (36), 185 (4), 171
(21), 143 (8), 105 (8), 91 (100). m/z (HRMS) Calc. for Mþ,
C27H32O6: 452.2199. Found: 452.2205.
ent-13-Acetoxy-2a,3a-epoxy-10b-hydroxy-16-oxo-17,20-
dinorgibberellane-7,19-dioic Acid 7-Methoxymethyl
Ester 19,10-Lactone 16
To a stirred solution of 15 (1.00 g, 2.39 mmol) in MeCN (50 mL)
at 08C was added 4 ꢀ 10ꢁ4 M Na2EDTA(aq) (1.5 mL), then a
mixture of NaHCO3 (2.01 g, 23.9 mmol) and Oxone (14.7 g,
23.9 mmol), followed by trifluoroacetone (5.35 mL,
59.8 mmol). After 15 h, the reaction was allowed to warm to rt,
concentrated under vacuum, and the resulting residue was then
taken up in water (90 mL) and EtOAc (90 mL). The aqueous
layer was separated and extracted with EtOAc (3 ꢀ 30 mL), and
the combined organic extracts were then washed with water
(2 ꢀ 30 mL). The combined aqueous layers were back-extracted
with EtOAc (2 ꢀ 20 mL), and the combined organic layers were
then washed with brine (100 mL) and dried (MgSO4). Concen-
tration under vacuum and column chromatography on silica
(EtOAc/hexane 2:3, increasing to 1:1) afforded 16 (1.69 g, 82%)
as a white foam, followed by epi-16 as a white foam (189 mg,
18%) that crystallized from EtOAc/hexane, mp 188–1908C.
n
max/cmꢁ1 2937, 2257, 1763, 1739, 1455, 1411, 1372, 1346,
1316, 1284, 1241, 1196, 1145, 1103, 1083, 1071, 1050, 1024,
991, 950, 923, 880, 834, 730. dH (300 MHz, CDCl3) 1.34 (3 H, s,
H-18), 1.65–1.90 (4 H, m), 2.02 (3 H, s, ꢁOCOCH3), 2.03–2.31
(5 H, m), 2.42 (1 H, d, J 16.9, H-1), 2.70 (1 H, m, H-14a),

RESEARCH FRONT
478
J. R. Crow, P. M. Chandler, and L. N. Mander
2.72 (1 H, d, J 10.3, H-6), 3.10–3.19 (3 H, m, H-2, H-3 and
H-5), 3.49 (3 H, s, ꢁCO2CH2OCH3), 5.15 (1 H, d, J 6.05,
ꢁCO2CH2OCH3), 5.38 (1 H, d, J 6.05, ꢁCO2CH2OCH3). dC
(75 MHz, CDCl3) 14.6 (C-18), 16.7 (C-11), 20.8 (ꢁOCOCH3),
30.5 (C-12), 31.7 (C-1), 37.4 (C-14), 47.6 (C-8), 47.7 (C-15),
48.0 (C-2 or C-3), 48.4 (C-4), 49.7 (C-2 or C-3), 51.3 (C-6),
53.9 (C-9), 56.4 (C-5), 58.2 (ꢁCO2CH2OCH3), 82.5 (C-13),
90.6 (C-10), 91.2 (ꢁCO2CH2OCH3), 169.8 (ꢁOCOCH3), 170.8
(C-7), 175.6 (C-19), 211.7 (C-16). m/z (EI) 433 (MHþ, 2%), 404
(4), 391 (16), 374 (62), 347 (44), 319 (40), 302 (77), 274 (26),
259 (27), 257 (43), 229 (41), 211 (34), 197 (21), 173 (21), 155
(32), 145 (17), 129 (16), 115 (12), 91 (27), 88 (16), 79 (15), 55
(30), 45 (100). m/z (HRMS) Calc. for Mþ, C23H28O8: 432.1784.
Found: 432.1781.
1158, 1101, 1079, 1054, 1025, 989, 965, 952, 919, 906, 872, 832,
801, 775, 732. dH (300 MHz, CDCl3) 1.31 (3 H, s, H-18), 1.33–
2.30 (8 H, m), 2.38 (1 H, dd, J 3.4, 11.5, H-14a), 2.71 (1 H, d, J
10.2, H-6), 2.99 (1 H, br s, ꢁOH), 3.10–3.18 (3 H, m, H-2, H-3
and H-5), 3.70 (3 H, s, ꢁCO2CH3). dC (75 MHz, CDCl3) 14.5
(C-18), 17.2 (C-11), 31.6 (C-1), 33.0 (C-12), 41.2 (C-14), 46.9
(C-8), 47.7 (C-15), 48.0 and 49.8 (C-2 and C-3), 48.4 (C-4), 51.8
(C-6), 52.4 (ꢁCO2CH3), 54.0 (C-9), 56.5 (C-5), 78.6 (C-13),
90.6 (C-10), 171.8 (C-7), 175.6 (C-19), 217.4 (C-16). m/z (EI)
362 (Mþ, 21%), 334 (6), 331 (16), 318 (29), 302 (100), 288 (30),
274 (22), 259 (19), 257 (17), 241 (7), 231 (14), 229 (28), 211
(17), 201 (14), 187 (17), 173 (26), 155 (35), 145 (21), 128 (16),
115 (17), 95 (10), 91 (36), 77 (24). m/z (HRMS) Calc. for Mþ,
C19H22O7: 362.1366. Found: 362.1364.
ent-10b,13-Dihydroxy-2a,3a-epoxy-20-norgibberell-16-
ene-7,19-dioic Acid 7-Methyl Ester 19,10-Lactone 18
ent-10b,13-Dihydroxy-2a,3a-epoxy-16-oxo-17,20-
dinorgibberellane-7,19-dioic Acid 7-Methoxymethyl
Ester 19,10-Lactone
To a stirred solution of the 13-hydroxy-16-nor ketone prepared
above (373 mg, 1.03 mmol) in DCM (18 mL) at 08C was added
Hu¨nig’s base (0.94 mL, 5.41 mmol) followed by TMSCl, and
the resulting mixture was allowed to warm to rt. After 18 h, the
reaction mixture was cooled to 08C and quenched by addition of
saturated aqueous NaHCO3 solution (1.5 mL), then diluted with
cold DCM (40 mL) and washed with cold water (10 mL). The
aqueous layer was back-extracted with DCM (5 mL), and the
combined organic layers were then washed with cold brine
(20 mL) and dried (MgSO4). Concentration under vacuum gave
the TMS ether 17, which was used directly in the next step.
To a stirred suspension of triphenylmethylphosphonium
iodide (2.49 g, 6.18 mmol) in THF (51.3 mL) was added drop-
wise 1.0 M KOtBu (5.7 mL) (prepared from KH (227 mg,
To a stirred solution of 16 (100 mg, 0.23 mmol) in THF (3 mL)
and EtOH (2.5 mL) was added 1.0 M aqueous K2CO3 (2.0 mL).
After 20 h, the reaction was diluted with 20% 2-butanol in
EtOAc (50 mL) and washed with water (2 ꢀ 10 mL). The com-
bined aqueous layers were back-extracted with 20% 2-butanol
in EtOAc (2 ꢀ 5 mL), and the combined organic layers were
then washed with brine (20 mL) and dried (MgSO4). Concen-
tration under vacuum and column chromatography on silica
(EtOAc/hexane 1:1, increasing to 2:1) afforded the title
compound (69 mg, 86% based on 88% conversion) as an oil.
n
max/cmꢁ1 3474, 2972, 2941, 2254, 1776, 1751, 1452, 1409,
1382, 1346, 1283, 1255, 1209, 1147, 1099, 1081, 1053, 1024,
989, 955, 941, 928, 906, 873, 832, 753, 733. dH (300 MHz,
CDCl3) 1.34 (3 H, s, H-18), 1.63–2.32 (8 H, m), 2.41 (1 H, dd, J
3.3, 11.5, H-14a), 2.74 (1 H, d, J 10.2, H-6), 3.11–3.19 (3 H, m,
H-2, H-3 and H-5), 3.44 (3 H, s, ꢁCO2CH2OCH3), 5.22 (1 H, d,
J 5.9, ꢁCO2CH2OCH3), 5.27 (1 H, d, J 5.9, ꢁCO2CH2OCH3).
dC (75 MHz, CDCl3) 14.6 (C-18), 17.3 (C-11), 31.7 (C-1), 32.9
(C-12), 41.3 (C-14), 46.9 (C-8), 47.5 (C-15), 48.0 (C-2 or C-3),
48.4 (C-4), 49.8 (C-2 or C-3), 51.8 (C-6), 54.3 (C-9), 56.4 (C-5),
58.1 (ꢁCO2CH2OCH3), 78.6 (C-13), 90.6 (C-10), 91.1
(ꢁCO2CH2OCH3), 171.0 (C-7), 175.6 (C-19), 217.3 (C-16). m/z
(EI) 392 (MH22þ, 22%), 362 (3), 349 (11), 347 (15), 331 (17), 319
(23), 302 (77), 288 (12), 274 (16), 259 (20), 257 (18), 255 (10),
241 (7), 229 (30), 211 (19), 197 (13), 173 (16), 155 (30), 143
(19), 131 (14), 116 (16), 105 (17), 91 (31), 77 (18), 65 (10), 55
(33), 45 (100). m/z (HRMS) Calc. for Mþ, C21H26O7: 390.1677.
Found: 390.1679.
t
5.67 mmol) and BuOH (5.7 mL)). After 15 min, stirring was
discontinued and the suspension allowed to settle, forming a
bright yellow solution.
To a stirred solution of the TMS ether (447 mg, 1.03 mmol) in
THF (12 mL) was added slowly via cannula the ylide solution
prepared above. After 2 h 50 min, the reaction was quenched
by addition of saturated aqueous NH4Cl solution (1.5 mL). The
reaction mixture was diluted with EtOAc (110 mL), washed
with brine (110 mL), dried (MgSO4) and concentrated under
vacuum. The resulting residue was taken up in MeOH
(30 mL), and pyridinium p-toluenesulphonate (PPTS) (259 mg,
1.03mmol) was added. After 25min, the reaction was con-
centrated under vacuum. Column chromatography on silica
(EtOAc/hexane 2:3) afforded 18 (291 mg, 78%) as a white foam.
n
max/cmꢁ1 3496, 3076,2957, 2938, 2881,2254, 1776, 1733,1661,
1449, 1437, 1382, 1343, 1315, 1284, 1256, 1197, 1166, 1101,
1079, 1054, 1024, 994, 967, 953, 922, 904, 873, 834, 815, 800,
754, 732. dH (300 MHz, CDCl3) 1.30(3H, s, H-18), 1.44–2.16(10
H, m), 2.27 (1 H, dd, J 4.0, 15.8, H-1), 2.65 (1 H, d, J 9.8, H-6),
3.07 (1 H, d, J 9.8, H-5), 3.12–3.17 (2 H, m, H-2 and H-3), 3.70 (3
H, s, ꢁCO2CH3), 4.94 (1H, s, H-17), 5.22 (1H, t, J 2.4, H0-17). dC
(75 MHz, CDCl3) 14.5 (C-18), 17.5 (C-11), 31.8 (C-1), 38.0 (C-
12), 42.7 (C-14), 45.7 (C-15), 48.1 (C-8), 48.2 and 49.8 (C-2 and
C-3), 49.8 (C-4), 50.4 (C-6), 52.1 (ꢁCO2CH3), 53.2 (C-9), 56.7
(C-5), 78.1 (C-13), 91.1 (C-10), 107.4 (C-17), 156.1 (C-16), 172.5
(C-7), 176.1 (C-19). m/z (EI) 360 (Mþ, 46%), 328 (100), 314 (7),
301 (47), 287 (9), 278 (24), 275 (25), 273 (7), 243 (10), 241 (11),
239 (16), 231 (72), 227 (14), 209 (16), 199 (14), 195 (12), 186
(13), 171 (11), 163 (53), 155 (23), 135 (32), 121 (26), 115 (22),
105 (17), 91 (42), 77 (35). m/z (HRMS) Calc. for Mþ, C20H24O6:
360.1573. Found: 360.1574.
ent-10b,13-Dihydroxy-2a,3a-epoxy-16-oxo-17,20-
dinorgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone
To a stirred solution of 16 (1.00 g, 2.30 mmol) in DCM (12 mL)
and MeOH (27 mL) was added K2CO3 (0.75 g). After 50 min,
the reaction was diluted with 20% 2-butanol in EtOAc (120 mL)
and washed with water (2 ꢀ 25 mL), and the combined aqueous
layers were then back-extracted with 20% 2-butanol in EtOAc
(2 ꢀ 30 mL). The combined organic layers were washed with
brine (150 mL) and dried (MgSO4). Concentration under vacu-
um and column chromatography on silica (EtOAc/hexane 1:1,
increasing to 2:1) afforded the title compound (797 mg, 96%) as
a white foam. nmax/cmꢁ1 3476, 2952, 2883, 2254, 1776, 1752,
1451, 1438, 1408, 1382, 1346, 1316, 1284, 1256, 1200, 1173,

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
479
ent-2b-Phenylmethoxy-3a,10b,13-trihydroxy-20-
norgibberell-16-ene-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone
72.3, 75.1, 77.2, 80.5, 82.5, 83.5, 92.0, 92.2, 94.6, 95.6, 96.2,
103.1, 107.7, 108.0, 127.4, 127.6, 128.2, 128.4, 137.7, 138.1,
154.0, 154.6, 173.0, 176.9. m/z (EI) 636 (Mþ, 1%), 605 (2), 554
(3), 552 (31), 512 (12), 468 (44), 450 (9), 446 (7), 440 (5), 401
(4), 377 (7), 359 (21), 345 (12), 327 (11), 299 (16), 275 (24), 257
(17), 255 (11), 239 (8), 227 (6), 181 (4), 169 (6), 121 (14), 91
(88), 85 (100). m/z (HRMS) Calc. for Mþ, C37H48O9: 636.3298.
Found: 636.3301.
To a stirred solution of 18 (65 mg, 0.181 mmol) and (C6F5)3B
(23 mg, 0.045 mmol) in 1,2-dichloroethane (1,2-DCE) (2.0 mL)
was added benzyl alcohol (19 mL, 0.181 mmol), and the result-
ing mixture was heated to 558C. After 7 h 30 min, a second
addition of benzyl alcohol (5 mL, 0.048 mmol) was made, and
after a further 23 h 30 min, the reaction was allowed to cool to
rt and the solvent then removed under vacuum. The resulting
residue was taken up in EtOAc (20 mL) and washed with satu-
rated aqueous NaHCO3 solution (2 ꢀ 15 mL), and then the
combined aqueous layers were back-extracted with EtOAc
(5 mL). The combined organic layers were washed with water
(7.5 mL), and the aqueous layer was then back-extracted with
EtOAc (4 mL). The combined organic layers were washed with
brine (30 mL) and dried (MgSO4). Concentration under vacuum
and column chromatography on silica (EtOAc/hexane 1:2,
increasing to 3:2) afforded starting material (21 mg, 32%) as an
oil followed by the benzyloxy adduct (40 mg, 47%, 70% based
on 68% conversion) as an oil. nmax/cmꢁ1 3459, 3067, 3032,
2937, 2251, 1760, 1737, 1660, 1644, 1513, 1497, 1462, 1380,
1329, 1283, 1253, 1204, 1167, 1097, 1058, 993, 962, 935, 908,
804, 734, 698. dH (300 MHz, CDCl3) 1.14 (3 H, s, H-18), 1.57–
2.11 (10 H, m), 2.25 (1 H, d, J 14.9, H-1), 2.35 (1 H, br s, ꢁOH),
2.70 (1 H, d, J 10.3, H-6), 3.18 (1 H, d, J 10.3, H-5), 3.68 (4 H, s,
ꢁCO2CH3 and H-2), 3.83 (1 H, s, H-3), 4.47 (1 H, d, J 12.4,
H-10), 4.51 (1 H, d, J 12.4, H0-10), 4.91 (1 H, s, H-17), 5.20 (1 H,
s, H0-17), 7.24–7.34 (5 H, m, H-200–H-600). dC (75 MHz, CDCl3)
14.8 (C-18), 17.2 (C-11), 33.0 (C-1), 38.2 (C-12), 42.9 (C-14),
45.1 (C-15), 49.7 (C-8), 50.8 and 51.7 (C-5 and C-6), 52.1 (C-4),
52.2 (ꢁCO2CH3), 52.6 (C-9), 71.0 (C-10), 73.0 (C-3), 76.6
(C-2), 78.2 (C-13), 92.7 (C-10), 107.4 (C-17), 127.4 (C-400),
127.6 (C-200 and C-600), 128.4 (C-300 and C-500), 137.6 (C-100),
156.5 (C-16), 173.2 (C-7), 177.4 (C-19). m/z (EI) 468 (Mþ, 8%),
437 (6), 408 (4), 377 (5), 359 (7), 344 (21), 315 (10), 300 (14),
271 (7), 255 (12), 243 (20), 215 (37), 201 (36), 187 (15), 168
(26), 135 (14), 121 (12), 91 (100). m/z (HRMS) Calc. for Mþ,
C27H32O7: 468.2148. Found: 468.2150.
ent-2b-Phenylmethoxy-3a,10b,13-trihydroxy-20-
norgibberell-16-ene-7,19-dioic Acid 19,10-Lactone 22
To a stirred, degassed suspension of NaH (240 mg, 10 mmol)
in HMPA (5 mL) was added dropwise freshly distilled propa-
nethiol (0.7 mL, 7.72 mmol), and the mixture stirred for 2 h,
then left to stand for 1 h. To a stirred solution of 18 (50 mg,
0.079 mmol) in HMPA (0.4 mL) was added the thiolate solution
(0.18 mL, 0.275 mmol) prepared above. After 16 h, the reaction
mixture was poured into a bilayer of water/saturated aqueous
NaHCO3 solution 10:1 (6 mL) and EtOAc (4 mL), and then the
organic layer was separated and extracted with water/saturated
aqueous NaHCO3 solution 10:1 (4 mL). The combined aqueous
layers were acidified to pH 3 with 1.0 M HCl, and then extracted
with EtOAc (3 ꢀ 5 mL). The combined organic layers were
washed with copper(II) chloride solution (2 ꢀ 4 mL), and the
combined aqueous layers were then back-extracted with EtOAc
(2 mL). The combined organic layers were then washed with
brine (10 mL) and dried (MgSO4). Concentration under vacuum
and chromatography through a short silica column (EtOAc/
hexane/AcOH 1:1:0.01) gave the crude carboxylic acid.
To a stirred solution of the crude acid in EtOH (4 mL) was
added PPTS (8 mg, 0.031 mmol), and the resulting mixture was
warmed to 608C. After 12 h, a second addition of PPTS (8 mg,
0.031 mmol) was made, and after a further 24 h, the reaction was
cooled to rt and concentrated under vacuum. Column chroma-
tography on silica (EtOAc/hexane/AcOH 5:1:0.01) afforded 22
(30 mg, 84%) as a white solid, which was further purified by
reverse-phase HPLC on C-18 stationary phase (50% methanol
and 50% water containing 0.1% acetic acid). Crystallization was
effected with EtOAc/hexane, mp 165–1678C. nmax/cmꢁ1 3402,
2929, 2881, 1755, 1718, 1660, 1496, 1431, 1379, 1329, 1280,
1253, 1205, 1168, 1097, 1054, 1002, 970, 953, 934, 903, 807,
773, 739, 698. dH (300 MHz, CDCl3) 1.18 (3 H, s, H-18), 1.64–
2.20 (8 H, m), 2.17–2.39 (3 H, m, H-1 and H-15), 2.60 (1 H, d, J
10.2, H-6), 3.21 (1 H, d, J 10.0, H-5), 3.71 (1 H, d, J 5.9, H-2),
3.76 (1 H, s, H-3), 4.47 (1 H, d, J 12.1, H-10), 4.54 (1 H, d, J 12.0,
H0-10), 4.93 (1 H, s, H-17), 5.19 (1 H, s, H0-17), 7.23–7.32 (5 H,
m, H-200-H-600). dC (75 MHz, CDCl3) 15.4 (C-18), 18.3 (C-11),
34.0 (C-1), 39.8 (C-12), 44.2 (C-14), 46.1 (C-15), 50.6 (C-8),
52.7, 53.3 and 53.8 (C-5, C-6 and C-9), 53.8 (C-4), 72.1 (benzyl-
C), 73.7 (C-3), 78.7 (C-13), 79.1 (C-2), 94.6 (C-10), 107.3
(C-17), 128.5 (C-400), 128.7 (C-200 and C-600), 129.2 (C-300 and
C-500), 139.6 (C-100), 158.2 (C-16), 175.8 (C-7), 180.0 (C-19).
m/z (EI) 454 (Mþ, 9%), 436 (6), 409 (3), 348 (5), 345 (16), 330
(28), 312 (19), 284 (21), 261 (10), 243 (21), 215 (42), 187 (10),
173 (7), 143 (6), 135 (13), 121 (15), 91 (100). m/z (HRMS) Calc.
for Mþ, C26H30O7: 454.1992. Found: 454.1995.
ent-3a,13-Bis-tetrahydropyranyloxy-10b-hydroxy-2b-
phenylmethoxy-20-norgibberell-16-ene-7,19-dioic Acid
7-Methyl Ester 19,10-Lactone 19
To a stirred solution of benzyloxy adduct prepared above
(75 mg, 0.16 mmol) and PPTS (24 mg, 0.096 mmol) in DCM
(6 mL) was added dihydropyran (117 mL, 1.28 mmol). After 7 h
30 min, the reaction was diluted with EtOAc (25 mL), washed
with brine/water 3:1 (16 mL) and dried (MgSO4). Concentration
under vacuum and column chromatography on silica (EtOAc/
hexane 1:8, increasing to 1:4) afforded 19 (80 mg, 79%) as an
oil. nmax/cmꢁ1 2944, 2870, 2248, 1778, 1737, 1660, 1518, 1497,
1454, 1440, 1378, 1353, 1330, 1284, 1253, 1199, 1160, 1120,
1091, 1076, 1032, 983, 936, 910, 870, 814, 734. dH (300 MHz,
CDCl3) 1.11 (3 H, s, H-18), 1.21 (6 H, s, H-18), 1.22 (3 H, s,
H-18), 1.24–2.30 (92 H, m), 2.71–2.77 (4 H, m, H-6), 3.14–3.20
(4 H, m, H-5), 3.39–3.68 (16 H, m), 3.69 (3 H, s, ꢁCO2CH3),
3.69 (3 H, s, ꢁCO2CH3), 3.70 (6 H, s, ꢁCO2CH3), 3.75–3.94
(8 H, m), 4.43–4.66 (16 H, m, THP and H-10), 4.93 (3 H, s, H-17),
4.95 (1 H, s, H-17), 5.08 (2 H, s, H0-17), 5.22 (2 H, s, H0-17),
7.22–7.35 (20 H, m, H-200–H-600). dC (75 MHz, CDCl3) 14.8,
15.3, 16.9, 17.4, 19.6, 20.1, 20.2, 21.0, 25.2, 25.3, 30.8, 31.6,
32.3, 33.7, 35.9, 38.2, 41.3, 41.9, 43.0, 43.7, 49.3, 50.1, 51.1,
51.5, 51.9, 52.1, 52.4, 52.9, 62.7, 62.9, 63.8, 64.0, 70.7, 71.0,
ent-2b-Phenethyloxy-3a,10b,13-trihydroxy-20-
norgibberell-16-ene-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone
To a stirred solution of 18 (69 mg, 0.192 mmol) and (C6F5)3B
(25 mg, 0.048 mmol) in 1,2-DCE (2.0 mL) was added

RESEARCH FRONT
480
J. R. Crow, P. M. Chandler, and L. N. Mander
phenethyl alcohol (23 mL, 0.192 mmol), and the resulting
mixture was heated to 558C. After 8 h, a second addition of
phenethyl alcohol (6 mL, 0.048 mmol) was made, and after a
further 22 h, reaction was allowed to cool to rt and the solvent
then removed under vacuum. The resulting residue was taken
up in EtOAc (25 mL) and washed with saturated aqueous
NaHCO3 solution (2 ꢀ 15 mL), and the combined aqueous
layers were then back-extracted with EtOAc (12 mL). The
combined organic layers were washed with brine (30 mL) and
dried (MgSO4). Concentration under vacuum and column
chromatography on silica (EtOAc/hexane 1:2, increasing
to 2:1) afforded starting material (30 mg, 43%) followed by
the title compound (51 mg, 55%, 98% based on 57% conver-
sion) as a white foam. nmax/cmꢁ1 3401, 2929, 2533, 1757,
1735, 1642, 1512, 1461, 1379, 1326, 1277, 1254, 1203, 1167,
1083, 993, 960, 935, 899, 757, 700. dH (300 MHz, CD3OD)
1.11 (3 H, s, H-18), 1.61–2.21 (11 H, m), 2.64 (1 H, d, J 10.2,
H-6), 2.77 (2H, td, J 2.8, 7.0, H-20), 3.20 (1 H, d, J 10.0, H-5),
3.56–3.68 (4 H, m, H-2, H-3 and H-10), 3.71 (3 H, s,
ꢁCO2CH3), 4.93 (1 H, s, H-17), 5.19 (1 H, t, J 2.1, H0-17),
7.14–7.28 (5 H, m, H-200–H-600). dC (75 MHz, CD3OD) 15.4
(C-18), 18.3 (C-11), 34.0 and 37.4 (C-1 and C-20), 39.7 (C-12),
44.1 (C-14), 46.1 (C-15), 50.1 (C-8), 52.4 (ꢁCO2CH3 and C-
4), 52.5 and 53.3 (C-5 and C-6), 53.7 (C-9), 71.9 (C-10), 73.9
(C-3), 78.7 (C-13), 79.9 (C-2), 94.6 (C-10), 107.6 (C-17),
127.1 (C-400), 129.3 (C-200 and C-600), 130.1 (C-300 and C-500),
140.3 (C-100), 157.9 (C-16), 174.5 (C-7), 179.8 (C-19). m/z (EI)
482 (Mþ, 3%), 328 (4), 239 (3), 168 (100), 137 (32), 104 (31),
99 (73), 93 (14), 75 (11). m/z (HRMS) Calc. for Mþ, C28H34O7:
482.2305. Found: 482.2308.
ent-2b-Phenethyloxy-3a,10b,13-trihydroxy-20-
norgibberell-16-ene-7,19-dioic Acid 19,10-Lactone 23
To a stirred, degassed suspension of NaH (240 mg, 10 mmol)
in HMPA (5 mL) was added dropwise freshly distilled propa-
nethiol (0.7 mL, 7.72 mmol), and the mixture stirred for 2 h,
then left to stand for 1 h. To a stirred solution of 20 (60 mg,
0.092 mmol) in HMPA (0.5 mL) was added the thiolate solution
(0.22 mL, 0.323 mmol) prepared above. After 16 h, the reaction
mixture was diluted with water (10 mL), acidified to pH 3 with
1.0 M HCl and then extracted with EtOAc (3 ꢀ 5 mL). The
combined organic layers were washed with copper(II) chloride
solution (2 ꢀ 4 mL), and the combined aqueous layers were
then back-extracted with EtOAc (2 mL). The combined organic
layers were then washed with brine (10 mL) and dried (MgSO4).
Concentration under vacuum and chromatography through a
short silica column (EtOAc/hexane/AcOH 1:1:0.01) gave the
crude carboxylic acid. To a stirred solution of the crude acid in
EtOH (2 mL) was added PPTS (23 mg, 0.092 mmol), and the
resulting mixture was warmed to 608C. After 24 h, the reaction
was cooled to rt and concentrated under vacuum. Column
chromatography on silica (EtOAc/hexane/AcOH 1:1:0.01,
increasing to 3:1:0.01) afforded 22 (30 mg, 69%) as a white
solid, which was further purified by reverse-phase HPLC on
C-18 stationary phase (50% methanol and 50% water containing
0.1% acetic acid).
Crystallization was effected from EtOAc/hexane, mp 139–
1418C. nmax/cmꢁ1 3419, 2932, 2878, 1755, 1603, 1496, 1477,
1453, 1430, 1380, 1329, 1281, 1252, 1205, 1167, 1097, 1051,
1003, 974, 952, 934, 902, 806, 771, 751, 700. dH (300 MHz,
CD3OD) 1.15 (3 H, s, H-18), 1.62–2.03 (8 H, m), 2.16–2.23 (2 H,
m, H-1 and H-15b), 2.36 (1 H, d, J 15.6, H-15a), 2.58 (1 H, d, J
10.2, H-6), 2.78 (2 H, td, J 2.7, 7.0, H-20), 3.18 (1 H, d, J 10.0,
H-5), 3.56–3.65 (4 H, m, H-2, H-3 and H-10), 3.76 (1 H, s, H-3),
4.93 (1 H, s, H-17), 5.19 (1 H, s, H0-17), 7.16–7.28 (5 H, m, H-
200–H-600). dC (75 MHz, CD3OD) 15.4 (C-18), 18.3 (C-11), 34.1
(C-1), 37.4 (C-20), 39.8 (C-12), 44.2 (C-14), 46.1 (C-15), 50.3
(C-8), 53.7 (C-4), 53.8 (C-9), 71.9 (C-10), 73.9 (C-3), 78.7 (C-
13), 80.0 (C-2), 94.7 (C-10), 107.3 (C-17), 127.1 (C-400), 129.2
(C-200 and C-600), 130.1 (C-300 and C-500), 140.3 (C-100), 158.2
(C-16), 180.1 (C-19). m/z (EI) 468 (Mþ, 28%), 450 (13), 422 (7),
404 (5), 364 (5), 346 (8), 328 (21), 301 (13), 290 (17), 284 (11),
273 (5), 255 (10), 239 (12), 229 (6), 199 (6), 169 (6), 163 (7), 136
(13), 121 (15), 105 (100), 91 (49), 79 (28). m/z (HRMS) m/z
Calc. for Mþ, C27H32O7: 468.2148. Found: 468.2147.
ent-3a,13-Bis-tetrahydropyranyloxy-10b-hydroxy-2b-
phenethyloxy-20-norgibberell-16-ene-7,19-dioic Acid
7-Methyl Ester 19,10-Lactone 20
To a stirred solution of the adduct prepared above (69 mg,
0.14 mmol) and PPTS (22 mg, 0.086 mmol) in DCM (8 mL) was
added dihydropyran (105 mL, 1.15 mmol). After 32 h, the reac-
tion was diluted with EtOAc (30 mL), washed with brine/water
3:1 (20 mL) and dried (MgSO4). Concentration under vacuum
and column chromatography on silica (EtOAc/hexane 1:8,
increasing to 1:2) afforded 20 (64 mg, 68%) as an oil. nmax/cmꢁ1
2944, 2870, 1778, 1736, 1518, 1496, 1454, 1378, 1353, 1325,
1284, 1252, 1199, 1160, 1119, 1077, 1032, 983, 936, 910, 870,
814, 752. dH (300 MHz, CDCl3) 1.09 (3 H, s, H-18), 1.19 (9 H, s,
H-18), 1.24–2.24 (92 H, m), 2.69–2.75 (4 H, m, H-6), 2.79–2.84
(4 H, m, H-20), 3.14–3.19 (4 H, m, H-5), 3.38–3.68 (24 H, m),
3.69 (6 H, s, ꢁCO2CH3), 3.70 (6 H, s, ꢁCO2CH3), 3.77–3.94
(8 H, m), 4.58–4.66 (8 H, m, THP), 4.93 (1 H, s, H-17), 4.96 (3 H,
s, H-17), 5.09 (2 H, s, H0-17), 5.22 (2 H, s, H0-17), 7.15–7.28 (20
H, m, H-200-H-600). dC (75 MHz, CDCl3) 14.8, 15.3, 16.9, 17.4,
19.5, 20.1, 21.0, 25.2, 25.3, 30.9, 31.6, 32.3, 33.6, 34.0, 35.9,
36.2, 36.4, 38.2, 41.2, 41.9, 43.1, 43.8, 49.3, 50.0, 51.1, 51.4,
51.9, 52.4, 52.8, 62.7, 62.9, 63.8, 64.0, 70.6, 70.8, 74.3, 75.5,
80.7, 82.5, 83.5, 91.9, 92.2, 94.7, 95.6, 96.2, 103.1, 107.7, 108.0,
126.0, 126.1, 128.2, 129.0, 138.7, 154.1, 154.6, 173.0, 176.9.
m/z (EI) (Mþ, 20%), 567 (33), 565 (12), 548 (10), 538 (14), 504
(11), 484 (11), 482 (15), 464 (12), 433 (8), 420 (11), 331 (6), 328
(7), 299 (10), 277 (5), 275 (22), 257 (9), 227 (4), 215 (11), 197
(4), 169 (10), 165 (8), 141 (9), 133 (12), 105 (100), 91 (34), 85
(88). m/z (HRMS) Calc. for Mþ, C38H50O9: 650.3455. Found:
650.3440.
ent-2b-(3-Phenylpropanoxy)-3a,10b,13-trihydroxy-
20-norgibberell-16-ene-7,19-dioic Acid 7-Methyl
Ester 19,10-Lactone
To a stirred solution of 18 (25 mg, 0.069 mmol) and (C6F5)3B
(9 mg, 0.017 mmol) in 1,2-DCE (1.25 mL) was added 3-
phenylpropanol (9 mL, 0.069 mmol), and the resulting mixture
was heated to 558C. After 7 h 15 min, the reaction was allowed
to cool to rt and a second addition of 2-phenylethanol (6 mL,
0.048 mmol) was made. After 17 h, the reaction was heated to
558C, and then after a further 8 h, allowed to cool to rt and the
solvent then removed under vacuum. The resulting residue was
taken up in EtOAc (15 mL) and washed with saturated aqueous
NaHCO3 solution (6 mL), and the combined aqueous layers
were then back-extracted with EtOAc (4 mL). The combined
organic layers were washed with brine (15 mL) and dried
(MgSO4). Concentration under vacuum and column chroma-
tography on silica (EtOAc/hexane 1:2, increasing to 3:2)

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
481
afforded starting material (4 mg, 16%) as an oil followed by
adduct (25 mg, 73%, 86% based on 84% conversion) as an oil.
n
dC (75 MHz, CDCl3) 14.9, 15.4, 17.3, 19.6, 20.3, 25.2, 25.2,
29.7, 30.9, 31.1, 31.9, 33.5, 33.8, 38.2, 43.1, 45.1, 49.7, 50.9,
50.9, 51.5, 52.0, 52.0, 52.4, 52.5, 52.9, 53.0, 62.9, 63.9, 68.3,
68.5, 74.1, 75.7, 76.5, 78.3, 80.9, 91.8, 92.1, 96.3, 103.1, 107.2,
125.6, 125.6, 128.2, 128.2, 128.6, 141.9, 142.1, 157.2, 172.9,
173.0, 176.7, 176.8. m/z (EI) 580 (Mþ, 12%), 549 (3), 498 (4),
496 (21), 478 (7), 450 (6), 434 (16), 432 (2), 395 (3), 360 (8), 333
(8), 318 (6), 298 (12), 275 (8), 255 (9), 239 (7), 203 (3), 166 (2),
135 (5), 118 (78), 91 (83), 85 (100). m/z (HRMS) Calc. for Mþ,
C34H44O8: 580.3036. Found: 580.3035.
max/cmꢁ1 3468, 2932, 2253, 1764, 1731, 1644, 1603, 1514,
1497, 1463, 1381, 1331, 1280, 1254, 1205, 1168, 1085, 1057,
994, 973, 962, 908, 814, 734, 701, 680. dH (300 MHz, CD3OD)
1.13 (3 H, s, H-18), 1.18–2.12 (12 H, m), 2.20 (1 H, d, J 14.9,
H-1), 2.57–2.67 (3 H, m, H-6, H-30 and O–H), 3.17 (1 H, d, J
10.2, H-5), 3.35 (2 H, t, J 6.3, H-10), 3.55 (1 H, d, J 5.0, H-2), 3.68
(3 H, s, ꢁCO2CH3), 4.93 (1 H, s, H-17), 5.19 (1 H, s, H0-17),
7.14–7.26 (5 H, m, H-200–H-600). dC (75 MHz, CD3OD) 14.7
(C-18), 17.3 (C-11), 31.0, 31.8 and 32.8 (C-1, C-20 and C-30),
38.1 (C-12), 42.7 (C-14), 45.2 (C-15), 49.7 (C-8), 50.8 and 51.7
(C-5 and C-6), 52.1 (ꢁCO2CH3 and C-4), 52.5 (C-9), 68.6
(C-10), 73.2 (C-3), 77.8 (C-2), 78.2 (C-13), 93.2 (C-10), 107.5
(C-17), 125.8 (C-400), 128.3 (C-200 and C-600), 128.4 (C-300 and
C-500), 141.6 (C-100), 156.1 (C-16), 173.3 (C-7), 177.9 (C-19).
m/z (EI) 496 (Mþ, 5%), 464 (3), 360 (4), 328 (9), 300 (5), 297
(3), 239 (4), 185 (3), 168 (100), 137 (21), 118 (87), 99 (56), 91
(52). m/z (HRMS) Calc. for Mþ, C29H36O7: 496.2461. Found:
496.2466.
ent-2b-(3-Phenylpropanoxy)-3a,10b,13-trihydroxy-20-
norgibberell-16-ene-7,19-dioic Acid 19,10-Lactone 24
To a stirred, degassed suspension of NaH (240 mg, 10 mmol)
in HMPA (5 mL) was added dropwise freshly distilled propa-
nethiol (0.7 mL, 7.72 mmol), and the mixture stirred for 2 h,
then left to stand for 1 h. To a stirred solution of 21 (38 mg,
0.057 mmol) and the mono-3-THP ether (15 mg, 0.026 mmol)
in HMPA (0.4 mL) was added the thiolate solution (0.19 mL,
0.291 mmol) prepared above. After 16 h, the reaction mixture
was diluted with water (10 mL) and acidified to pH 3 with 1.0 M
HCl, then extracted with EtOAc (3 ꢀ 5 mL). The combined
organic layers were washed with copper(II) chloride solution
(2 ꢀ 4 mL), and the combined aqueous layers were then back-
extracted with EtOAc (2 mL). The combined organic layers
were then washed with brine (10 mL) and dried (MgSO4).
Concentration under vacuum and chromatography through a
short silica column (EtOAc/hexane/AcOH 1:1:0.01) gave the
crude carboxylic acid. To a stirred solution of the crude acid in
EtOH (2 mL) was added PPTS (21 mg, 0.083 mmol), and the
resulting mixture was warmed to 608C. After 14 h, the reaction
was cooled to rt and concentrated under vacuum. Column
chromatography on silica (EtOAc/hexane/AcOH 1:1:0.01,
increasing to 3:1:0.01) afforded 24 (28 mg, 70%) as a white
solid, which was further purified by reverse-phase HPLC on
C-18 stationary phase (67% methanol and 33% water containing
0.1% acetic acid). Crystallization was effected from EtOAc/
hexane, mp 136–1388C. nmax/cmꢁ1 3417, 2932, 2880, 1755,
1602, 1496, 1453, 1431, 1379, 1328, 1280, 1252, 1205, 1167,
1099, 1043, 973, 933, 903, 806, 748, 700. dH (300 MHz,
CD3OD) 1.17 (3 H, s, H-18), 1.65–2.04 (10 H, m), 2.20–2.25
(2 H, m, H-1 and H-15b), 2.36 (1 H, d, J 15.8, H-15a), 2.60 (1 H,
d, J 10.2, H-6), 2.60–2.68 (2 H, m, H-30), 3.21 (1 H, d, J 10.0,
H-5), 3.38 (2 H, m, H-10), 3.56 (1 H, d, J 5.8, H-2), 3.65 (1 H, s,
H-3), 4.90 (1 H, s, H-17), 5.20 (1 H, s, H0-17), 7.11–7.27 (5 H, m,
H-200–H-600). dC (75 MHz, CD3OD) 15.5 (C-18), 18.4 (C-11),
32.7, 33.0 and 33.9 (C-1, C-20 and C-30), 39.8 (C-12), 44.2 (C-
14), 46.1 (C-15), 50.3 (C-8), 52.7 and 53.3 (C-5 and C-6), 53.8
(C-9), 69.4 (C-10), 74.0 (C-3), 78.7 (C-13), 79.9 (C-2), 94.6 (C-
10), 107.4 (C-17), 126.7 (C-400), 129.2 (C-200 and C-600), 129.7
(C-300 and C-500), 143.4 (C-100), 158.2 (C-16), 175.8 (C-7), 179.9
(C-19). m/z (EI) 482 (Mþ, 12%), 464 (5), 436 (3), 420 (5), 346
(6), 328 (11), 290 (4), 284 (5), 239 (3), 173 (3), 129 (5), 118
(100), 105 (12), 91 (72). m/z (EI) m/z Calc. for Mþ, C28H34O7:
482.2305. Found: 482.2302.
ent-3a,13-Bis-tetrahydropyranyloxy-10b-hydroxy-2b-
(3-phenylpropanoxy)-20-norgibberell-16-ene-7,19-dioic
Acid 7-Methyl Ester 19,10-Lactone 21 and
ent-10b,13-Dihydroxy-2b-(3-phenylpropanoxy)-3a-
tetrahydropyranyloxy-20-norgibberell-16-ene-
7,19-dioic Acid 7-Methyl Ester 19,10-Lactone
To a stirred solution of adduct prepared above (60 mg,
0.12 mmol) and PPTS (9 mg, 0.036 mmol) in DCM (4 mL) was
added dihydropyran (DHP) (55 mL, 0.61 mmol). After 23 h, a
second addition of PPTS (3 mg, 0.013 mmol) followed by DHP
(28 mL, 0.31 mmol) was made. After a further 30 h, the reaction
was diluted with EtOAc (20 mL), washed with brine/water 4:1
(12.5 mL) and dried (MgSO4). Concentration under vacuum and
column chromatography on silica (EtOAc/hexane 1:8, increas-
ing to 1:4) afforded 21 (46 mg, 58%) as an oil, followed by the
mono-3-THP ether (16 mg, 23%) as an oil.
21: nmax/cmꢁ1 2944, 2870, 1778, 1736, 1518, 1496, 1454,
1378, 1353, 1325, 1284, 1252, 1199, 1160, 1119, 1077, 1032,
983, 936, 910, 870, 814, 752. dH (300 MHz, CDCl3) 1.11 (6 H, s,
H-18), 1.21 (6 H, s, H-18), 1.25–2.27 (100 H, m), 2.62–2.67 (8 H,
m, H-30), 2.72–2.77 (4 H, m, H-6), 3.15–3.21 (4 H, m, H-5), 3.33–
3.70 (24 H, m), 3.71 (12 H, s, ꢁCO2CH3), 3.78–3.94 (8 H, m),
4.57 (2 H, s, THP-H1), 4.63 (6 H, s, THP-H1), 4.94 (1 H, s, H-17),
4.97 (3H, s, H-17), 5.10 (3H, s, H0-17), 5.23 (1H, s, H0-17), 7.13–
7.28 (20 H, m, H-200–H-600). dC (75 MHz, CDCl3) 14.9, 15.4,
17.0, 19.6, 20.1, 20.4, 24.2, 25.4, 30.9, 31.1, 31.7, 31.9, 33.4,
33.7, 38.2, 41.2, 43.8, 49.3, 51.1, 51.5, 51.9, 52.5, 52.9, 62.7,
62.9, 63.9, 68.3, 68.4, 74.1, 75.7, 80.9, 83.6, 92.0, 94.7, 96.3,
103.1, 107.7, 125.6, 128.2, 128.6, 141.9, 154.1, 173.1. m/z (EI)
664 (Mþ, 2%), 633 (1), 581 (4), 580 (12), 518 (3), 497 (9), 496
(21), 479 (8), 450 (6), 360 (7), 328 (3), 299 (8), 257 (7), 221 (5),
119 (21), 118 (28), 117 (6), 105 (4), 91 (42), 85 (100). m/z
(HRMS) Calc. for Mþ, C39H52O9: 664.3611. Found: 664.3614.
Mono-3-THP ether: nmax/cmꢁ1 3468, 2938, 2864, 1777,
1736, 1496, 1454, 1378, 1324, 1282, 1252, 1198, 1160, 1100,
1077, 1032, 998, 932, 904, 871, 812, 748, 701. dH (300 MHz,
CDCl3) 1.12 (3 H, s, H-18), 1.22 (3 H, s, H-18), 1.55–2.25 (50 H,
m), 2.62–2.67 (4 H, m, H-30), 2.71–2.76 (2 H, m, H-6), 3.17–
3.22 (2 H, m, H-5), 3.33–3.62 (12 H, m), 3.71 (3 H, s,
ꢁCO2CH3), 3.72 (3 H, s, ꢁCO2CH3), 3.76–3.91 (4 H, m),
4.58 (1 H, s, THP-H1), 4.65 (1 H, s, THP-H10), 4.94 (2 H, m,
H-17), 5.25 (2 H, m, H0-17), 7.13–7.28 (10 H, m, H-200–H-600).
ent-10b,17-Dihydroxy-3a-methoxymethoxy-20-
norgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone
To a stirred solution of 29 (8.41 g, 21.57 mmol) in THF
(300 mL) at 08C was added dropwise BH3ꢂDMS (11.24 mL,
17.98 mmol), and the resulting mixture was then allowed to
warm to rt. After 5 h 30 min, the reaction mixture was cooled to

RESEARCH FRONT
482
J. R. Crow, P. M. Chandler, and L. N. Mander
08C, and EtOH (24 mL) was added, followed by 2.0 M NaOAc
(60 mL) and then 30% H2O2 (43 mL). The mixture was allowed
to warm to rt and stirred for 16 h, then poured into water
(300 mL) and extracted with EtOAc (3 ꢀ 400 mL). The com-
bined organic extracts were washed with brine (400 mL) and
dried (MgSO4). Concentration under vacuum and column
chromatography on silica (EtOAc/hexane 1:2, increasing to 5:2)
afforded the title compound (7.7 g, 88%) as a white foam,
in benzene (45 mL) and pyridine (2.2 mL, 27.3 mmol). After
15 min, DMF (0.2 mL) was added dropwise. After a further 16 h,
the reaction mixture was filtered through oven-dried Celite
under an atmosphere of N2. The precipitate washed with ben-
zene (250 mL) and the combined organic layers were then
concentrated under vacuum. Residual oxalyl chloride was re-
moved by azeotropic distillation with benzene (3 ꢀ 40 mL) to
give the crude acid chloride.
n
max/cmꢁ1 3510, 2943, 2878, 1773, 1735, 1454, 1378, 1329,
To a stirred solution of diazomethane in Et2O (60 mL) at
08C was added via cannula the crude acid chloride in benzene
(100 mL). After 1 h, reaction was allowed to warm to rt. After a
further 17 h, the excess diazomethane was blown off under a
stream of N2. Concentration under vacuum and column chro-
matography on silica (EtOAc/hexane 1:2, increasing to 1:1)
afforded diazoketone 31 (1.5 g, 88%) as a yellow foam.
1279, 1254, 1217, 1197, 1148, 1098, 1033, 922, 873, 801, 731.
dH (300 MHz, CDCl3) 1.12 (3 H, s, H-18), 1.41–1.80 (13 H, m),
1.94–2.04 (2 H, m), 2.25–2.35 (2 H, m, H-13 and H-16), 2.65
(1 H, d, J 10.7, H-6), 3.14 (1 H, d, J 10.7, H-5), 3.39 (3 H, s,
ꢁOCH2OCH3), 3.55–3.69 (3 H, m, H-3, H-17 and H0-17), 3.70
(3 H, s, ꢁCO2CH3), 4.62 (1 H, d, J 7.0, ꢁOCH2OCH3), 4.74
(1 H, d, J 6.9, ꢁOCH2OCH3). dC (75 MHz, CDCl3) 14.8 (C-18),
15.3 (C-11), 20.3 (C-12), 25.0 (C-1), 27.7 (C-2), 33.3 (C-13),
38.2 (C-14), 40.0 (C-15), 43.1 (C-16), 51.5 (C-8), 51.6 (C-5),
51.9 (ꢁCO2CH3), 52.6 (C-6), 54.3 (C-4), 55.8 (ꢁOCH2OCH3),
56.2 (C-9), 64.3 (C-17), 75.5 (C-3), 93.8 (C-10), 95.8
(ꢁOCH2OCH3), 173.2 (C-7), 178.0 (C-19). m/z (EI) 408 (Mþ,
33%), 390 (4), 377 (20), 363 (9), 346 (66), 331 (22), 318 (100),
302 (71), 290 (57), 271 (26), 259 (34), 243 (86), 197 (15), 183
(31), 169 (18), 157 (21), 129 (27), 105 (37), 91 (56), 79 (34), 67
(20). m/z (HRMS) Calc. for Mþ, C22H32O7: 408.2148. Found:
408.2149.
n
max/cmꢁ1 3092, 2948, 2880, 2842, 2251, 2104, 1772, 1735,
1639, 1453, 1371, 1331, 1314, 1282, 1257, 1216, 1175, 1148,
1103, 1078, 1033, 988, 923, 872, 802, 733, 647. dH (300 MHz,
CDCl3) 1.10 (3 H, s, H-18), 1.14–2.07 (13 H, m), 2.52 (1 H, m,
H-13), 2.63 (1 H, d, J 10.9, H-6), 3.02 (1 H, m, H-16), 3.18 (1 H,
d, J 10.9, H-5), 3.38 (3 H, s, ꢁOCH2OCH3), 3.62 (1 H, s, H-3),
3.68 (3 H, s, ꢁCO2CH3), 4.62 (1 H, d, J 6.9, ꢁOCH2OCH3),
4.73 (1 H, d, J 7.0, ꢁOCH2OCH3), 5.24 (1 H, s, ꢁCOCHN2). dC
(75 MHz, CDCl3) 14.8 (C-18), 15.1 (C-11), 22.6 (C-12), 25.0
(C-1), 27.6 (C-2), 36.0 (C-13), 36.4 and 38.1 (C-14 and C-15),
50.5 (C-16), 51.4 (C-5), 51.6 (C-8), 51.8 (ꢁCO2CH3), 52.3
(C-6), 52.8 (ꢁCOCHN2), 54.3 (C-9), 54.8 (C-4), 55.8
(ꢁOCH2OCH3), 75.5 (C-3), 93.9 (C-10), 95.8 (ꢁOCH2OCH3),
172.7 (C-7), 178.0 (C-19), 195.0 (C-17). m/z (EI) 446 (Mþ,
17%), 418 (31), 390 (21), 373 (13), 356 (42), 328 (53), 300 (64),
271 (41), 253 (70), 227 (40), 183 (92), 155 (57), 129 (62), 105
(56), 91 (100). m/z (HRMS) Calc. for Mþ, C23H30N2O7:
446.2053. Found: 446.2057.
ent-10b-Hydroxy-3a-methoxymethoxy-20-
norgibberellane-7,17,19-trioic Acid 7-Methyl
Ester 19,10-Lactone 30
To a stirred solution of the 17-ol prepared above (580mg,
1.43 mmol) in acetone (70 mL) at 08C was added dropwise
Jones’ reagent, until TLC analysisindicated that the reaction was
complete. The reaction was then quenched by addition of iso-
propyl alcohol, diluted with EtOAc (200mL) and washed with
water (2 ꢀ 60 mL). The combined aqueous layers were back-
extracted with EtOAc (2 ꢀ 40 mL), and the combined organic
extracts were then washed with brine (100 mL) and dried
(MgSO4). Concentration under vacuum and column chroma-
tography on silica (EtOAc/hexane 3:1) afforded 30 (565mg,
94%) as a white foam. nmax/cmꢁ1 3167, 2949, 2882, 2254, 1774,
1735, 1703, 1454, 1438, 1378, 1328, 1281, 1256, 1217, 1197,
1175, 1148, 1096, 1033, 920, 873, 804, 732, 647. dH (300MHz,
CDCl3) 1.13 (3 H, s, H-18), 1.37–2.04 (13 H, m), 2.66 (1 H, d, J
10.8, H-6), 2.67 (1 H, m, H-13), 3.10 (1 H, m, H-16), 3.20 (1 H, d,
J 10.8, H-5), 3.40 (3 H, s, ꢁOCH2OCH3), 3.65 (1 H, s, H-3), 3.71
(3 H, s, ꢁCO2CH3), 4.64 (1 H, d, J 6.9, ꢁOCH2OCH3), 4.75
(1 H, d, J 7.0, ꢁOCH2OCH3). dC (75 MHz, CDCl3) 14.8 (C-18),
15.2 (C-11), 23.6 (C-12), 25.0 (C-1), 27.7 (C-2), 35.5 (C-13),
37.6 and 37.9 (C-14 and C-15), 47.1 (C-16), 51.6 (C-5), 51.8
(C-8), 52.0 (ꢁCO2CH3), 52.3 (C-6), 54.3 (C-4), 54.7 (C-9), 55.8
(ꢁOCH2OCH3), 75.5 (C-3), 93.8 (C-10), 95.8 (ꢁOCH2OCH3),
172.9 (C-7), 178.0 (C-19), 179.5 (C-17). m/z (EI) 422 (Mþ,
97%), 408 (6), 394 (45), 377 (17), 360 (88), 345 (23), 332 (100),
316 (81), 272 (50), 257 (71), 243 (58), 228 (21), 211 (23), 183
(41), 155 (30), 129 (35), 105 (43), 91 (58). m/z (HRMS) Calc. for
Mþ, C22H30O8: 422.1941. Found: 422.1939.
ent-10b-Hydroxy-3a-methoxymethoxy-17-oxo-20-nor-
12a,17-methanogibberellane-7,19-dioic Acid 7-Methyl
Ester 19,10-Lactone 32
To a stirred solution of Rh2(OAc)4 (103 mg, 0.22 mmol) in DCM
(600 mL) at reflux was added via syringe pump (0.6 mL minꢁ1
)
31 (2.00 g, 4.48 mmol) in DCM (110 mL). After addition was
complete, the reaction mixture was heated at reflux for a further
25 min, then allowed to cool to rt. Concentration under vacuum
and column chromatography on silica (EtOAc/hexane 1:1,
increasing to 3:1) afforded 32 (1.83 g, 88%) as a white foam,
n
max/cmꢁ1 2946, 2879, 2824, 2253, 1774, 1735, 1455, 1438,
1405, 1377, 1330, 1281, 1259, 1236, 1215, 1193, 1159, 1088,
1037, 986, 931, 919, 891, 880, 861, 830, 806, 784, 732, 647. dH
(300 MHz, CDCl3) 1.12 (3 H, s, H-18), 1.22–2.07 (12 H, m),
2.57–2.70 (3 H, m, H-13 and H-21), 2.70 (1 H, d, J 11.0, H-6),
2.83 (1 H, m, H-16), 3.17 (1 H, d, J 11.0, H-5), 3.39 (3 H, s,
ꢁOCH2OCH3), 3.62 (1 H, d, J 2.2, H-3), 3.70 (3 H, s,
ꢁCO2CH3), 4.62 (1 H, d, J 7.0, ꢁOCH2OCH3), 4.73 (1 H, d, J
7.0, ꢁOCH2OCH3). dC (75 MHz, CDCl3) 14.7 (C-18), 23.9
(C-11), 24.9 (C-1), 27.5 (C-2), 31.9 (C-12), 37.3 (C-14), 39.1
(C-13), 41.7 (C-15), 47.0 (C-21), 48.6 (C-16), 50.7, 51.1 and
51.6 (C-5, C-6 and C-9), 50.9 (C-8), 52.0 (ꢁCO2CH3), 54.4
(C-4), 55.9 (ꢁOCH2OCH3), 75.3 (C-3), 93.4 (C-10), 95.8
(ꢁOCH2OCH3), 172.4 (C-7), 177.9 (C-19), 222.9 (C-17). m/z
(EI) 18 (Mþ, 56%), 390 (92), 356 (33), 328 (100), 300 (97), 272
(39), 253 (81), 183 (22), 157 (17), 143 (21), 129 (24), 105 (32),
91 (47). m/z (HRMS) Calc. for Mþ, C23H30O7: 418.1992.
Found: 418.1988.
ent-17-Diazomethyl-10b-hydroxy-3a-methoxymethoxy-
20-norgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone 31
To a stirred solution of oxalyl chloride (3.65 mL, 41.8 mmol) in
benzene (110 mL) was added via cannula 30 (1.62 g, 3.84 mmol)

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
483
ent-10b,21-Dihydroxy-3a-methoxymethoxy-17-oxo-
20-nor-12a,17-methanogibberellane-7,19-dioic Acid
7-Methyl Ester 19,10-Lactone 33
and 43.0 (C-13 and C-16), 45.4 (C-15), 50.3, 50.4 and 51.5 (C-5,
C-6 and C-12), 51.3 (ꢁCO2CH3), 52.0 (ꢁCO2CH3), 53.4 (C-8),
53.5 (C-9), 53.6 (C-4), 55.9 (ꢁOCH2OCH3), 76.0 (C-3), 93.9
(C-10), 95.8 (ꢁOCH2OCH3), 173.7 and 173.9 (C-7 and C-17),
177.9 (C-19), 201.6 (C-21). m/z (EI) 464 (Mþ, 76%), 450 (14),
433 (90), 419 (21), 402 (75), 390 (14), 374 (100), 358 (39), 346
(62), 330 (88), 314 (54), 298 (59), 286 (43), 255 (22), 244 (37),
227 (19), 211 (25), 197 (23), 183 (73), 166 (23), 157 (31), 143
(40), 129 (52), 117 (31), 105 (53), 91 (78). m/z (HRMS) Calc. for
Mþ, C24H32O9: 464.2046. Found: 464.2049.
To a stirred solution of 32 (1.00 g, 2.39 mmol) in DCM (50 mL)
at 08C was added dropwise t-butyldimethylsilul triflate
(TBSOTf) (600 mL, 2.63 mmol) followed by Et3N (10 mL,
7.17 mmol). After 15 min, a second addition of TBSOTf
(250 mL, 1.10 mmol) was made, followed after a further 10 min
by a third addition of TBSOTf (250 mL, 1.10 mmol). After a
further 10 min, the reaction mixture was poured into water
(50 mL), and the aqueous layer was then separated and extracted
with DCM (2 ꢀ 50 mL). The combined organic layers were
dried (MgSO4) and concentrated under vacuum to give the crude
silyl enol ether.
ent-12b-Formyl-10b-hydroxy-3a-methoxymethoxy-
20-norgibberellane-7,17,19-trioic Acid 7-Methyl
Ester 19,10-Lactone 35
To a stirred solution of the resulting silyl enol ether (1.27 g,
2.39 mmol) in DCM (41 mL) at 08C was added via cannula
0.1 M dimethyldioxirane solution in acetone (72 mL). After
17 h, a second addition of 0.1 M dimethyldioxirane solution
in acetone (40 mL) was made. After a further 2 h, the reaction
mixture was concentrated under vacuum. Column chromato-
graphy on silica (EtOAc/hexane 1:3, increasing to 3:1) afforded
33 (909 mg, 88%) as a white foam, nmax/cmꢁ1 3437, 2946, 2252,
1775, 1738, 1455, 1438, 1377, 1331, 1277, 1253, 1234, 1216,
1196, 1149, 1090, 1029, 986, 929, 917, 890, 878, 835, 784, 730.
dH (300 MHz, CDCl3) 1.10 (3 H, s, H-18), 1.33–2.01 (11 H, m),
2.49 (1 H, t, J 8.1, H-12), 2.69 (1 H, d, J 10.7, H-6), 2.84 (1 H, t, J
8.3, H-16), 3.04 (1 H, dt, J 5.3, 8.1, H-13), 3.17 (1 H, d, J 10.7,
H-5), 3.37 (3 H, s, ꢁOCH2OCH3), 3.62 (1 H, d, J 2.1, H-3), 3.67
(1 H, s, H-21), 3.70 (3 H, s, ꢁCO2CH3), 4.61 (1 H, d, J 7.0,
ꢁOCH2OCH3), 4.71 (1 H, d, J 7.0, ꢁOCH2OCH3). dC (75 MHz,
CDCl3) 14.7 (C-18), 20.4 (C-11), 24.9 (C-1), 27.5 (C-2), 36.8
(C-14), 37.7 and 39.9 (C-12 and C-13), 41.4 (C-15), 46.9 (C-16),
50.9 (C-8), 51.3, 51.3 and 51.6 (C-5, C-6 and C-9), 52.0
(ꢁCO2CH3), 54.3 (C-4), 55.8 (ꢁOCH2OCH3), 75.3 (C-3),
80.3 (C-21), 93.3 (C-10), 95.8 (ꢁOCH2OCH3), 172.4 (C-7),
177.6 (C-19), 220.6 (C-17). m/z (EI) 434 (Mþ, 57%), 402 (100),
389 (16), 372 (27), 357 (12), 344 (33), 328 (63), 312 (46), 298
(36), 284 (32), 269 (59), 241 (27), 227 (19), 199 (25), 183 (72),
155 (37), 129 (41), 105 (39), 91 (65). m/z (HRMS) Calc. for Mþ,
C23H30O8: 434.1941. Found: 434.1943.
To a stirred solution of 34 (67 mg, 0.144 mmol) in MeOH
(25 mL) and water (1 mL) was added NaOH (320 mg,
8.0 mmol). After 20 min, the reaction mixture was poured into
1.0 M HCl (9.6 mL), and diluted with EtOAc (60 mL). The
organic layer was separated and washed with water (2 ꢀ
25 mL), and the combined aqueous layers were back-extracted
with EtOAc (2 ꢀ 25 mL). The combined organic layers were
extracted with saturated aqueous NaHCO3 solution
(2 ꢀ 20 mL), and the combined aqueous layers were acidified to
pH 3 with 1 M HCl and then extracted with EtOAc (3 ꢀ 30 mL).
The combined organic layers were washed with water
(3 ꢀ 30 mL), and the combined aqueous layers were then back-
extracted with EtOAc (2 ꢀ 20 mL). The combined organic
layers were washed with brine (200 mL) and dried (MgSO4).
Concentration under vacuum afforded 35 (63 mg, 97%) as a
white foam. nmax/cmꢁ1 3022, 2952, 2850, 2725, 2255, 1772,
1732, 1455, 1438, 1379, 1330, 1281, 1255, 1215, 1198, 1176,
1148, 1095, 1034, 991, 914, 875, 755, 733, 667, 648. dH
(300 MHz, CDCl3) 1.11 (3 H, s, H-18), 1.45–2.09 (11 H, m),
2.24 (1 H, m, H-13), 2.66 (1 H, d, J 11.0, H-6), 3.01 (1 H, m, H-
12), 3.23 (1 H, m, H-16), 3.24 (1 H, d, J 11.0, H-5), 3.39 (3 H, s,
ꢁOCH2OCH3), 3.64 (1 H, s, H-3), 3.71 (3 H, s, ꢁCO2CH3),
4.63 (1 H, d, J 7.0, ꢁOCH2OCH3), 4.74 (1 H, d, J 7.0,
ꢁOCH2OCH3), 9.63 (1 H, s, H-21). dC (75 MHz, CDCl3) 14.8
(C-18), 16.4 (C-11), 24.9 (C-1), 27.6 (C-2), 35.2 (C-13), 36.7
(C-14), 37.8 (C-15), 46.9 (C-16), 47.9 (C-12), 51.6 (C-8), 51.7
and 52.2 (C-5 and C-6), 52.1 (ꢁCO2CH3), 53.6 (C-9), 54.6
(C-4), 55.9 (ꢁOCH2OCH3), 75.3 (C-3), 93.2 (C-10), 98.5
(–OCH2OCH3), 172.5 (C-7), 178.4 (C-17 and C-19), 201.2 (C-
21). m/z (EI) 450 (Mþ, 21%), 422 (18), 388 (26), 360 (47), 332
(40), 285 (26), 255 (20), 183 (41), 155 (27), 129 (37), 91 (100).
m/z (HRMS) Calc. for Mþ, C23H30O9: 450.1890. Found:
450.1888.
ent-12a-Formyl-10b-hydroxy-3a-methoxymethoxy-
20-norgibberellane-7,17,19-trioic Acid 7,17-Dimethyl
Ester 19,10-Lactone 34
To a stirred solution of 33 (690 mg, 1.59 mmol) in DCM (25 mL)
and MeOH (25 mL) at 08C was added Pb(OAc)4 (1.06 g,
2.38 mmol). After 15 min, the reaction was poured into water
(100 mL) and EtOAc (100 mL). The aqueous layer was sepa-
rated and extracted with EtOAc (2 ꢀ 75 mL), and the combined
organic layers were then washed with brine (200 mL) and dried
(MgSO4). Concentration under vacuum and column chromato-
graphy on silica (EtOAc/hexane 2:3) afforded 34 (634 mg, 86%)
as a white foam. nmax/cmꢁ1 2950, 2888, 2725, 1774, 1733, 1454,
1437, 1374, 1329, 1307, 1284, 1246, 1200, 1167, 1150, 1097,
1031, 994, 973, 929, 871, 827, 753, 735. dH (300 MHz, CDCl3)
1.17 (3 H, s, H-18), 1.64–2.16 (11 H, m), 2.50 (1 H, m, H-13),
2.56 (1 H, d, J 6.9, H-6), 3.02–3.12 (2 H, m, H-12 and H-16),
3.13 (1 H, d, J 6.9, H-5), 3.35 (3 H, s, ꢁOCH2OCH3), 3.49 (3 H,
s, ꢁCO2CH3), 3.65 (1 H, s, H-3), 3.68 (3 H, s, ꢁCO2CH3), 4.59
(1 H, d, J 7.0, ꢁOCH2OCH3), 4.70 (1 H, d, J 7.0,
ꢁOCH2OCH3), 9.52 (1 H, s, H-21). dC (75 MHz, CDCl3) 14.5
(C-18), 15.4 (C-11), 24.7 (C-1), 26.7 (C-2), 35.9 (C-14), 38.0
ent-10b-Hydroxy-12b-hydroxymethyl-3a-
methoxymethoxy-20-norgibberellane-7,17,19-trioic
Acid 7-Methyl Ester 19,10-Lactone
To a stirred solution of 35 (100 mg, 0.22 mmol) in MeOH (4 mL)
was added NaBH4 (25 mg, 0.67 mmol). After 15 min, a second
addition of NaBH4 (25 mg, 0.67 mmol) was made, and after a
further 10 min, the reaction was quenched by addition of 0.5 M
HCl (3 mL). The reaction mixture was extracted with EtOAc
(3 ꢀ 15 mL), and the combined organic layers were then washed
with brine (100 mL) and dried (MgSO4). Concentration under
vacuum and column chromatography on silica (EtOAc/hexane/
AcOH 3:1:0.01, increasing to 5:1:0.01) afforded the title
compound (87 mg, 87%) as a colourless oil. nmax/cmꢁ1 3458,
2948, 1773, 1735, 1455, 1438, 1387, 1329, 1281, 1255, 1197,

RESEARCH FRONT
484
J. R. Crow, P. M. Chandler, and L. N. Mander
1175, 1148, 1108, 1095, 1036, 990, 923, 874, 804, 754, 705, 666.
dH (300 MHz, CDCl3) 1.12 (3 H, s, H-18), 1.19–2.01 (12 H, m),
2.44 (1 H, m, H-13), 2.65 (1 H, d, J 11.0, H-6), 3.13 (1 H, m, H-
16), 3.23 (1 H, d, J 11.0, H-5), 3.40 (3 H, s, ꢁOCH2OCH3), 3.64
(1 H, s, H-3), 3.71 (3 H, s, ꢁCO2CH3), 4.64 (1 H, d, J 7.0,
ꢁOCH2OCH3), 4.75 (1 H, d, J 7.0, ꢁOCH2OCH3). dC (75 MHz,
CDCl3) 14.8 (C-18), 19.6 (C-11), 25.0 (C-1), 27.6 (C-2), 36.5
(C-14), 37.8 (C-15), 38.0 (C-12), 38.5 (C-13), 47.3 (C-16), 51.7
and 52.4 (C-5 and C-6), 51.9 (C-8), 52.0 (ꢁCO2CH3), 54.3
(C-9), 54.4 (C-4), 55.9 (ꢁOCH2OCH3), 67.0 (C-21), 75.4 (C-3),
93.7 (C-10), 95.8 (ꢁOCH2OCH3), 172.7 (C-7), 177.9 and 178.0
(C-17 and C-19). m/z (EI) 452 (Mþ, 1%), 450 (12), 434 (3), 420
(48), 406 (2), 390 (23), 372 (91), 358 (26), 344 (100), 330 (44),
316 (50), 302 (23), 286 (40), 269 (21), 241 (22), 197 (24), 183
(32), 143 (31), 129 (33), 105 (57), 91 (73), 77 (38). m/z (HRMS)
Calc. for Mþ – CH3OH, C22H28O8: 420.1784. Found: 420.1786.
reaction mixture was diluted with EtOAc (10 mL) and water
(3 mL), and the aqueous layer was then separated and extracted
with EtOAc (2 ꢀ 5 mL). The combined organic layers were
washed with brine (20 mL) and dried (MgSO4). Concentration
under vacuum and column chromatography on silica (EtOAc/
hexane 2:1, increasing to 3:1) afforded starting material (18 mg,
10%) followed by the title compound (126 mg, 74%, 83% at
90% conversion) as a colourless oil. nmax/cmꢁ1 3523, 2947,
2888, 2826, 2253, 1773, 1737, 1454, 1438, 1376, 1366, 1330,
1278, 1246, 1215, 1197, 1175, 1149, 1098, 1037, 990, 922, 874,
859, 803, 732, 647. dH (300 MHz, CDCl3) 1.11 (3 H, s, H-18),
1.29–2.01 (12 H, m), 2.06 (3 H, s, ꢁOC(O)CH3), 2.12 (1 H, m,
H-13), 2.35 (1 H, m, H-16), 2.66 (1 H, d, J 11.0, H-6), 3.19 (1 H,
d, J 10.8, H-5), 3.39 (3 H, s, ꢁOCH2OCH3), 3.58–3.70 (3 H, m,
H-3 and H-17), 3.72 (3 H, s, ꢁCO2CH3), 3.83–4.02 (2 H, m,
H-21), 4.63 (1 H, d, J 7.0, ꢁOCH2OCH3), 4.74 (1 H, d, J 7.0,
ꢁOCH2OCH3). dC (75 MHz, CDCl3) 14.7 (C-18), 19.5 (C-11),
20.9 (ꢁOC(O)CH3), 24.9 (C-1), 27.6 (C-2), 30.6 (C-12), 36.3
(C-14), 36.8 (C-13), 39.6 (C-15), 43.2 (C-16), 51.6 (C-8), 51.7
and 52.6 (C-5 and C-6), 52.0 (ꢁCO2CH3), 54.3 (C-4), 55.8
(C-9), 55.8 (ꢁOCH2OCH3), 63.4 (C-17), 68.9 (C-21), 75.3
(C-3), 93.4 (C-10), 95.8 (ꢁOCH2OCH3), 171.1 (ꢁOC(O)CH3),
173.1 (C-7), 178.0 (C-19). m/z (EI) 480 (Mþ, 31%), 449 (20),
418 (21), 390 (43), 374 (33), 358 (48), 314 (46), 281 (22), 255
(55), 231 (31), 197 (27), 181 (62), 131 (100), 88 (55). m/z
(HRMS) Calc. for Mþ, C25H36O9: 480.2359. Found: 480.2360.
ent-12b-Acetoxymethyl-10b-hydroxy-3a-
methoxymethoxy-20-norgibberellane-7,17,19-trioic
Acid 7-Methyl Ester 19,10-Lactone 36
To a stirred solution of the alcohol prepared above (42 mg,
0.093 mmol) in DCM (6 mL) was added pyridine (60 mL,
0.743 mmol), Ac2O (70 mL, 0.743 mmol), and 4-dimethylamino-
pyridine (DMAP) (cat.). After 4 h, the solvent was removed
under vacuum. The resulting residue was taken up in pyridine
(0.5 mL), and to this stirred solution were added several ice
chips. After 15 min, the reaction mixture was diluted with DCM
(30 mL) and washed with water (3 ꢀ 10 mL). The combined
aqueous layers were back-extracted with DCM (2 ꢀ 10 mL),
and the combined organic layers were then washed with brine
(40 mL) and dried (MgSO4). Concentration under vacuum
and column chromatography on silica (EtOAc/hexane/AcOH
1:1:0.01, increasing to 2:1:0.01) afforded a 2:1 endo/exo mixture
of C-16 epimers of 36 (36 mg, 85%) as a colourless oil.
ent-12b-Acetoxymethyl-10b-hydroxy-3a-
methoxymethoxy-17-(2’-nitrophenylselenyl)-20-
norgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone 37
To a stirred, degassed solution of 17-ol prepared above
(18 mg, 0.038 mmol) and o-nitrophenylselenocyanate (21 mg,
0.091 mmol) in THF (1.3 mL) at 08C was added dropwise
n-Bu3P (88 mL, 0.15 mmol). After 30 min, the reaction was
allowed to warm to rt, and after a further 2 h, the reaction solvent
was removed under vacuum. The resulting residue was taken up
in EtOAc (25 mL) and filtered, and the precipitate was then
washed with EtOAc (3 ꢀ 10 mL). The combined organic layers
were washed with saturated aqueous NaHCO3 solution (7 mL),
with water (7 mL), with brine (20 mL) and then dried (MgSO4).
Concentration under vacuum and column chromatography on
silica (EtOAc/hexane 2:3) afforded 37 (22 mg, 88%) as a bright
yellow oil. nmax/cmꢁ1 2946, 1773, 1735, 1590, 1566, 1512,
1452, 1364, 1332, 1304, 1277, 1237, 1197, 1173, 1148, 1096,
1037, 990, 923, 874, 852, 784, 753, 732. dH (300 MHz, CDCl3)
1.11 (3 H, s, H-18), 1.13–2.08 (12 H, m), 2.07 (3 H, s, ꢁOC(O)
CH3), 2.14 (1 H, m, H-13), 2.46 (1 H, m, H-16), 2.64 (1 H, d,
J 11.0, H-6), 2.90 (2 H, m, H-17), 3.19 (1 H, d, J 11.0, H-5), 3.38
(3 H, s, ꢁOCH2OCH3), 3.63 (1 H, m, H-3), 3.72 (3 H, s,
ꢁCO2CH3), 3.77–4.07 (2 H, m, H-21), 4.62 (1 H, d, J 7.0,
ꢁOCH2OCH3), 4.73 (1 H, d, J 7.0, ꢁOCH2OCH3), 7.31 (1 H, m,
H-40), 7.44–7.55 (2 H, m, H-50 and H-60), 8.27 (1 H, dd, J 1.3,
8.2, H-30). dC (75 MHz, CDCl3) 14.6 (C-18), 19.4 (C-11), 21.0
(ꢁOC(O)CH3), 24.9 (C-1), 27.6 (C-2), 29.3 (C-17), 30.8 (C-12),
36.7 (C-14), 38.8 and 39.3 (C-13 and C-16), 44.6 (C-15), 51.7
and 52.6 (C-5 and C-6), 51.9 (C-8), 52.0 (ꢁCO2CH3), 54.3
(C-4), 55.8 (ꢁOCH2OCH3), 56.0 (C-9), 68.4 (C-21), 75.3 (C-3),
93.2 (C-10), 95.9 (ꢁOCH2OCH3), 125.4 (C-30), 126.5 and 128.9
(C-40 and C-60), 133.5 (C-10), 133.6 (C-50), 146.7 (C-20), 171.2
(ꢁOC(O)CH3), 172.9 (C-7), 177.8 (C-19). m/z (EI) 665 (Mþ,
27%), 635 (6), 601 (2), 588 (7), 543 (3), 500 (5), 483 (12), 431
n
max/cmꢁ1 2949, 2892, 2826, 2255, 1774, 1737, 1597, 1454,
1438, 1376, 1329, 1278, 1238, 1197, 1176, 1149, 1096, 1037,
991, 969, 921, 874, 862, 809, 791, 732, 704, 647. dH (300 MHz,
CDCl3) 1.10 (3 H, s, H-18), 1.20–2.07 (12 H, m), 2.01 (3 H, s,
ꢁOC(O)CH3), 2.42 (1 H, m, H-13), 2.64 (1 H, d, J 11.0, H-6),
3.11 (1 H, m, H-16), 3.21 (1 H, d, J 11.0, H-5), 3.38 (3 H, s,
ꢁOCH2OCH3), 3.62 (1 H, s, H-3), 3.70 (3 H, s, ꢁCO2CH3),
3.70–4.05 (2 H, m, H-21 and H0-21), 4.62 (1 H, d, J 7.0,
ꢁOCH2OCH3), 4.73 (1 H, d, J 7.0, ꢁOCH2OCH3). dC (75 MHz,
CDCl3) 14.6 (C-18), 19.3 (C-11), 20.9 (ꢁOC(O)CH3), 24.8
(C-1), 27.5 (C-2), 34.5 (C-12), 36.3 (C-14), 37.6 (C-15), 38.5
(C-13), 47.2 (C-16), 51.6 and 52.2 (C-5 and C-6), 51.7 (C-8),
51.9 (ꢁCO2CH3), 54.0 (C-9), 54.3 (C-4), 55.8 (ꢁOCH2OCH3),
68.1 (C-21), 75.4 (C-3), 93.4 (C-10), 95.8 (ꢁOCH2OCH3),
171.3 (ꢁOC(O)CH3), 172.7 (C-7), 178.0 and 178.2 (C-17 and
C-19). m/z (EI) 494 (Mþ, 68%), 477 (4), 463 (42), 449 (14), 432
(27), 417 (12), 404 (74), 388 (66), 372 (100), 357 (23), 344 (91),
328 (87), 288 (36), 269 (51), 255 (45), 241 (26), 223 (20), 195
(42), 155 (41), 129 (43). m/z (HRMS) m/z Calc. for Mþ,
C25H34O10: 494.2152. Found: 494.2157.
ent-12b-Acetoxymethyl-10b,17-dihydroxy-3a-
methoxymethoxy-20-norgibberellane-7,19-dioic
Acid 7-Methyl Ester 19,10-Lactone
To a stirred solution of acid 36 (175 mg, 0.35 mmol) in THF
(5 mL) at ꢁ188C was added dropwise over 4 min BH3ꢂDMS
(222 mL, 0.38 mmol), and the resulting mixture was allowed to
warm slowly to rt. After 17 h, the reaction was cooled to 08C, and
water (1.25 mL) was added, followed by K2CO3 (500 mg). The

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
485
(3), 399 (15), 385 (2), 339 (15), 327 (8), 311 (11), 297 (100), 281
(19), 269 (6), 255 (12), 237 (33), 221 (4), 209 (10), 195 (18), 155
(13), 141 (7), 131 (12), 117 (8), 106 (21), 91 (31). m/z (HRMS)
Calc. for Mþ, C31H39NO1080Se: 665.1771. Found: 665.1739.
CDCl3) 1.11 (3 H, s, H-18), 1.15–2.10 (13 H, m), 2.43 (1 H, m,
H-16), 2.64 (1 H, d, J 11.0, H-6), 2.87 (1 H, m, H-17), 2.96 (1 H,
m, H0-17), 3.19 (1 H, d, J 11.0, H-5), 3.31–3.45 (2 H, m, H-21),
3.39 (3 H, s, ꢁOCH2OCH3), 3.64 (1 H, s, H-3), 3.72 (3 H, s,
ꢁCO2CH3), 4.51 (1 H, d, J 11.9, H-100), 4.51 (1 H, d, J 12.0,
H0-100), 4.63 (1 H, d, J 7.0, ꢁOCH2OCH3), 4.74 (1 H, d, J 7.0,
ꢁOCH2OCH3), 7.24–7.34 (6 H, m, H-40 and H-2000–H-6000),
7.44–7.53 (2 H, m, H-50 and H-60), 8.28 (1 H, dd, J 1.4, 8.3,
H-30). dC (75 MHz, CDCl3) 14.7 (C-18), 20.2 (C-11), 24.9 (C-1),
27.6 (C-2), 29.8 (C-17), 32.0 (C-12), 37.1 (C-14), 39.4 (C-13
and C-16), 44.5 (C-15), 51.7 and 52.7 (C-5 and C-6), 52.0
(ꢁCO2CH3), 54.3 (C-4), 55.8 (ꢁOCH2OCH3), 56.3 (C-9), 73.3
and 75.6 (C-21 and C-100), 75.4 (C-3), 93.5 (C-10), 95.9
(ꢁOCH2OCH3), 125.3 (C-30), 126.4 and 129.0 (C-40 and C-60),
127.5 (C-2000, C-4000 and C-6000), 128.4 (C-3000 and C-5000), 133.6
(C-10), 133.8 (C-50), 138.3 (C-1000), 146.6 (C-20), 173.0 (C-7),
178.0 (C-19). m/z (EI) 713 (Mþ, 1%), 683 (32), 681 (17), 679
(11), 590 (30), 588 (16), 573 (9), 571 (8), 558 (4), 556 (3), 528
(4), 502 (5), 500 (5), 483 (9), 478 (16), 463 (13), 449 (6), 447
(28), 446 (13), 434 (10), 419 (14), 405 (13), 389 (21), 371 (8),
357 (26), 339 (24), 327 (27), 313 (100), 297 (76), 283 (41), 281
(38), 267 (20), 257 (35), 255 (47), 253 (52), 237 (37), 223 (35),
209 (22), 197 (63), 181 (58), 173 (54), 155 (45), 143 (51), 129
(48). m/z (HRMS) Calc. for Mþ, C36H41NO980Se: 611.1947.
Found: 611.1818.
ent-10b-Hydroxy-12b-hydroxymethyl-3a-
methoxymethoxy-17-(2’-nitrophenylselenyl)-20-
norgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone
To a stirred solution of acetate 37 (121 mg, 0.182 mmol) in
MeOH (4.5 mL) was added 1.0 M aqueous K2CO3 (0.35 mL).
After 1 h 30 min, the reaction was diluted with EtOAc (15 mL)
and washed with water (2 ꢀ 5 mL), and the combined aqueous
layers were then back-extracted with EtOAc (5 mL). The com-
bined organic layers were washed with brine (20 mL) and dried
(MgSO4). Concentration under vacuum and column chromato-
graphy on silica (EtOAc/hexane 3:2) afforded the title com-
pound (112 mg, 99%) as a bright yellow oil. nmax/cmꢁ1 3522,
2940, 2254, 1771, 1735, 1590, 1566, 1512, 1453, 1377, 1332,
1304, 1279, 1251, 1197, 1148, 1096, 1037, 989, 921, 874, 852,
784, 731, 647. dH (300 MHz, CDCl3) 1.11 (3 H, s, H-18), 1.13–
2.03 (12 H, m), 2.14 (1 H, m, H-13), 2.50 (1 H, m, H-16), 2.64
(1 H, d, J 11.0, H-6), 2.93 (2 H, m, H-17), 3.19 (1 H, d, J 11.0,
H-5), 3.39 (3 H, s, ꢁOCH2OCH3), 3.54 (2 H, dd, J 1.3, 6.8,
H-21), 3.63 (1 H, s, H-3), 3.72 (3 H, s, ꢁCO2CH3), 4.62 (1 H, d,
J 7.0, ꢁOCH2OCH3), 4.73 (1 H, d, J 7.0, ꢁOCH2OCH3), 7.32
(1 H, m, H-40), 7.46–7.55 (2 H, m, H-50 and H-60), 8.28 (1 H, dd,
J 1.3, 8.3, H-30). dC (75 MHz, CDCl3) 14.9 (C-18), 19.9 (C-11),
25.2 (C-1), 27.8 (C-2), 30.0 (C-17), 34.3 (C-12), 37.3 (C-14),
39.1 and 39.4 (C-13 and C-16), 44.9 (C-15), 52.0 and 53.0 (C-5
and C-6), 52.3 (ꢁCO2CH3), 54.6 (C-4), 56.1 (ꢁOCH2OCH3),
56.4 (C-9), 68.0 (C-21), 75.3 (C-3), 93.7 (C-10), 96.2
(ꢁOCH2OCH3), 125.7 (C-30), 126.7 and 129.3 (C-40 and C-60),
133.7 (C-10), 133.9 (C-50), 146.7 (C-20), 173.3 (C-7), 178.3
(C-19). m/z (EI) 623 (Mþ, 24%), 621 (13), 605 (3), 593 (7), 591
(12), 573 (31), 571 (22), 559 (7), 545 (3), 533 (4), 530 (54), 515
(13), 500 (6), 483 (22), 481 (10), 479 (4), 465 (4), 420 (4), 388
(18), 371 (8), 359 (11), 357 (52), 339 (12), 329 (32), 314 (92),
297 (52), 283 (35), 271 (20), 255 (90), 253 (37), 237 (32), 223
(29), 213 (17), 193 (20), 184 (39), 181 (46), 173 (41), 169 (35),
157 (28), 143 (41), 131 (45), 129 (52), 119 (33), 115 (31). m/z
(HRMS) Calc. for Mþ, C29H37NO980Se: 623.1634. Found:
623.1651.
ent-3a,10b-Dihydroxy-17-(2’-nitrophenylselenyl)-
12b-phenylmethoxymethyl-20-norgibberellane-
7,19-dioic Acid 7-Methyl Ester 19,10-Lactone
To a stirred solution of 38 (57 mg, 0.080 mmol) in isopropyl
alcohol (5 mL) was added tetrabromomethane (16 mg,
0.047 mmol), and the resulting mixture was heated to 808C.
After 24 h, the reaction was allowed to cool to rt and the solvent
was removed under vacuum. Column chromatography on silica
(EtOAc/petrol 1:1, increasing to 2:1) afforded the title com-
pound (48 mg, 89%) as a bright yellow oil. nmax/cmꢁ1 3481,
2934, 2875, 2253, 1768, 1735, 1590, 1566, 1511, 1453, 1437,
1376, 1360, 1332, 1304, 1279, 1251, 1198, 1171, 1096, 1060,
1038, 1027, 1004, 946, 923, 874, 852, 784, 731, 699, 680, 647.
dH (300 MHz, CDCl3) 1.12 (3 H, s, H-18), 1.14–2.11 (13 H, m),
2.43 (1 H, m, H-16), 2.65 (1 H, d, J 10.8, H-6), 2.88 (1 H, m,
H-17), 2.98 (1 H, m, H0-17), 3.19 (1 H, d, J 10.8, H-5), 3.32–3.45
(2 H, m, H-21), 3.72 (3 H, s, ꢁCO2CH3), 3.83 (1 H, s, H-3), 4.51
(1 H, d, J 11.9, H-100), 4.52 (1 H, d, J 12.0, H0-100), 7.25–7.34
(6 H, m, H-40 and H-2000–H-6000), 7.45–7.53 (2 H, m, H-50 and H-
60), 8.29 (1 H, dd, J 1.3, 8.2, H-30). dC (75 MHz, CDCl3) 14.6
(C-18), 20.2 (C-11), 27.2 and 28.0 (C-1 and C-2), 29.8 (C-17),
32.0 (C-12), 37.1 (C-14), 39.4 (C-13 and C-16), 44.5 (C-15),
51.1 and 52.6 (C-5 and C-6), 52.1 (C-8), 52.1 (ꢁCO2CH3), 54.6
(C-4), 56.3 (C-9), 70.0 (C-3), 73.3 and 75.6 (C-21 and C-100),
93.8 (C-10), 125.3 (C-30), 126.4 and 129.0 (C-40 and C-60), 127.5
(C-2000, C-4000 and C-6000), 128.4 (C-3000 and C-5000), 133.6 (C-50),
133.8 (C-10), 138.3 (C-1000), 146.7 (C-20), 173.1 (C-7), 178.1
(C-19). m/z (EI) 448 (3%), 434 (4), 343 (2), 267 (3), 241 (2), 219
(6), 191(5), 169 (9), 125 (12), 111 (23), 97 (41), 91 (52), 57 (94).
m/z (HRMS) Calc. for Mþ, C34H39NO880Se: 669.1841. Found:
669.1870.
ent-10b-Hydroxy-3a-methoxymethoxy-17-(2’-
nitrophenylselenyl)-12b-phenylmethoxymethyl-20-
norgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone 38
To a stirred solution of the 17-ol prepared above (65 mg,
0.104 mmol) in DCM (3 mL) was added benzyltri-
chloroacetimidate (38 mL, 0.204 mmol) followed by CF3SO3H
(2 mL, 0.020 mmol). After 2 h, the reaction solvent was removed
under vacuum, and the resulting residue was taken up in EtOAc
(15 mL) and filtered through a plug of silica to remove the
precipitated trichloroacetamide. The filtrate was washed with
saturated aqueous NaHCO3 solution (10 mL), with brine
(20 mL), and then dried (MgSO4). Concentration under vacuum
and column chromatography on silica (EtOAc/hexane 1:1)
afforded 38 (57 mg, 77%) as a bright yellow oil, nmax/cmꢁ1
2945, 2880, 2253, 1772, 1735, 1590, 1566, 1512, 1453, 1437,
1361, 1332, 1304, 1279, 1251, 1196, 1173, 1148, 1096, 1037,
989, 959, 922, 874, 852, 784, 732, 699, 647. dH (300 MHz,
ent-3a,10b-Dihydroxy-12b-phenylmethoxymethyl-
20-norgibberell-16-ene-7,19-dioic Acid 7-Methyl
Ester 19,10-Lactone 39
To a stirred solution of the 3b-ol prepared above (24 mg,
0.036 mmol) in THF (3 mL) at 08C was added 30% H2O2

RESEARCH FRONT
486
J. R. Crow, P. M. Chandler, and L. N. Mander
(1.5 mL). After 30 min, the reaction was allowed to warm to rt,
and after a further 17 h, the reaction was quenched by dropwise
addition of water (10 mL). The reaction mixture was diluted
with water (15 mL) and extracted with EtOAc (3 ꢀ 25 mL). The
combined organic layers were washed with saturated aqueous
NaHCO3 (3 ꢀ 15 mL), and the combined aqueous layers were
then back-extracted with EtOAc (2 ꢀ 10 mL). The combined
organic layers were washed with water (20 mL), and the aqueous
layer was then back-extracted with EtOAc (10 mL). The
combined organic layers were washed with brine and dried
(MgSO4). Concentration under vacuum and column chro-
matography on silica (EtOAc/hexane 2:3, increasing to 1:1)
afforded 39 (13 mg, 78%) as a colourless oil. nmax/cmꢁ1 3469,
2938, 2875, 1772, 1736, 1655, 1496, 1453, 1436, 1379, 1281,
1196, 1172, 1102, 1063, 1001, 946, 921, 875, 805, 751, 698. dH
(300 MHz, CDCl3) 1.13 (3 H, s, H-18), 1.23–2.12 (12 H, m),
2.56 (1 H, m, H-13), 2.69 (1 H, d, J 11.1, H-6), 3.21 (1 H, d, J
11.1, H-5), 3.31 (2 H, m, H-21), 3.70 (3 H, s, ꢁCO2CH3), 3.83
(1 H, s, H-3), 4.50 (1 H, d, J 12.0, H-10), 4.53 (1 H, d, J 12.0,
H0-10), 4.87 (1 H, s, H-17), 5.01 (1 H, s, H0-17), 7.27–7.38 (5 H,
m, H-200–H-600). dC (75 MHz, CDCl3) 14.6 (C-18), 20.7 (C-11),
27.4 and 28.0 (C-1 and C-2), 34.7 (C-14), 41.8 (C-12), 43.4
(C-13), 44.7 (C-15), 51.1 and 51.4 (C-5 and C-6), 51.7 (C-8),
52.0 (ꢁCO2CH3), 52.9 (C-9), 54.5 (C-4), 70.1 (C-3), 73.0 and
74.5 (C-21 and C-10), 93.8 (C-10), 108.0 (C-17), 127.5 (C-400),
127.5 (C-200 and C-600), 128.3 (C-300 and C-500), 138.4 (C-100),
155.7 (C-16), 173.0 (C-7), 178.2 (C-19). m/z (EI) 466 (Mþ,
16%), 448 (28), 434 (46), 420 (6), 406 (42), 388 (12), 375 (6),
358 (6), 343 (24), 328 (13), 313 (36), 297 (32), 267 (39), 223
(17), 197 (9), 181 (16), 129 (13), 105 (17), 91 (100). m/z
(HRMS) Calc. for Mþ, C28H34O6: 466.2355. Found: 466.2356.
(15), 343 (27), 327 (22), 313 (100), 297 (43), 281 (35), 267 (46),
253 (41), 235 (28), 223 (37), 209 (16), 197 (45), 181 (37), 169
(26), 155 (32), 145 (19), 129 (37). m/z (HRMS) Calc. for Mþ,
C33H42O7: 550.2931. Found: 550.2934.
ent-3a,10b-Dihydroxy-12b-phenylmethoxymethyl-20-
norgibberell-16-ene-7,19-dioic Acid 19,10-Lactone 40
To a stirred, degassed suspension of NaH (240 mg, 10 mmol)
in HMPA (5 mL) was added dropwise freshly distilled propa-
nethiol (0.7 mL, 7.72 mmol), and the mixture stirred for 2 h, then
left to stand for 1 h. To a stirred solution of the ester prepared
above (20 mg, 0.036 mmol) in HMPA (0.3 mL) was added the
thiolate solution (85 mL, 0.13 mmol). After 18 h, the reaction
mixture was diluted with water (5 mL), acidified to pH 3 with
cold 2.0 M HCl, and then extracted with 5% 2-butanol in EtOAc
(3 ꢀ 4 mL). The combined organic layers were washed to pH 4.5
with saturated aqueous KH2PO4, then with copper(II) chloride
solution (2.5 mL), back-extracting each time with 5% 2-butanol
in EtOAc. The combined organic layers were washed with brine
(15 mL) and dried (MgSO4). Concentration under vacuum and
purification through a short column of silica (EtOAc/hexane/
AcOH 2:3:0.01) gave the crude acid.
To a stirred solution of the crude acid in EtOH (2 mL) was
added PPTS (3 mg, 0.011 mmol), and the resulting mixture was
heated to 608C. After 24 h, the reaction was allowed to cool to rt,
then diluted with EtOAc (7.5 mL), washed with brine/water
3:1 (4 mL) and dried (MgSO4). Concentration under vacuum
and column chromatography on silica (EtOAc/hexane/AcOH
2:3:0.01, increasing to 3:2:0.01) afforded acid 40 (13 mg, 80%)
as a white solid, which was further purified by reverse-phase
HPLC on C-18 stationary phase (78% methanol and 22% water
containing 0.1% acetic acid). Crystallization was effected from
EtOAc/hexane, mp 128–1308C. nmax/cmꢁ1 3385, 2934, 2852,
1755, 1656, 1577, 1498, 1452, 1410, 1355, 1273, 1208, 1152,
1103, 1063, 1004, 955, 921, 876, 741, 698. dH (300 MHz,
CD3OD) 1.11 (3 H, s, H-18), 1.28–2.12 (12 H, m), 2.56 (1 H,
m, H-13), 2.58 (1 H, d, J 11.0, H-6), 3.17 (1 H, d, J 11.1, H-5),
3.38 (2 H, m, H-21), 3.67 (1 H, s, H-3), 4.53 (1 H, d, J 11.9, H-10),
4.53 (1 H, d, J 12.0, H0-10), 4.88 (1 H, s, H-17), 5.01 (1 H, s, H0-
17), 7.26–7.36 (5 H, m, H-200–H-600). dC (75 MHz, CD3OD) 15.2
(C-18), 21.6 (C-11), 28.5 and 29.2 (C-1 and C-2), 35.9 (C-14),
43.4 (C-12), 45.0 (C-13), 45.7 (C-15), 52.5 and 53.2 (C-5 and
C-6), 54.2 (C-9), 56.3 (C-4), 70.7 (C-3), 74.0 and 75.6 (C-21
and C-10), 95.6 (C-10), 108.1 (C-17), 128.6 (C-400), 128.8 (C-200
and C-600), 129.4 (C-300 and C-500), 139.9 (C-100), 157.7 (C-16),
175.7 (C-7), 180.7 (C-19). m/z (EI) 452 (Mþ, 20%), 434 (66),
416 (4), 406 (47), 390 (5), 388 (7), 361 (5), 343 (36), 331 (23),
325 (11), 313 (51), 297 (53), 285 (89), 267 (100), 259 (10), 241
(44), 223 (24), 197 (27), 181 (28), 169 (24), 157 (26), 143 (27),
129 (37). m/z (HRMS) Calc. for Mþ, C27H32O6: 452.2199.
Found: 452.2192.
ent-10b-Hydroxy-12b-phenylmethoxymethyl-3a-
tetrahydropyranyloxy-20-norgibberell-16-ene-7,19-dioic
Acid 7-Methyl Ester 19,10-Lactone
To a stirred solution of 39 (22 mg, 0.047 mmol) in DCM (2 mL)
was added PPTS (4 mg, 0.014 mmol) followed by DHP (22 mL,
0.236 mmol). After 17 h, the reaction mixture was diluted with
EtOAc (10 mL), washed with brine (10 mL) and then dried
(MgSO4). Concentration under vacuum and column chroma-
tography on silica (EtOAc/hexane 1:4, increasing to 2:3)
afforded the title compound (20 mg, 79%, 91% based on 87%
conversion) as a colourless oil followed by starting material
(2.9 mg, 13%). nmax/cmꢁ1 2941, 2852, 1774, 1737, 1656, 1496,
1453, 1377, 1353, 1281, 1199, 1173, 1150, 1117, 1102, 1076,
1062, 1033, 1004, 984, 945, 923, 907, 872, 810, 748, 698. dH
(300 MHz, CDCl3) 1.00 (3 H, s, H-18), 1.10 (3 H, s, H-18), 1.17–
2.07 (36 H, m), 2.48 (2 H, m, H-13), 2.59 (1 H, d, J 11.1, H-6),
2.60 (1 H, d, J 11.1, H-6), 3. 15 (1 H, d, J 11.1, H-5), 3. 16 (1 H, d,
J 11.1, H-5), 3.20–3.27 (4 H, m, H-21), 3.41–3.46 (2 H, m, THP),
3.56 (1 H, d, J 1.8, H-3), 3.62 (3 H, s, ꢁCO2CH3), 3.63 (3 H, s,
ꢁCO2CH3), 3.72 (1 H, s, H-3), 3.86–3.75 (2 H, m, THP), 4.42
(2 H, d, J 12.0, H-10), 4.46 (2 H, d, J 12.0, H0-10), 4.55 (1 H, m,
THP-H1), 4.64 (1 H, m, THP-H10), 4.79 (2 H, s, H-17), 4.93
(2 H, s, H0-17), 7.17–7.30 (10 H, m, H-200–H-600). dC (75 MHz,
CDCl3) 14.7, 15.1, 19.3, 20.7, 23.0, 25.3, 25.4, 26.9, 27.5, 28.0,
29.7, 30.9, 31.0, 34.8, 41.8, 43.5, 44.8, 51.5, 51.5, 51.7, 51.9,
52.8, 52.9, 54.1, 54.7, 62.3, 63.3, 72.0, 73.0, 74.5, 78.0, 93.5
(C-10), 93.8 (C-10), 94.0 (THP–C1), 102.1 (THP–C10), 107.8
(C-17), 127.5 (C-400), 127.5 (C-200 and C-600), 128.3 (C-300 and
C-500), 138.5 (C-100), 155.9 (C-16), 155.9 (C-16), 172.9 (C-7),
178.2 (C-19), 178.3 (C-19). m/z (EI) 550 (Mþ, 8%), 530 (2), 519
(4), 466 (64), 448 (34), 434 (56), 406 (47), 388 (9), 373 (8), 358
ent-21-Acetoxy-3a,10b-dihydroxy-17-(2’-
nitrophenylselenyl)-20-norgibberellane-7,19-dioic
Acid 7-Methyl Ester 19,10-Lactone
To a stirred solution of acetate 37 (71 mg, 0.11 mmol) in iso-
propyl alcohol (7 mL) was added tetrabromomethane (8 mg,
0.025 mmol), and the resulting mixture was heated to 808C.
After 3 h 40 min, a second addition of tetrabromomethane (4 mg,
0.013 mmol) was made. After a further 20 h, the reaction was
allowed to cool to rt and the solvent was removed under vacuum.
Column chromatography on silica (EtOAc/hexane 1:1,
increasing to 2:1) afforded the title compound (50 mg, 76%) as a

RESEARCH FRONT
Photoaffinity Labelling of Gibberellin Receptors
487
bright yellow oil. nmax/cmꢁ1 3479, 2945, 1768, 1734, 1590,
1566, 1511, 1452, 1366, 1332, 1304, 1249, 1171, 1097, 1048,
1037, 1004, 947, 923, 874, 852, 784, 754, 732, 666. dH
(300 MHz, CDCl3) 1.11 (3 H, s, H-18), 1.13–2.17 (13 H, m),
2.08 (3 H, s, ꢁOC(O)CH3), 2.46 (1 H, m, H-16), 2.66 (1 H, d, J
11.0, H-6), 2.91 (2 H, m, H-17), 3.20 (1 H, d, J 11.0, H-5), 3.72
(3 H, s, ꢁCO2CH3), 3.82 (1 H, d, J 2.1, H-3), 3.85–4.07 (2 H, m,
H-21), 7.31 (1 H, m, H-40), 7.45–7.55 (2 H, m, H-50 and H-60),
8.27 (1 H, dd, J 1.2, 8.3, H-30). dC (75 MHz, CDCl3) 14.6 (C-18),
19.5 (C-11), 21.0 (ꢁOC(O)CH3), 27.3 (C-1), 27.9 (C-2), 29.3
(C-17), 30.8 (C-12), 36.8 (C-14), 38.8 and 39.3 (C-13 and C-16),
44.6 (C-15), 51.1 and 52.5 (C-5 and C-6), 51.9 (C-8), 52.1
(ꢁCO2CH3), 54.6 (C-4), 56.0 (C-9), 68.4 (C-21), 69.9 (C-3),
93.6 (C-10), 125.4 (C-30), 126.5 and 128.9 (C-40 and C-60), 133.5
(C-10), 133.6 (C-50), 146.7 (C-20), 171.3 (ꢁOC(O)CH3), 173.0
(C-7), 178.0 (C-19). m/z (EI) 621 (Mþ, 20%), 619 (11), 591 (8),
587 (4), 544 (11), 540 (9), 482 (3), 439 (16), 437 (10), 419 (4),
387 (17), 359 (38), 341 (29), 327 (26), 299 (70), 297 (66), 281
(47), 255 (28), 237 (32), 235 (21), 195 (28), 186 (26), 169 (18),
143 (21), 106 (27), 91 (36). m/z (HRMS) Calc. for Mþ,
C29H35NO980Se: 621.1477. Found: 621.1465.
0.563 mmol) and the diol prepared above (342 mg, 0.704 mmol)
in DCM (15 mL) was added CF3SO3H (10 mL, 0.113 mmol).
After 22 h, a second addition of CF3SO3H (5 mL, 0.056 mmol)
was made. After a further 5 h, the reaction was diluted with
EtOAc (125 mL) and washed with saturated aqueous NaHCO3
(15 mL), with brine (70 mL), and then dried (MgSO4). Con-
centration under vacuum and column chromatography on silica
(EtOAc/hexane 1:10, increasing to 3:1) afforded the title com-
pound (142 mg, 28%) as a bright yellow oil, followed by starting
material (178 mg, 55%). nmax/cmꢁ1 3502, 2936, 2875, 1768,
1735, 1591, 1566, 1551, 1512, 1452, 1333, 1304, 1279, 1230,
1188, 1158, 1098, 1058, 1036, 1003, 950, 923, 874, 852, 820,
755, 731. dH (300 MHz, CDCl3) 1.12 (3 H, s, H-18), 1.16–2.18
(13 H, m), 2.46 (1 H, m, H-16), 2.66 (1 H, d, J 10.9, H-6), 2.90–
2.97 (2 H, m, H-17), 3.20 (1 H, d, J 10.9, H-5), 3.38–3.53 (2 H,
m, H-21), 3.72 (3 H, s, ꢁCO2CH3), 3.83 (1 H, s, H-3), 4.44 (2 H,
s, H-100), 7.31 (1 H, m, H-6000), 7.46–7.54 (4 H, m, H-50, H-60,
H-3000 and H-5000), 8.28 (1 H, d, J 8.1, H-30). dC (75 MHz, CDCl3)
14.6 (C-18), 20.1 (C-11), 27.2 (C-1), 27.8 (q, J 46, C-30000), 28.0
(C-2), 29.7 (C-17), 31.9 (C-12), 37.1 (C-14), 39.2 and 39.4
(C-13 and C-16), 44.6 (C-15), 51.1 and 52.6 (C-5 and C-6), 52.1
(C-8), 52.1 (ꢁCO2CH3), 54.6 (C-4), 56.3 (C-9), 70.0 (C-3), 76.1
and 76.3 (C-21 and C-100), 93.7 (C-10), 97.2 (C-2000), 121.8 (q, J
275.4, ꢁCF3), 125.4 (C-30), 126.4 (C-40 or C-60 and C-5000),
128.5 (C-6000), 128.9 (C-40 or C-60), 129.8 (C-4000), 133.6 (C-50),
133.6 (C-10), 136.7 (C-3000), 142.6 (C-1000), 146.7 (C-20), 173.1
(C-7), 178.1 (C-19). m/z (EI) 737 (1%), 708 (3), 672 (7), 631 (2),
591 (3), 459 (5), 443 (3), 363 (5), 357 (7), 327 (8), 316 (17),
278 (8), 232 (6), 219 (24), 203 (9), 147 (8), 111 (8), 97 (17),
83 (19). m/z (HRMS) Calc. for [Mþ ꢁ (C6H4NO2Se)ꢁOH],
C29H32N2O5F3I: 672.1317. Found: 672.1308.
ent-17-(2’-Nitrophenylselenyl)-3a,10b,21-trihydroxy-
20-norgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone
To a stirred solution of the diol prepared above (425 mg,
0.684 mmol) in MeOH (15 mL) was added 1.0 M K2CO3
(1.2 mL). After 1 h, the reaction was diluted with EtOAc
(75 mL) and washed with water (25 mL), and the aqueous layer
was then back-extracted with EtOAc (15 mL). The combined
organic layers were washed with brine (30 mL) and dried
(MgSO4). Concentration under vacuum and column chroma-
tography on silica (EtOAc/hexane 3:2, increasing to 4:1)
afforded the title compound (385 mg, 97%) as a bright yellow
oil. nmax/cmꢁ1 3469, 2938, 2875, 1765, 1590, 1566, 1511, 1453,
1379, 1332, 1304, 1280, 1251, 1203, 1170, 1096, 1051, 1037,
1002, 947, 923, 874, 852, 784, 754, 731, 666. dH (300 MHz,
CDCl3) 1.10 (3 H, s, H-18), 1.14–2.29 (13 H, m), 2.44 (1 H, m,
H-16), 2.64 (1 H, d, J 10.9, H-6), 2.93 (2 H, m, H-17), 3.18 (1 H,
d, J 11.0, H-5), 3.53 (2 H, m, H-21), 3.71 (3 H, s, ꢁCO2CH3),
3.80 (1 H, s, H-3), 7.31 (1 H, m, H-40), 7.46–7.51 (2 H, m, H-50
and H-60), 8.25 (1 H, m, H-30). dC (75 MHz, CDCl3) 14.6 (C-18),
19.6 (C-11), 27.2 (C-1), 27.9 (C-2), 29.7 (C-17), 33.9 (C-12),
37.0 (C-14), 38.8 and 39.1 (C-13 and C-16), 44.5 (C-15), 51.1
and 52.6 (C-5 and C-6), 52.0 (C-8), 52.1 (ꢁCO2CH3), 54.7
(C-4), 56.1 (C-9), 67.6 (C-21), 69.9 (C-3), 93.9 (C-10), 125.5
(C-30), 126.4 and 129.1 (C-40 and C-60), 133.4 (C-10), 133.7
(C-50), 146.6 (C-20), 173.2 (C-7), 178.3 (C-19). m/z (EI) 579
(Mþ, 23%), 544 (18), 482 (2), 439 (20), 359 (11), 345 (34), 333
(7), 317 (71), 313 (34), 299 (100), 297 (23), 281 (31), 271 (21),
255 (33), 253 (31), 237 (21), 223 (12), 221 (8), 196 (23), 187
(12), 181 (26), 173 (35), 157 (18), 143 (22), 131 (18), 117 (12),
106 (32), 91 (41). m/z (HRMS) Calc. for Mþ, C27H33NO880Se:
579.1371. Found: 579.1362.
ent-3a,10b-Dihydroxy-12b-(2’’-iodo-4’’-
(3’’’-trifluoromethyl-3’’’H-diazirin-3’’’-yl)
phenylmethoxymethyl)-20-norgibberell-16-ene-
7,19-dioic Acid 7-Methyl Ester 19,10-Lactone
To a stirred solution of the selenide prepared above (45 mg,
0.05 mmol) in CHCl3 (2 mL) was added portionwise over 1 h
Davis oxaziridine (14 mg, 0.055 mmol). After 1 h 15 min, the
reaction was diluted with EtOAc (15 mL) and washed with
1.0 M HCl (4 mL), and then with water (3 ꢀ 4 mL). The com-
bined aqueous layers were back-extracted with EtOAc
(2 ꢀ 4 mL), and the combined organic layers were then washed
with brine (20 mL) and dried (MgSO4). Concentration under
vacuum and column chromatography on silica (EtOAc/hexane
1:5, increasing to 1:2) afforded the title compound (29 mg, 84%)
as an oil. nmax/cmꢁ1 3469, 2936, 2875, 1769, 1736, 1654, 1616,
1551, 1449, 1436, 1379, 1340, 1280, 1231, 1188, 1158, 1103,
1060, 1032, 1001, 950, 921, 887, 820, 756, 735. dH (300 MHz,
CDCl3) 1.14 (3 H, s, H-18), 1.25–2.13 (12 H, m), 2.59 (1 H, m,
H-13), 2.71 (1 H, d, J 11.1, H-6), 3.22 (1 H, d, J 11.1, H-5), 3.42
(2 H, d, J 6.7, H-21), 3.71 (3 H, s, ꢁCO2CH3), 3.84 (1 H, s, H-3),
4.44 (1 H, d, J 13.6, H-10), 4.45 (1 H, d, J 13.6, H0-10), 4.89 (1 H,
s, H-17), 5.02 (1 H, s, H0-17), 7.25 (1 H, m, H-500), 7.46 (1 H, d, J
8.1, H-600), 7.56 (1 H, d, J 1.8, H-300). dC (75 MHz, CDCl3) 14.6
(C-18), 20.6 (C-11), 27.4 (C-1), 28.0 (C-2), 29.7 (C-3000, partially
obscured), 34.8 (C-14), 41.9 (C-12), 43.5 (C-13), 44.7 (C-15),
51.1 and 51.4 (C-5 and C-6), 51.7 (C-8), 52.0 (ꢁCO2CH3), 52.9
(C-9), 54.5 (C-4), 70.1 (C-3), 75.1 and 76.1 (C-21 and C-10),
93.8 (C-10), 97.1 (C-200), 108.1 (C-17), 121.8 (q, J 274.8,
ꢁCF3), 126.5 (C-500), 128.3 (C-600), 129.7 (C-400), 136.7 (C-300),
142.8 (C-100), 155.7 (C-16), 172.9 (C-7), 178.1 (C-19). m/z (EI)
ent-3a,10b-Dihydroxy-12b-(2’’’-iodo-4’’’-(3’’’’-
trifluoromethyl-3’’’’H-diazirin-3’’’’-yl)
phenylmethoxymethyl)-17-(2’-nitrophenylselenyl)-
20-norgibberellane-7,19-dioic Acid 7-Methyl Ester
19,10-Lactone
To
30H-diazirin-30-yl)phenylmethyl trichloroacetimidate (326 mg,
a
stirred solution of 2-iodo-4-(30-(trifluoromethyl)-

RESEARCH FRONT
488
J. R. Crow, P. M. Chandler, and L. N. Mander
755 (5%), 640 (3), 626 (13), 612 (3), 594 (7), 584 (16), 566 (6),
359 (5), 331 (4), 328 (14), 299 (63), 283 (32), 271 (35), 255 (23),
240 (15), 223 (23), 213 (11), 197 (21), 195 (31), 183 (12), 170
(100), 151 (32), 149 (28), 131 (22), 119 (23), 105 (31). m/z
(HRMS) Calc. For [M3þ ꢁ N2], C30H29O6F3I1: 669.0961.
Found: 669.0968.
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To a stirred solution of 3b-ol prepared above (26 mg,
0.037 mmol) in DCM (1.5 mL) was added PPTS (5 mg,
0.019 mmol) followed by DHP (24 mL, 0.26 mmol). After 24 h,
the reaction was diluted with EtOAc (15 mL), washed with brine
(15 mL) and dried (MgSO4). Concentration under vacuum and
column chromatography on silica (EtOAc/hexane 1:10, in-
creasing to 2:3) afforded the title compound (20 mg, 72%) as an
oil followed by starting material (7 mg, 27%). nmax/cmꢁ1 2938,
2874, 2854, 1775, 1739, 1617, 1551, 1455, 1436, 1378, 1340,
1281, 1231, 1188, 1157, 1118, 1103, 1077, 1061, 1034, 1005,
984, 950, 923, 885, 873, 819. dH (300 MHz, CDCl3) 1.08 (3 H, s,
H-18), 1.18 (3 H, s, H-18), 1.28–2.16 (36 H, m), 2.59 (2 H, m,
H-13), 2.68 (1 H, d, J 11.1, H-6), 2.69 (1 H, d, J 11.1, H-6), 3.22–
3.26 (2 H, m, H-5), 3.42 (4 H, m, H-21), 3.48–3.54 (2 H, m,
THP), 3.64 (1 H, s, H-3), 3.70 (3 H, s, ꢁCO2CH3), 3.71 (3 H, s,
ꢁCO2CH3), 3.81 (1 H, s, H0-3), 3.83–3.90 (2 H, m, THP), 4.44
(2 H, d, J 13.6, H-10), 4.45 (2 H, d, J 13.6, H0-10), 4.62 (1 H, m,
THP-H1), 4.73 (1 H, m, THP-H10), 4.88 (2 H, s, H-17), 5.01
(2 H, s, H0-17), 7.25 (2 H, m, H-500), 7.46 (2 H, d, J 8.0, H-600),
7.56 (1 H, s, H-300). dC (75 MHz, CDCl3) 14.7, 15.1, 19.3, 20.0,
20.6, 22.7, 23.1, 25.3, 25.4, 26.9, 27.3, 27.6, 27.8, 28.1, 29.3,
29.7, 30.3, 30.9, 31.0, 31.9, 34.8, 41.9, 43.5, 44.7, 44.7, 51.4,
51.5, 51.5, 51.7, 51.8, 51.9, 52.8, 52.8, 54.1, 54.5, 54.7, 62.4,
63.3, 72.0, 75.2, 76.1, 77.9, 93.5, 93.7, 95.0, 97.1, 102.1, 107.9,
120.0, 123.7, 126.5 (C-500), 128.3 (C-600), 129.7 (C-400), 136.7
(C-300), 142.8 (C-100), 155.8 (C-16), 155.8 (C-16), 172.9 (C-7),
178.2 (C-19), 178.3 (C-19). m/z (EI) 753 (1%), 700 (4), 682 (3),
374 (1), 316 (4), 313 (10), 281 (5), 253 (7), 241 (2), 219 (9), 212
(5), 181 (6), 170 (14), 153 (4), 143 (6), 119 (17), 105 (4), 91
(12), 85 (100). m/z (HRMS) Calc. for [Mþ ꢁ OCH3],
C34H37N2O6F3I1: 753.1648. Found: 753.1653.
6626. doi:10.1021/JA00541A071
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Accessory Publication
NMR spectra for all compounds are available on the Journal’s
website.
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Acknowledgements
The authors thank Carol Harding (CSIRO) for technical assistance.