Synthesis of steroid-porphyrin conjugates from oestradiol, oestrone, and lithocholic acid

Article abstract of DOI:10.1071/CH14080

The synthesis of porphyrin-steroid conjugates is examined using the natural steroids oestradiol, oestrone, and lithocholic acid as precursors. Two strategies differing in the timing of formation of the steroid-porphyrin linkage leading to four different construction motifs are explored. Two approaches are based on a strategy of introduction of steroidal components in the porphyrin-forming reaction involving condensation of steroidal-alkylaldehydes and pyrrole to give 5,10,15,20-tetrakis(steroidal-alkyl)porphyrins and differ in the way in which the required aldehyde is introduced to the steroidal component. In the other strategy, a steroidal component is introduced by post-porphyrin synthesis reactions and here also two approaches were explored, one involving nucleophilic substitution and the other esterification. Of the four approaches investigated, the most efficient and most versatile one attaches the steroidal components late in the sequence to a 5,10,15,20-tetra(ω-haloalkyl)porphyrin by a nucleophilic substitution reaction. In this way, a 5,10,15,20-tetrakis [oestrone-linked-heptyl)porphyrin was obtained in 47% yield.

Full text of DOI:10.1071/CH14080

CSIRO PUBLISHING
Aust. J. Chem. 2014, 67, 1632–1645
Full Paper
http://dx.doi.org/10.1071/CH14080
Synthesis of Steroid–Porphyrin Conjugates from Oestradiol,
Oestrone, and Lithocholic Acid*
A
A
A
A
Fargol Taba, Tze Han Sum, Paul J. Sintic, Ann H. Lundmark,
,
A B
and Maxwell J. Crossley
A
School of Chemistry, The University of Sydney, NSW 2006, Australia.
Corresponding author. Email: maxwell.crossley@sydney.edu.au
B
The synthesis of porphyrin–steroid conjugates is examined using the natural steroids oestradiol, oestrone, and lithocholic
acid as precursors. Two strategies differing in the timing of formation of the steroid–porphyrin linkage leading to four
different construction motifs are explored. Two approaches are based on a strategy of introduction of steroidal components
in the porphyrin-forming reaction involving condensation of steroidal-alkylaldehydes and pyrrole to give 5,10,15,20-
tetrakis(steroidal-alkyl)porphyrins and differ in the way in which the required aldehyde is introduced to the steroidal
component. In the other strategy, a steroidal component is introduced by post-porphyrin synthesis reactions and here also
two approaches were explored, one involving nucleophilic substitution and the other esterification. Of the four approaches
investigated, the most efficient and most versatile one attaches the steroidal components late in the sequence to a
5,10,15,20-tetra(v-haloalkyl)porphyrin by a nucleophilic substitution reaction. In this way, a 5,10,15,20-tetrakis
[oestrone-linked-heptyl)porphyrin was obtained in 47 % yield.
Manuscript received: 17 February 2014.
Manuscript accepted: 21 March 2014.
Published online: 26 May 2014.
Introduction
to that locale where the properties of the porphyrin, such as
generation of active oxygen species, can be utilized. For this
reason, there is an advantage in having the components con-
nected by a flexible linker and our syntheses have focussed on
formation of fuctionalized 5,10,15,20-tetraalkylporphyrins to
achieve the desired fluxional behaviour. This class of porphyrins
has very rarely been exploited in research; indeed, the number of
papers in the literature constitutes less than 0.02 % of the total
porphyrin-related output, because ofdifficulty in preparingthem
in sufficient quantities. They are now much more accessible
owing to a multigram methodology that we introduced in
The development of steroid–porphyrin conjugates for tailored
applications in anion sensing, molecular recognition, and drug
delivery is of increasing interest.
the steroidal component enables biomimicry of specialized
binding interactions found in biological systems, which pro-
vides an inbuilt mechanism for the accumulation of porphyrin
at specific sites.
jugates are useful lead compounds in targeted photodynamic
therapy (PDT) as they have been shown to bind tumour-
expressed saccharides.
been created using steroid–porphyrin scaffolds to exploit metal
and hydrogen-bonding interactions.
[
1–6]
The complex chirality of
[
7–9]
For instance, porphyrin–cholic acid con-
[
3,10]
Supramolecular receptors have also
[20]
[21]
1998, and on a smaller scale by the Lindsey methodology.
[2,11,12]
The lipophilic
In this work, the synthesis of a series of steroid–porphyrin
conjugates incorporating oestradiol 1, oestrone 2, and litho-
cholic acid 3 were prepared (Chart 1). Four different construc-
tion motifs were explored following two general synthetic
strategies, one by way of introduction of the steroidal compo-
nent in the porphyrin-forming reaction using appropriately
protected steroid-aldehydes and the second involving introduc-
tion of the steroid by exploiting peripheral functionalization
post-porphyrin synthesis.
Two methodologies are explored for each of these general
strategies. The latter approach involving post-porphyrin synthe-
sis peripheral functionalization allows the incorporation of
extended spacers such as phenyl and alkyl chains between
porphyrin and steroid. Chemical modification at the C-3 posi-
tion on the steroidal ring is also investigated, in particular, the
generation of hydroxyl functionality that would assist in lower-
ing the lipophilicity of such highly lipophilic compounds, as
steroid substituents also offer the potential to be incorporated
into cell membranes, via hormone receptors, which in effect can
[6,13,14]
anchor macrocycles to biological surfaces.
Although the utility of cholic acid derivatives has been well
[
15]
documented,
represented in the literature.
stimulators of the oestrogen receptor (ER) and a large number
oestrogen steroid conjugates are less well
[
16–19]
As oestrogens are strong
[
9]
of breast cancers have been shown to be ER-positive, it is
envisaged that the steroid can be used as a vehicle for the
delivery of cytotoxins to the overexpressed ER. Hence, oestro-
gen conjugates offer an attractive alternative for the treatment of
hormone-sensitive cancers.
An important consideration for the design of steroid–
porphyrin conjugates for potential pharmaceutical applications
is to retain the ability of the steroid component to interact at its
natural bindingsite, therebydelivering theporphyrin component
*
The corresponding author, Maxwell J. Crossley, is the winner of the 2013 RACI Leighton Memorial Medal.
Journal compilation Ó CSIRO 2014
www.publish.csiro.au/journals/ajc

Synthesis of Steroid–Porphyrin Conjugates
1633
well as the introduction or embedding of functionality amenable
to further synthetic elaboration. This allows the functionalized
steroid–porphyrin conjugates to be considered as potential
building blocks for the construction of complex biologically
active porphyrin arrays. Fig. 1 displays a quadrant representa-
tion of these functional objectives.
Method 1: Appending a Functionalized Chain in Order to
Install the Aldehyde Group in the Steroid Component
The ethyl-linked oestradiol–porphyrin conjugate 8 was
prepared using a modified 17b-oestradiol 6, which contains a
short spacer, to overcome steric issues that might arise during
its condensation reaction with pyrrole 7 (Scheme 1). The
required aldehyde component was installed by attachment of
an allyl group and its conversion into an appended propional-
dehyde unit. Thus, oestrone 2 was first converted into 3-O-
Results and Discussion
Two strategies for the synthesis of steroid–porphyrin conjugates
are explored and differ in the timing of the porphyrin-forming
reaction and incorporation of the steroidal component, such that
it is either a simultaneous process or a sequential process.
methyl-17b-oestradiol 4 in good yields following literature
Compound 4 was then converted into the 17b-
[22,23]
methods.
O-(3-hydroxypropyl) derivative 5 by treatment with NaH to
generate the 17b-alkoxide, alkylation with allyl bromide,
hydroboration of the resultant allyl ether using 9-borabicyclo
Strategy 1: Attachment of the Steroidal Component
in the Porphyrin-forming Reaction
[
3,3,1]nonane (9-BBN), and then oxidation of the hydroborane
Our first approach for the synthesis of steroid–porphyrin con-
jugates, via the condensation of an appropriate aldehyde and
pyrrole, required the synthesis of steroid aldehydes as these
compounds are not naturally occurring. Such an aldehyde group
can be installed by appending an appropriately functionalized
chain to the steroidal component or by functional group modi-
fication such as partial reduction of an existing carboxylic acid.
We have explored both strategies, which we now report.
to the 17b-O-(3-hydroxypropyl) ether with basic hydrogen
peroxide; compound 5 was obtained from diol 4 in overall
9
prepared by a different route involving an oestrone-17-ketal
intermediate in other work and converted into a 1 : 1 chlorin–
oestrogen ether.
The 17b-O-(3-hydroxypropyl) derivative 5 was oxidized
1 % yield. A 17b-O-(3-bromopropyl) analogue of 5 has been
[
19]
with pyridinium chlorochromate to afford the corresponding
1
OH
7b-(propanal-3-oxy)-steroid 6 in 55 % yield.
The ethyl-linked oestradiol–porphyrin conjugate 5,10,15,20-
H
tetrakis[2-(3-methyloxyestra-1,3,5(10)-trienyl-17b-oxy)ethyl]
porphyrin 8 was obtained in 12 % yield by trifluoroacetic
acid-catalyzed condensation of aldehyde 6 and pyrrole 7 at
room temperature under nitrogen, followed by treatment of
the product with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone
H
H
1
HO
HO
O
H
(
DDQ) (Scheme 1). Although the porphyrin yield is modest, it
H
H
2
3
is typical of the yields in porphyrin macrocycle synthesis in
which there is a sequence of at least 12 reactions involved in
the one pot.
Electrospray ionization (ESI) and Fourier transform ion
cyclotron resonance – electrospray ionization (FTICR-ESI)
mass spectrometry and spectroscopic data of the product were
fully consistent with that expected for free-base oestradiol–
O
OH
H
H
H
HO
1
H
porphyrin conjugate 8. The H NMR spectrum of the porphyrin
component ofconjugate 8showeda broad singlet atd ꢀ2.65ppm,
Chart 1.
due to the inner-periphery N–H protons, confirming formation
Steroidal groups put in place
during porphyrin synthesis
X
X
O
Boxes indicate positions for
further modification
N
H
N
N
H
N
O
O
X
O
Steroidal groups put in place
after porphyrin synthesis
O
Fig. 1. Schematic representation of the porphyrin macrocycle divided into quadrants to highlight the four
structural motifs of steroid–porphyrin conjugates and sites (enclosed in boxes) where synthetic elaboration is
possible that were generated in this work.

1
634
F. Taba et al.
of the porphyrin ring. This signal is broadened by exchange of
the protons on the inner periphery nitrogens that results in two
degenerate tautomeric forms, a feature of all symmetrically
substituted free-base porphyrins and the signal is signifi-
cantly upfield owing to the protons being inside the aromatic
5,10,15,20-tetraethylporphyrin, and again this indicates that
there is no significant p–p interaction between the porphyrin
and steroid aromatic rings.
[
24–27]
Oestradiol conjugates have not been extensively reported in
the literature previously but are of interest as they contain
biological hormones and as such can play are role in a variety
[
28]
ring current of the porphyrin macrocycle.
pyrrolic protons give rise to a slightly broadened singlet
because of the tautomeric exchange taking place, the
The eight b-
[
16]
of applications.
occurring of the oestrogens and the most potent of them in
humans.
Oestradiols are the most abundant naturally
(
4
[31]
J coupling to the inners protons is not resolved) at d 9.57.
The H and C NMR spectra indicated that the four
1
13
This reaction sequence (Scheme 1) highlights the relative
simplicity with which these molecules can be prepared, the
porphyrin synthesis serving to assemble the steroidal compo-
nents with their innate chirality into a more intricate molecule, in
this case having 20 stereogenic centres.
appended steroidal groups of conjugate 8 are in essentially
equivalent environments on the NMR timescale as there is only
one set of steroidal resonances in each case; this suggests that the
flexible alkyl linker connecting the steroid and porphyrin enti-
ties allows fluxional movement. The chemical shifts of the
protons of the aromatic ring of each of the four oestradiol units
Method 2: Installing the Aldehyde Group in the
Steroid Component by Modifying an Existing
Carboxylic Acid Group
0
0
0
lie at d 7.08, 6.66 and 6.60, due to the H-1 , H-2 , and H-4
protons respectively; these resonances are not significantly
different from those of the preceding steroids in the synthetic
sequence, indicating that there is not significant p–p interaction
between the porphyrin and steroid aromatic rings. In simple
cases of aromatic substrates where the substrate is not connected
directly to the porphyrin ring, a 1 : 1 p–p complex with the
porphyrin is often formed and very substantial upfield shifts of
the substrate aromatic protons are observed. In the case of the
conjugate 8, two factors significantly lessen such an interaction:
geometrical constraints imposed by the linkage unit and the
steric effects introduced by the non-planar steroid unit. Assign-
The other approach that we explored for synthesis of steroid–
porphyrin conjugates from an appropriate steroidal-aldehyde
started from a steroid with an existing carboxylic acid group.
This approach has been reported previously to convert
3-methoxymethyl-protected cholic acid into a steroid–porphyrin
[
3]
conjugate for saccharide sensing, and cholic acid and litho-
cholic acid have been converted into steroidal methyl ketones
[
32]
and reacted with pyrrole to give steroidal calix[4]pyrroles. In
the present work, lithocholic acid 3 was used as its side chain
carboxylic acid group can be readily converted into the corre-
sponding aldehyde after protection of the 3-hydroxyl group. In
principle, other steroids such as cholesterol could be used but
installing the requisite aldehyde group is a lot more difficult.
The reaction sequence used for the preparation of three
different lithocholic acid-derived O-protected porphyrin
conjugates 12a–c is shown in Scheme 2. 3a-Hydroxy-5b-
cholan-24-oic acid (lithocholic acid) 3 was converted into
the corresponding 3a-methoxy-, 3a-methoxymethoxy-, and
1
13
ment of H and C NMR signals due to the steroidal compo-
[
29]
nents was aided by an extensive earlier studies of 400 steroids
[
23,30]
and of 17a-oestradiol ethers.
The UV-visible spectrum of
the conjugate 8 revealed a very strong B (Soret) band and four
major distinct peaks in the Q band region that are typical of a
free-base porphyrin; the B band occurred at lmax 419 nm and the
Q bands at lmax 519, 553, 597, and 654 nm, wavelengths that are
almost identical to those seen in the spectrum of the simpler
OH
O
O
OH
(ii)
O
H
H
H
(
i)
H
H
H
H
H
H
H CO
H CO
H CO
6
3
4
3
5
3
OCH3
H CO
3
(
iii)
H
H
N
H
H
H
H
H
O
O
7
O
O
N
H
N
N
H
N
H
H
H
H
H
H
8
OCH3
H CO
3
Scheme 1. Reagents and conditions: (i) (a) NaH, NaI, K
nonane (9-BBN), THF, 1 h, (c) NaOH, H , 2 h; (ii) pyridinium chlorochromate, CH
iii) (a) TFA, rt under N , 24 h, (b) 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), rt, 2 h.
2
3
CO , dry THF, allyl bromide, 1 h, (b) 9-borabicyclo[3,3,1]
2
O
2
2
2
Cl , room temperature (rt), 16 h;
(
2

Synthesis of Steroid–Porphyrin Conjugates
1635
3
respectively using a four-step procedure. The procedures used
in this work are modifications of already reported methods
and the aldehydes were obtained in good yields overall. The
a-butyldimethylsilyloxy-functionalized aldehydes 11a–c
attaching an appropriately functionalized chain at an hydroxyl
group, is more general.
[33–36]
Strategy 2: Attachment of the Steroidal Component
to a Preformed Porphyrin
aldehyde 11a and the O-methoxymethyl-protected series 9b,
1
0b, and 11b are new compounds. The known compounds in
The second strategy that we explored for the synthesis of
steroid–porphyrin conjugates was to couple a steroidal entity to
a porphyrin macrocycle. This has the advantage of being more
economical in the use of steroid as it is now not used in the
low-yielding porphyrin-forming process. We envisaged that
the tetraalkylporphyrin motif is beneficial as the alkyl chains
help introduce a spacer between the porphyrin and steroid and
so we developed a new class of porphyrins, v-functionalized
some cases have only rudimentary partial characterization in the
literature; for completeness, we include more complete charac-
terization of these compounds in the Supplementary Material.
[
21]
Condensation of pyrrole 7 and aldehydes 11a–c,
using
analogous conditions to those used for formation of the conju-
gate 8 above, gave the steroid–porphyrin conjugates 12a, 12b,
and 12c in yields of 12, 3, and 3.5 % respectively (Scheme 2). In
each case, mass spectra (ESI and FTICR-ESI) and spectroscopic
data were fully consistent with that expected for the appropriate
free-base porphyrin. Again the equivalence of the corresponding
5,10,15,20-tetraalkylporphyrins, that can undergo nucleophilic
substitution reactions on the side chains.
1
proton resonances in the H NMR spectrum within each com-
Method 3: Introduction of the Steroid Component
by Nucleophilic Substitutions on 5,10,15,20-
Tetra(7 -iodoheptyl)porphyrin
pound indicated that the four appended steroidal groups are in
essentially equivalent environments on the NMR timescale.
The synthesis of the steroid–porphyrin conjugates 12a–c
was found to be dependent on the amount of solvent used. For
instance, the yield of the porphyrin 12a was improved from
0
0
5,10,15,20-Tetra(7 -iodoheptyl)porphyrin 14 was prepared
as is outlined in Scheme 3 and uses the p-toluenesulfonic acid-
,6 to 12 % under more dilute conditions. Best yields were
obtained when using 0.01 M aldehyde as recommended by
catalyzed porphyrin-forming reaction that we introduced in
[
20]
earlier work.
was prepared from 8-iodo-1-octanol 13a
The aldehyde precursor 8-iodooctanal 13b
[37]
[21]
Lindsey.
The lower yields of 12b and 12c were attributed
by oxidation with
to the greater instability of the protecting groups, the methox-
ymethyl ester and the butyldimethylsilyl ether, compared with
the methyl ether. Nonetheless, this approach has also yielded a
series of compounds with multiple (36) stereogenic centres.
A limitation of the approach involves the need to have a pre-
existing carbon atom within the starting steroid that can be
efficiently converted into an aldehyde group. In this respect, as
most steroids have an –OH group, the sequence demonstrated
in Scheme 1 whereby an aldehyde group can be installed by
pyridinium chlorochromate. Porphyrin 14 was obtained from
condensation of 13b and pyrrole 7 in 4 % yield. The synthesis
can be carried out on a moderate scale, affording the porphyrin
14 in multigram amounts. The alkyl chains have the potential to
permeate the cell membrane, thereby acting as anchors that can
fix steroid–porphyrin conjugates and as such assist in the
delivery of steroids to biologically active sites. Other porphyrins
with varying alkyl chain lengths and various v-functional
groups have been prepared and will be reported elsewhere.
O
OCH3
OH
RO
O
H
H
H
(i) (ii)
(iii)
(iv)
3
H
H
H
H
H
H
RO
RO
H
H
H
9a–c
10a–c
11a–c
RO
OR
(
v)
H
H
H
H
H
H
N
H
H
H
7
N
H
N
H
N
a R ϭ CH3
b R ϭ CH OCH3
N
2
c R ϭ Si(CH ) C(CH )
3
2
3 3
H
H
H
H
H
H
H
H
12a–c
RO
OR
Scheme 2. Reagents and conditions: (i) acetyl chloride, MeOH, room temperature (rt), 3 days; (ii) for 9a: CH
rt, 7 days; for 9b: dimethoxymethane, phosphoric oxide, CHCl
CH Cl , rt, 19 h; (iii) LiAlH , dry diethyl ether, rt, 3 days; (iv) pyridinium chlorochromate, CH
, 2 h for 12a, 1 day for 12b, 2 days for 12c, (b) DDQ, rt, 2 h.
3
I, Ag O, dry DMF,
2
3
, rt, 3 days; for 9c: tert-butyldimethylsilyl chloride, imidazole, dry
Cl , rt, 1 day; (v) (a) TFA, rt under
2
2
4
2
2
N
2

1
636
F. Taba et al.
Steroid units were attached by nucleophilic substitution of
the iodo groups of 14. Thus, oestrone 2 was treated with NaH to
adduct 15 in 10 % yield as the minor product along with a small
amount of unreacted starting material. NMR spectroscopy and
matrix-assisted laser desorption–ionization time-of-flight
(MALDI-TOF) mass spectrometry confirmed the formation of
the mono-appended adduct. As expected, the C NMR spec-
trum of the mono-appended steroid–porphyrin 15 is more
complex than that of the symmetrical tetra-appended steroid–
porphyrin 16 and three sets of alkyl chain signals in a ratio
generate the corresponding aryloxide, which was reacted with
0
5
,10,15,20-tetra(7 -iodoheptyl)porphyrin 14 in dry THF heated
1
3
at reflux for 72 h (Scheme 4). Isolation of the reaction products
using column chromatography gave the tetra-appended product
1
6 in 47 % yield as the major product and the mono-appended
1
: 2 : 1 corresponding to the chains at the 5-position, the 10- and
I
R
the 20-positions, and the 15-position, are seen. MALDI-TOF
MS displayed the loss of three HI fragment(s) (three separate m/z
128) from the alkyl chain of adduct 15, which confirmed the
presence of three iodine groups and one oestrone unit.
1
1
3a R ϭ CH OH
2
(
i)
3b R ϭ CHO
ϩ
N
H
Reaction of the porphyrin 14 with the 3-benzyloxyestra-
[38]
(ii)
7
I
1,3,5(10)-triene-17b-ol 17
using the same conditions (heat-
I
ing for 72 h) as for the synthesis of 16 and separation of the
resultant mixture by column chromatography gave only 4 %
yield of the tetra-adduct 19 (Scheme 5), as well as mixed
fractions of the mono-, di-, and tri-substituted oestradiol
porphyrin and some starting material 14 (19 %). The mono-
steroidal adduct 18 was isolated from this mixture in 33 %
yield. The MALDI-TOF mass spectrum of 19 showed the
expected parent peak and fragment ions resulting from sequen-
N
H
N
N
H
N
I
tial loss of three (C H O ) steroidal units. There was no HI
25 30 2
I
14
(
m/z 128) detected in the MALDI-TOF mass spectrum of 19,
confirming that the iodo groups had all been displaced, whereas
the spectrum of the triiodomonosteroid conjugate 18 showed
the loss of 3 HI molecules.
Scheme 3. Reagents and conditions: (i) pyridinium chlorochromate,
CH Cl , room temperature (rt), 16 h; (ii) p-TsOH, toluene, heat, 2 h; then
2
2
2,3,5,6-tetrachloro-1,4-benzoquinone (TCQ) added, heat further 2 h.
I
I
O
N
H
H
N
N
ϩ
H
H
H
N
HO
2
I
I
(i)
14
O
O
O
H
H
H
H
H
H
H
H
H
I
O
O
O
O
5
5
N
5
5
5
N
H
5
H
ϩ
N
N
N
N
H
N
H
N
I
I
O
5
5
15
16
H
H
H
H
H
H
O
Scheme 4. Reagents and conditions: (i) 2 treated with NaH and added to dry THF solution of 14, heat under N
O
2
, 72 h.

Synthesis of Steroid–Porphyrin Conjugates
1637
I
I
OH
N
H
H
N
N
ϩ
H
H
H
N
BzO
1
7
I
I
1
4
BzO
OBz
(i)
H
H
H
H
H
H
OBz
H
H
O
O
H
I
O
5
5
5
5
5
N
N
H
H
N
N
ϩ
N
N
H
N
H
N
I
I
5
5
5
1
8
O
O
H
H
H
H
H
H
1
9
BzO
OBz
, 72 h.
Scheme 5. Reagents and conditions: (i) 17 treated with NaH and added to dry THF solution of 14, heat under N
2
The low overall yields in this case where the nucleophile is
the secondary alkoxide derived from the 3-O-benzyl oestradiol
ether 17 are presumably due to steric hindrance about the
oxygen at the 17-position. This contrasts with the phenoxide
character and no steric impedance in the case of the much-
higher-yielding reaction involving oestrone above (Scheme 4).
Interestingly, compounds 15, 16, 18, and 19, with the heptyl
linkers between the porphyrin and steroidal components,
all displayed liquid-crystal-like properties, which we are
investigating.
TLC analysis indicated the formation of a polar dark-purple
band as well as the presence of some unreacted steroidal and
baseline material. The reaction mixture was subjected to column
chromatography and the dark-purple band was isolated to give
the oestradiol–porphyrin tetraester conjugate 21 in 8 % yield.
This poor yield further highlights the low reactivity of the
sterically hindered 17-hydroxyl of the benzyl ether 17.
The formation of the tetrasteroidal-appended porphyrin 21
was confirmed by mass spectrometry, which gave an expected
parent peak for the molecular formula C148H142N O , and by
4
12
1
H NMR (integrals of signals show four appended steroidal
units) and IR (ester carbonyl stretch in the spectrum at
719 cm ) spectroscopic data that were also fully consistent
Method 4: Formation of an Ester Linkage
by Reaction of Steroid With 5,10,15,20-Tetra(4-
chlorocarbonylphenyl)porphyrin
ꢀ1
1
with the structure. This approach yields more rigidly defined
conjugates in that the two components are linked by an aryl
group and such compounds are likely to be less valuable in
biological studies involving molecular recognition of steroidal
components in relatively confined binding pockets, such as the
Most steroids have an –OH group so generation of an ester
linkage offers another possibility for conjugate formation. This
was explored by reaction of 5,10,15,20-tetrakis(4-chlorocarbonyl-
[
39]
phenyl)porphyrin 20,
and the free OH group on 3-O-benzyl
0
[9]
oestradiol ether 17 to give 4 -functionalized tetraphenylpor-
phyrins. The synthetic procedure used in the synthesis of the
oestradiol–porphyrin tetraester conjugate 21 is outlined in
Scheme 6.
oestrogen receptor. Other compounds have been prepared
from 5,10,15,20-tetrakis(4-chlorocarbonyl-phenyl)porphyrin
[
39]
20
peptides, and diamines to give synthetic receptors for protein
by formation of amides by reaction with amino acids,
[
39,40]
Sodium hydride was used to deprotonate the hydroxyl of
[
surface recognition;
in these cases, the targets for recogni-
38]
3
ture was treated with the porphyrin-tetra(acid chloride) 20 in
-benzyloxyestra-1,3,5(10)-triene-17b-ol 17
and the mix-
tion are much more accessible. The use of a flexible linker
between the components would enhance to utility of the conju-
gate for targeting confined binding sites. Use of a steroid with a
dry THF and the reaction heated at reflux for 72 h. At this stage,

1
638
F. Taba et al.
O
O
Cl
Cl
OH
N
H
H
N
N
ϩ
H
H
H
N
BzO
1
7
Cl
Cl
20
O
(i)
O
H
H
H
H
O
O
H
BzO
H
OBz
O
O
N
H
N
N
H
N
O
O
BzO
H
H
H
H
OBz
2
1
H
O
O
H
Scheme 6. Reagents and conditions: (i) 17 treated with NaH and added to dry THF solution of 20, heat under
, 72 h.
N
2
0
less-hindered OH group should give better yields in the esterifi-
cation reaction but we put this method aside because esters are
likely to be unstable in a biological context owing to the
abundance of esterases that can target them.
carbons. An identical pattern is seen for C-3 hydrogen of the
bromo derivative 22 (see Supplementary Material).
Attempts to grow crystals of 12a and 22 proved unsuccessful
as only shiny films of crystalline-like material were obtained.
This propensity to form semi-crystalline films might be useful in
Some Reactions at the Steroid Component
of the Steroid–Porphyrin Conjugates
[43]
a variety of nanoscience applications. The bromo functional
groups also allow further functionalization at the steroid moie-
ties that will be of use when preparing biologically active
compounds.
Post-conjugate synthesis modification of the steroidal compo-
nent of several conjugates was explored in a limited way in order
to investigate the stability of the conjugates to ether deprotection
and modification conditions.
Treatment of the methoxymethyl-protected conjugate 12b
with 6 M HCl afforded the tetraalcohol 5,10,15,20-tetrakis[3a-
hydroxy-24-nor-5b-cholan-23-yl]porphyrin 23 in 5 % yield
(Scheme 7). The remaining material was a mixture of partially
hydrolyzed and decomposition products. Similar treatment of
the butyldimethylsilyloxy-functionalized conjugate 12c gave
the tetraalcohol 23 in 9 % yield, along with a mixture of partially
hydrolyzed and decomposition products as before, whereas
treatment of 12c using tetrabutylammonium fluoride trihydrate
gave the tetraalcohol 23 in 10 % yield with analogous by-
It has long been known that BBr treatment will convert
3
[41]
b-methoxycholestane into a mixture of 3-bromocholestanes,
3
and that 3b-hydroxy-5a-androstan-17b-ol is similarly con-
verted into a 4 : 1 mixture of the 3b-bromo and 3a-bromo
[
42]
derivatives.
4-nor-5b-cholan-23-yl]porphyrin 12a with excess BBr3
afforded the 5,10,15,20-tetrakis[3a-bromo-24-nor-5b-cholan-
Treatment of 5,10,15,20-tetrakis[3a-methoxy-
2
23-yl]porphyrin 22 in 77 % yield with complete retention of
0
stereochemistry at the 3 -position (Scheme 7).
1
products. H NMR spectra showed the absence of resonances
High-resolution mass spectroscopy (HRMS) of the central
molecular ion agreed to within 3.4 ppm with the required mass
obtained from the displaced functional groups and HRMS was in
agreement with the expected molecular weight of the product
23. The poor yields for the hydrolysis step indicate that the
steroid–porphyrin conjugates are sensitive to acid and that
the tetrahydroxy product 23 may be unstable. Similar instability
of the conjugates was encountered when the benzyl ethers 18
1
of the tetrabromo compound 22. The H NMR spectrum of the
conjugate 22 showed the neighbouring four protons at the C2
and C4 positions on the steroid had shifted downfield from
d 3.19 in the starting material to d 4.08 in 22, confirming the
1
[44]
presence of the electron-rich bromo group. H NMR data
indicate retention of stereochemistry at C3. In each of the
and 19 were subjected to these acid conditions. In other work,
we observed that when porphyrin p-cation radicals are generated,
tetraalkylporphyrins can undergo monodealkylation through a
carbocation intermediate that can be trapped. In the longer
term, the use of less harsh, probably non-acid, conditions will
be required.
compounds 9, 10, 11, and 12 in the three series a, b, and c
0
(
Scheme 2 and Supplementary Material), the C-3 hydrogen
occupies an axial conformation and shows two axial–axial and
two axial–equatorial couplings to protons on the adjacent

Synthesis of Steroid–Porphyrin Conjugates
1639
RO
H
OR
Br
Br
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
N
H
N
H
(i)
N
N
12a R ϭ CH3
N
N
H
N
H
N
H
H
H
H
H
H
H
H
H
H
H
22
H
H
H
H
H
RO
OR
Br
Br
(
(
ii)
ii)
1
1
2b R ϭ CH OCH3
2
2c R ϭ Si(CH ) C(CH )
3 3
23 R ϭ H
3
2
(iii)
Scheme 7. Reagents and conditions: (i) BBr
3 2 2 2
, freshly distilled CH Cl , room temperature (rt) under N , 16 h. (ii) 6 M HCl,
THF, rt, 15 h; (iii) tetrabutylammonium fluoride trihydrate, THF, rt, 29 h.
Conclusion
reaction on 3b-methoxy-5a-cholestane and on 3b-hydroxy-5a-
androstan-17b-ol. The latter compounds have a trans-fused AB
ring system unlike 12a (and 22), in which the ring junction is
cis-fused. Deprotection of some of the generated steroid–
porphyrin conjugates was also investigated but only low yields
of the desired tetraol 5,10,15,20-tetrakis[3a-hydroxy-24-nor-
The synthesis of porphyrin-steroid conjugates using the natural
steroids oestradiol, oestrone, and lithocholic acid as precursors
was achieved. Four different construction motifs were explored,
two involving the introduction of the steroid components in the
porphyrin-forming reaction and two involving their introduc-
tion by post-porphyrin synthesis reactions. 5,10,15,20-Tetrakis
5b-cholan-23-yl]porphyrin 23 were obtained under acidic
conditions. Although these compounds have poor aqueous sol-
ubility, there is a possibility to deliver these in vivo if a suitable
carrier molecule or nanoparticle delivery method is used. Pos-
sible carriers are micelles that can be created through appendage
(steroidal-alkyl)porphyrins were synthesized using appropriate
steroidal-alkylaldehydes and pyrrole condensation procedures.
In one approach, 17b-oestradiol was first converted into the
3
-O-methyl and 17b-O-(3-hydroxypropyl) derivative and the
[
45,46]
of a block copolymer to the porphyrin,
cyclodextrins,
latter group then oxidized to the steroid-propionaldehyde. In
the other approach, the steroid side chain carboxylic acid of
three 3-O-protected lithocholic acids was modified to the
required aldehyde. The yield of the steroid–porphyrin con-
jugates ranged from 3 to 12 %. Introduction of the steroidal
component post-porphyrin synthesis also followed two
human albumin, and/or emulsifiers such as Triton X. Therefore,
partially appended molecules can be conceived as building
blocks towards the construction of complex porphyrin arrays. Of
the four approaches to steroid–porphyrin conjugates investi-
gated, the most efficient and most versatile one attaches the
steroid components late in the sequence to the relatively easily
prepared 5,10,15,20-tetra(v-haloalkyl)porphyrins by a nucleo-
philic substitution reaction.
0
approaches. In one approach, the novel 5,10,15,20-tetra(7 -
iodoheptyl)porphyrin 14 was reacted with the 17b-hydroxyl of
oestradiol 3-benzyl ether and with the phenolic 3-hydroxyl of
oestrone; 5,10,15,20-tetrakis(steroidal-heptyl)porphyrin was
isolated in both cases in yields up to 47 %. Some substituted
mono-steroidal- and tri-steroidal-appended derivatives were
also isolated; these compounds have the potential to be further
elaborated by reaction with other components. The other
approach formed the steroid–porphyrin conjugate through
generation of ester linkages by reaction of the 17b-hydroxyl
group of oestradiol 3-benzyl ether with the acid chloride
Experimental
General Remarks
[
47]
All commercial grade solvents were purified before use.
Column chromatography was carried out using either gravity
feed or flash chromatography techniques on Merck Kieselgel 60
silica gel (40–63 mm, 230–400 mesh) or the same type of silica
from Grace & Co. Thin-layer chromatography (TLC) was per-
formed using Merck Kieselgel 60 F254 pre-coated sheets
(0.2 mm). Solvent mixtures (v/v) were used as specified. Infra-
red spectra were recorded on a Shimadzu Model 8400 Fourier-
transform (FT)-IR spectrometer as solutions or on the Bruker
Optics model Alpha IR spectrometer (with a Zn-Se cell) as
either oils (in the case of steroids) or dried solutions or solids.
Hence, the end product was either a film of solid or oil placed on
5,10,15,20-tetra(4-chlorocarbonyl-phenyl)porphyrin 20 to
0
give 4 -functionalized tetraphenylporphyrin 21. Treatment
of 5,10,15,20-tetrakis[3a-methoxy-24-nor-5b-cholan-23-yl]
porphyrin 12a with excess BBr afforded the 5,10,15,20-tetrakis
3
[
3a-bromo-24-nor-5b-cholan-23-yl]porphyrin 22 in 77 % yield
0
with complete retention of stereochemistry at the 3 -position,
a much higher stereoselectivity than has been seen in the BBr3

1
640
F. Taba et al.
the cell alone or with a solvent, if stated. Electronic absorption
spectra of porphyrins were recorded on a Cary 5E UV-vis-NIR
spectrophotometer and a Cary 4000 spectrophotometer (sol-
vents as stated). NMR spectra were recorded on a Bruker
Avance DPX 200 spectrometer (200 MHz), a Bruker Avance
DPX 300 spectrometer (300 MHz) or a Bruker Avance DPX 400
OCH ), 3.41 (1H, t, J 8.2, 17a-CH), 3.14 (1H, s, OH), 2.84–2.88
2
(2H, m, C6-CH ), 1.15–2.30 (15H, m, steroid, OCH CH
CH OH), 0.81 (3H, s, 18-CH ). d (100 MHz, CDCl ) 157.14
2
2
2-
2
3
C
3
(C-3), 137.49 (C-5), 132.25 (C-10), 125.95 (C-1), 113.50 (C-4),
111.14 (C-2), 89.17, 69.03, 61.60, 54.77, 49.89, 43.60, 42.93,
38.33, 37.63, 32.09, 29.48, 27.73, 26.96, 26.12, 22.82, 11.45. m/z
(atmospheric pressure chemical ionization; APCI) 345.2 [Mþ
(400 MHz) as stated. Samples were dissolved in deacidified
CDCl either with or without tetramethylsilane (TMS), and
þ
þ
H ]; [C H O þ H ] requires 345.0. m/z (HRAPCI-FTICR)
þ þ
22 32 3
3
22 32 3
chemical shifts are reported in parts per million (ppm) refer-
enced to TMS or residual solvent peak. Low-resolution ESI
mass spectra were recorded on a ThermoQuest Finnigan LCQ
ion-trap mass spectrometer equipped with Xcaliber processing
software. High-resolution mass spectra were recorded on a
Bruker Fourier-transform ion cyclotron resonance (FTICR)
mass spectrometer in electrospray mode with a 4.7-T super-
conducting magnet. The matrix used for MALDI-TOF spectra
was trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]
malononitrile (dctb).
345.2432 [Mþ H ]; anal. calc. for [C H O þ H ] 345.2424.
1
1
7b-(3-Propanal-oxy)-3-methyloxyestra-
,3,5(10)-triene 6
To a solution of 17b-(3-hydroxypropoxy)-3-methyloxyestra-
1,3,5(10)-triene 5 (3.98 g, 0.0116 mol) in dry dichloromethane
(100 mL) was added pyridinium chlorochromate (2.99 g,
0.0139 mol). The reaction mixture was stirred under a nitrogen
atmosphere for 16 h at rt. The resulting mixture was filtered
through Florisil, eluting with dichloromethane, and the filtrate
evaporated to dryness to afford 17b-(3-propanal-oxy)-3-
methyloxyestra-1,3,5(10)-triene 6 (2.19 g, 55 %) as a pale
Synthesis of Oestradiol–Porphyrin Conjugate 8
1
1
7b-(3-Hydroxypropoxy)-3-methyloxyestra-
,3,5(10)-triene 5
yellow-white pasty solid, mp 74–768C. R 0.54 (7 : 3 light
f
ꢀ1
petroleum/ethyl acetate). nmax/cm (CHCl ) 3445w, 2925s,
3
To a mixture of sodium hydride (60 % dispersion in mineral
oil) (2.50 g, 104 mmol), sodium iodide (7.85 g, 52.4 mmol), and
anhydrous potassium carbonate (1.30 g. 9.43 mmol) in dry
tetrahydrofuran (50 mL) was added 3-methyloxyestra-1,3,5
2864m (aliphatic CH ), 2728w, 1872w, 1725s (C¼O), 1610m,
2
1576w, 1500s, 1459m, 1384w, 1351w, 1309w, 1249s, 1137w,
1102s, 1038s, 869w. d (400 MHz, CDCl ) 9.81 (1H, t, J 2.0,
H
3
CHO), 7.20 (1H, d, J 8.5, 1-CH steroid ring A), 6.71 (1H, dd,
J 2.7, 8.5, 2-CH steroid ring A), 6.63 (1H, d, J 2.7, 4-CH steroid
ring A), 3.79–3.86 (2H, m, OCH CH CHO), 3.78 (3H, s,
(
10)-trien-17b-ol 4 (3.00 g, 10.5 mmol). The reaction mixture
˚
was then treated with 4-A molecular sieves and heated to 808C
under nitrogen for 1 h. Allyl bromide (6.30 g, 52.1 mmol) was
added and the resulting mixture was stirred for an additional 5 h
at room temperature (rt) under nitrogen. The solvent was
removed under vacuum and the crude residue was extracted
with ethyl acetate (3 ꢁ 50 mL); the organic layers were com-
bined and washed with water (2 ꢁ 50 mL) and saturated sodium
chloride solution (2 ꢁ 50 mL), dried over anhydrous magnesium
sulfate, filtered, and the solvent removed under reduced pressure
to afford the allyl-substituted methyl oestradiol intermediate as a
pale yellow-brown oil, which was subjected to hydroxyboration–
oxidation without further purification.
2
2
OCH ), 3.41 (1H, t, J 8.3, 17a-CH), 2.84–2.88 (2H, m,
3
C6-CH ), 2.64 (2H, m, J 2.0, 6.0, OCH CH CHO), 1.16–2.32
(13H, m, steroid), 0.78 (3H, s, 18-CH ). d (100 MHz, CDCl )
2
2
2
3
C
3
201.57 (CHO), 157.40 (C-3), 137.86 (C-5), 132.58 (C-10),
126.24 (C-1), 113.75 (C-4), 111.41 (C-2), 89.46, 63.75, 55.12,
50.20, 44.21, 43.87, 43.30, 38.58, 37.89, 29.75, 27.92, 27.18,
þ
26.36, 23.03, 11.50. m/z (APCI) 343.2 [M þ H ]; [C H O þ
2
2 30 3
þ
H ] requires 343.1. m/z (HRAPCI-FTICR) 365.2085 [M þ
þ
þ
Na ]; anal. calc.for [C H O þ Na ] 365.2087.
2
2 30 3
0
5
,10,15,20-Tetrakis{2 -[3-methyloxyestra-1,3,5(10)-
trienyl-17b –oxy]ethyl}porphyrin 8
A solution of the foregoing allyl-substituted oestradiol inter-
mediate (4.17 g, 12.8 mmol) in dry tetrahydrofuran (50 mL) was
treated with a solution of 9-BBN (5.57 g, 22.8mmol) in dry
tetrahydrofuran (10 mL) and was then stirred under nitrogen for
To a solution of foregoing aldehyde 6 (2.19 g, 6.39 mmol) in
dry dichloromethane (1.5 L) was added trifluoroacetic acid
(0.542 mL, 7.03 mmol) portion-wise over 2 min with stirring.
Pyrrole 7 (0.472 g, 7.03 mmol) was then added portion-wise
over 2 min with stirring. The reaction mixture was then stirred
under a dark nitrogen atmosphere at room temperature for 24 h.
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (1.16 g, 5.12mmol)
was added and the resulting mixture was stirred for a further 2 h
under nitrogen in the dark at room temperature. The solvent was
removed under reduced pressure and the crude residue was
further purified by column chromatography over silica (10 %
diethyl ether in dichloromethane) to afford the conjugate
1
.5 h at rt. A mixture of sodium hydroxide (2M, 89.0 mmol) and
hydrogen peroxide (30% w/v, 89.0mmol) was added while the
reaction mixture was cooled in an ice-bath. The reaction mixture
was then stirred for an additional 2 h at rt under nitrogen. The
solvent was removed under vacuum and the crude residue was
extracted with ethyl acetate (3ꢁ 50mL); the organic phases were
combined and washed with water (2ꢁ 50 mL) and saturated
sodium chloride solution (2 ꢁ 50mL), dried over anhydrous
magnesium sulfate, filtered, and evaporated to dryness, leaving
behind a clear yellowish oil, which solidified on standing. The
crude residue was further purified by column chromatography
over silica (light petroleum/ethyl acetate, 7 : 3) to afford 17b-(3-
hydroxypropoxy)-3-methyloxyestra-1,3,5(10)-triene 5 (3.28 g,
0
5,10,15,20-tetrakis{2 -[3-methyloxyestra-1,3,5(10)-trienyl-17b
–oxy]ethyl}porphyrin 8 (300.0 mg, 12.0 %) as a lustrous dark-
purple microcrystalline solid, mp 148–1508C. R 0.79 (3 %
f
diethyl ether in dichloromethane). lmax/nm (CHCl ) (log e)
3
9
1%) as a clear pale-yellow viscous oil. R 0.35 (7 : 3 light
f
419 (5.65), 486 (3.43), 519 (4.17), 553 (3.81), 597 (3.61), 654
ꢀ1
ꢀ
1
petroleum/ethyl acetate). nmax/cm
(CHCl ) 3417m (OH),
3
(3.66). nmax/cm (CHCl ) 3368w, 3320 (NH), 2926s, 2863m
3
2
926s, 2865m (aliphatic CH ), 1610m, 1577w, 1499s, 1458m,
(aliphatic CH ), 1728w, 1671w, 1609m, 1574w, 1498s, 1462w,
1350w, 1248s, 1137w, 1097s, 1039w, 966w, 915w. dH
(200 MHz, CDCl ) 9.57 (8H, s, b-pyrrolic H), 7.08 (4H, d,
2
2
1349w, 1309w,1248s, 1138w,1096s, 1038s, 973w.d (400MHz,
CDCl ) 7.19 (1H, d, J 8.5, 1-CH steroid ring A), 6.71 (1H, dd,
H
3
3
J 2.6, 8.5, 2-CH steroid ring A), 6.64 (1H, d, J 2.6, 4-CH steroid
ring A), 3.77–3.79 (5H, m, CH OH and OCH ), 3.68 (2H, m,
J 8.5, 1-CH), 6.66 (4H, dd, J 2.6, 8.5, 2-CH), 6.60 (4H, d, J 2.6,
4-CH), 5.20 (8H, m, OCH CH -porphyrin), 4.42–4.55 (8H,
2
3
2
2

Synthesis of Steroid–Porphyrin Conjugates
1641
m, –OCH CH –), 3.76 (12H, s, OCH ), 3.39 (4H, t, J 8.2, 17a-
3a-methoxymethoxy-5b-cholan-24-ate 9b (10.2 g, 3.71 mmol)
in dry diethyl ether (750 mL) under nitrogen at 58C. The reaction
was allowed to warm to rt and was stirred for 36 h. The reaction
mixture was then cooled and slowly quenched with water and
filtered. The residue was washed with ethyl acetate (100 mL)
and the aqueous filtrate was extracted with ethyl acetate
(50 mL). The combined organic fractions were washed with
water (2 ꢁ 300 mL), dried over anhydrous Na SO , and
2
2
3
CH), 2.73–2.87 (8H, m), 0.88 (12H, s, 18-CH ), 0.92–2.10 (52H,
3
m, steroid), ꢀ2.82 (2H, s, inner NH). d (50 MHz, CDCl3)
C
1
1
5
2
57.35 (C-3), 145.46, 137.84 (C-5), 132.58 (C-10), 128.82,
26.18 (C-1), 114.16, 113.74 (C-4), 111.33 (C-2), 89.60,
5.12, 50.06, 43.71, 43.33, 38.50, 37.92, 36.36, 29.71, 28.18,
7.07, 26.32, 23.02, 11.80 (one quaternary carbon signal wasn’t
þꢂ
þꢂ
located). m/z (ESI) 1560.73 [M ]; [C104H126N O ] requires
4
8
2
4
þ
1
560.97. m/z (HRAPCI-FTICR) 1560.9674 [M ]; anal. calc. for
þ
adsorbed onto silica and subjected to column chromatography,
eluting with 1 : 4 ethyl acetate/hexane. This afforded 3a-
methoxymethoxy-5b-cholan-24-ol 10b (6.93 g, 72 %) as a white
[C104H126N O ]: 1559.9687.
4
8
crystalline solid. mp 55–578C. R (1 : 4 ethyl acetate/hexane)
f
Synthesis of 5,10,15,20-Tetrakis(3a-methoxy-24-nor-
b-cholan-23-yl)porphyrin 12a
a-Methoxy-5b-cholan-24-al 11a Pyridinium chlorochro-
mate (2.80g, 13.0 mmol) was added to a solution of 3a-methoxy-
ꢀ
1
.40. nmax/cm (CHCl ) 3000–2850s, 1464m, 1376m, 1079m.
0
dH (400 MHz, CDCl ) 4.61 (m, 2H, CH -O-CH -), 3.62–3.57
5
3
3
3
2
3
(m, 2H, C-23), 3.26 (s, 3H, OCH ), 3.61–3.40 (m, 1H, C-3b),
1.97–1.85 (m, 2H), 1.84–0.83 (m, 33 H), 0.55 (s, 3H). m/z (ESI)
3
[
34]
5
b-cholan-24-ol 10a (mp 123–1248C. (lit.
not determined)) (3.75 g, 9.96 mmol) in dry dichloromethane
240 mL) over molecular sieves and the reaction stirred under
white solid, mp
þ
3
double bond at C-3); [C H O ] requires 406.6.
45.0 [M ꢀ 62] (loss of OCH OCH and an H introduces a
2
3
þ
2
6 46 3
(
3
a-Methoxymethoxy-5b-cholan-24-al
chlorochromate (9.01 g, 41.8 mmol) was added to a solution of
a-methoxymethoxy-5b-cholan-24-ol 7 (14.2 g, 34.8 mmol) in
11b Pyridinium
nitrogen at rt for 14 h. The solution was filtered through a
column of Florisil under vacuum, eluting with 1 : 9 diethyl
ether/dichloromethane. The filtrate was evaporated to give 3a-
methoxy-5b-cholan-24-al 11a (2.25 g, 82 %) as white crystals,
mp 96–988C. R (25 % ethyl acetate in hexane) 0.24; R
3
dry dichloromethane (425 mL) over molecular sieves at rt and
the reaction stirred under nitrogen for 23 h. The solution was
filtered through a column of Florisil under vacuum, eluting with
1 : 9 diethyl ether/dichloromethane. The filtrate was evaporated
to give 3a-methoxymethoxy-5b-cholan-24-al 11b (12.3 g,
f
f
(
dichloromethane) 0.54; R (5 : 95 diethyl ether/dichloro-
f
ꢀ1
methane) 0.85. nmax/cm
(CHCl ) 3000–2850s, 2709w,
3
1
725s, 1463s, 1378m, 1101s. d (400 MHz, CDCl ) 9.77–9.76
H 3
8
7 %), as white crystals. R (1 : 4 ethyl acetate/hexane) 0.51.
f
(s, 1H, CHO), 3.35 (s, 3H, OCH ), 3.16–3.01 (m, 1H, C-3b),
3
d (400 MHz, CDCl ) 9.70 (s, 1H, CHO), 4.60 (m, 2H, CH -O-
H
3
3
2
(
.47–2.20 (m, 2H), 1.98–1.90 (m, 2H), 1.89–0.89 (m, 30H), 0.63
s, 3H). dC (75 MHz, CDCl ) 203.63 (CHO), 80.81, 56.86,
CH -), 3.45–3.41 (m, 1H, C-3b), 3.28 (s, 3H, OCH ), 2.41–2.10
3
2
3
(
[
m, 2H), 1.98–0.80 (m, 32H), 0.56 (s, 3H). m/z (APCI) 341.0
þ
5
3
1
3
6.36, 55.94, 42.44, 41.32, 40.73, 40.55, 36.24, 35.71, 35.28,
3.17, 28.64, 28.36, 27.71, 27.19, 26.77, 24.60, 23.80, 21.19,
8.75, 12.44 (three quaternary signals are missing). m/z (ESI)
M ꢀ 62] (loss of OCH OCH and H introduces a double bond
2
3
þ
6 44 3
at C-3); [C H O ] requires 404.6.
2
þ
þ
5,10,15,20-Tetrakis(3a-methoxymethoxy-24-nor-5b-cholan-
3-yl)porphyrin 12b Trifluoroacetic acid (200 mL, 2.72 mmol)
75.0 [M þ H ]; [C H O þ H ] requires 375.6.
2
5 42 2
2
5
,10,15,20-Tetrakis(3a-methoxy-24-nor-5b-cholan-23-yl)
was added slowly to a stirring solution of 3a-methoxymethoxy-
porphyrin 12a Trifluoroacetic acid (620 mL, 8.35 mmol) was
added slowly to a stirring solution of aldehyde 11a (3.00 g,
5b-cholan-24-al11b (980mg, 2.42 mmol) and pyrrole7 (70.0 mL,
2.72 mmol) in dry dichloromethane (1.51 L) under nitrogen at rt.
After 45 h, 2,3-dicyano-5,6-dichloro-1,4-benzoquinone (655mg,
8
.00 mmol) and pyrrole 7 (560 mL, 8.07 mmol) in dichloro-
methane (460 mL) under nitrogen at rt. After 2 h, 2,3-dicyano-
,6-dichloro-1,4-benzoquinone (1.40 g, 6.17 mmol) was added
2
2
.66 mmol) was added and the reaction was stirred for a further
h. The reaction solvent was evaporated and the residue was
5
and the reaction was stirred for a further 2.25 h. The solution was
then concentrated, filtered through a short plug of silica, and
subjected to flash chromatography (1 : 9 diethyl ether/CH Cl )
dissolved in dichloromethane and filtered through a plug of
silica. The crude porphyrin was adsorbed onto silica and the
product was isolated by flash chromatography over silica (1 : 9
diethyl ether/dichloromethane). The porphyrin, 5,10,15,20-
tetrakis(3a-methoxymethoxy-24-nor-5b-cholan-23-yl)porphyrin
2
2
to give 5,10,15,20-tetrakis[3a-methoxy-24-nor-5b-cholan-23-
yl]porphyrin 12a as a dark-red crystalline solid (400 mg, 30 %),
mp 245–2478C. R (2 : 98 diethyl ether/dichloromethane) 0.83.
f
1
2b was obtained as a dark-red crystalline solid (133 mg, 3 %),
lmax/nm (CHCl ) (log e) 418s (5.34), 519s (3.59), 553m (3.48),
3
ꢀ1
mp 169–1718C. R (1 : 9 ether/dichloromethane) 0.58. lmax/nm
f
6
01w (3.01), 661m (3.35). nmax/cm (CHCl ) 3683w, 3619w,
3
(
CHCl ) (log e) 418 (5.30), 520 (4.14) 553 (4.07), 602 (3.73),
3
3
(
020–2860s, 2433w, 2399m, 1522m, 1423m, 1210s. dH
300 MHz, CDCl ) 9.44 (s, 8H, b-pyrrolics), 5.02 (m, 4H),
6
6
1
61 (3.95); (THF) (log e) 418 (1008.1), 521 (46.6) 555 (37.1),
02 (18.2), 662 (23.9). nmax/cm (Zn-Se cell) 2925m (NH),
3
ꢀ1
4
2
.77 (m, 4H), 3.35 (s, 12H, OCH ), 3.16 (m, 4H, steroid C-3),
3
.63 (m, 4H), 2.35 (m, 4H), 2.4–0.5 (m, 132H, steroid), ꢀ2.6
447w, 1098m (ether), 780w, 472s. d (400 MHz, CDCl ) 9.43
H
3
(s, 8H, b-pyrrolics), 5.09–4.95 (m, 4H), 4.81–4.71 (m, 4H),
(s, 2H, NH). d (75 MHz, CDCl ) 136.19, 128.65, 125.92,
C 3
4
C-3), 3.36 (s, 12H, OCH ), 2.69–2.59 (m, 4H), 2.40–2.26 (m,
.71–4.64 (m, 8H, CH -O-CH -), 3.60–3.47 (m, 4H, steroid
3
2
1
4
2
19.07, 80.85 (OCH ), 56.94, 56.46, 55.93, 43.35, 42.50,
3
3
0.81, 40.73, 37.93, 36.34, 35.77, 35.36, 33.18, 30.73, 30.10,
7.78, 27.24, 27.80, 27.24, 24.80, 23.88, 21.33.6, 19.80, 12.61.
4
H), 2.22–2.14 (m, 4H), 2.09–1.95 (m, 8H), 1.92–1.00 (m, 84H,
), ꢀ2.62 (s, 2H, NH). m/z
m/z (HRMS)1689.3665 [M þ Hþ]; [C116H174O N þ H ]
þ
steroid), 1.00–0.78 (3 ꢁ s, 36H, CH
3
4
4
þ
þ
(
ESI) 1809.80 [M þ H ]; [C
H
20 182
N O þ H ] requires
1
4
8
requires 1689.3665.
1
808.75.
,10,15,20-Tetrakis(3a-tert-butyldimethysilyloxy-24-nor-5b-
cholan-23-yl)porphyrin 12c Freshly distilled pyrrole
5
Synthesis of 5,10,15,20-Tetrakis(3a-methoxymethoxy-
4-nor-5b-cholan-23-yl)porphyrin 12b
a-Methoxymethoxy-5b-cholan-24-ol 10b LiAlH (4.40 g,
7
2
[36]
(104 mL, 1.51 mmol) was added to aldehyde 11c
(650 mg,
3
1.37 mmol) at rt and then trifluoroacetic acid (112 mL,
1.51 mmol) was added over 2 min and the reaction was stirred
4
1
21 mmol) was added to a stirring solution of methyl

1
642
F. Taba et al.
under nitrogen for a further 47 h. Then 2,3-dicyano-5,6-
dichloro-1,4-benzoquinone (337 mg, 1.37 mmol) was added
and the mixture was stirred another 2.5 h. The reaction solvent
was evaporated and the residue was dissolved in dichloro-
methane and filtered through a column of silica. The crude
porphyrin was further purified and the product was isolated by
flash chromatography over silica eluting with 1 : 9 diethyl ether/
dichloromethane to afford 5,10,15,20-tetrakis(3a-tert-butyldi-
methysilyloxy-24-nor-5b-cholan-23-yl)porphyrin 12c as purple–
was collected, evaporated to dryness and recrystallized from
dichloromethane/methanol to afford 5,10,15,20-tetrakis
0
(7 -iodoheptyl)porphyrin 14 (1.90 g, 4 %) as a dark-purple
microcrystalline solid, mp 102–1048C. R 0.50 (1 : 1 light
f
petroleum/dichloromethane). lmax/nm (CHCl ) (log e) 419
3
(5.57), 461 (3.34), 488 (3.56), 521 (4.12), 557 (3.97), 601
ꢀ
1
(3.64), 659 (3.81). nmax/cm (CHCl ) 3318w (NH), 3120w,
3
2923s, 2852m (aliphatic CH ), 1786w, 1684w, 1565w, 1472m,
1354w, 1292w, 1236w, 1194w, 1166w, 1072w, 959w. dH
(400 MHz, CDCl ) 9.45 (8H, s, b-pyrrolic H), 4.92 (8H, t,
2
red crystals (100.1 mg, 3.5 %). mp .3208C. R (1 : 9 diethyl
f
3
ether/dichloromethane) 0.94. lmax/nm (CHCl ) (log e) 421
J 8.0, 4 ꢁ CH -porphyrin), 3.19 (8H, t, J 7.0, 4 ꢁ CH -I),
3
2
2
ꢀ1
(5.57), 524 (4.10), 559 (4.04), 602 (3.72), 661 (3.91). nmax/cm
2.47–2.55 (8H, m, 4 ꢁ CH -CH -porphyrin), 1.75–1.89 (16H,
2 2 C
2
2
(
CHCl ) 2936m, 2858m, 1097m (ether), 872m, 835s, 774s,
m, CH ), 1.43–1.57 (16H, m, CH ), ꢀ2.64 (2H, s, inner NH). d
3
4
5
2
36s, 420s. dH (400 MHz, CDCl ) 9.43 (s, 8H, b-pyrrolics),
3
.05–4.94 (m, 4H), 4.79–4.69 (m, 4H), 3.68–3.55 (m, 4H), 2.68–
.56 (m, 4H), 2.38–2.26 (m, 4H), 2.21–2.13 (m, 4H), 2.06–1.95
(100 MHz, CDCl ) 143.33, 128.34, 118.20, 38.42, 35.40, 33.53,
3
þ
30.50, 30.26, 28.62, 7.19. m/z (ESI) 1207.1 [M þ H ]
þ
[C H N I þ H ] requires 1207.1. m/z (HRESI-FTICR)
4
8 66 4 4
þ
þ
(m, 8H), 1.91–1.75 (m, 14H), 1.65–0.99 (m, 82H, steroid), 0.99–
1207.15337 [M þ H ]; anal. calc. for [C H N I þ H ]
4
8 66 4 4
0
0
.93 (2ꢁ s, 12H, CH ), 0.91–0.86 (s, 36H, silyl 12 ꢁ CH ), 0.84–
1207.15390.
3
3
.78 (s, 12H, CH ), 0.083–0.042 (s, 24H, silyl 8ꢁ CH ), ꢀ2.68
3
3
Synthesis of 1 : 1 Oestrone–Porphyrin Conjugate 15
and 4 : 1 Oestrone–Porphyrin Conjugate 16
(s, 2H, inner NH). d (100 MHz, CDCl ) 118.68, 73.03,
C 3
7
3
2
1
1.98, 56.86, 56.61, 56.19, 45.53, 43.05, 42.53, 40.64, 40.46,
7.62, 37.16, 35.83, 34.82, 34.78, 34.62, 31.28, 27.72,
7.70, 26.28, 26.16, 24.53, 23.63, 23.58, 21.10, 19.50, 18.48,
To a solution of oestrone 2 (200 mg, 0.740 mmol) in dry
tetrahydrofuran (20 mL) was added sodium hydride (60 %
dispersion in mineral oil) (178 mg, 7.40 mmol). The reaction
mixture was stirred under nitrogen at rt for 2 h. A solution
þ
2.32. m/z (MALDI-TOF þ dctb matrix) 2089.64776 [M ];
þ
[C
H
36 222
N O Si ] requires 2089.64699. m/z (HRFTICR-
4
1
4
4
þ
þ
0
MALDI) 2089.64699 [M ]; anal. calc. for [C136H222N O Si ] :
4
of 5,10,15,20-tetrakis(7 -iodoheptyl)porphyrin 14 (179 mg,
4
4
2
089.65247.
0.148 mmol) in dry tetrahydrofuran (10 mL) was added and
the resulting mixture was heated at reflux with stirring under a
dark nitrogen atmosphere for 72 h. The reaction mixture was
cooled to room temperature and the solvent removed under
vacuum. The crude residue was fractionated by column chro-
matography over silica (1 : 3 light petroleum/dichloromethane)
to give three dark-purple bands.
0
Synthesis of 5,10,15,20-Tetrakis(7 -iodoheptyl)
porphyrin 14
8-Iodo-1-octanal 13b Pyridinium chlorochromate (54.3 g,
.252 mol) was added to a solution of 8-iodo-1-octanol
[37]
0 13a
53.8 g, 0.210 mol) in dry dichloromethane (200 mL) and stirred
(
under a nitrogen atmosphere for 16 h at rt. The solution was
filtered through Florisil, eluting with dichloromethane, and the
filtrate evaporated to dryness to afford pure 8-iodo-1-octanal
The front-running dark-purple band was collected and evap-
0
orated to dryness to afford unreacted 5,10,15,20-tetrakis(7 -
iodoheptyl)porphyrin 14 (2.42 mg, 1.35 %) as a dark-purple
pasty solid.
The second running dark-purple band was collected and
1
3b (41.1 g, 77.0 %) as a clear orange viscous oil. R 0.45 (20 : 80
f
ꢀ1
ethyl acetate/light petroleum). nmax/cm
(CHCl ) 3430w,
3
0
2
927s, 2855s (aliphatic CH str), 2717m (C–H ald. str.), 1720s
evaporated to dryness to afford 5-{7 -[estra-1,3,5(10)-trien-
0
2
br (C¼O str.), 1457m, 1358w, 1188m, 1074m, 1010m, 857w,
17-on-3-oxy]heptyl}-10,15,20-tris(7 -iodoheptyl)porphyrin 15
(19.8 mg, 10 %) as a dark-purple pasty solid. R 0.48 (1 : 3 light
7
3
1
6
3
84w, 722m. d (400 MHz, CDCl ) 9.72 (t, J 1.7, 1H, CHO),
H
3
f
.14 (t, J 7.0, 2H, CH I), 2.38 (dt, J 1.7, 7.3, 2H, CH CHO),
2
petroleum/dichloromethane). lmax/nm (CHCl ) (log e) 420
2
3
ꢀ1
.74–1.81 (m, 2H, CH ), 1.55–1.62 (m, 2H, CH ), 1.27–1.39 (m,
2
(5.53), 522 (4.10), 557 (3.96), 603 (3.64), 660 (3.79). nmax/cm
2
H, CH ). d (400 MHz, CDCl ) 202.40 (C¼O), 43.63 (a-CH ),
(CHCl ) 3319w (NH), 3205w, 3117w, 2924s, 2855m (aliphatic
CH ), 1733s (C¼O), 1672w, 1609w, 1569w, 1464m, 1355w,
2
C
3
2
3
3.22 (CH I), 30.08, 28.75, 28.09, 21.77, 6.94 (aliphatic CH ).
2
2
2
þ
þ
m/z (ESI) 255.0 [M þ H ]; [C H IO þ H ] requires 255.0.
1282w, 1241w, 1162w, 1100w, 1057w, 1014w, 976w. dH
(200 MHz, CDCl ) 9.44 (8H, s, b-pyrrolic H), 7.07–7.20
8
15
0
5
,10,15,20-Tetrakis(7 -iodoheptyl)porphyrin 14 A solu-
3
tion of p-toluenesulfonic acid monohydrate (p-TsOHꢃH O)
(1H, m, 1-CH steroid ring A), 6.64–6.84 (2H, m, 2-CH and
4-CH steroid ring A), 4.70–5.32 (8H, m, porphyrin-CH2),
3.94 (2H, t, J 6.2, CH O), 3.19 (6H, t, J 6.8, CH -I), 2.82–2.86
2
(
585 mg, 3.40 mmol) in toluene (1.5 L) was heated in the dark
at reflux for 2 h under nitrogen in a round-bottom flask (2 L)
fitted with a Dean–Stark trap and condenser for azeotropic
removal of water. Pyrrole 7 (13.7 g, 204 mmol) and 8-iodo-1-
octanal 13b (41.1 g, 170 mmol) were added slowly over 15 min
and the reaction mixture was heated at reflux for a further 5 h.
2
2
(2H, m), 0.78–2.51 (56H, m, includes steroid protons and
18-CH of steroid), ꢀ2.63 (2H, s, inner NH). d (50 MHz,
3
C
CDCl ) 188.53, 157.72, 154.24, 138.55, 132.49, 127.05,
3
126.85, 118.35, 115.87, 115.19, 113.42, 112.70, 104.52,
64.33, 50.97, 48.59, 44.50, 38.91, 36.45, 32.14, 31.10, 30.65,
30.20, 30.03, 27.04, 26.72, 26.49, 22.15, 14.43. m/z (HRFTICR-
2
,3,5,6-Tetrachloro-1,4-benzoquinone (TCQ) (41.7 g, 170 mmol)
dissolved in toluene (50 mL) was added, and the mixture was
heated at reflux for another 2 h, allowed to cool, and the solvent
removed under reduced pressure. The residue was dissolved in
dichloromethane, filtered through a short plug of silica, washed
with additional dichloromethane and the eluent was collected
and evaporated to dryness. The crude residue was further
purified by column chromatography over silica (1 : 1 light
petroleum/dichloromethane). The major dark-purple band
þꢂ
þꢂ
]
2
ESI) 1348.39304 [M ]; anal. calc. for [C H N O
4
6
6
87
1348.39576.
The third-running dark-purple band was collected and evap-
0
orated to dryness to afford 5,10,15,20-tetrakis{7 -[estra-1,3,5
(10)-trien-17-on-3-oxy]heptyl}porphyrin 16 (0.0913 g, 46.6 %)
ꢀ1
as a dark-purple pasty solid. R 0.18 (chloroform). nmax/cm
f
(CHCl ) 3321w (NH), 3124w, 2926s, 2858m (aliphatic CH ),
3
2

Synthesis of Steroid–Porphyrin Conjugates
1643
1
1
731s (C¼O), 1610w, 1498m, 1461m, 1352w, 1285w, 1242s,
160w, 1054w, 1011w, 912s. d (200 MHz, CDCl ) 9.45 (8H, s,
(9.6 mg, 4.05 %) as a dark-purple pasty solid. R 0.61 (CHCl ).
f
3
lmax/nm (CHCl ) (log e) 420 (5.03), 521 (3.75), 557 (3.60), 602
H
3
3
ꢀ
1
b-pyrrolic H), 7.07–7.20 (4H, m, 4 ꢁ CH steroid ring A), 6.53–
.84 (8H, m, 8 ꢁ CH steroid ring A), 4.70–5.02 (8H, m,
porphyrin-CH ), 4.21–4.24 (8H, m, alkyl chain), 3.95 (8H, t, J
(3.39), 659 (3.31). nmax/cm (CHCl ) 3316 (NH), 3234w,
3
6
3069w, 2925s, 2857m (aliphatic CH ), 1712m, 1671w,
1611w, 1497w, 1460m, 1374w, 1241m, 1140w, 1105w,
1029w, 914w, 791m, 734m, 700w, 638w, 577w, 531w. dH
2
2
6
.2, 4 ꢁ CH O), 2.77–2.82 (8H, m), 0.80–2.56 (96H, m,
2
includes steroid protons, C18-CH and alkyl chains), ꢀ2.64
(200 MHz, CDCl ) 9.47 (8H, s, b-pyrrolic H), 7.41 (8H, d,
3
3
0
0
0
0
(2H, s, inner NH). d (50 MHz, CDCl ) 221.66, 184.40, 157.72,
C
J 6.4, 2 -CH, 6 -CH (benzyl)), 7.38 (8H, t, J 7.6, 3 -CH, 5 -CH
0
3
1
6
3
38.57, 132.54, 127.06, 126.84, 115.86, 113.42, 105.74, 64.33,
0.20, 50.97, 48.60, 44.51, 44.08, 38.92, 36.45, 32.14, 31.06,
0.20, 30.03, 28.86, 27.04, 26.50, 22.13, 17.32, 14.43.
(benzyl)), 7.30–7.42 (4H, t, J 7.6, 4 -CH (benzyl)), 7.23–7.10
(4H, m, 4 ꢁ CH steroid ring A), 6.85–6.68 (8H, m, 8 ꢁ CH
steroid ring A), 5.03 (8H, s, OCH -Ph), 4.95 (8H, m, J 7.9,
2
porphyrin–CH –), 3.37–3.59 (4H, m, 17a-CH), 3.23–3.35 (8H,
2
Synthesis of 1 : 1 (3-O-Benzyl-oestradiol)–Porphyrin
Conjugate 18 and 4 : 1 (3-O-Benzyl-oestradiol)–
Porphyrin Conjugate 19
m, J 8.3, CH –O–steroid ring D), 2.80–2.89 (8H, m), 0.90–2.52
2
(
(
92H, m, steroid and alkyl chain), 0.89 (12H, s, 18-CH ), ꢀ2.63
3
2H, s, inner NH). d (50 MHz, CDCl ) 157.31, 139.41, 138.17,
C
3
To a solution of 3-benzyloxyestra-1,3,5(10)-triene-17b-ol
(200 mg, 0.552 mmol) in dry tetrahydrofuran (20 mL) was
137.73, 132.73, 128.97, 128.28, 127.85, 126.74, 115.35, 114.89,
112.81, 70.39, 50.81, 48.40, 44.37, 38.75, 36.26, 34.28, 32.38,
32.01, 30.49, 30.15, 30.05, 29.81, 29.44, 26.92, 26.32, 23.14,
[
38]
1
added sodium hydride (60 % dispersion in mineral oil) (132 mg,
7
5
at rt for 2 h. A solution of 5,10,15,20-tetrakis(7 -iodoheptyl)
porphyrin 14 (133 mg, 0.110 mmol) in dry tetrahydrofuran
(10 mL) was added and the resulting mixture was heated at
reflux with stirring under a dark nitrogen atmosphere for 72 h.
The reaction mixture was cooled to rt and the solvent removed
under vacuum. The crude residue was further fractionated by
column chromatography over silica (1 : 3 light petroleum/
dichloromethane) into four dark-purple bands.
.52 mmol). The reaction mixture was stirred under nitrogen
0
21.98, 14.56, 14.26. m/z (HRMALDI-TOF (dctb matrix))
þꢂ
1781.16719 (which infers the loss of one steroidal unit) [M
þꢂ
ꢀ
C H O ]; anal. calc. for [C123H152N O ] 1781.17064; and
4
2
5
30
2
4
1418.94884 (which is obtained by loss of two steroidal units)
þꢂ
þꢂ
[M ꢀ C H O ]; anal. calc. for [C H N O ] 1418.94606.
50
60
4
98 122
4
4
(3-O-Benzyl Oestradiol)-tetraarylporphyrin conjugate
21. To a solution of 3-benzyloxyestra-1,3,5(10)-triene-17b-
[
38]
ol 17 (100.0 mg, 0.276 mmol) in dry tetrahydrofuran (20 mL)
was added sodium hydride (60 % dispersion in mineral oil)
(66.2 mg, 2.76 mmol). The reaction mixture was stirred
under nitrogen at rt for 2 h. A solution of 5,10,15,20-tetrakis
[4-(chlorocarbonyl)phenyl]porphyrin 20 (59.6mg, 0.0689mmol)
in dry tetrahydrofuran (10 mL) was added and the resulting
mixture was heated at reflux with stirring under a dark nitrogen
atmosphere for 72 h. The reaction mixture was cooled to room
temperature and the solvent removed under vacuum. The crude
residue was further purified by column chromatography over
silica (1 : 4 dichloromethane/light petroleum). The major dark-
purple band was collected and evaporated to dryness to afford
the tetra-ester conjugate 21 (0.0121 g, 8.1 %) as a dark-pink–
The front-running dark-purple band was collected and evap-
orated to dryness to afford unreacted 5,10,15,20-tetrakis
0
(7 -iodoheptyl)porphyrin 14 (25.7 mg, 19.3 %) as a dark-purple
pasty solid.
The second-running dark-purple band was collected and
0
evaporated to dryness to afford 5-{7 -[3-benzyloxyestra-
0
1,3,5(10)-triene-17b-oxy]heptyl}-10,15,20-tris(7 -iodoheptyl)
porphyrin 18 (0.0520 g, 32.7 %) as a dark purple pasty solid.
ꢀ1
Rf 0.79 (1 : 3 light petroleum/dichloromethane). nmax/cm
CHCl ) 3318 (NH str.), 3065w, 2922s, 2856m (aliphatic
CH str.), 1736s, 1609w, 1577w, 1498m, 1458m, 1375w,
(
3
2
1
9
242s, 1158w, 1102w, 1025w, 913m. dH (300 MHz, CDCl )
3
purple pasty solid. R 0.78 (1 : 4 dichloromethane/light petro-
f
0
0
ꢀ1
.47 (8H, s, b-pyrrolic H), 7.45 (2H, d, J 7.2, 2 -CH, 6 -CH
0
leum). nmax/cm (CHCl ) 3404w, 3318w (NH), 3030w, 2926s,
3
0
(benzyl)), 7.40 (2H, t, J 6.2, 3 -CH, 5 -CH (benzyl)), 7.36 (1H, t,
J 7.8, 4 -CH (benzyl)), 7.20 (1H, d, J 8.5, 1-CHsteroid ring A),
2865w, 1719s (C¼O), 1608m (C¼C), 1499m, 1457w, 1379w,
0
1276s, 1171w, 1116m, 1023m, 920w. dH (300 MHz, CDCl )
3
6
4
.81–6.82 (1H, m, 2-CH steroid ring A), 6.75–6.76 (1H, m,
-CH), 5.05 (2H, s, OCH -benzyl group), 4.94 (8H, t, J 7.7,
8.84 (8H, s, b-pyrrolic H), 8.47 (8H, d, J 1.7, 6.4, ArH), 8.28
(8H, d, J 1.7, 6.4, ArH), 7.40 (4H, d, J 7.2, CH (benzyl)), 7.36
(8H, t, J 7.2, CH (benzyl)), 7.30 (8H, t, J 7.2, 4 -CH (benzyl)),
7.21 (4H, d, J 8.6, CH), 6.78 (4H, d, J 2.7, 8.6, CH), 6.72 (8H, d, J
2
0
CH -porphyrin), 3.46–3.48 (1H, m, 17a-CH), 3.31 (8H, t, J 8.2,
C H ), 2.86–2.90 (2H, m, 6a-CH, 6b-CH), 1.30–2.58 (53H, m,
2
b
2
steroid and alkyl chain), 0.92 (3H, s, 18-CH ), ꢀ2.62 (2H, br s,
2.4, CH), 5.04 (8H, s, OCH –Ph), 3.74 (4H, t, J 8.4, 17a-CH),
2.82–2.87 (8H, m), 1.18–2.34 (48H, m, steroid), 0.79 (12H, s,
3
2
inner NH). d (300 MHz, CDCl ) 157.51, 139.45, 138.20,
C
3
1
1
3
2
36.73, 132.74, 128.99, 128.23, 127.65, 126.77, 115.34,
14.82, 112.85, 89.45, 70.39, 50.81, 48.40, 44.37, 38.75,
6.26, 34.28, 32.38, 32.01, 30.49, 30.11, 30.15, 30.05, 29.81,
9.44, 26.92, 26.32, 23.14, 21.98, 14.56, 14.26. m/z
C-18 CH ), ꢀ2.65 (2H, s, inner NH). d (75 MHz, CDCl3)
3
C
221.28, 171.62, 167.08, 157.29, 157.22, 146.94, 138.39, 138.21,
137.75, 132.74, 128.28, 128.37, 127.84, 126.76, 115.33, 112.77,
70.38, 50.83, 48.41, 44.40, 43.97, 39.10, 38.76, 36.27, 32.00,
30.18, 30.06, 26.95, 26.31, 21.99, 14.26. m/z (ESI) 2169.6
(
HRMALDI-TOF (dctb matrix)) 1056.72182 (which infers the
þꢂ
þꢂ
þ
þ
loss of 3 HI units) [M ꢀ 3(HI)]; anal. calc. for [C H N O
]
[M þ H] ; [C148H142N O þ H ] requires 2169.1.
7
3
92
4
2
4 12
1
056.72148.
The third fraction isolated contained a mixture of the mono-
and the disubstituted benzyl oestradiol and tri-substituted
3-O-benzyl oestradiol) porphyrin conjugates as judged by
5,10,15,20-Tetrakis[3a-bromo-24-nor-5b-cholan-23-yl]
porphyrin 22 Boron tribromide (1 M in dichloromethane,
1.6 mL) was added to a stirring solution of porphyrin 12a
(22 mg, 13.0 mmol) in freshly distilled dichloromethane
(65 mL). The reaction mixture was stirred at rt under nitrogen
for 16 h. The reaction was then quenched with MeOH (60 mL)
and water (100 mL), and the aqueous phase extracted with ethyl
acetate (100 mL). The combined organic extracts were dried
over anhydrous Na SO and the desired product isolated by
(
1
MALDI-TOF mass spectrometry and H NMR spectroscopy
of this mixture and of partially further fractionated material.
The fourth-running dark-purple band was collected and
evaporated to dryness to afford 5,10,15,20-tetrakis{7 -[3-
benzyloxyestra-1,3,5(10)-triene-17b-oxy]heptyl}porphyrin 19
0
2
4

1
644
F. Taba et al.
column chromatography eluting with dichloromethane to give
supports the stereochemical assignment, low- and high-resolution
mass spectra, and NMR spectra for all new compounds.
5,10,15,20-tetrakis[3a-bromo-24-nor-5b-cholan-23-yl]porphyrin
2
2 as a dark-red crystalline solid (17 mg, 77 %), mp 143–1458C.
lmax/nm (CHCl ) (log e) 418s (5.24), 520m (3.61), 553m (3.48),
Acknowledgements
3
6
02w (3.02), 660m (3.30). d (400 MHz, CDCl ) 9.43 (8H, s,
H 3
The authors thank the Australian Research Council for partial funding of this
research (Discovery Grant DP1092560). A.H.L. was an exchange student
from G o¨ teborgs Universitet, Sweden. The authors thank The University of
Sydney for an Australian Postgraduate Award to F.T.
b-pyrrolics), 5.10–4.92 (4H, m) 4.85–4.66 (4H, m), 4.06 (4H, m,
C-3), 2.61–2.63 (8H, m), 2.4–0.5 (132H, m, steroid), ꢀ2.61 (2H,
s, NH). d (50 MHz, CDCl ) 159.26, 119.09, 56.85, 56.46,
C
3
4
2
1
3.35, 40.91, 37.80, 36.17, 34.87, 32.32, 31.30, 30.43, 30.09,
9.75, 27.47, 26.77, 24.75, 24.12, 23.88, 23.08, 21.28, 19.81,
4.50, 12.60 (two quaternary signals missing). m/z (MALDI-
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