The choice of phosphane reagent in Fukuyama-Mitsunobu alkylation: Intramolecular selectivity between primary and secondary alcohols in the preparation of asymmetric tetraamine building blocks for synthesis of philanthotoxins

Article abstract of DOI:10.1002/ejoc.200300186

Philanthotoxin-433 (PhTX-433) is a polyamine wasp toxin that antagonizes certain ionotropic receptors noncompetitively. Four analogues of PhTX-433, C-methylated in the polyamine chain, were synthesized from (RS)-1,3-butanediol, two diamine building blocks, and an activated/protected tyrosine derivative. Use of a phosphane reagent more bulky than trimethylphosphane gave a high intramolecular selectivity between primary and secondary hydroxy groups in the Fukuyama-Mitsunobu reaction. Thus, trimethylphosphane proved to be the only phosphane reagent that enabled alkylation of 2-nitrobenzenesulfonamides with a wide range of secondary alcohols, whereas tributylphosphane was selective for primary alcohol groups. This selectivity was utilized to obtain orthogonally protected, asymmetric, branched tetraamines, employed for solution-phase synthesis of philanthotoxin analogues. The branched philanthotoxin analogues thus obtained were tested in an electrophysiological assay using rat brain ionotropic glutamate receptors expressed in Xenopus laevis oocytes. Their potencies proved to be similar to the corresponding nonbranched analogues. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejoc.200300186

FULL PAPER
The Choice of Phosphane Reagent in Fukuyama؊Mitsunobu Alkylation:
Intramolecular Selectivity Between Primary and Secondary Alcohols in the
Preparation of Asymmetric Tetraamine Building Blocks for Synthesis of
Philanthotoxins
Christian A. Olsen,[a] Malene R. Jørgensen,[a] Matthias Witt,[b] Ian R. Mellor,[c]
Peter N. R. Usherwood,[c] Jerzy W. Jaroszewski,[a] and Henrik Franzyk*[a]
Keywords: Natural products / Alkylation / Sulfonamides / Phosphanes / Amines
Philanthotoxin-433 (PhTX-433) is a polyamine wasp toxin
that antagonizes certain ionotropic receptors noncompetit-
secondary alcohols, whereas tributylphosphane was select-
ive for primary alcohol groups. This selectivity was utilized
ively. Four analogues of PhTX-433, C-methylated in the poly- to obtain orthogonally protected, asymmetric, branched
amine chain, were synthesized from (RS)-1,3-butanediol, two
diamine building blocks, and an activated/protected tyrosine
derivative. Use of a phosphane reagent more bulky than tri-
methylphosphane gave a high intramolecular selectivity be-
tween primary and secondary hydroxy groups in the
Fukuyama−Mitsunobu reaction. Thus, trimethylphosphane
tetraamines, employed for solution-phase synthesis of phil-
anthotoxin analogues. The branched philanthotoxin ana-
logues thus obtained were tested in an electrophysiological
assay using rat brain ionotropic glutamate receptors ex-
pressed in Xenopus laevis oocytes. Their potencies proved to
be similar to the corresponding nonbranched analogues.
proved to be the only phosphane reagent that enabled al- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
kylation of 2-nitrobenzenesulfonamides with a wide range of
Germany, 2003)
Introduction
e.g. nicotinic acetylcholine receptors[4,5] and ionotropic glu-
tamate receptors.[6Ϫ9] A large number of philanthotoxin
analogues have been synthesized and evaluated pharmaco-
Polyamine structural elements are found in various natu- logically in order to obtain structure-activity relationships
ral products such as antibiotics and toxins from animals (SAR).[4,9Ϫ12] Despite the recent focus on variations in the
and plants. Many important biological activities have been polyamine chain of philanthotoxins,[10,12] only two ana-
reported for these naturally occurring polyamine derivatives logues containing a branched polyamine moiety have been
as well as for their synthetic analogues.[1] Philanthotoxins described so far.[13,14] These are the PhTX-433 analogues 4
constitute a group of polyamine toxins composed of a poly- and 5, containing a methyl or an n-butyl group in the 7-
amine chain connected via an amide bond to a relatively position (Figure 2). Using a locust muscle twitch contrac-
nonpolar head group, consisting of an N-acylated amino tion inhibition assay, the n-butyl analogue showed a 5.6-
acid.[2Ϫ4] Philanthotoxin-433 (PhTX-433, 1) was originally fold increase in potency compared to the native toxin 1.[14]
isolated from the venom of the female Egyptian digger The fact that the biological consequences of the presence of
wasp Philanthus triangulum L.[2,3] The structures of PhTX-
433 (1) and its synthetic analogues PhTX-334 (2) and
PhTX-343 (3) are shown in Figure 1. These toxins antagon-
ize noncompetitively various classes of ionotropic receptors,
[a]
Department of Medicinal Chemistry, Danish University of
Pharmaceutical Sciences,
Universitetsparken 2, 2100 Copenhagen, Denmark
Fax: (internat.) ϩ 45-35306040
E-mail: hf@dfh.dk
[b]
Bruker Daltonik GmbH,
Fahrenheitstrasse 4, 28359, Bremen, Germany
[c]
Division of Molecular Toxicology, School of Life and
Environmental Sciences, University of Nottingham,
Nottingham, NG7 2RD, UK
Figure 1. General structure of philanthotoxins PhTX-klm, where
numerals klm denote the number of methylene groups separating
the nitrogen atoms in the polyamine chain
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DOI: 10.1002/ejoc.200300186
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The Choice of Phosphane Reagent in FukuyamaϪMitsunobu Alkylation
FULL PAPER
(triflamide or p-toluenesulfonamide) with the 1-O-benzoyl
derivative of 1,3-butanediol under Mitsunobu con-
ditions.[26,27] This type of activation, however, did not seem
very appealing since quite harsh Birch conditions[28] are
necessary for deprotection of the resulting polyamine. The
more recently described Tsunoda conditions, employing tri-
butylphosphane (TBP) and 1,1Ј-(azodicarbonyl)dipiperid-
ide (ADDP),[29] were reported to give excellent yields in the
alkylation of 2-nitrobenzenesulfonamides in the synthesis
of polyamine toxins on solid phase.[30] Consequently, this
reagent combination was selected, along with the less hin-
dered N,N,NЈ,NЈ-tetramethylazodicarboxamide (TMAD)[31]
and trimethylphosphane (TMP)[32,33] for our investigation
of the alkylation of 2-nitrobenzenesulfonamides (Ns-am-
ides) with secondary alcohols. The Ns group is convenient
in both solid and solution phase syntheses, because it is
readily removed under mild conditions. Tsunoda et al. ob-
tained 34% and 40% yields in the alkylation of 2-octanol
with N-methyl-p-toluenesulfonamide using ADDP-TBP
and TMAD-TBP, respectively.[31]
Results
Figure 2. Structures of branched philanthotoxin analogues 4؊9
Using ADDP-TBP or TMAD-TBP and a number of sec-
ondary alcohols, no or very little conversion was observed
with sulfonamides other than N-methyl-p-toluenesulfonam-
a branch in the polyamine chain of polyamine toxins have ide. This emphasizes the need of a careful choice of the
not been investigated systematically is due to the present test sulfonamide for systematic examination of reagents and
lack of generally applicable synthetic routes to such philan- optimisation of the reaction conditions for this particular
thotoxin analogues.
reaction. We have selected 2-nitro-N-(2-phenylethyl)ben-
The synthetic strategies generally used for construction zenesulfonamide (10), which is convenient with respect to
of polyamines by sequential chain elongation may be classi- reactivity, as benzylic or allylic sulfonamides should be avo-
fied into three major groups: (i) classical alkylation reac- ided due to their often enhanced reactivity. The test al-
tions, (ii) Mitsunobu reactions, and (iii) methods based on cohols should preferably comprise aliphatic and alicyclic
reduction of intermediary amides or imines.[15] Thus, in all compounds together with allylic, homoallylic and benzylic
previously reported procedures, polyamine toxins have been representatives. The results of alkylations using either 1-bu-
synthesized from diamines (often activated as sulfonamides) tanol or 2-butanol (presented in Table 1), showed that the
in combination with halides,[16,17] amino alcohols,[18Ϫ20] choice of the azo-reagent in combination with TMP had
amino aldehydes[21,22] or amino acids.[23]
only a minor effect on the yield. Thus, compounds 11 and
By contrast, the method presented in this work involves 12 (prepared by Method B or C) were obtained in 51Ϫ83%
preparation of polyamine moieties of philanthotoxin ana- yields, the lowest yields being observed with the secondary
logues from diamines (activated as sulfonamides) and diols. alcohol. On the other hand, the yield was strongly dimin-
One of our aims was to develop a general procedure for ished in the case of 2-butanol when TBP was used (12,
the incorporation of secondary alcohols into the polyamine Method A; in Table 1). This indicated that the alkoxytribu-
chain. The selected diol, (RS)-1,3-butanediol, enables syn- tylphosphonium intermediate[25] that was presumably in-
thesis of the four branched analogues 6؊9 shown in Fig- volved in the reaction was too sterically congested, or was
ure 2.
not formed at all. The combination TMP-ADDP worked
Initially, we considered the conventional FukuyamaϪ satisfactorily with a variety of secondary alcohols to give
Mitsunobu conditions employing diethyl azodicarboxylate products 13؊18, as shown in Table 2. It was not possible
and triphenylphosphane in CH2Cl2, which allows primary to isolate any of the expected coupling product 19 using
alcohols to alkylate 2-nitrobenzenesulfonamides.[24,25] Ear- menthol, and since its hydroxy group is particularly hin-
lier work in this area appears to be limited to the alkylation dered, this observation confirms that steric hindrance of the
of
sulfonamide-activated
methylamine
derivatives alcohol group is of major importance in the reaction.
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H. Franzyk et al.
FULL PAPER
Table 1. Isolated yields from FukuyamaϪMitsunobu reactions be-
tween 10 and 1-butanol or 2-butanol
[a]
[b]
[c]
Method A (toluene).
toluene).
Method B (THF). Method C (THF/
Scheme 1. Reagents: i) TBP, TMAD, THF, 24 h, 63%; ii) TMP,
ADDP, THF, 40 h, 66%
Table 2. Isolated yields from FukuyamaϪMitsunobu couplings be-
tween 10 and secondary alcohols using the TMP-ADDP reagent
system
The observed intramolecular selectivity in the
FukuyamaϪMitsunobu alkylation of primary and second-
ary alcohol groups was utilized in the synthesis of four
branched philanthotoxin analogues, namely 8-methyl-
PhTX-433 (6), 6-methyl-PhTX-433 (7), 5-methyl-PhTX-334
(8), and 7-methyl-PhTX-334 (9). These four analogues were
obtained from only four building blocks: two selectively
protected and activated diamine derivatives 22 and 23, the
N-acylated tyrosine active ester 24, and (RS)-1,3-butanediol
(Scheme 2). Compound 22 was prepared in two steps from
1,4-butanediamine. In the first step, N-(2-nitrobenzenesul-
fonyl)-1,4-butanediamine was prepared by treatment with
2-nitrobenzenesulfonyl chloride (NsCl);[16] the resulting
crude product was protected with a 2-(trimethylsilyl)ethoxy-
carbonyl (Teoc) group using 2-(trimethylsilyl)ethyl 4-nitro-
phenyl carbonate.[34,35] Compound 23 was prepared by
treatment of 1,3-propanediamine with NsCl followed by di-
(tert-butyl) dicarbonate [(Boc)2O] as described by Hidai et
al.[36] Conversion of O-(tert-butyl)tyrosine into 24 was per-
formed by successive acylation with butyryl chloride[37] and
formation of the pentafluorophenyl ester (Pfp-ester) using
A very high intramolecular selectivity between a primary pentafluorophenyl trifluoroacetate.[38]
and a secondary hydroxy group could be obtained by the
A six-step synthesis of 8-methyl-PhTX-433 (6) from the
proper choice of the trialkylphosphane reagent. Thus, when above-mentioned building blocks was carried out as shown
(RS)-1,3-butanediol was subjected to alkylation with 10 in Scheme 3. In the first step, sulfonamide 22 was N-alkyl-
using the TBP-TMAD reagent pair (Scheme 1), the ated with 1,3-butanediol, and by choosing the TBP-ADDP
monoalkylation product 20 was isolated in 63% yield along reagent system 25 could be isolated in 53% yield. The vac-
with only 4% of the dialkylation product 21. The modest uum liquid chromatography (VLC) purification was, how-
yield of 20 (based on the diol) may be due to an intramol- ever, quite tedious and some additional, impure fractions of
1
ecular ether formation as a side reaction. The obtained sul- 25 were obtained (analysis by H NMR indicated a total
fonamide 20 could then react further with 10, using the re- yield of approximately 70%). In the next step, 25 was alkyl-
agent pair TMP-ADDP, to give the bis-sulfonamide 21 in ated with 23 using the TMP-ADDP system to give the fully
66% yield. The observed selectivity in the alkylation with protected polyamine 26. The N-Teoc group was selectively
(RS)-1,3-butanediol is quite remarkable considering that cleaved with tetrabutylammonium fluoride (TBAF)[39,40] to
this secondary alcohol belongs to the least sterically hin- give 27, which was acylated using the tyrosine building
dered ones.
block 24.[41] This afforded the fully protected, branched phi-
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The Choice of Phosphane Reagent in FukuyamaϪMitsunobu Alkylation
FULL PAPER
Scheme 2. Reagents: i) Et3N, NsCl, CH2Cl2, 4 h, 60%; ii) 2-trime-
thylsilylethyl p-nitrophenylcarbonate, DIPEA, THF, 50 °C, 2 h,
89%; iii) Boc2O, MeOH, N2, 22 h, 94%; iv) butyryl chloride, THF,
2  NaOH; v) pentafluorophenyl trifluoroacetate, pyridine, DMF,
5 h, 57% (for iv and v)
lanthotoxin analogue 28, which was treated with diazabicy-
clo[5.4.0]undec-7-ene (DBU) and 2-mercaptoethanol[42,43]
to remove the Ns groups. Finally removal of the tert-butyl
and Boc groups in 29 using trifluoroacetic acid (TFA) gave
8-methyl-PhTX-433 (6) as a tris(TFA) salt.
Similarly, a six-step synthesis of 6-methyl-PhTX-433 (7)
was performed as depicted in Scheme 4. The sequence dif-
fers from that described above only with respect to the or-
der of the two FukuyamaϪMitsunobu alkylations. Thus, 23
was alkylated with 1,3-butanediol using TBP-ADDP to give
30, which was further alkylated with 22 using the TMP-
ADDP system. This reversed incorporation of the two
building blocks resulted in the fully protected polyamine
31. Selective cleavage of the N-Teoc group, acylation and
deprotection were performed as above, to give 6-methyl-
PhTX-433 (7) as a tris(TFA) salt.
5-Methyl-PhTX-334 (8) was synthesized in four steps
from fully protected polyamine 26 (Scheme 5). Here the N-
Boc group was cleaved selectively with p-toluenesulfonic
acid (TsOH) in diethyl ether; hence the acid-labile N-Teoc
group proved stable under these conditions, as previously
reported by Rosowsky et al.[35,44] The resulting amine 35
was acylated with 24 to give 36. Deprotection was per-
formed via 37 as already described, yielding the tris(TFA)
salt of 5-methyl-PhTX-334 (8). A similar pathway starting
with 31 and leading, via 38؊40, to the tris(TFA) salt of 7-
methyl-PhTX-334 (9), was performed as shown in
Scheme 3. Reagents: i) TBP, ADDP, THF, 24 h, 70%; ii) TMP,
ADDP, THF, 40 h, 68%; iii) TBAF, THF, 50 °C, 2 h, 62%; iv) DI-
PEA, DMF, 2 h, 88%; v) 2-mercaptoethanol, DBU, DMF, 2 h,
67%; vi) TFA, CH2Cl2, 3 h, 92%
In vitro Electrophysiology: Concentration-inhibition re-
lationships for the four branched philanthotoxin derivatives
6؊9 and PhTX-343, obtained in an electrophysiological
glutamate receptor assay,[7,8] provided the IC50 values
shown in Table 3. Xenopus laevis oocytes were injected with
rat brain RNA and incubated at 18 °C for 4Ϫ9 days. A
two-electrode voltage-clamp (TEVC) was used to record the
responses to agonist alone (100 µM kainic acid) and to co-
application of agonist (100 µM kainic acid) and each of the
philanthotoxin analogues at a holding potential (VH) of
Ϫ80 mV. In this assay, responses to kainic acid are mediated
by AMPA receptors.[45]
Discussion
Four novel philanthotoxin analogues 6, 7, 8 and 9, C-
Scheme 6. The tris(TFA) salts of 6؊9 were purified by pre- methylated at α-positions to the nitrogen atoms in the poly-
parative, reversed-phase HPLC and characterized by amine chain, were synthesized by applying a novel and ver-
1
HRMS, H and 13C NMR spectroscopy. All four philan- satile solution-phase strategy. The intermediate, orthog-
thotoxin analogues 6؊9 represent mixtures of stereoiso- onally protected tetraamines 26 and 31 were synthesized
mers with respect to the stereogenic centers in the polyam- from two diamine building blocks 22 and 23 and the com-
ine chains.
mercially available (RS)-1,3-butanediol, utilizing two trialkyl-
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H. Franzyk et al.
FULL PAPER
Scheme 6. Reagents: i) pTsOH, diethyl ether, 50 °C, 1 h, 63%; ii)
DIPEA, DMF, 2 h, 83%; iii) 2-mercaptoethanol, DBU, DMF, 2 h,
54%; iv) TFA, CH2Cl2, 3 h, 99%
Table 3. Antagonism by PhTX-343 and branched analogues of rat-
brain AMPA receptors expressed in Xenopus laevis oocytes
Compound
IC50, µM (n ϭ 5 oocytes)
3 (PhTX-343)
6 (8-Methyl-PhTX-433)
7 (6-Methyl-PhTX-433)
0.13 Ϯ 0.03
0.26 Ϯ 0.08
0.07 Ϯ 0.02
0.13 Ϯ 0.02
0.17 Ϯ 0.03
Scheme 4. Reagents: i) TBP, ADDP, THF, 24 h, 56%; ii) TMP,
ADDP, THF, 40 h, 69%; iii) TBAF, THF, 50 °C, 2 h, 62%; iv) DI-
PEA, DMF, 2 h, 91%; v) 2-mercaptoethanol, DBU, DMF, 2 h, 8 (5-Methyl-PhTX-334)
62%; vi) TFA, CH2Cl2, 3 h, 96%
9 (7-Methyl-PhTX-334)
phosphane reagents (TMP and TBP) to achieve differen-
tiation between primary and secondary hydroxy groups in
the FukuyamaϪMitsunobu alkylation method. The applied
solution-phase strategy is compatible with an easy scale-up.
Moreover, since FukuyamaϪMitsunobu alkylations have
previously been applied on solid phase,[30,46,47] we believe
that our strategy is applicable to parallel synthesis of polya-
mines on solid supports.
The protocol presented here employs for the first time
diols as building blocks for synthesis of philanthotoxin ana-
logues. This is an advantage because of the variety of diols
that are commercially available. This broader availability of
diols as compared to, e.g., dihalides or amino alcohols, al-
lows easy synthetic access to a variety of novel philantho-
toxin analogues. A major advantage of the present method-
ology is that protection of the hydroxy groups of diols is
not necessary. This may be exploited either in bisalkylation
reactions with two mol of a 2-nitrobenzenesulfonamide re-
agent, or in monoalkylation reactions as those in Scheme 2
and 3, simply by the proper choice of the trialkylphosphane.
If monoalkylation of a symmetric diol (with two primary
or two secondary hydroxy groups) is required, monoprotec-
Scheme 5. Reagents: i) pTsOH, diethyl ether, 50 °C, 1 h, 70%; ii)
DIPEA, DMF, 2 h, 76%; iii) 2-mercaptoethanol, DBU, DMF, 2 h,
77%; iv) TFA, CH2Cl2, 3 h, 97%
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The Choice of Phosphane Reagent in FukuyamaϪMitsunobu Alkylation
FULL PAPER
14 mL/min, using water/acetonitrile/TFA, 85:15:0.1 as mobile
phase. High-resolution mass (HRMS) measurements for exact
mass determination were performed with a Bruker APEX III Four-
ier transform mass spectrometer equipped with a 7-Tesla supercon-
ducting magnet and an external electrospray ion source (Apollo
source). The spectra were externally calibrated with a capillary
skimmer dissociation spectrum of LHRH (luteinizing hormone re-
leasing hormone). The samples were introduced into the electro-
spray ion source using a 250-µL syringe, with a syringe pump flow
2 µL/min.
tion is necessary. Thus, it was demonstrated that alcohols
protected as silyl ethers are compatible with the reaction
conditions (e.g. leading to 18). In such cases an N-Boc pro-
tected sulfonamide building block should be introduced be-
fore an N-Teoc protected sulfonamide in order to allow
selective removal of the silyl ether protective group.
Selective cleavage of the N-Boc and N-Teoc groups in the
two protected tetraamines 26 and 31 gave rise to four differ-
ent partially protected polyamines 27, 32, 35 and 38, ready
for acylation with the Pfp-ester of an N-acylated amino acid
such as 24. In general, the Pfp-ester couplings[40,48] pro-
ceeded in high yields (76Ϫ92%), whereas the final two-step
deprotection gave moderate to good yields (54Ϫ75%). The
overall yields of the purified final products 6؊9, based on
compounds 22 or 23 were in the range 11Ϫ17%. The purifi-
cation was readily achieved by reversed-phase preparative
HPLC.
The four branched philanthotoxin analogues 6؊9 anta-
gonized AMPA receptors expressed in Xenopus laevis
oocytes. The observed potencies were all within twofold of
the potency of PhTX-343 (3), a usual reference compound
(Table 3). Thus, the introduction of C-methyl groups in
PhTX analogues, placed as in 6؊9, does not significantly
enhance the antagonistic potency as compared to 3. Never-
theless, the synthetic methodology presented here is poten-
tially useful for further exploration of the structure-activity
2-Nitro-N-(2-phenylethyl)benzenesulfonamide (10): 2-Phenylethyl-
amine (0.42 mL, 3.3 mmol) and Et3N (0.60 mL, 4.3 mmol) were
dissolved in dry CH2Cl2 (3 mL) and stirred on an ice-bath. To this
solution 2-nitrobenzenesulfonyl chloride (880 mg, 4.0 mmol, 1.2
equiv.) in CH2Cl2 (3 mL) was added, the ice-bath was removed,
and the mixture was stirred at room temperature overnight. Then
the mixture was diluted with CH2Cl2 (50 mL) and washed with
brine (2 ϫ 50 mL). The combined aqueous phases were extracted
with CH2Cl2 (3 ϫ 30 mL), and the combined organic layers were
dried (Na2SO4), filtered and concentrated in vacuo. The residue
was taken up in CH2Cl2 (3 mL) and loaded onto a VLC column
(4 ϫ 4 cm). Elution with hexane, hexane/EtOAc (10:1 and 4:1) af-
1
forded 10[50] (907 mg; 89%) as white crystals (m.p. 90Ϫ91 °C). H
NMR (400 MHz, CDCl3): δ ϭ 2.83 (t, J ϭ 7.0 Hz, 2 H, CH2Ph),
3.39 (dt, J ϭ 6.1 Hz, 2 ϫ 7.0 Hz, 2 H, CH2N), 5.31 (br. s, 1 H,
NH), 7.01 (m, 2 H, Ph), 7.23 (m, 3 H, Ph), 7.72 (m, 2 H, Ns), 7.82
(m, 1 H, Ns), 8.01 (m, 1 H, Ns) ppm. 13C NMR (75 MHz, CDCl3):
δ ϭ 36.0, 45.1, 125.7, 127.2, 128.9 (2 C), 129.0 (2 C), 131.2, 133.1,
relationships of philanthotoxins. In a recent study by Kro- 133.7, 134.0, 137.6 ppm.
mann et al.,[49] the position of the secondary amino group
N-Butyl-2-nitro-N-(2-phenylethyl)benzenesulfonamide (11). Method
in PhTX-83 was systematically moved along the triamine
chain. PhTX-56 was shown to be a highly potent antagonist
of homomeric GluR1 receptors, with an IC50 value in the
low nanomolar region.[49] Thus, pharmacological evalu-
ation of philanthotoxins combining the presence of C-alky-
A: 1-Butanol (26 µL, 0.3 mmol, 1.5 equiv.) and 10 (61 mg,
0.2 mmol) were dissolved in toluene (3 mL) and stirred in a septum-
sealed flask on an ice-bath. To this solution TBP (75 µL, 0.3 mmol,
1.5 equiv.) and TMAD (51 mg, 0.3 mmol, 1.5 equiv.) were added,
and stirring was continued at room temperature for 20 h. Then the
lation sites with altered positions of the secondary amino mixture was concentrated in vacuo and the residue was taken up
in CH2Cl2 (2 mL) and loaded onto a VLC column (3 ϫ 3 cm).
Elution with hexane and hexane/EtOAc (15:1 and 7:1) afforded 11
(64 mg; 89%) as a colourless syrup. For spectroscopic data see 11
(Method C) below.
groups may be of interest.
Experimental Section
N-Butyl-2-nitro-N-(2-phenylethyl)benzenesulfonamide (11). Method
B: 1-Butanol (26 µL, 0.3 mmol, 1.5 equiv.) and 10 (61 mg,
0.2 mmol) were dissolved in THF (1 mL) and stirred in a septum-
sealed flask. To this solution TMP (3 mL, 1.0  in THF, 0.3 mmol,
1.5 equiv.) and TMAD (51 mg, 0.3 mmol, 1.5 equiv.) were added
and stirring was continued at room temperature for 20 h. Then the
mixture was concentrated in vacuo, and the residue was taken up
in CH2Cl2/hexane (1:1) (2 mL) and loaded onto a VLC column
(2.7 ϫ 3 cm). Elution with hexane and hexane/EtOAc (15:1 and
6:1) afforded 11 (58 mg; 80%) as a colourless syrup. For spectro-
scopic data see 11 (Method C) below.
General Procedures: Unless otherwise stated, starting materials
were obtained from commercial suppliers. O-(tert-Butyl)tyrosine
was obtained from Novabiochem (Läufelingen, Switzerland).
Tetrahydrofuran (THF) was distilled under N2 from sodium/benzo-
phenone immediately before use. Dry dichloromethane was distilled
˚
from P2O5 and kept over 4 A molecular sieves. Water for reversed-
phase high-performance liquid chromatography (HPLC) was fil-
tered through a 0.22-µm pore filter. 1H NMR and 13C NMR spec-
tra were recorded at 400.13 MHz and 100.62 MHz, respectively,
with
a Bruker AMX 400 spectrometer, or at 300.06 and
75.45 MHz, respectively, with a Varian Gemini 2000 spectrometer,
using CDCl3 or CD3OD as solvent and tetramethylsilane (TMS)
as internal standard. Coupling constants (J values) are given in
N-Butyl-2-nitro-N-(2-phenylethyl)benzenesulfonamide (11). Method
C: 1-Butanol (26 µL, 0.3 mmol, 1.5 equiv.) and 10 (61 mg,
0.2 mmol) were dissolved in toluene (2 mL) and stirred on an ice-
bath in a septum-sealed flask. To this solution TMP (0.3 mL, 1.0
 in THF, 0.3 mmol, 1.5 equiv.) and ADDP (75 mg, 0.3 mmol, 1.5
equiv.) were added and stirring was continued for 20 h at room
1
Hertz (Hz) and multiplicities of H NMR signals are reported as
follows: s, singlet; d, doublet; t, triplet; q, quartet; p, pentet; m,
multiplet, br., broad signal. Vacuum liquid chromatography (VLC)
was performed using Merck silica gel 60 H, particle size Ͻ 45 µm
(90%). Preparative HPLC system consisted of a Waters model 590 temperature. Then the mixture was concentrated in vacuo and the
pump, a Waters Lambda-Max model 481 spectrophotometric de-
tector and a 25 ϫ 2.12 cm Phenomenex Luna 5-C18(2) column, 5
µm. The chromatograph operated isocratically at a flow-rate of
residue was taken up in CH2Cl2 (2.5 mL) and loaded onto a VLC
column (3 ϫ 3 cm). Elution with hexane and hexane/EtOAc (15:1
and 7:1) afforded 11 (60 mg; 83%) as a reddish oil. 1H NMR
Eur. J. Org. Chem. 2003, 3288Ϫ3299
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3293

H. Franzyk et al.
FULL PAPER
(400 MHz, CDCl3): δ ϭ 0.89 (t, J ϭ 7.3 Hz, 3 H, CH3), 1.29 (m, 3.99 (sextet, J ϭ 6.9 Hz, 1 H, NCH), 7.21Ϫ7.31 (m, 5 H, Ph), 7.57
2 H, CH2CH3), 1.54 (m, 2 H, CH2CH2CH3), 2.85 (m, 2 H, CH2Ph), (m, 1 H, Ns), 7.66 (m, 2 H, Ns), 8.03 (m, 1 H, Ns) ppm. 13C NMR
3.33 (m, 2 H, NCH2CH2Ph), 3.51 (m, 2 H, NCH2CH2CH2CH3), (100 MHz, CDCl3): δ ϭ 13.8, 19.2, 19.6, 37.8, 38.5, 45.1, 54.3,
7.15Ϫ7.26 (m, 5 H, Ph), 7.60Ϫ7.66 (m, 3 H, Ns), 7.96 (m, 1 H, 123.9, 126.6, 128.5, 128.6, 128.7, 128.8, 130.8, 131.4, 133.3, 133.9,
Ns) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 13.7, 19.8, 30.2, 35.2, 138.7, 148.1 ppm. HRMS: [C19H24N2O4S ϩ Na]ϩ calculated,
47.6, 48.8, 124.4, 126.9, 128.8 (2 C), 129.0 (2 C), 130.9, 131.8, 133.6,
133.9, 138.3, 148.3 ppm. HRMS: [C18H22N2O4S ϩ Na]ϩ calcu-
lated, 385.11925; found, 385.11924.
399.13490; found, 399.13495.
N-(1-Methylbut-2-enyl)-2-nitro-N-(2-phenylethyl)benzenesulfon-
amide (14): Prepared from 10 (61 mg, 0.2 mmol) as described for
12 (Method C) to give 14 (40 mg; 58%) as a colourless syrup. H
1
N-(sec-Butyl)-2-nitro-N-(2-phenylethyl)benzenesulfonamide
(12).
Method A: 2-Butanol (23 µL, 0.25 mmol, 1.5 equiv.) and 10 (53 mg,
0.17 mmol) were dissolved in toluene (3 mL) and stirred in a sep-
tum-sealed flask. To this solution TBP (64 µL, 0.26 mmol, 1.5
equiv.) and TMAD (45 mg, 0.26 mmol, 1.5 equiv.) were added and
stirring was continued at room temperature for 20 h. Then another
0.17 mmol (1.0 equiv.) of TBP and TMAD were added and stirring
was continued for an additional 22 h. The mixture was then con-
centrated in vacuo, the residue was taken up in CH2Cl2 (2.5 mL)
and loaded onto a VLC column (3 ϫ 3 cm). Elution with hexane
and hexane/EtOAc (15:1 and 6:1) afforded 12 (2 mg; 3%) as a
colourless syrup, along with unchanged 10 (44 mg; 83%). For spec-
troscopic data see 12 (Method C) below.
NMR (400 MHz, CDCl3): δ ϭ 1.30 (d, J ϭ 6.9 Hz, 3 H,
NCHCH3), 1.66 (dt, J ϭ 1.5 Hz, 6.4 Hz, 3 H, CHϭCHCH3),
2.88Ϫ2.95 (m, 2 H, CH2Ph), 3.38 (m, 2 H, NCH2), 4.56 (m, 1 H,
NCH), 5.44 (dq, J ϭ 3 ϫ 7.0 Hz and 15.5 Hz, 1 H, CHϭCHCH3),
5.58 (m, 1 H, CHϭCHCH3), 7.16Ϫ7.29 (m, 5 H, Ph), 7.60Ϫ7.69
(m, 3 H, Ns), 8.03 (m, 1 H, Ns) ppm. 13C NMR (100 MHz,
CDCl3): δ ϭ 17.8, 18.4, 38.1, 45.8, 54.9, 124.0, 126.5, 128.2, 128.6
(2 C), 128.7 (2 C), 130.4, 130.7, 131.5, 133.3, 134.1, 138.6,
148.0 ppm. HRMS: [C19H22N2O4S ϩ Na]ϩ calculated, 397.11925;
found, 397.11919.
N-(1-Methylbut-3-enyl)-2-nitro-N-(2-phenylethyl)benzenesulfon-
amide (15): Prepared from 10 (61 mg, 0.2 mmol) as described for
12 (Method C) to give 15 (31 mg; 42%) as a pale yellow oil. 1H
NMR (400 MHz, CDCl3): δ ϭ 1.19 (d, J ϭ 6.9 Hz, 3 H,
NCHCH3), 2.22 and 2.33 (ddd, J ϭ 6.7 Hz, 6.9 Hz, 13.5 Hz, 2 H,
CH2CHϭCH2), 2.98 (m, 2 H, CH2Ph), 3.43 (m, 2 H, NCH2), 4.06
(m, 1 H, NCH), 4.99 (m, 2 H, CH2ϭCH), 5.67 (m, 1 H, CHϭ
CH2), 7.21Ϫ7.31 (m, 5 H, Ph), 7.60 (m, 1 H, Ns), 7.66 (m, 2 H,
Ns), 8.04 (m, 1 H, Ns) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ
19.0, 38.4, 40.2, 45.4, 54.3, 117.7, 124.0, 126.6, 128.6, 128.7, 128.8
(2 C), 130.9, 131.4, 133.4, 134.0, 134.3, 138.6 148.0 ppm. HRMS:
[C19H22N2O4S ϩ Na]ϩ calculated, 397.11925; found, 397.11936.
N-(sec-Butyl)-2-nitro-N-(2-phenylethyl)benzenesulfonamide
(12).
Method B: 2-Butanol (28 µL, 0.3 mmol, 1.5 equiv.) and 10 (61 mg,
0.2 mmol) were dissolved in toluene (2 mL) and stirred in a septum-
sealed flask. To this solution TMP (0.3 mL, 1.0  in THF,
0.3 mmol, 1.5 equiv.) and TMAD (51 mg, 0.3 mmol, 1.5 equiv.)
were added and stirring was continued at room temperature for
20 h. Then additional portions of TMP and TMAD (0.2 mmol,
1.0 equiv. of each) were added and stirring was continued for an
additional 22 h. The mixture was concentrated in vacuo, and the
residue was taken up in CH2Cl2/hexane (3:1) (4 mL) and loaded
onto a VLC column (3 ϫ 3 cm). Elution with hexane and hexane/
EtOAc (15:1 and 7:1) afforded 12 (37 mg; 51%) as a colourless
syrup, along with unchanged 10 (22 mg; 36%). For spectroscopic
data see 12 (Method C) below.
2-Nitro-N-(2-phenylethyl)-N-(1-phenylpropyl)benzenesulfonamide
(16): Prepared from 10 (61 mg, 0.2 mmol) as described for 12
(Method C) to give 16 (75 mg; 88%) as a reddish oil. 1H NMR
(400 MHz, CDCl3): δ ϭ 0.84 (t, J ϭ 7.2 Hz, 3 H, CH2CH3), 1.81
(m, 1 H, CH2CH3), 2.22, 2.77 and 3.29 (m, 4 H, CH2CH3 and
CH2Ph), 3.29 and 3.48 (m, 2 H, NCH2), 5.00 (m, 1 H, NCHPh),
6.99 (m, 2 H, Ph), 7.00Ϫ7.23 (m, 3 H, Ph), 7.33Ϫ7.38 (m, 5 H,
Ph), 7.59Ϫ7.65 (m, 3 H, Ns), 7.89 (m, 1 H, Ns) ppm. 13C NMR
(100 MHz, CDCl3): δ ϭ 11.1, 24.6, 37.7, 46.7, 62.5, 124.0, 126.5 (2
C), 128.3 (2 C), 128.5 (2 C), 128.6 (2 C), 128.7 (2 C), 130.6, 131.5,
133.4, 134.5, 137.6, 138.6, 148.1 ppm. HRMS: [C23H24N2O4S ϩ
Na]ϩ calculated, 447.13490; found, 447.13490.
N-(sec-Butyl)-2-nitro-N-(2-phenylethyl)benzenesulfonamide
(12).
Method C: 2-Butanol (28 µL, 0.3 mmol, 1.5 equiv.) and 10 (61 mg,
0.2 mmol) were dissolved in toluene (2.5 mL) and stirred on an ice-
bath in a septum-sealed flask. To this solution TMP (0.3 mL, 1.0
 in THF, 0.3 mmol, 1.5 equiv.) and ADDP (75 mg, 0.3 mmol, 1.5
equiv.) were added and stirring was continued for 20 h at room
temperature. Then another portion of TMP and ADDP (0.2 mmol,
1.0 equiv. of each) were added and stirring was continued for 22 h.
The mixture was concentrated in vacuo and the residue was taken
up in CH2Cl2 (2.5 mL) and loaded onto a VLC column (3 ϫ 3 cm).
Elution with hexane and hexane/EtOAc (15:1 and 7:1) afforded 12
(51 mg; 71%) as a pale orange syrup. 1H NMR (400 MHz, CDCl3):
δ ϭ 0.86 (t, J ϭ 7.3 Hz, 3 H, CH2CH3), 1.16 (d, J ϭ 6.9 Hz, 3 H,
CHCH3), 1.55 (m, 2 H, CH2CH3), 3.00 (m, 2 H, CH2Ph), 3.39 (m,
2 H, NCH2), 3.90 (sextet, J ϭ 6.9 Hz, 1 H, NCH), 7.21Ϫ7.30 (m,
5 H, Ph), 7.57 (m, 1 H, Ns), 7.66 (m, 2 H, Ns), 8.05 (m, 1 H, Ns)
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 11.0, 19.0, 28.5, 38.4, 45.0,
56.1, 124.0, 126.7, 128.7 (2 C), 128.8 (2 C), 130.9, 131.5, 133.4,
134.0, 138.8, 148.0 ppm. HRMS: [C18H22N2O4S ϩ Na]ϩ calcu-
lated, 385.11925; found, 385.11921.
N-Cyclopentyl-2-nitro-N-(2-phenylethyl)benzenesulfonamide
(17):
Prepared from 10 (61 mg, 0.2 mmol) as described for 12 (Method
1
C) to give 17 (46 mg; 61%) as a reddish oil. H NMR (400 MHz,
CDCl3): δ ϭ 1.42Ϫ1.86 (8 H, 4 ϫ CH2), 2.96 (m, 2 H, CH2Ph),
3.39 (m, 2 H, NCH2), 4.20 (m, 1 H, NCH), 7.19Ϫ7.33 (m, 5 H,
Ph), 7.58 (m, 1 H, Ns), 7.66 (m, 2 H, Ns), 8.02 (m, 1 H, Ns) ppm.
13C NMR (100 MHz, CDCl3): δ ϭ 23.2 (2 C), 29.6 (2 C), 38.3,
46.2, 59.5, 124.1, 126.7, 128.7 (2 C), 128.8 (2 C), 130.6, 131.5, 133.4,
134.0, 138.5, 148.0 ppm. HRMS: [C19H22N2O4S ϩ K]ϩ calculated,
413.09319; found, 413.09319.
N-[3-(tert-Butyldiphenylsilanyloxy)-1-methylpropyl]-2-nitro-N-(2-
phenylethyl)benzenesulfonamide (18): Prepared from 10 (61 mg,
0.2 mmol) as described for 12 (Method C) to give 18 (25 mg; 56%)
and 1-O-(tert-butyl)diphenylsilyl-1,3-butanediol[51] as a 3:2 mixture,
N-(1-Methylbutyl)-2-nitro-N-(2-phenylethyl)benzenesulfonamide
(13): Prepared from 10 (61 mg, 0.2 mmol) as described for 12
(Method C) to give 13 (50 mg; 67%) as a pale yellow syrup. 1H
NMR (400 MHz, CDCl3): δ ϭ 0.86 (t, J ϭ 7.3 Hz, 3 H, CH2CH3), which was inseparable by VLC chromatography. 1H NMR
1.13 (d,
J
ϭ
6.9 Hz,
3
H, NCHCH3), 1.27Ϫ1.44 (4 H,
(400 MHz, CDCl3): δ ϭ 1.05 (s, 9 H, tBu), 1.16 (d, J ϭ 6.9 Hz, 3
CH2CH2CH3), 2.88Ϫ3.06 (m, 2 H, CH2Ph), 3.39 (m, 2 H, NCH2), H, NCHCH3), 1.57 (m, 2 H, CH2CH), 2.93 (m, 2 H, CH2Ph), 3.34
3294
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3288Ϫ3299

The Choice of Phosphane Reagent in FukuyamaϪMitsunobu Alkylation
(m, 2 H, NCH2), 3.56 (m, 2 H, CH2OSi), 4.16 (m, 1 H, NCH), The syrup was dissolved in THF (100 mL), DIPEA (26.7 mL,
FULL PAPER
7.20Ϫ7.67 (m, 18 H, Ph and Ns), 7.99 (m, 1 H, Ns) ppm.
153.3 mmol, 4 equiv.) was added followed by 2-trimethylsilylethyl
p-nitrophenylcarbonate (11.86 g, 34.9 mmol, 0.9 equiv.), and the
mixture was stirred at 50 °C for 2 h, and then at room temperature
overnight. After 14 h the solvent was evaporated in vacuo, the resi-
due was diluted with CH2Cl2 (250 mL) and washed with 0.1  HCl
(2 ϫ 100 mL), water (2 ϫ 100 mL) and brine (100 mL). The com-
bined aqueous layers were extracted with CH2Cl2 (2 ϫ 100 mL)
and the organic phases were pooled, dried (Na2SO4), filtered and
concentrated. The residue was taken up in CH2Cl2 (25 mL) and
loaded onto a VLC column (7 ϫ 9.5 cm). Elution with hexane/
EtOAc (10:1 and 2:1) afforded 22 (14.22 g; 89%) as a yellow syrup.
1H NMR (400 MHz, CDCl3): δ ϭ 0.02 [s, 9 H, (CH3)3Si], 0.96 (t,
J ϭ 7.2 Hz, 2 H, CH2Si), 1.55 (m, 4 H, 2 ϫ CH2), 3.12 (m, 4 H, 2
ϫ CH2N), 4.13 (m, 2 H, CH2O), 4.57 (br. t, 1 H, NHCO), 5.38
(br. t, 1 H, NHSO2), 7.74 (m, 2 H, Ns), 7.86 (m, 1 H, Ns), 8.13
(m, 1 H, Ns) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ Ϫ1.5 (3 C),
17.8, 26.8, 27.1, 40.2, 43.4, 63.0, 125.4, 131.1, 132.8, 133.6, 133.7,
148.0, 156.9 ppm. HRMS: [C16H27N3O6Ssi ϩ Na]ϩ calculated,
440.12820; found, 440.12830.
N-[4-Methyl-2-(1-methylethyl)cyclohexyl]-2-nitro-N-(2-phenylethyl)-
benzenesulfonamide (19): Synthetic procedure starting from 10
(61 mg, 0.2 mmol) and carried out similarly as described above for
12 (Method C) did not result in any isolable product.
N-(3-Hydroxybutyl)-2-nitro-N-(2-phenylethyl)benzenesulfonamide
(20): 1,3-Butanediol (18 µL, 0.2 mmol) and 10 (92 mg, 0.3 mmol,
1.5 equiv.) were dissolved in THF (1 mL) and stirred in a septum-
sealed flask. TBP (80 µL, 0.32 mmol, 1.5 equiv.) and TMAD
(51 mg, 0.3 mmol, 1.5 equiv.) were added successively and stirring
was continued overnight. After 24 h the mixture was concentrated
and the residue was taken up in CH2Cl2 (2 mL) and loaded onto a
VLC column (3 ϫ 3 cm). Elution with hexane/EtOAc (5:1, 2:1 and
1:1) afforded 20 (48 mg; 63%) as a colourless syrup, together with
a small amount of the di-substituted product 21 (5 mg; 4%). 1H
NMR (400 MHz, CDCl3): δ ϭ 1.18 (d, J ϭ 6.2 Hz, 3 H, CH3),
1.62 and 1.71 (m, 2 H, CH2CH), (br. s, 1 H, OH), 2.86 (m, 2 H,
CH2Ph), 3.37Ϫ3.60 (br. m, 4 H, 2 ϫ CH2N), 3.88 (m, 1 H, CHOH),
7.15Ϫ7.25 (m, 5 H, Ph), 7.60Ϫ7.67 (m, 3 H, Ns), 7.92 (m, 1 H,
Ns) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ 23.6, 35.2, 37.4, 45.2,
49.4, 64.8, 124.3, 126.8, 128.7 (2 C), 128.9 (2 C), 130.6, 131.8, 133.5,
133.6, 138.6, 148.0 ppm. HRMS: [C18H22N2O5S ϩ Na]ϩ calcu-
lated, 401.11416; found, 401.11417.
N-(tert-Butoxycarbonyl)-NЈ-(2-nitrobenzenesulfonyl)-1,3-propane-
diamine (23): N-(Ns)-1,3-propanediamine (1.04 g, 4.0 mmol), pre-
pared as described above for N-(Ns)-1,4-butanediamine, was dis-
solved in dry MeOH (15 mL) and the solution was stirred under
N2 on an ice-bath. Di-tert-butyl dicarbonate (1.33 g, 6.1 mmol, 1.5
equiv.) dissolved in dry MeOH (3 mL) was added over 10 min and
the mixture was allowed to reach room temperature, after which it
was stirred overnight. After 22 h the solvent was evaporated in va-
cuo, the residue was taken up in CH2Cl2 (5 mL) and loaded onto
a VLC column (5 ϫ 5 cm). Elution with hexane/EtOAc (10:1 and
2:1) afforded 23 (1.35 g; 94%) as a yellow syrup. 1H NMR
(400 MHz, CDCl3): δ ϭ 1.42 (br. s, 9 H, 3 ϫ CH3), 1.69 (p, J ϭ
6.4 Hz, 2 H, CH2), 3.15 (dt, J ϭ 3.15 Hz and 2 ϫ 6.4 Hz, 2 H,
CH2N), 3.20 (br. dt, J ϭ 3.20 Hz, 2 ϫ 6.4 Hz, 2 H, CH2N), 4.72
(br. s, 1 H, NHSO2), 5.91 (br. s, 1 H, NHCOO), 7.73 (m, 2 H, Ns),
7.84 (m, 1 H, Ns), 8.13 (m, 1 H, Ns) ppm. 13C NMR (100 MHz,
CDCl3): δ ϭ 28.2, 28.4, 28.6, 30.6, 37.2, 40.9, 79.6, 125.3, 130.9,
132.8, 133.5, 134.0, 148.1, 156.5 ppm.
2-Nitro-N-[3-(2-nitrophenyl)sulfonyl-(2-phenylethylamino)butyl]-N-
(2-phenylethyl)benzenesulfonamide (21): 10 (57 mg, 0.19 mmol, 1.5
equiv.) and 20 (47 mg, 0.12 mmol) were dissolved in THF (1.5 mL).
TMP (0.2 mL, 1.0  in THF, 0.2 mmol, 1.5 equiv.) and ADDP
(47 mg, 0.19 mmol, 1.5 equiv.) in THF (0.3 mL) were added suc-
cessively, and the mixture was stirred in a septum-sealed flask at
room temperature overnight. After 24 h additional portions of
TMP (0.2 mL, 1.0  in THF, 1.5 equiv.) and ADDP (47 mg,
0.19 mmol, 1.5 equiv.) in THF (0.3 mL) were added and stirring
was continued for an additional 18 h. The mixture was then con-
centrated and the residue was taken up in CH2Cl2 (3 mL) and
loaded onto a VLC column (3 ϫ 3 cm). Elution with hexane/
EtOAc (4:1, 2:1 and 1:1) afforded 21 (55 mg; 66%) as a colourless
syrup, together with unchanged 10 (7 mg; 15%). 1H NMR
(400 MHz, CDCl3): δ ϭ 1.16 (d, J ϭ 6.9 Hz, 3 H, CH3), 1.68 and
1.86 (m, 2 H, CH2CH), 2.78 and 2.94 (m, 2 H, CH2Ph), 3.16Ϫ3.47
(br. m, 6 H, 3 ϫ NCH2), 3.95 (m, 1 H, NCH), 7.10Ϫ7.31 (br. m,
10 H, 2 ϫ Ph), 7.55Ϫ7.66 (m, 6 H, Ns), 7.89 (m, 1 H, Ns), 8.03
(m, 1 H, Ns) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ 19.3, 34.5,
34.9, 38.2, 45.3, 45.4, 49.2, 52.2, 124.1, 124.2, 126.7 (2 C), 128.6 (2
C), 128.7 (4 C), 128.8 (2 C), 130.7, 131.1, 131.8 (2 C), 132.9, 133.0,
133.6, 133.7, 137.8, 138.3, 148.0 (2 C) ppm. HRMS:
[C32H34N4O8S2 ϩ Na]ϩ calculated, 689.17103; found, 689.17218.
N-(1-Oxobutyl)-O-(tert-butyl)tyrosine Pentafluorophenyl Ester (24):
O-(tert-Butyl)tyrosine (502 mg, 2.12 mmol) was dissolved in 2 
NaOH (2.15 mL, 4.3 mmol, 2 equiv.) and THF (4.3 mL). To this
solution butyryl chloride (0.89 mL, 8.5 mmol, 4 equiv.) was added
over 30 min and the mixture was stirred at room temperature for
2.5 h. Then EtOAc (100 mL) was added and the organic phase was
washed with water (4 ϫ 50 mL) and brine (50 mL), dried (Na2SO4),
filtered and concentrated. The residue was dried overnight in vacuo
(oil-pump) and then taken up in CH2Cl2 (4 mL) and loaded onto
a VLC column (4 ϫ 4 cm). Elution with hexane/EtOAc (10:1) and
EtOAc afforded the crude product (603 mg; 92%), which was dis-
solved in dry DMF (5 mL) and treated with dry pyridine (0.24 mL)
N-[(2-Nitrophenyl)sulfonyl]-NЈ-[2-(trimethylsilyl)ethoxycarbonyl]-
1,4-butanediamine (22): 1,4-Butanediamine (16.73 g, 190 mmol, 3
equiv.) and Et3N (26 mL, 188 mmol, 3 equiv.) were dissolved in dry and pentafluorophenyl trifluoroacetate (0.47 mL, 2.74 mmol, 1.3
CH2Cl2 (30 mL) and the mixture was stirred under N2 on an ice-
bath. NsCl (14.02 g, 63 mmol) dissolved in dry CH2Cl2 (70 mL)
was added in 5 portions and stirring was continued at room tem-
equiv.) for 5 h. After dilution with EtOAc (50 mL) the organic
phase was washed with 0.1  HCl (2 ϫ 50 mL), saturated aq.
NaHCO3 (2 ϫ 50 mL) and brine (50 mL). The organic phase was
perature for 3 h. The mixture was diluted with CH2Cl2 (200 mL) dried (Na2SO4), filtered, concentrated and dried in vacuo to give
1
and water (150 mL) was added. A turbid organic layer was sepa-
24 (672 mg; 57%) as a yellow syrup. H NMR (400 MHz, CDCl3):
rated and an emulsion was taken aside, dried (Na2SO4), filtered δ ϭ 0.91 (t, J ϭ 7.4 Hz, 3 H, CH3), 1.34 (br. s, 9 H, 3 ϫ CH3),
and pooled with the organic layer. Finally, the aqueous layer was
extracted with CH2Cl2 (2 ϫ 50 mL), and all the organic extracts
were pooled, dried (Na2SO4), filtered, concentrated and dried in
vacuo. This afforded 10.40 g (60%) of crude N-(Ns)-1,4-butanedia-
mine as a yellow syrup, which was used directly in the next step.
1.62 (sextet, J ϭ 7.4 Hz, 2 H, CH2), 2.19 (t, J ϭ 7.4 Hz, 2 H,
CH2CO), 3.21 (dd, J ϭ 6.5 Hz and 14.3 Hz, 2 H, β-CH2), 3.29 (dd,
J ϭ 6.1 Hz and 14.3 Hz, 1 H, β-CH2), 5.21 (ddd, J ϭ 6.1 Hz,
6.6 Hz, 7.7 Hz, 1 H, α-CH), 5.90 (br. d, J ϭ 7.7 Hz, 1 H, NHCO),
6.96 (m, 2 H, Ph), 7.11 (m, 2 H, Ph) ppm. 13C NMR (100 MHz,
Eur. J. Org. Chem. 2003, 3288Ϫ3299
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3295

H. Franzyk et al.
FULL PAPER
CDCl3): δ ϭ 17.6, 19.0, 28.3 (3 C), 37.7, 40.0, 53.0, 79.0, 124.0 (2 5 ϫ CH2N), 3.92 (m, 1 H, NCH), 4.13 (m, 2 H, CH2O), 5.01 (m,
C), 124.5, 130.9 (3 C), 137.4 (br. d, J ϭ 240 Hz, 2 C), 139.3 (br. d, 2 H, 2 ϫ NHCO), 7.62 (m, 2 H, Ns), 7.71 (m, 4 H, Ns), 7.93 (m,
J ϭ 252 Hz, 1 C), 140.7 (br. d, J ϭ 243 Hz, 2 C), 147.7, 156.8, 1 H, Ns), 8.02 (m, 1 H, Ns) ppm. 13C NMR (100 MHz, CDCl3):
173.8 ppm. HRMS: [C23H24F5NO4 ϩ Na]ϩ calculated, 496.15177;
found, 496.15176.
δ ϭ Ϫ1.6 (3 C), 17.6, 19.0, 27.3, 28.2 (2 C), 28.3 (2 C), 28.5, 34.6,
37.3, 40.0, 43.1, 45.5, 45.7, 51.9, 62.6, 79.0, 123.9, 124.0, 130.3,
130.8, 131.7, 131.8, 132.6, 133.1, 133.5, 133.6, 147.7, 147.9, 156.0,
156.8 ppm. HRMS: [C34H55N6O12S2Si]ϩ calculated, 831.30832;
found, 831.30931.
Fully Protected Tetraamine 26: Compound 22 (871 mg, 2.09 mmol)
was dissolved in freshly distilled THF (20 mL). To this solution
1,3-butanediol (187 µL, 2.09 mmol) and TBP (825 µL, 3.34 mmol,
1.6 equiv.) were added followed by ADDP (790 mg, 3.13 mmol, 1.5
equiv.). The mixture was stirred under N2 at room temperature
overnight. After 18 h the solvent was evaporated in vacuo. VLC
[toluene/acetone (20:1, 15:1, 12:1 and 11:1)] afforded compound 25
Fully Protected 8-Methyl-PhTX-433 (28): Bu4NF·3H2O (95 mg,
0.30 mmol, 2.5 equiv.) and 26 (100 mg, 0.12 mmol) were dissolved
in THF (5 mL) and stirred at 50 °C for 4 h. The mixture was then
diluted with EtOAc (50 mL) and the organic layer was washed with
(543 mg; 53%) as a yellowish syrup. The total yield of 25, including water (2 ϫ 50 mL) and brine (50 mL), dried (Na2SO4), filtered,
impure VLC fractions, was 711 mg (70%). 13C NMR (75 MHz, concentrated and dried in vacuo. The resulting syrup was taken up
CDCl3): δ ϭ Ϫ1.5 (3 C), 17.7, 23.5, 25.3, 27.0, 37.4, 40.0, 44.7, in CH2Cl2 (2 mL) and loaded onto a VLC column (3 ϫ 3 cm).
47.4, 62.9, 64.7, 124.0, 130.3, 131.5, 132.9, 133.3, 147.8, 156.7.
Elution with CH2Cl2/MeOH (200:5) and CH2Cl2/MeOH/concd.
Compound 25 (491 mg, 1.0 mmol) was then dissolved in freshly
ammonia (150:10:1) afforded 27 (51 mg; 62%) as a light yellow
distilled THF (11 mL). To this solution 23 (539 mg, 1.5 mmol) in syrup, along with unchanged 26 (28 mg; 28%). 13C NMR
7 mL THF and TMP (1.60 mL, 1.0  in THF, 1.60 mmol, 1.6
equiv.) was added followed by ADDP (378 mg, 1.50 mmol, 1.5
equiv.), and the mixture was stirred under N2 at room temperature
for 6 h. Then additional amounts of TMP (1.60 mL, 1.0  in THF,
(100 MHz, CDCl3): δ ϭ 19.1, 25.6, 28.4 (2 C), 28.5, 30.2, 32.0,
34.6, 37.9, 41.2, 41.4, 45.2, 47.9, 52.2, 79.2, 124.1, 124.2, 130.6,
131.1, 131.8, 131.9, 133.1, 133.2, 133.6, 133.7, 147.9, 148.1, 156.2
ppm. Compound 27 (51 mg, 0.07 mmol) and DIPEA (20 µL,
1.60 mmol, 1.6 equiv.) and ADDP (378 mg, 1.50 mmol, 1.5 equiv.) 0.11 mmol, 1.6 equiv.) were dissolved in dry DMF (2 mL), and 24
were added and stirring was continued overnight. The solvent was
evaporated and the residue was taken up in CH2Cl2 (5 mL) and
loaded onto a VLC column (5 ϫ 5 cm). Elution with toluene/ace-
(42 mg, 0.09 mmol, 1.3 equiv.) dissolved in dry DMF (1 mL) was
added. The mixture was stirred under N2 for 2 h and then diluted
with EtOAc (50 mL). The organic solution was washed with water
tone 20:1, 18:1 and 16:1 afforded 26 (567 mg; 68%) as a yellow (2 ϫ 50 mL) and brine (50 mL), dried (Na2SO4), filtered and con-
foam. 1H NMR (400 MHz, CDCl3): δ ϭ 0.02 [s, 9 H, (CH3)3Si],
centrated in vacuo. The residue was dissolved in CH2Cl2 (2 mL)
0.96 (t, J ϭ 8.3 Hz, 2 H, CH2Si), 1.14 (d, J ϭ 6.7 Hz, 3 H, and loaded onto a VLC column (3 ϫ 3 cm). Elution with toluene
NCHCH3), 1.45 (br. s, 9 H, 3 ϫ CH3), 1.46Ϫ1.91 (br. m, 8 H, 4 ϫ and toluene/acetone (4:1) afforded 28 (63 mg; 88%) as a light yel-
1
CH2), 3.14 (m, 5 H, CH2N), 3.27 (m, 5 H, CH2N), 3.92 (m, 1 H, low syrup. H NMR (400 MHz, CDCl3): δ ϭ 0.83 (t, J ϭ 7.3 Hz,
NCH), 4.12 (m, 2 H, CH2O), 5.01 (m, 2 H, 2 ϫ NHCO), 7.60 (m, 3 H, CH3CH2), 1.14 (d, J ϭ 6.5 Hz, 3 H, CH3CH), 1.30 (br. s, 9
2 H, Ns), 7.70 (m, 4 H, Ns), 7.93 (m, 1 H, Ns), 8.02 (m, 1 H, Ns)
H, 3 ϫ CH3, Tyr-tBu), 1.45 (br. s, 9 H, 3 ϫ CH3, NBoc), 1.36Ϫ1.56
ppm. 13C NMR (100 MHz, CDCl3): δ ϭ Ϫ1.6 (3 C), 17.6, 19.0, (br. m, 6 H, 3 ϫ CH2), 1.66Ϫ1.93 (br. m, 4 H, 2 ϫ CH2), 2.12 (m,
25.3, 26.9, 28.2, 28.3, (2 C), 31.8, 34.6, 37.7, 40.0, 41.0, 45.1, 47.6, 2 H, CH2CO), 2.96 (m, 2 H, β-CH2), 2.99Ϫ3.29 (br. m, 10 H, 5 ϫ
52.0, 62.7, 79.0, 124.0 (2 C), 130.3, 130.9, 131.7 (2 C), 132.7, 133.0,
133.5, 133.6, 147.7, 147.9, 156.0, 156.8 ppm. HRMS:
[C34H55N6O12S2Si]ϩ calculated, 831.30832; found, 831.30900.
CH2N), 3.94 (m, 1 H, NCH), 4.58 (dd, J ϭ 7.3 Hz and 7.7 Hz, 1
H, α-CH), 6.88 (d, J ϭ 8.4 Hz, 2 H, Ph), 7.00 (d, J ϭ 8.4 Hz, 2 H,
Ph), 7.61 (m, 2 H, Ns), 7.69 (m, 4 H, Ns), 7.93 (m, 1 H, Ns), 8.02
(m, 1 H, Ns) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ 13.6, 19.0,
25.5, 26.4, 28.3, 28.4, 28.5, 28.6, 28.7, 28.8, 28.9, 32.1, 35.0, 37.5,
38.3, 38.5, 41.2, 45.4, 47.7, 52.3, 54.5, 54.7, 78.4, 79.1, 124.2, 124.3,
129.0, 129.6 (2 C), 129.7, 129.8, 130.5, 130.6, 131.7, 131.9, 133.0,
133.2, 133.6, 133.7, 148.0, 148.1, 154.2, 156.3, 171.3, 173.2 ppm.
HRMS: [C45H65N7O13S2 ϩ Na]ϩ calculated, 998.39740; found,
998.39820.
Fully Protected Tetraamine 31: Compound 23 (517 mg, 1.44 mmol)
was dissolved in freshly distilled THF (15 mL). To this solution
1,3-butanediol (150 µL, 1.67 mmol, 1.16 equiv.) and TBP (570 µL,
2.3 mmol, 1.6 equiv.) were added followed by ADDP (547 mg,
2.16 mmol, 1.5 equiv.). The mixture was stirred under N2 at room
temperature overnight. After 20 h the solvent was evaporated in
vacuo. VLC [toluene/acetone (20:1, 15:1, 13:1, 12:1 and 11:1)] af-
forded compound 30 (347 mg; 56%). 13C NMR (100 MHz, CDCl3): Fully Protected 6-Methyl-PhTX-433 (33): Deprotection of 31
δ ϭ 23.7, 28.5 (3 C), 28.7, 37.6, 45.2, 45.8, 47.3, 79.3, 124.3, 130.3,
131.9, 133.0, 133.7, 148.1, 156.2 ppm. Compound 30 (193 mg,
0.45 mmol) was then dissolved in freshly distilled THF (10 mL). To
this solution 22 (281 mg, 0.67 mmol, 1.5 equiv.) and TMP
(0.72 mL, 1.0  in THF, 0.72 mmol, 1.6 equiv.) were added fol-
lowed by ADDP (170 mg, 0.68 mmol, 1.5 equiv.), and the mixture
(100 mg), carried out as described above for 26, afforded 32 (35 mg;
42%) as a light yellow syrup, together with unchanged 31 (49 mg;
49%). 13C NMR (100 MHz, CDCl3): δ ϭ 19.2, 28.3, 28.4, 28.5,
28.8, 29.0, 30.9, 35.0, 37.4, 41.5, 43.6, 45.7, 45.9, 52.1, 79.2, 124.1,
124.2, 130.6, 131.1, 131.8, 131.9, 132.9, 133.5, 133.6, 133.7, 147.9,
148.1, 156.0 ppm. Compound 32 (35 mg; 0.04 mmol) and DIPEA
was stirred under N2 at room temperature for 8 h. Then additional (13 µL, 0.07 mmol, 1.75 equiv.) were dissolved in dry DMF (2 mL),
amounts of TMP (0.72 mL, 1.0  in THF, 0.72 mmool, 1.6 equiv.)
and 24 (29 mg, 0.06 mmol, 1.5 equiv.) dissolved in dry DMF
and ADDP (170 mg, 0.68 mmol, 1.5 equiv.) were added and stir-
(1 mL) was added. The mixture was stirred under N2 for 2 h and
ring was continued overnight. The solvent was evaporated, the resi- then diluted with EtOAc (50 mL). After workup and purification
due was taken up in CH2Cl2 (5 mL) and loaded onto a VLC col-
as described above for 28, 33 (46 mg; 92%) was obtained as a light
umn (4 ϫ 5 cm). Elution with hexane/EtOAc (3:1, 5:2, 2:1 and 1:1)
yellow syrup. 1H NMR (400 MHz, CDCl3): δ ϭ 0.83 (t, J ϭ 7.5 Hz,
1
afforded 31 (256 mg; 69%) as a yellow foam. H NMR (400 MHz, 3 H, CH3CH2), 1.12 (d, J ϭ 6.5 Hz, 3 H, CH3CH), 1.31 (br. s, 9
CDCl3): δ ϭ 0.03 [s, 9 H, (CH3)3Si], 0.97 (t, J ϭ 8.3 Hz, 2 H, H, 3 ϫ CH3, Tyr-tBu), 1.44 (br. s, 9 H, 3 ϫ CH3, NBoc), 1.45Ϫ1.75
CH2Si), 1.12 (d, J ϭ 6.7 Hz, 3 H, CHCH3), 1.43 (br. s, 9 H, 3 ϫ
(br. m, 8 H, 4 ϫ CH2), 1.86 (m, 2 H, CH2), 2.12 (m, 2 H, CH2CO),
CH3), 1.45Ϫ1.95 (br. m, 8 H, 4 ϫ CH2), 3.10Ϫ3.33 (br. m, 10 H, 3.00 (m, 2 H, β-CH2), 3.01Ϫ3.35 (br. m, 10 H, 5 ϫ CH2N), 3.92
3296
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2003, 3288Ϫ3299

The Choice of Phosphane Reagent in FukuyamaϪMitsunobu Alkylation
FULL PAPER
(m, 1 H, NCH), 4.59 (dd, J ϭ 7.3 Hz and 7.8 Hz, 1 H, α-CH), 6.89
(d, J ϭ 8.4 Hz, 2 H, Ph), 7.09 (m, J ϭ 8.4 Hz, 2 H, Ph), 7.61 (m,
2 H, Ns), 7.69 (m, 4 H, Ns), 7.93 (m, 1 H, Ns), 8.02 (m, 1 H, Ns)
3 ϫ CH3, Tyr-tBu), 1.48Ϫ1.70 (br. m, 8 H, 4 ϫ CH2), 1.93 (m, 2
H, CH2), 2.12 (m, 2 H, CH2CO), 2.94 (m, 2 H, β-CH2), 3.05Ϫ3.30
(br. m, 10 H, 5 ϫ CH2N), 3.92 (m, 1 H, NCH), 4.13 (t, J ϭ 8.1 Hz,
ppm. 13C NMR (100 MHz, CDCl3): δ ϭ 13.6, 19.0, 26.9, 28.4 (2 2 H, CH2O), 4.61 (dd, J ϭ 6.9 Hz and 7.6 Hz, 1 H, α-CH), 6.89
C), 28.5, 28.6 (2 C), 28.7, 28.8 (2 C), 28.9, 35.1, 37.5, 38.3, 38.5, (d, J ϭ 8.4 Hz, 2 H, Ph), 7.09 (d, J ϭ 8.4 Hz, 2 H, Ph), 7.60 (m, 2
43.3, 45.9, 46.1, 52.2, 54.5, 54.6, 78.4, 79.1, 124.1, 124.2, 124.3,
128.3, 129.6, 129.7, 129.8, 130.5, 131.0, 131.8, 131.9, 132.8, 133.3,
133.7 (2 C), 148.0, 148.1, 154.2, 156.1, 171.3, 173.2 ppm. HRMS:
[C45H65N7O13S2 ϩ Na]ϩ calculated, 998.39740; found, 998.39795.
H, Ns), 7.70 (m, 4 H, Ns), 7.92 (m, 1 H, Ns), 8.02 (m, 1 H, Ns)
ppm. 13C NMR (100 MHz, CDCl3): δ ϭ Ϫ1.5 (3 C), 13.6, 17.8,
19.0, 27.5, 28.0, 28.6, 28.7, 28.8, 28.9, 29.0, 35.3, 36.1, 37.3, 38.3,
40.2, 43.4, 46.1, 46.2, 52.2, 54.5, 62.9, 78.4, 124.0, 124.1, 124.3,
124.4, 129.6, 129.7, 130.4, 130.9, 131.8 (2 C), 132.0, 132.5, 133.4,
133.7 (2 C), 147.9, 148.1, 154.2, 157.0, 171.4, 173.4 ppm. HRMS:
[C46H70N7O13S2Si]ϩ calculated, 1020.42368; found, 1020.42468.
Fully Protected 5-Methyl-PhTX-334 (36): p-Toluenesulfonic acid
(TsOH) (46 mg, 0.24 mmol) and 26 (200 mg, 0.24 mmol) were sus-
pended in diethyl ether (5 mL) and placed on a rotary evaporator
at 50 °C for 1 h. The residue was then dissolved in EtOAc (50 mL)
and the organic layer was washed with water (2 ϫ 50 mL), dried
(Na2SO4), filtered, and concentrated and dried in vacuo. The re-
sulting syrup was taken up in CH2Cl2 (2 mL) and loaded onto a
VLC column (3 ϫ 3 cm). Elution with CH2Cl2/MeOH (200:5 and
CH2Cl2/MeOH/concd. ammonia (200:10:1) afforded 35 (122 mg;
8-Methyl-PhTX-433 (6): Compound 28 (53 mg, 0.05 mmol) was
dissolved in dry DMF (3 mL) and treated with 2-mercaptoethanol
(40 µL, 0.57 mmol, 11 equiv.) and DBU (40 µL, 0.27 mmol, 5
equiv.). After stirring for 2 h under N2 the mixture was diluted with
EtOAc (50 mL), the organic solution was washed with water (2 ϫ
50 mL), dried (Na2SO4), filtered and concentrated in vacuo. The
residue was taken up in CH2Cl2 (2 mL) and loaded onto a VLC
column (2 ϫ 2 cm). Elution with CH2Cl2/MeOH/concd. ammonia
(180:10:1, 150:10:1 and 70:10:1) afforded 29 (22 mg; 67%) as a
colourless syrup. Compound 29 (20 mg, 0.03 mmol) was then dis-
solved in TFA/CH2Cl2 (1:9) (2.5 mL) and stirred at room tempera-
ture for 3 h. The mixture was concentrated in vacuo, and 6 was
isolated as the tris(TFA) salt by reversed-phase HPLC. Yield:
24 mg (92%). 1H NMR (400 MHz, CD3OD): δ ϭ 0.85 (t, J ϭ
7.5 Hz, 3 H, CH3CH2), 1.38 (d, J ϭ 6.2 Hz, 3 H, CH3CH),
1.49Ϫ1.59 (br. m, 6 H, 3 ϫ CH2), 1.91Ϫ2.36 (br. m, 4 H, 2 ϫ
CH2), 2.16 (t, J ϭ 7.6 Hz, 2 H, CH2CO), 2.94Ϫ3.17 (br. m, 12 H,
5 ϫ CH2N and β-CH2), 3.31 (br. s, 1 H, NCH), 4.42 (dd, J ϭ
7.0 Hz and 7.6 Hz, 1 H, α-CH), 6.70 (d, J ϭ 8.6 Hz, 2 H, Ph), 7.05
(d, J ϭ 8.6 Hz, 2 H, Ph) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ
13.9, 16.1, 20.3, 24.3, 25.5, 27.2, 30.6, 37.8, 38.2, 38.7, 39.3, 43.2,
45.0, 48.6, 53.5, 56.9, 116.2, 116.3, 129.1, 131.3, 131.4, 157.3, 174.1,
176.1 ppm. HRMS: [C24H44N5O3]ϩ calculated, 450.34387; found,
450.34376.
70%) as a white foam, along with unchanged 26 (21 mg; 11%). 13
C
NMR (100 MHz, CDCl3): δ ϭ Ϫ1.5 (3 C), 17.8, 19.1, 25.5, 27.0,
28.4, 35.0, 39.6, 40.2, 41.5, 45.4, 47.8, 52.2, 62.9, 124.2 (2 C), 130.7,
131.1, 131.8 (2 C), 133.0, 133.5, 133.6, 133.7, 148.0, 148.1, 156.9
ppm. Compound 35 (67 mg, 0.09 mmol) and DIPEA (24 µL,
0.14 mmol, 1.55 equiv.) were dissolved in dry DMF (2 mL), and 24
(52 mg, 0.11 mmol, 1.25 equiv.) dissolved in dry DMF (1 mL) was
added. The mixture was stirred under N2 for 2 h and was diluted
with EtOAc (50 mL). The organic solution was washed with water
(2 ϫ 50 mL) and brine (50 mL), dried (Na2SO4), filtered and con-
centrated in vacuo. The residue was dissolved in CH2Cl2 (2 mL)
and loaded onto a VLC column (3 ϫ 3 cm). Elution with toluene
and toluene/acetone (4:1) afforded 36 (71 mg; 76%) as a light yel-
low syrup. 1H NMR (400 MHz, CDCl3): δ ϭ 0.03 [br. s, 9 H,
(CH3)3Si], 0.80 (t, J ϭ 7.3 Hz, 3 H, CH3CH2), 0.96 (t, J ϭ 8.1 Hz,
2 H, CH2Si), 1.13 (d, J ϭ 6.7 Hz, 3 H, CH3CH), 1.30 (br. s, 9 H,
3 ϫ CH3, Tyr-tBu), 1.45Ϫ1.53 (br. m, 6 H, 3 ϫ CH2), 1.67Ϫ1.94
(br. m, 4 H, 2 ϫ CH2), 2.12 (m, 2 H, CH2CO), 2.94 (m, 2 H, β-
CH2), 3.01Ϫ3.35 (br. m, 10 H, 5 ϫ CH2N), 3.94 (m, 1 H, NCH),
4.13 (t, J ϭ 8.1 Hz, 2 H, CH2O), 4.59 (dd, J ϭ 6.9 Hz and 7.8 Hz,
1 H, α-CH), 6.89 (d, J ϭ 8.3 Hz, 2 H, Ph), 7.10 (d, J ϭ 8.3 Hz, 2
H, Ph), 7.60 (m, 2 H, Ns), 7.70 (m, 4 H, Ns), 7.92 (m, 1 H, Ns),
8.01 (m, 1 H, Ns) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ Ϫ1.5
(3 C), 13.6, 17.8, 18.8, 19.1, 25.5, 27.1, 28.7, 28.8, 28.9, 31.1, 35.0,
36.6, 37.2, 38.3, 40.3, 40.9, 45.5, 47.9, 52.2, 54.5, 63.0, 78.4, 124.0,
124.2, 124.3, 129.5, 129.6 (2 C), 129.7, 130.5, 131.8, 131.9, 132.0,
133.0, 133.1, 133.7, 133.7, 147.9, 148.1, 154.2, 157.0, 171.5,
173.4 ppm. HRMS: [C46H70N7O13S2Si]ϩ calculated, 1020.42368;
found, 1020.42451.
6-Methyl-PhTX-433 (7): Deprotection of 33 (42 mg, 0.04 mmol)
was performed as described above for 28, to give 34 (16 mg; 62%)
as a colourless syrup. Compound 34 (16 mg, 0.03 mmol) was then
dissolved in TFA/CH2Cl2 (1:9) (2 mL) and stirred at room tempera-
ture for 3 h, the mixture was concentrated in vacuo, and 7 was
isolated as the tris(TFA) salt by reversed-phase HPLC. Yield:
20 mg (96%). 1H NMR (400 MHz, CD3OD): δ ϭ 0.85 (t, J ϭ
7.3 Hz, 3 H, CH3CH2), 1.36 (d, J ϭ 6.2 Hz, 3 H, CH3CH),
1.50Ϫ1.59 (br. m, 6 H, 3 ϫ CH2), 1.87Ϫ2.36 (br. m, 4 H, 2 ϫ
CH2), 2.16 (t, J ϭ 7.5 Hz, 2 H, CH2CO), 2.76Ϫ3.06 (br. m, 6 H, 2
ϫ CH2N and β-CH2), 3.25 (m, 6 H, 3 ϫ CH2), 3.45 (br. s, 1 H,
NCH), 4.41 (dd, J ϭ 7.0 Hz and 8.1 Hz, 1 H, α-CH), 6.70 (d, J ϭ
8.6 Hz, 2 H, Ph), 7.02 (d, J ϭ 8.6 Hz, 2 H, Ph) ppm. 13C NMR
(100 MHz, CDCl3): δ ϭ 13.9, 16.3, 20.3, 24.4, 25.4, 27.3, 30.5, 37.8,
38.2, 38.7, 39.2, 45.3, 45.8, 46.0, 53.1, 56.9, 116.2 (2 C), 129.1, 131.3
(2 C), 157.3, 174.2, 176.1 ppm. HRMS: [C24H44N5O3]ϩ calculated,
450.34387; found, 450.34388.
Fully Protected 7-Methyl-PhTX-334 (39): Deprotection of 31
(100 mg) with TsOH, performed as described above for 26, afforded
38 (55 mg; 63%) as a yellow syrup, along with unchanged 31
(11 mg; 11%). 13C NMR (100 MHz, CDCl3): δ ϭ Ϫ1.6 (3 C), 17.6,
19.0, 27.4, 28.7, 31.6, 34.8, 38.8, 40.0, 43.2, 45.4, 45.7, 52.0, 62.7,
123.9, 124.0, 124.1 (2 C), 130.5, 130.9, 131.7, 131.8, 133.2, 133.6,
147.8, 148.0, 156.9 ppm. Compound 38 (55 mg, 0.08 mmol) and
DIPEA (20 µL, 0.11 mmol, 1.4 equiv.) were dissolved in dry DMF
5-Methyl-PhTX-334 (8): Deprotection of 36 (69 mg, 0.07 mmol)
was performed as described above for 28, to give 37 (34 mg, 77%)
(2 mL), and 24 (43 mg, 0.09 mmol, 1.15 equiv.) in dry DMF (1 mL) as a colourless syrup. Compound 37 (34 mg, 0.05 mmol) was dis-
was added. The mixture was stirred under N2 for 2 h and then
diluted with EtOAc (50 mL). After workup and purification as de-
scribed above for 36, 39 (64 mg; 83%) was obtained as a light yel-
solved in TFA/CH2Cl2 (1:9) (4 mL) and stirred at room tempera-
ture for 3 h, the mixture was concentrated in vacuo, and 8 was
isolated as the tris(TFA) salt by reversed-phase HPLC. Yield:
low syrup. 1H NMR (400 MHz, CDCl3): δ ϭ 0.03 [br. s, 9 H, 40 mg (97%). 1H NMR (400 MHz, CD3OD): δ ϭ 0.86 (t, J ϭ
(CH3)3Si], 0.82 (t, J ϭ 7.3 Hz, 3 H, CH3CH2), 0.96 (t, J ϭ 8.1 Hz, 7.5 Hz, 3 H, CH3CH2), 1.34 (d, J ϭ 6.4 Hz, 3 H, CH3CH), 1.54
2 H, CH2Si), 1.12 (d, J ϭ 6.9 Hz, 3 H, CH3CH), 1.29 (br. s, 9 H,
(m, 2 H, CH2CH3), 1.77Ϫ2.20 (br. m, 8 H, 4 ϫ CH2), 2.18 (t, J ϭ
Eur. J. Org. Chem. 2003, 3288Ϫ3299
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3297

H. Franzyk et al.
FULL PAPER
[12]
[13]
K. Strømgaard, K. Andersen, P. Krogsgaard-Larsen, J. W. Ja-
roszewski, Mini Rev. Med. Chem. 2001, 1, 317Ϫ338.
R. Goodnow, K. Konno, M. Niwa, T. Kallimopoulos, R. Bu-
kownik, D. Lenares, K. Nakanishi, Tetrahedron 1990, 46,
3267Ϫ3286.
M. Bruce, R. Bukownik, A. T. Eldefrawi, M. E. Eldefrawi, R.
Goodnow, T. Kallimopoulos, K. Konno, K. Nakanishi, M.
Niwa, P. N. R. Usherwood, Toxicon 1990, 28, 1333Ϫ1346.
V. Kuksa, R. Buchan, P. K. T. Lin, Synthesis 2000, 1189Ϫ1207.
Y. Hidai, T. Kan, T. Fukuyama, Tetrahedron Lett. 1999, 40,
4711Ϫ4714.
7.5 Hz, 2 H, CH2CO), 2.86 (m, 2 H, β-CH2), 2.95Ϫ3.31 (br. m, 11
H, 5 ϫ CH2N and CHN), 4.39 (dd, J ϭ 7.0 Hz and 7.4 Hz, 1 H,
α-CH), 6.72 (d, J ϭ 8.4 Hz, 2 H, Ph), 7.05 (d, J ϭ 8.4 Hz, 2 H,
Ph) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ 13.9, 16.3, 20.3, 24.4,
25.4, 27.3, 30.5, 37.8, 38.2, 38.7, 39.2, 45.3, 45.8, 46.0, 53.1, 56.9,
116.2 (2 C), 129.1, 131.3 (2 C), 157.3, 174.2, 176.1 ppm. HRMS:
[C24H44N5O3]ϩ calculated, 450.34387; found, 450.34385.
[14]
[15]
[16]
7-Methyl-PhTX-334 (9): Deprotection of 39 (62 mg, 0.06 mmol)
was performed as described above for 28, to give 40 (21 mg; 54%)
as a colourless syrup. Compound 40 (18 mg, 0.03 mmol) was dis-
solved in TFA/CH2Cl2 (1:9) (2 mL) and stirred at room tempera-
ture for 3 h. The mixture was concentrated in vacuo, and 9 was
isolated as the tris(TFA) salt by reversed-phase HPLC. Yield:
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
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22 mg (Ͼ 99%). H NMR (400 MHz, CD3OD): δ ϭ 0.86 (t, J ϭ
7.5 Hz, 3 H, CH3CH2), 1.38 (d, J ϭ 6.4 Hz, 3 H, CH3CH), 1.55
(m, 2 H, CH2CH3), 1.77Ϫ2.20 (br. m, 8 H, 4 ϫ CH2), 2.18 (t, J ϭ
7.5 Hz, 2 H, CH2CO), 2.87 (m, 2 H, β-CH2), 2.94Ϫ3.30 (m, 10 H,
5 ϫ CH2N, 3.42 (br. s, 1 H, CHN), 4.38 (dd, J ϭ 7.0 Hz and
7.4 Hz, 1 H, α-CH), 6.71 (d, J ϭ 8.4 Hz, 2 H, Ph), 7.05 (d, J ϭ
8.4 Hz, 2 H, Ph) ppm. 13C NMR (100 MHz, CDCl3): δ ϭ 13.9,
16.2, 20.2, 24.4, 25.6, 27.3, 30.7, 36.8, 37.9, 38.6, 40.0, 45.2, 45.4,
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Acknowledgments
We thank the Danish Technical Research Council (Grant No.
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3298
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 3288Ϫ3299

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Received March 19, 2003
Eur. J. Org. Chem. 2003, 3288Ϫ3299
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3299