Multicomponent synthesis of novel amino acid-nucleobase chimeras: aA versatile approach to PNA-monomers

Bioorganic & Medicinal Chemistry 8 (2000) 1343±1360

Multicomponent Synthesis of Novel Amino Acid±Nucleobase

Chimeras: a Versatile Approach to PNA-Monomers

Wolfgang Maison, Imre Schlemminger, Ole Westerho and Jurgen Martens*

Fachbereich Chemie, Universitat Oldenburg, D-26111 Oldenburg, Germany

È

Received 14 June 1999; accepted 4 February 2000

AbstractÐThis paper describes a multicomponent approach to novel totally protected precursors of PNA-monomers via Ugi 4CC.

The obtained bisamides are converted into several partially protected PNA-monomers or derivatives thereof using three dierent

procedures. Methods for hydrolysis are shown to be dependent on the nature of the isocyano component required for Ugi 4CC.

Several novel monomers suitable for oligomer synthesis are prepared demonstrating the high versatility of the reaction sequence.

Introduction

the properties of PNAs and lead to the synthesis of a

number of new structures,⁸e.g., side chain-modi®ed poly-

amide backbones and terminal substituted derivatives.⁹

The design and synthesis of structurally modi®ed oligo-

nucleotides has attracted much interest since some of

them show high anity and sequence speci®c binding

to RNA and DNA. Therefore, they represent promising

drug candidates in the antisense and antigene therapy,

and may also provide new tools in molecular biology

and diagnostics.¹A large number of structurally mod-

i®ed oligonucleotides has been reported throughout the

last years, either modi®ed at the sugar-phosphate back-

bone or at the nucleobases in order to optimize their

properties.²Nielsen and co-workers reported a radically

changed structure of a nucleic acid mimic called Peptide

Nucleic Acids (PNAs). In these compounds the sugar-

phosphate backbone of DNA is completely substituted

by a pseudo-peptide structure (Fig. 1).³

Also changes in PNA-structure leading to PNA analo-

gues like retro-inverso PNA,¹⁰Aromatic Peptide

Nucleic Acids (APNAs),¹¹Phosphonic Ester Nucleic

Acids (PHONAs)¹²and several other derivatives built

up from a- or b-amino acids were investigated, some of

them showing interesting properties.¹³Since research in

this area is still an ongoing challenge a systematic

investigation of structure±function relationships using

combinatorial libraries seems to be attractive.¹⁴Having

these considerations in mind we focussed our studies on

the design of a general and versatile synthetic route to

PNA-monomers. The Ugi four component condensation

(Ugi 4CC) serves as a powerful tool in combinatorial and

peptide chemistry.^15,18Herein we describe the synthesis

of a novel class of totally protected PNA-monomers

and some analogues thereof via Ugi 4CC. The obtained

bisamides could be selectively hydrolyzed under acidic

or alkaline conditions to give N-terminal protected

PNA-monomers or their derivatives, respectively.

These oligonucleotide analogues showed a high binding

anity to complementary single stranded DNA, mRNA

and PNA by duplex formation as well as to double

stranded DNA by triplex formation.⁴In vitro studies

demonstrated both good antisense and antigene activity

of PNAs.⁵Furthermore PNA is not known to be a

substrate for any enzymes which degrade peptides or

nucleic acids.⁶However there are some limitations for

the use of PNAs in diagnostic and research applications,

for example their low solubility in water and their

tendency towards self-aggregation.⁷Many eorts were

made to circumvent these drawbacks and to optimize

Results and Discussion

The usefulness of the Ugi 4CC in the synthesis of

nucleobase±amino acid chimeras was recently demon-

strated.¹⁶The use of a functionalized amine, a carboxylic

acid, a suitable oxo compound and an isocyanide as

starting materials generates bisamides of type A for the

synthesis of PNA-monomers. Employment of dierent

*Corresponding author. Fax: +49-441-798-3757; e-mail: juergen.

martens@uni-oldenburg.de

PII: S0968-0896(00)00066-3

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W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

bisamides can be converted to dierent carboxylic acid

derivatives by nucleophilic attack under acidic condi-

tions. However, the common procedures for the pre-

paration of cyclohexenyl isocyanide were not practical

for large scale synthesis.^19,20,24Besides the large number

of steps the overall yields are also lowered because of

decomposition during distillation or diculties arising

from coevaporation of the product while the solvent is

removed after chromatography. To overcome these

problems we ®rst developed a shorter route to some

derivatives of cyclohexenyl isocyanide (Scheme 2).

The starting cyclohexanones were converted into their

corresponding cyclohexen-1-yl derivatives 1 in high

yields by treatment with formamide. It is equally

important to note that these reactions could be per-

formed in large scale. These were easily dehydrated

using the phosgene method²¹to give the desired iso-

cyanides 2. Compared to 2a the new isocyanides 2b, c

are much more easy to handle because of their less

extensive odour. They are stable solids which can be

stored under argon at 0 ^ꢀC for several months. Appli-

cation of the vinylic isocyanides 2 to Ugi 4CC as out-

lined in Table 1 yielded the bisamides 6 in moderate to

excellent yields.

Figure 1. B=adenine, cytosine, guanine, thymine.

reactants determines the generation of precursors of

PNA-monomers, known structural derivatives, or com-

pletely new analogues, respectively. However, applica-

tion of the generated a-amino acid derivatives in peptide

coupling reactions suers from a big problem since the

generated secondary amide `protecting' the amino acid

carboxyl function in A is usually dicult to cleave in a

selective manner to give carboxylic acid B.¹⁷Most

methods reported for the cleavage of secondary amides

require harsh conditions and are incompatible with

many functional groups within the same molecule

(Scheme 1).¹⁸

The versatility of the Ugi 4CC in the synthesis of totally

protected PNA-monomers is demonstrated by the

structural variety of the obtained bisamides 6. Ugi-

adducts were generally obtained in high yields. Lower

yield of compound 6d was due to the low solubility of

the required G^Bn-AcOH in organic solvents. It should

be noted that the preparative versatility is accompanied

by the ease of puri®cation either by recrystallization or

column chromatography on silica gel. All four natural

nucleobases were incorporated into the totally protected

PNA-monomers 6a±d starting from the corresponding

nucleobase acetic acids in the Ugi 4CC. The substitution

pattern of the generated aminoethylglycine (aeg) deri-

vatives was varied by employment of dierent aldehydes

or ketones as oxo components to obtain novel mono- or

dialkylated glycinederivatives 6b±m. Even unusual or

sterically crowded a-amino acid analogues like 6b or 6e

were accessible by this one pot process. Common pro-

tecting groups for the second amino function in ethyl-

endiamine derivatives 4a±d were tolerated resulting in

the synthesis of bisamides 6e±f and j (Scheme 3).

Two routes seem to be promising for the selective clea-

vage of secondary amides: acid mediated hydrolysis of

A or alkaline mediated hydrolysis. However, both

routes require the synthesis of suitable isocyanides nee-

ded for the generation of bisamides A via Ugi 4CC.

Synthesis of totally protected PNA-monomers with an

acid labile C-terminal protecting group

Recently Keating demonstrated cyclohexenyl isocyanide

to be a suitable isocyano compound in Ugi 4CC reac-

tions.¹⁹This attracted our interest because the obtained

Scheme 1. Ugi 4CC and regioselective hydrolysis to mono-protected PNA-monomers.

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1345

Scheme 2. Synthesis of vinylic isocyanides 2a±c. Reagents and conditions: (i) formamide, H₂SO₄, toluene, Dean±Stark conditions; (ii) phosgene,

NEt₃, 0 ^ꢀC.

Table 1. Totally protected PNA-monomers 6 obtained from isocyanides 2

Educt

Product

R¹

R²

R³

B

X

Pg^a

Yield (%)

2a, 4a, 5a

2b, 4a, 5c

2a, 4a, 5d

2a, 4a, 5f

2c, 4b, 5a

2c, 4c, 5a

2c, 4a, 5a

2a, 4a, 5g

2b, 4a, 5h

2b, 4d, 5i

6a

6b

6c

6d

6e

6f

6g

6h

6i

H

t-Bu

H

Ph

H

t-Bu

2-Cl-Ph

H

T

C^Z

A^Z

G^Bn

T

CH₂

CH-n-Bu

o-Bz

Boc

Etoc

Z

Boc

Ac

76

97

78

31

98

80

90

39

52

55

±(CH₂)₅±

2-Cl-Ph

t-Bu

Ph

H

t-Bu

T

C^Z

6j

^aPg, protecting group.

Scheme 3. Examples of totally protected PNA-monomers (R=4-tert-butyl-cyclohex-1-enyl). Reagents and conditions: (i) cyclohexane, 5a, 2b,

MeOH, rt; (ii) 4-biphenylcarbaldehyde, 5a, 2b, MeOH, rt; (iii) benzaldehyde, 5a, 2b, triethylamine, MeOH, rt.

1346

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

Apart from classical nucleobase acetyl-aeg PNA-struc-

tures, many modi®ed analogues may be synthesized

using our one pot procedure. Among them the deriva-

tives 6h±j comprise a nucleobase linker-modi®ed aeg-

structure. These derivatives were synthesized using

novel nucleobase derivatives 5g±i. Incorporation of an

aromatic ring system into backbone structures was per-

formed by employment of mono-Ib-phenylen diamine

4f as a diamino compound in the Ugi 4CC to give 6l.

Use of O-benzyl-ethanolamine 4e as a functionalized

amino compound gave rise to the synthesis of 6k.

Employment of the nitrophenyl isocyanides 3a, b in the

one pot Ugi 4CC procedure described above gave rise to

the totally protected PNA monomers 7.

Again, variation of the remaining three components

(oxo compound, amino compound, acid compound)

could be utilized to get a wide variety of products.

Monomers 7a±f with a conventional aminoethylglycine

(aeg) structure were generally synthesized in good

yields, using formaldehyde as the oxo compound,

mono-Boc ethylendiamine 4a and a nucleobase acetic

acid 5a±f (Table 2). All natural nucleobases were incor-

porated by variation of the acid compound. The lower

yields of the guanine containing structures 7e, 7f re¯ect

the hindered reaction due to low solubility of G^Z-

AcOH. Unfortunately the use of G^Bn-AcOH seemed to

produce some by-products during Ugi reaction because

of competitive aminal formation of the free amino

group of guanine and formaldehyde.

Synthesis of totally protected PNA-monomers with a

base labile C-terminal protecting group

As mentioned above, the cleavage of secondary amides

under mild conditions is still a challenge in modern

chemistry since it needs rigorous conditions in general.¹⁷

The alkaline saponi®cation of A oers an alternative

access to the carboxylic deprotected monomer B

(Scheme 1). As the cleavage is initiated by nucleophilic

attack of a hydroxy ion at the amide carbonyl, the

alkaline sensitivity of the amide depends on the location

of the lone pair of the corresponding nitrogen atom.

The substitution pattern of phenylamides allows mod-

ulation of the location of the nitrogen lone pair via p

electron communication. In order to take advantage of

this eect we used two nitro substituted phenyl iso-

cyanides 3a, b as precursors for the formation of elec-

tron depleted amides. The isocyanides were synthesized

according to Ugi's method.²¹Unfortunately destabiliza-

tion of the formed amide with further electron with-

drawing groups attached to the phenyl moiety (i.e., a

second nitro substituent) proved to go along with rising

problems in synthesis and stability of the corresponding

isocyanide. However, isocyanides 3a, b were easily

accessible and fairly stable in ambient conditions.

Variation of the amino compound allowed modi®cation

of the aminoethyl unit (Scheme 4). In this way PNA

monomers with a wide variety of diamino and amino-

alcohol units were accessible in good yield. Alkylated,

cyclic and aromatic mono-protected diamino units were

incorporated in 7k±m. 7g represents an example of the

utilization of O-protected aminoalcohols in Ugi 4CC,

thus providing a protected, hydroxy terminus for a

possible coupling to DNA monomers to generate DNA±

PNA-chimeras.²²

In case of Ugi reactions involving mono-Boc-ethyl-

endiamine and formaldehyde formation of a by-product

Mom-7a was observed. Excess of formaldehyde lead

to methoxymethylenation of Boc-NH (Scheme 5).

Since the resulting Boc-Mom-protection of the amino

group is acid sensitive, the by-product shows the same

Table 2. Totally protected PNA-monomers 7 obtained from isocyanides 3

Educt

Product

R¹

R²

R³

R⁴

R⁵

B

XPg^a

Yield (%)

3a, 4a, 5a

3a, 4a, 5c

3a, 4a, 5b

3a, 4a, 5d

3a, 4a, 5f

3a, 4a, 5e

3a, 4e, 5a

3a, 4a, 5a

3b, 4a, 5a

3a, 4a, 5a

3a, 4h, 5a

7a

7b

7c

7d

7e

7f

7g

7h

7i

OCH₃

NO₂

OCH₃

NO₂

H

T

C^Z

U

A^Z

G^Bn

G^Z

T

NHBoc

OBn

NHBoc

64

69

32

20

85

83

70

41

64

H

1,4-DOSD^b

H

7j

7k

OCH₃

Ph

H

CH₃

H

^aPg, protecting group.

^b1,4-DOSD, 1,4-Dioxaspiro[4.5]dec-8-yl-.

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1347

Scheme 4. Employment of cyclic diamines in the 4CC; only one enantiomer for racemic 7l is shown (R=4-methoxy-2-nitro-phenyl). Reagents and

conditions: (i) formaldehyde, 5a, 3a, MeOH, rt; (ii) formaldehyde, 5a, 3a, MeOH, rt.

Scheme 5. Methoxymethylenation of aeg-monomers (R=4-methoxy-2-nitro-phenyl).

behaviour as the Boc protected monomer and may not

be separated.

In general, the synthesis of Boc-protected monomers

requires special precautions. In some cases instability of

Boc-amides under acidic reaction conditions leads to

partial removal of the Boc-protecting group. As a con-

sequence side reactions occur since free amino functions

may act as nucleophiles, resulting in complex product

mixtures.^19,23Boc removal largely depends on acid

concentration and reaction temperature. However, we

succeeded in the synthesis of compounds 8a, 8c, 8g, 8i at

0 ^ꢀC in moderate to good yields.

As the use of formaldehyde lead to the formation of a

glycine unit in 7a±g and 7k±m almost any other a-amino

acid unit is accessible through variation of the oxo

compound in the Ugi 4CC. As examples, we would like

to present compounds 7h±j and 7n leading to natural

and unnatural amino acid units in totally protected

PNA-monomers (Fig. 2).

Furthermore oxo compounds with additional (pro-

tected) functional groups allow the generation of poly-

functional PNA-monomers. The totally protected PNA-

monomer 7n contains a further carboxylic ending in the

amino acid side chain as an additional coupling moiety

for oligomerization or linkage of useful subunits. 7n

resulted from ethyl laevulinate as starting material in

the Ugi transformation.

Some other Ugi-adducts like 6b failed to give the corre-

sponding Boc-protected PNA-monomers upon acidic

hydrolysis and only complex product mixtures were

obtained. Therefore, substitution of Boc-protecting group

by acid stable protecting groups lead to the formation

of 8e, 8f, 8k, 8l in high yields at room temperature. 8k

Table 3. Yields of partially protected PNA-monomers 8

Acidic hydrolysis to partially protected monomers

Vinylic amides 6 serve as versatile precursors of N-

protected PNA-monomers and structural analogues

thereof. We exposed compounds 6 to hydrolysis analo-

gous to Keating's procedure¹⁹by treatment with THF/

concd HCl to obtain the partially protected PNA-

monomers 8. Hydrolysis of Ugi-adduct 6a lead to the

formation of the known Boc-protected PNA-monomer

8a²⁸in moderate yield (Table 3).

PNA-monomer 8

Educt

R¹

R²

R³

B

X

Yield (%)

6a

6c

6e

6f

6g

6i

8a

8c

8e

8f

8g

8i

H

2-Cl-Ph

±(CH₂)₅±

t-Bu

±(CH₂)₅±

4-biPh^a

H

Boc-ae^b

Etoc-ae^b

Z-ae^b

T

A^z

T

CH₂

o-Bn

CH₂

63²⁸

38

78

82

47

91

66

Boc-ae^b

Bn-oe^d

H

6k

6l

8k

8l

O-Ib-An^c

^a4-biPh, 4-biphenyl.

^bae: aminoethyl.

Figure 2. Polyfunctional PNA-monomer (R=4-methoxy-2-nitro-

phenyl).

^co-Ib-An, o-N-isobutyryl-aniline.

^doe, oxyethyl.

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W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

Especially is an interesting monomer for the possible

conjunction of PNA and DNA fragments in the synth-

esis of PNA-DNA±chimeras.²²

Table 4. Yields of partially protected PNA-monomers 9 (R=4-meth-

oxy-2-nitrophenyl)

When Ugi ®rst reported on the synthesis of cyclohex-

enyl isocyanide and its use in the Ugi 4CC he observed

an acid promoted conversion of the vinylic amide of the

obtained bisamides to primary amides, which is in con-

trast to Keating's results.²⁴Keating explained these

contrasting observations by means of structural assign-

ments of the starting Ugi-adducts.¹⁹Another factor

in¯uencing the course of the reaction may be the con-

centration of the desired nucleophile. In order to exam-

ine this we started some corresponding experiments.

Treatment of 6m with TFA in THF containing exactly

one equivalent of water gave the primary amide 10 in

good yield. Further hydrolysis of the carbamoyl group

in 10 was not observed. Thus, no carboxylic acid was

obtained upon hydrolysis of 6m. The TFA mediated

cleavage of Ugi-adducts like 6m lead to interesting pre-

cursors 10 for novel aminals like 11. The aminal 11 may

serve as educt for the synthesis of retro-inverso PNAs.

The synthesis of 11 starting from 10 should be possible

following generally known Hofmann rearrangement

and subsequent Boc-protection (Scheme 6).²⁵

PNA-monomer 9

Educt

R¹

R²

R³

Time (h)^a

Yield (%)

7g

7j

7l

7m

9g

9j

9l

9m

H

Ph

H

Bn-oe^c

Boc-ae^b

Boc-ac^d

o-Ib-An^e

4

71

80

68²⁹

83

72

20

19

H

^aReaction time according to GP6.

^bae, aminoethyl.

^coe, oxyethyl.

^do-Ib-An, o-N-isobutyryl-aniline.

^eac, 2-aminocyclohexyl.

A convincing workaround for the synthesis of sterically

crowded PNA-monomers was found in the substitution

of the nucleobase by a hydroxy group in the carboxylic

acid component for the Ugi 4CC. Scheme 7 shows the

totally protected monomer 12 derived from glycolic acid

with a hydroxy group as a nucleobase synthon.

Alkaline hydrolysis to partially protected monomers

In order to obtain the PNA-monomers 8a, 9g, 9j, 9l and

9m, we have studied the alkaline deprotection of the

corresponding Ugi products 7a, 7g, 7j, 7l and 7m.

Hydrolysis of the anilides was performed in methanol

with six equivalents of KOH at room temperature and

was monitored by TLC (Table 4).

The Ugi reaction with glycolic acid caused no problems

and formed the totally protected PNA-precursor 12 in

high yield. The regioselective alkaline cleavage to 13 was

rapidly performed under standard conditions due to a

stabilized transition state. In comparison the related

thymine containing monomers lacking the hydroxy

group in the side chain, like 7h, were stable under these

conditions for several weeks. The conversion of pro-

tected precursors for PNA-monomers like 13 via Mit-

sunobu reaction as outlined in Scheme 7 should be

possible according to known protocols.²⁷

We found that glycine containing bisamides 7a and 7g

could easily be hydrolyzed to give the mono-protected

monomers 8a²⁸and 9g with a free carboxylic acid within

a few hours. The quality of the N-alkyl/aryl linker sec-

tion did not in¯uence the success of alkaline hydrolysis,

but it prolonged the reaction time with increasing steric

demands (9l, 9m versus 8a, 9g). Table 4 shows some

synthesized glycine containing monomers with a free

carboxylic acid obtained via alkaline hydrolysis.

Conclusion

The a-substituted species 7h±j and 7n proved to be

much more resistant against alkaline hydrolysis com-

pared to their glycine analogues, e.g., 7g. In particular

the anilides 7h and 7i with R³and R⁴H (see Table 2)

were remarkably resistant to alkaline hydrolysis. As a

consequence no regioselective cleavage of the amide

bond was observed.²⁶

In this article we described the synthesis of a novel class

of totally protected monomers 6, 7 for the preparation

of PNAs or derivatives thereof. The protected PNA-

monomers 6, 7 are formed in a one pot procedure via

Ugi±4CC with variable substitution pattern. They are

converted to the mono-protected PNA-monomers 8 and

9 via regioselective acidic or alkaline hydrolysis.

Scheme 6. Synthesis of a `retro-inverso' PNA-monomer.

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1349

Scheme 7. Synthesis of PNA-monomers via precursors 12 and 13 (R=4-methoxy-2-nitro-phenyl, R¹=t-butyl). Reagents and conditions: (i) pival-

aldehyde, 3a, 4a, MeOH, rt; (ii) 6 equiv KOH, MeOH.

The obtained cyclohexenyl amides 6 oer two routes of

acid mediated conversions. The ®rst route, a HCl-

mediated hydrolysis with an excess of water, lead to N-

protected PNA-monomers 8. A lot of acid stable N-

protecting groups are tolerated within the reaction

sequence as demonstrated with the synthesis of 8e±f and

8k±l. In some cases even requirement of the acid labile

Boc-protecting group lead to the formation of the

desired N-protected monomers. The second route, a

TFA-mediated cleavage of the secondary amides, lead

to primary amides like 10. These are useful precursors

for monomers like 11 required for the synthesis of

`retro-inverso' PNAs.

compounds were prepared according to literature

procedures: 4-methoxy-2-nitrophenyl isocyanide 3a,^21b

2-methoxy-4-nitrophenyl isocyanide 3b,^21bmono-Boc-

ethylendiamine 4a,³⁷mono-Etoc-ethylendiamine 4b,³⁰

mono-Z-ethylendiamine 4c,³¹mono-acetyl-ethylendi-

amine 4d,³²O-benzyl-ethanolamine 4e,³³mono-Boc-

cyclohexylendiamine 4g,²⁹N-1-carboxymethylthymine

5a,³⁶N-1-carboxymethyluracil 5b,³⁴N⁴-Z-N-1-carboxy-

methylcytosine 5c,²⁸N⁶-Z-N-9-carboxymethyladenine

5d,²⁸N²-Z-N-9-carboxymethylguanine 5e,³⁵2-amino-6-

benzyloxy-N-9-carboxymethylpurine 5f.²⁸Thin layer

chromatography (TLC) analyses were performed on

silica gel Polygram¹plates and ¯uorescence indicator

from Macherey Nagel Co., Duren. For preparative

chromatography Merck silica gel 60, 230±400 mesh, was

used. Melting points were determined in open capillaries

in a Dr. Lindstrom instrument and are uncorrected.

¹H NMR and ¹³C NMR spectra were recorded on a

Bruker-Karlsruhe AM 300 spectrometer (300 MHz/

75 MHz) and on a Bruker-Karlsruhe ARX 500 spectro-

meter (500 MHz). Chemical shifts, d, are presented in

part per million (ppm) and coupling constants, J, in

Hertz (Hz) from tetramethylsilane (TMS) as the internal

standard in deuterated solvents such as CDCl₃and

DMSO-d₆. The NMR spectral assignments were estab-

lished by analysis of the H,H-COSY, HMQC, HMBC

NMR spectra. Mass spectra were obtained on a Finni-

gan-MAT 212 instrument in CI mode with iso-butane

or NH₃as reactant gas. Elemental analyses were per-

formed on a C, H, N-Analyser EA 1108 from Fisons

Instruments.

The nitrophenyl amides 7a, 7g, 7j, 7l and 7m were

hydrolyzed to the corresponding PNA-monomers 8a,

9g, 9j, 9l and 9m under alkaline conditions in case of the

glycine derivatives. Hydrolysis of a-substituted mono-

mers has not been successful yet. However, a work-

around was found by the substitution of the nucleobase

acetic acid by glycolic acid. The introduction of the

nucleobase into the resulting carboxylic acid 13 should

be possible according to known protocols.

Further routes for the alkaline³⁸and acidic³⁹cleavage of

Ugi products have recently been reported and may pro-

vide attractive alternatives. Investigations in this direc-

tion are in progress.

Experimental

General remarks

General procedure for the synthesis of cyclohex-1-enyl-

formamides 1 (GP1)

If indicated with `abs.', solvents were puri®ed prior to

use as follows: dichloromethane was distilled from

CaCl₂, THF and Et₂O were distilled from sodium and

benzophenone, MeOH was distilled from magnesium

turns. The following abbreviations are employed: thy-

min-1-yl (T), N²-Z-guanin-9-yl (G^Z), 2-amino-6-benzyl-

oxy-purin-9-yl (G^Bn), N⁶-Z-adenin-9-yl (A^Z), N⁴-Z-

cytosin-1-yl (C^Z), tri¯uoroacetic acid (TFA), tert-butyl-

oxycarbonyl (Boc), ethoxycarbonyl (Etoc), benzyloxy-

carbonyl (Z), acetyl (Ac), isobutyryl (Ib). The following

The appropriate cyclohexanone derivative (2 mol) and

99.1 g (2.2 mol) formamide were dissolved in 1000 mL

toluene and treated with 1 mL concd H₂SO₄. The mix-

ture was heated to re¯ux under Dean±Stark-conditions

for 12 h. The solution was washed with water (200 mL)

and brine (200 mL) and subsequently dried over

MgSO₄. The solvent was removed under reduced pres-

sure and the obtained crude product recrystallized from

a suitable solvent.

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W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

General procedure for the preparation of isocyanides 2

(GP2)

extracted ®ve times with 20 mL of dichloromethane.

The combined dichloromethane phases were dried and

evaporated in vacuo. If necessary the products were

recrystallized from dichloromethane to give the N-pro-

tected PNA-monomers.

The appropriate formamide 1 (0.2 mol) and 64 ml abs.

triethylamine were dissolved in 500 mL dichloro-

methane. The solution was cooled to 0 ^ꢀC and 20 g

(0.202 mol) phosgene were introduced over a period

of about 2 min. After stirring for 1 h at 0 ^ꢀC 140 mL

water were added and the layers were separated. The

organic layer was washed with 140 mL water two times

and dried over MgSO₄. After evaporation of the solvent

in vacuo the residue was subjected to ¯ash chromato-

graphy on silica gel.

N-Cyclohex-1-enyl-formamide 1a. The title compound

was prepared according to GP1 using 196.3 g (2 mol)

cyclohexanone as starting material. The enamide was

recrystallized from n-hexane to yield 190.3 g (76%) of a

colourless solid. Analytical data were consistent with

literature data.¹⁹

rac-N-4-tert-Butyl-cyclohex-1-enyl-formamide 1b. The

title compound was prepared according to GP1 using

308.5 g (2 mol) 4-tert-butylcyclohexanone as starting

material. The enamide was recrystallized from n-hexane

to yield 293.7 g (81%) of a colourless solid, mp: 108±

General procedure for the preparation of totally

protected PNA-monomers 6 (GP3)

The appropriate amino (2.5 mmol) and oxo compound

(2.0 mmol) were dissolved in 7 mL abs. MeOH. The

carboxylic acid (2.5 mmol) and isocyanide (2.0 mmol)

were added and the solution was stirred for 48 h at

room temperature. The solvent was removed in vacuo

and the resulting crude product puri®ed by column

chromatography.

ꢀ

1

110 C. H NMR (300 MHz, CDCl₃, due to the exis-

tence of two rotamers in a 70:30 ratio several signals

were doubled): d 0.86 (ma.), 0.87 (mi.) (2s, 9H, tert-

butyl-CH₃), 1.2±1.6 (m, 7H, CH, CH₂), 5.29 (ma.), 6.09

(mi.) (2m, 1H, CCH), 6.59 (mi.), 7.74 (ma.) (br, 1H,

3

NH), 8.14 (mi.), 8.32 (ma.) (s, d, 1H, OCH, J=11.6

Hz). ¹³C NMR (75 MHz, CDCl₃): d 23.51, 25.34, 27.15,

27.55, 27.98, 43.76, 110.73, 132.33, 161.27. MS (CI-iso-

butane): m/z (%)=182 (100) [MH⁺]. C₁₁H₁₉NO

(181.3): calcd C 72.88, H 10.56, N 7.73; found C 73.08,

H 10.62, N 7.81.

General procedure for hydrolysis of vinylic amides 6 to

N-protected PNA-monomers 8 (GP4)

Vinyl amide 6 was dissolved in a stock solution of 1 mL

concd HCl and 9 mL THF at 0 ^ꢀC. The solution was

stirred for 5 h while slowly warming up to room tem-

perature. Solid Na₂CO₃was added for neutralization

and the solution was ®ltered. The ®ltrate was evapo-

rated to dryness in vacuo and the residue recrystallized

from a suitable solvent to give the N-protected PNA-

monomers 8.

rac-N-4-Phenyl-cyclohexen-1-yl-formamide 1c. The title

compound was prepared according to GP1 using 348.4 g

(2 mol) 4-phenyl-cyclohexanone as starting material.

The resulting crude product was stirred with hot n-hex-

ane and ®ltered o after cooling to yield 322.0 g (80%)

ꢀ

1

of a white solid, mp: 128±129 C. H NMR (300 MHz,

CDCl₃, due to the existence of isomers in a 56:22:22

ratio several signals were trebled): d 1.5±2.8 (m, 7H,

CH+CH₂), 5.37 (ma.), 6.18 (mi.), 6.59 (mi.) (3m, 1H,

CCH), 7.1±7.3 (m, 5H, arH), 7.99 (br, 1H, NH), 7.76

(mi.), 8.14 (mi.) (s, 0.44H, OCH), 8.36 (ma.) (d, 0.56H,

General procedure for the preparation of totally

protected PNA-monomers 7 (GP5)

Each 2.00 mmol of an amino compound and an oxo

compound were dissolved in 7 mL of abs. MeOH. After

a few minutes 2.00 mmol of a nitrophenylisocyanide and

2.00 mmol of a carboxylic acid were added and the

mixture was stirred at room temperature for 48 h. After

evaporation of the solvents in vacuo, the crude product

was stirred in dichloromethane and formed amide by-

product of compounds 4 and 5 was removed by ®ltra-

tion. The concentrated ®ltrate was precipitated from

ether or puri®ed via column chromatography on silica

gel with dichloromethane:methanol (95:5).

3

OCH, J=11.6 Hz). ¹³C NMR (75 MHz, CDCl₃, major

isomer): d 27.06, 29.11, 31.83, 39.51, 109.98, 126.28,

126.71, 128.42, 132.43, 145.66, 161.43. MS (CI-iso-

butane): m/z (%)=202 (100) [MH⁺]. C₁₃H₁₅NO

(201.3): calcd C 77.58, H 7.51, N 6.96; found C 77.32, H

7.43, N 7.03.

Cyclohexen-1-yl-isocyanide 2a. The title compound was

prepared according to GP2 using 25.0 g (0.2 mol) of

formamide 1a as starting material. The resulting crude

product was puri®ed by ¯ash chromatography (n-

hexane:ethyl acetate, 95:5) to yield 15.2 g (71%) of a

colourless liquid. Analytical data were consistent with

literature data.¹⁹

General procedure for the alkaline hydrolysis of nitro

anilides 7a, 7g, 7j, 7l, 7m to N-protected

PNA-monomers 8a, 9g, 9j, 9l, 9m (GP6)

0.30 mmol of a nitro anilide protected monomer 7 was

dissolved in 6 mL of MeOH and 0.90 mL of a 2 N solu-

tion of KOH in MeOH (6 equiv of KOH) was added.

The mixture was stirred at room temperature and TLC

monitored. After complete hydrolysis, 20 mL of water

was added, the mixture was washed three times, each

with 20 mL of ether, slightly acidi®ed with HCl and

rac-4-tert-Butyl-cyclohexen-1-yl-isocyanide 2b. The title

compound was prepared according to GP2 using 36.3 g

(0.2 mol) of formamide 1b as starting material. The

resulting crude product was puri®ed by ¯ash chromato-

graphy (n-hexane:ethyl acetate, 95:5) to yield 26.1 g

(80%) of a colourless solid, mp: ꢁ30 ^ꢀC. ¹H NMR

(300 MHz, CDCl₃): d 0.87 (s, 9H, CH₃), 1.2±1.4 (m, 7H,

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1351

cyclohexenyl-CH+CH₂), 6.02 (m, 1H, cyclohexenyl-

CCH). ¹³C NMR (75 MHz, CDCl₃): d 23.13, 23.41,

25.68, 26.99, 27.20, 29.60, 31.98, 32.16, 38.45, 42.71,

45.98, 115.77, 129.05, 160.44. MS (CI-isobutane): m/z

(%)=164 (100) [MH⁺]. C₁₁H₁₇N (163.3): calcd C

80.93, H 10.50, N 8.59; found C 80.03, H 11.01, N 8.64.

temperature. The solution was evaporated to dryness in

vacuo and the residue was dissolved in 200 mL di-

chloromethane and 200 mL water. After separation of

the two phases the water phase was extracted three

times with 50 mL dichloromethane. The combined

organic extracts were dried with MgSO₄, ®ltered o and

evaporated to dryness in vacuo. The resulting yellowish

oil was dissolved in 100 mL 2 N NaOH and heated to

re¯ux for 2 h. After cooling to room temperature the

solution was adjusted to pH 1 with 4 N HCl. The

resulting precipitate was ®ltered o, washed with ether

and dried in vacuo. The product was obtained as a col-

ourless solid in 8.77 g (73%) yield, mp: 192 ^ꢀC. ¹H

NMR (CDCl₃/DMSO-d₆): d 0.84 (t, 3H, (CH₂)₃CH₃),

1.27 (m, 4H, (CH₂)₂), 1.79 (s, 3H, thyminyl-CH₃), 1.95

(m, 2H, CH₂±(CH₂)₂±CH₃), 4.97 (q, 1H, CH), 7.33 (s,

1H, CCH). ¹³C NMR (CDCl₃/DMSO-d₆): d 11.98,

12.62, 21.42, 27.55, 28.79, 57.02, 108.96, 138.60, 151.07,

163.79, 171.35. MS (CI-isobutane): m/z (%)=241 (100)

[MH⁺]. C₁₁H₁₆N₂O₄(240.3): calcd C 54.99, H 6.71, N

11.66; found C 55.23, H 6.79, N 11.81.

rac-4-Phenyl-cyclohexen-1-yl-isocyanide 2c. The title

compound was prepared according to GP2 using 40.2 g

(0.2 mol) of formamide 1c as starting material. The

resulting crude product was puri®ed by ¯ash chromato-

graphy (dichloromethane:methanol, 99:1) to yield 26.0 g

(71%) of a colourless solid, mp: ꢁ40 ^ꢀC. ¹H NMR

(300 MHz, CDCl₃): d 1.8±2.8 (m, 7H, cyclohexenyl-

CH+CH₂), 6.10 (m, 1H, cyclohexenyl-CCH), 7.1±7.3

(m, 5H, arH). ¹³C NMR (75 MHz, CDCl₃): d 28.86,

28.90, 31.94, 38.54, 124.65, 124.80, 126.54, 126.65,

128.41, 128.57, 144.88, 160.96. MS (CI-isobutane): m/z

(%)=184 (100) [MH⁺]. C₁₃H₁₃N (183.3): calcd C

85.21, H 7.15, N 7.64; found C 86.12, H 7.31, N 7.71.

N-2-Amino-phenyl-isobutyramide 4f. To a well stirred

solution of 2.16 g (20 mmol) ortho-phenylendiamine in

150 ml dichloromethane (abs.) was added a mixture of

1.07 g (10 mmol) isobutyryl chloride and 50 ml di-

chloromethane (abs.) at room temperature via a drop-

ping funnel (time: 30 min). The resulting suspension was

stirred overnight at room temperature, ®ltered o and

the ®ltrate was evaporated to dryness in vacuo. The

resulting yellowish precipitate was identi®ed as the

mono-protected diamine 4f. Yield: 1.48 g (83%). ¹H

NMR (CDCl₃/DMSO-d₆): d 1.16 (d, 6H, CH±(CH₃)₂),

2.71 (m, 1H, CH-(CH₃)₂), 6.44±7.42 (m, 4H, arH), 8.97

(s, 1H, NH). ¹³C NMR (CDCl₃/DMSO-d₆): d 18.25,

33.25, 115.01, 115.53, 123.51, 123.95, 124.43, 140.16,

174.21. MS (CI-isobutane): m/z=179 (100) [MH⁺].

2-(Thymin-1-yl)-methyl-benzoic acid 5h. 10.1 g (80 mmol)

Thymine, 21.28 g methyl ortho-bromomethylen-benzo-

ate and 13 g potassium carbonate were suspended in

300 mL abs. dimethylformamide and heated to re¯ux

for 2 h. The yellowish solution was stirred for 2 days

at room temperature. The solution was ®ltered o and

the ®ltrate was evaporated to dryness in vacuo. The

residue was dissolved in 150 mL dichloromethane and

150 mL water. After separation of the two phases the

water phase was extracted three times with 50 mL di-

chloromethane. The combined organic extracts were

dried over MgSO₄, ®ltered o and evaporated to dry-

ness in vacuo. The resulting yellowish oil was dissolved

in 150 mL 2 N NaOH and stirred for 2 days. The solu-

tion was adjusted to pH 1 with 4 N HCl. The resulting

precipitate was ®ltered o, washed with ether and dried

in vacuo. The product was obtained as a colourless solid

in 6.70 g (32%) yield, mp: 249 ^ꢀC (dec.). ¹H NMR

(CDCl₃/DMSO-d₆): d 1.81 (s, 3H, thyminyl-CH₃), 5.30

(s, 2H, CH₂±Ph), 7.14±7.98 (m, 4H, arH), 7.42 (s, 1H,

thyminyl-H). ¹³C NMR (CDCl₃/DMSO-d₆): d 11.99,

49.16, 109.06, 126.29, 127.23, 129.21, 130.79, 132.51,

138.32, 141.79, 151.14, 164.40, 168.09. MS (CI-iso-

butane): m/z (%)=261 (100) [MH⁺]. C₁₃H₁₂N₂O₄

(260.3): calcd C 60.00, H 4.65, N 10.76; found C 60.21,

H 4.86, N 10.89.

rac-1-Boc-amino-2-aminopropane 4h. To a well stirred

solution of 62 g (836 mmol) rac-1,2-propylendiamine in

200 mL abs. dimethylformamide was added a solution

of 20 g (83,6 mmol) tert-butyl-4-nitrophenyl-carbonate

in 150 mL abs. dimethylformamide at room temperature

via a dropping funnel (time: 1 h). The yellowish solution

was stirred overnight at room temperature. The solution

was evaporated to dryness in vacuo and the residue was

dissolved in 150 mL water. The solution was adjusted to

pH 4 at 0 ^ꢀC and extracted three times with 50 mL di-

chloromethane. After extraction the water phase was

adjusted to pH 10 and extracted three times with 50 mL

chloroform. The combined organic extracts were dried

with MgSO₄, ®ltered o and evaporated to dryness in

vacuo. The resulting yellowish oil was identi®ed as the

mono-protected diamine 4h. Yield: 5.56 g (38%). ¹H

NMR (CDCl₃): d 0.97 (d, 3H, CH₂±CH±CH₃), 1.38 (s,

9H, (CH₃)₃), 2.71±3.10 (m, 3H, CH₂±CH±CH₃), 5.18 (s,

1H, NH). ¹³C NMR (CDCl₃, 75 MHz): d 21.22, 28.20,

46.71, 48.35, 78.83, 156.12.

2-(N⁴-Z-Cytosin-1-yl)-methyl-benzoic acid 5i. 19.6 g

(80 mmol) N⁴-Z-cytosine, 21.28 g methyl ortho-bromo-

methylen-benzoate and 13 g potassium carbonate were

suspended in 300 mL dimethylformamide (abs.) and

heated to re¯ux for 2 h. The suspension was stirred for

2 days at room temperature. The solution was ®ltered

o and the ®ltrate was evaporated to dryness in vacuo.

The residue was dissolved in 150 mL dichloromethane

and 150 mL water. After separation of the two phases

the water phase was extracted three times with 50 mL

dichloromethane. The combined organic extracts were

dried over MgSO₄, ®ltered o and evaporated to dryness

in vacuo. The resulting yellowish oil was dissolved

in 150 mL 2 N NaOH and stirred for two days. The

rac-2-(Thymin-1-yl)-hexanoic acid 5g. 6.3 g (50 mmol)

Thymine, 10.45 g methyl rac-2-bromocapronate and

7.5 g potassium carbonate were suspended in 250 mL

abs. dimethylsulfoxide and heated to re¯ux for 2 h.

The yellowish solution was stirred for 20 h at room

1352

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

3

solution was adjusted to pH 1 with 4 N HCl. The

resulting precipitate was ®ltered o, washed with ether

and dried in vacuo. The product was obtained as a col-

ourless solid in 15.48 g (51%) yield, mp: 197±199 ^ꢀC

C-Z-Ac-CHCH, J=7.0 Hz), 7.32 (m, 5H, arH), 7.63

(ma.), 7.90 (mi.) (2d, 1H, C-Z-Ac-CHCH, ³J=

7.0 Hz), 7.97 (br, 1H, 4-tert-butyl-cyclohexenyl-NH),

8.6 (br, 1H, Z-NH). MS (CI-NH₃): m/z (%)=695 (50)

[MH⁺], 712 (40) [MH⁺+NH₃]. C₃₇H₅₄N₆O₇(694.9):

calcd C 63.96, H 7.83, N 12.09; found C 63.78, H 7.91,

N 12.03.

1

(dec.). H NMR (DMSO-d₆): d 5.21 (s, 2H, CH₂±Ph),

5.38 (s, 2H, Z±CH₂), 6.96±8.12 (m, 9H, arH), 7.06 (d,

1H, cytosine-CH), 7.96 (d, 1H, cytosine-CH). ¹³C NMR

(DMSO-d₆): d 51.22, 66.48, 94.41, 126.88, 127.33,

127.92, 128.15, 128.47, 129.48, 130.72, 132.39, 135.98,

137.85, 150.37, 153.21, 155.12, 163.06, 168.09. MS (CI-

isobutane): m/z (%)=380 (100) [MH⁺]. C₁₃H₁₂N₂O₄

(379.4): calcd C 63.32, H 4.52, N 11.08; found C 63.30,

H 4.57, N 11.21.

rac-2-[(2-Boc-aminoethyl)-N⁶-Z-adeninacetyl-amino]-ortho-

chlorophenylacetic acid-(cyclohexen-1-yl)-amide 6c. The

title compound was prepared according to GP3 using

0.40 g (2.5 mmol) mono-Boc-ethylendiamine 4a, 0.28 g

(2 mmol) 2-chlorobenzaldehyde, 0.65 g (2 mmol) N⁶-Z-

N-9-carboxymethyl adenine 5d, and 0.21 g (2.0 mmol)

isocyanide 2a as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (dichloro-

methane:methanol, 95:5) to yield 1.12 g (78%) of a

2-[(2-Boc-aminoethyl)-thyminacetyl-amino]-acetic acid-

(cyclohexen-1-yl)-amide 6a. The title compound was

prepared according to GP3 using 0.40 g (2.5 mmol)

mono-Boc-ethylendiamine 4a, 0.06 g (2 mmol) para-

formaldehyde, 0.46 g (2.5 mmol) N-1-carboxymethyl-

thymine 5a, and 0.21 g (2.0 mmol) isocyanide 2a as

starting materials. The resulting crude product was

puri®ed by ¯ash chromatography (dichloromethane:

methanol, 95:5) to yield 0.70 g (76%) of a colourless

colourless solid, mp: 154±155 ^ꢀC. H NMR (300 MHz,

1

DMSO-d₆): d 1.33 (s, 9H, Boc-CH₃), 1.50 (m, 4H,

cyclohexenyl-CH₂), 2.02 (m, 4H, cyclohexenyl-CH₂),

2.61 (m, 1H, NCH₂CH₂), 3.18 (m, 1H, NCH₂CH₂), 3.34

(m, 1H, NCH₂CH₂), 3.54 (m, 1H, NCH₂CH₂), 5.23 (s,

2H, Z-CH₂), 5.46 (s, 2H, cyclohexenyl-CCH, NCH),

6.02 (d, 1H, A-Z-Ac-CH₂, ²J=14.9 Hz), 6.17 (d, 1H, A-

solid, mp: 154 ^ꢀC. H NMR (300 MHz, DMSO-d₆, due

1

2

to the existence of two rotamers in a 60:40 ratio several

signals were doubled): d 1.32 (s, 9H, Boc-CH₃), 1.4±2.1

(m, 8H, cyclohexenyl-CH₂), 1.71, 1.73 (2s, 3H, T-Ac-

CH₃), 2.8±3.2 (m, 4H), 3.91 (ma.), 4.05 (mi.) (s, 2H,

CH₂), 4.48 (mi.), 4.62 (ma.) (s, 2H, CH₂), 6.00 (ma.),

6.08 (mi.) (m, 1H, cyclohexenyl-CCH), 6.92 (mi.), 7.07

(ma.) (br, 1H, Boc-NH), 7.30 (mi.), 7.35 (ma.) (s, 1H, T-

Ac-C=CH), 8.86 (ma.), 9.25 (mi.) (s, 1H, cyclohexenyl-

NH), 11.25 (br, 1H, T-Ac-NH). ¹³C NMR (75 MHz,

DMSO-d₆, due to the existence of two rotamers in a

60:40 ratio several signals were doubled): d 11.85, 15.12,

21.73, 22.11, 23.49, 27.13, 28.16, 30.76, 35.78, 37.30,

37.92, 45.12, 47.27, 47.61, 49.31, 50.15, 62.80, 64.90,

77.68, 78.00, 107.26, 108.08, 110.29, 110.83, 133.27,

142.10, 142.81, 151.04, 155.61, 161.29, 162.31, 164.40,

166.32, 167.07, 167.85, 170.44. MS (CI-NH₃): m/z

(%)=481 (15) [MH⁺+NH₃]. C₂₂H₃₃N₅O₆(463.5):

calcd C 57.01, H 7.18, N 15.11; found C 57.06, H 7.24,

N 15.16.

Z-Ac-CH₂, J=14.9 Hz), 6.83 (br, 1H, Boc-NH), 7.39

(m, 9H, arH), 8.42 (s, 1H, A-Z-Ac-NCH), 8.63 (s, 1H,

A-Z-Ac-NCH), 9.63 (s, 1H, cyclohexenyl-NH), 10.63

(br, 1H, Z-NH). ¹³C NMR (75 MHz, DMSO-d₆): d

21.60, 22.03, 23.49, 26.93, 28.80, 43.98, 44.22, 48.57,

59.96, 66.22, 77.92, 111.23, 122.94, 127.77, 127.89,

128.34, 129.72, 129.97, 130.33, 132.99, 133.23, 134.82,

136.35, 145.31, 149.37, 151.52, 152.13, 152.33, 155.54,

166.74, 166.97, 167.19. MS (CI-NH₃): m/z (%)=735

(15) [MH⁺+NH₃]. C₃₆H₄₁N₈O₆Cl (717.2): calcd C

60.29, H 5.76, N 15.62; found C 60.25, H 5.72, N 15.62.

rac-2-[(2-Boc-aminoethyl)-(2-amino-6-benzyloxy-N-9-

purinacetyl)-amino]-ortho-chlorophenylacetic acid-(cyclo-

hexen-1-yl)-amide 6d. The title compound was prepared

according to GP3 using 0.40 g (2.5 mmol) mono-Boc-

ethylendiamine 4a, 0.28 g (2 mmol) 2-chlorobenz-

aldehyde, 0.75 g (2.5 mmol) 2-amino-6-benzyloxy-N-9-

carboxymethyl purine 5f, and 0.21 g (2.0 mmol) iso-

cyanide 2a as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (di-

chloromethane:methanol, 95:5) to yield 0.43 g (31%)

of a colourless solid, mp: 120±121 ^ꢀC. ¹H NMR

(300 MHz, CDCl₃): d 1.39 (s, 9H, Boc-CH₃), 1.5±2.0 (m,

8H, cyclohexenyl-CH₂), 2.8±3.6 (m, 4H, NCH₂CH₂),

2-[(2-Boc-aminoethyl)-(N⁴-Z-cytosinacetyl)-amino]-3,3-

dimethyl-butyric acid-(4-tert-butyl-cyclohexen-1-yl)-amide

6b. The title compound was prepared according to

GP3 using 0.40 g (2.5 mmol) mono-Boc-ethylendiamine

4a, 0.17 g (2 mmol) pivalaldehyde, 0.76 g (2.5 mmol) N⁴-

Z-N-1-carboxymethyl cytosine 5c, and 0.33 g (2.0 mmol)

isocyanide 2b as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (di-

chloromethane:methanol, 95:5) to yield 1.35 g (97%) of

3

4.84 (d, 2H, G-Bz-Ac-CH₂, J=16.5 Hz), 5.02 (m, 2H,

G-Bz-Ac-CH₂, Boc-NH), 5.49 (s, 2H, Z-CH₂), 5.94 (m,

1H, cyclohexenyl-CCH), 6.07 (s, 1H, NCH), 6.12 (br,

2H, NH₂), 7.1±7.5 (m, 9H, arH), 7.86 (s, 1H, G-Bz-Ac-

CH). MS (CI-NH₃): m/z (%)=707 (20) [MH⁺+NH₃].

C₃₅H₄₁N₈O₅Cl (689.2): calcd C 60.99, H 6.00, N 16.26;

found C 60.86, H 5.89, N 16.30.

1

a colourless solid. H NMR (300 MHz, CDCl₃, due to

the existence of two diastereomers in a 63:37 ratio

several signals were doubled): d 0.81 (s, 9H, 4-tert-

butyl-cyclohexenyl-CH₃), 0.98 (ma.), 1.07 (mi.) (2s, 9H,

C(CH₃)₃), 1.35 (mi.), 1.36 (ma.) (2s, 9H, Boc-CH₃), 1.7±

2.2 (m, 7H, 4-tert-butyl-cyclohexenyl-CH, CH₂), 3.1±4.0

(m, 4H), 4.04 (ma.), 4.38 (mi.) (2s, 1H, CHC(CH₃)₃),

4.76 (m, 1H, C-Z-Ac-CH₂), 5.07 (m, 1H, C-Z-Ac-CH₂),

5.15 (ma.), 5.17 (mi.) (2s, 2H, Z-CH₂), 5.94 (ma.), 6.08

(2m, 1H, 4-tert-butyl-cyclohexenyl-CCH), 7.18 (d, 1H,

rac-1-[(2-Etoc-aminoethyl)-thyminacetyl-amino]-cyclo-

hexancarboxylic acid-(4-tert-butyl cyclohexen-1-yl-amide

6e. The title compound was prepared according to

GP3 using 0.33 g (2.5 mmol) mono-Etoc-ethylendiamine

4b, 0.20 g (2 mmol) cyclohexanone, 0.46 g (2.5 mmol)

N-1-carboxymethylthymine 5a, and 0.33 g (2.0 mmol)

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1353

isocyanide 2c as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (di-

chloromethane:methanol, 95:5) to yield 1.10 g (98%)

of a colourless solid, mp: 165 ^ꢀC (dec.). ¹H NMR

(300 MHz, CDCl₃): d 0.82 (s, 9H, C(CH₃)₃), 1.25 (t, 3H,

CDCl₃): d 12.16, 22.44, 25.21, 26.87, 28.28, 29.40, 32.33,

32.57, 39.56, 41.12, 41.82, 43.61, 49.94, 50.43, 66.58,

79.91, 110.30, 113.63, 125.98, 126.66, 128.26, 128.47,

132.82, 141.39, 146.36, 151.22, 156.58, 164.49, 169.04,

172.09. MS (CI-NH₃): m/z (%)=626 (10) [MH⁺+

NH₃]. C₃₃H₄₅N₅O₆(607.8): calcd C 65.22, H 7.46, N

11.52; found C 65.10, H 7.44, N 11.49.

3

CH₂CH₃, J=7.6 Hz), 1.4±2.4 (m, 17H), 1.87 (s, 3H, T-

Ac-CHC), 3.27±3.61 (m, 4H), 4.12 (q, 2H, CH₂CH₃,

³J=7.6 Hz), 4.64 (br, 2H, T-Ac-CH₂), 5.78 (br, 1H,

Etoc-NH), 6.17 (m, 1H, 4-tert-Bu-cyclohexenyl-

CCH), 6.94 (s, 1H, T-Ac-CHCCH₃), 7.74 (br, 1H,

NH), 9.94 (br, 1H, T-Ac-NH). ¹³C NMR (75 MHz,

CDCl₃): d 12.07, 14.51, 22.37, 23.63, 25.38, 27.00, 27.34,

28.91, 31.91, 32.37, 41.29, 43.38, 49.93, 53.34, 61.00,

66.40, 109.98, 113.57, 132.89, 141.49, 151.19, 157.53,

164.58, 168.77, 171.81. MS (CI-NH₃): m/z (%)=577

(10)[MH⁺+NH₃]. C₂₉H₄₅N₅O₆(559.4): calcd C 62.23,

H 8.10, N 12.51; found C 62.68, H 7.95, N 12.62.

2-[(2-Boc-aminoethyl)-(2-thyminhexanoyl)-amino]-ortho-

chlorophenyl-acetic acid-(cyclohexen-1-yl)-amide 6h. The

title compound was prepared according to GP3 using

0.40 g (2.5 mmol) mono-Boc-ethylendiamine 4a, 0.28 g

(2 mmol) 2-chlorobenzaldehyde, 0.60 g (2.5 mmol) rac-2-

(thyminyl-1-yl)-hexanoic acid 5g, and 0.21 g (2.0 mmol)

isocyanide 2a as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (di-

chloromethane:methanol, 95:5) to yield 0.49 g (39%) of

a colourless solid (mixture of two diastereomers in a

1

rac-1-[(2-Z-Aminoethyl)-thyminacetyl-amino]-cyclohexan-

carboxylic acid-(4-phenyl cyclohexen-1-yl)-amide 6f. The

title compound was prepared according to GP3 using

0.49 g (2.5 mmol) mono-Z-ethylendiamine 4c, 0.20 g

(2mmol) cyclohexanone, 0.46g (2.5mmol) N-1-carboxy-

methylthymine 5a, and 0.37 g (2.0 mmol) isocyanide 2c

as starting materials. The resulting crude product was

puri®ed by ¯ash chromatography (dichloromethane:

methanol, 95:5) to yield 1.02 g (80%) of a colourless

50:50 ratio). H NMR (300 MHz, CDCl₃): d 0.81 (m,

3H, C₃H₆±CH₃), 1.12±1.40 (m, 4H, CH₂±(CH₂)₂±CH₃),

1.31, 1.35 (2 s, 9H, Boc-CH₃), 1.49±1.68, 1.99±2.18 (2m,

8H, cyclohexenyl-CH₂), 1.71±1.95 (m, 2H, CH₂±(CH₂)₂±

CH₃), 1.76, 1.81 (2s, 3H, thyminyl-CH₃), 2.89±3.46 (m,

4H), 4.86 (m, 1H, C₄H₉±CH), 6.00, 6.02 (2s, 1H, cyclo-

hexenyl-CCH), 6.43, 6.45 (2s, 1H), 7.29±7.54 (m, 5H,

thyminyl-H, ar-H). MS (CI-NH₃): m/z (%)=648 (10)

[MH⁺+NH₃]. C₃₂H₄₄ClN₅O₆(630.18): calcd C 60.99,

H 7.04, N 11.11; found C 60.62, H 7.17, N 11.09.

solid, mp: 154 ^ꢀC (dec.). H NMR (300 MHz, CDCl₃,

1

due to the existence of two rotamers in a 60:40 ratio

several signals were doubled and extremely broadened):

d 1.3±2.7 (m, 17H), 1.81 (s, 3H, T-Ac-CHC), 3.39±

3.72 (m, 4H), 4.52 (m, 0.8H, T-Ac-CH₂), 5.12 (m, 1.2H,

T-Ac-CH₂), 5.5±5.7 (m, 1H, Z-NH), 6.0±6.5 (m, 3H,

Z-CH₂+4-phenyl-cyclohexenyl-CCH), 6.81 (s, 0.6H,

T-Ac-CHCCH₃), 7.00 (s, 0.4H, T-Ac-CHCCH₃),

7.1±7.4 (m, 10H, ar-H), 7.80 (br, 1H, NH), 9.76 (br,

0.6H, T-Ac-NH), 10.84 (br, 0.4H, T-Ac-NH). ¹³C NMR

(75 MHz, CDCl₃): d 12.16, 22.46, 25.19, 28.37, 29.31,

30.46, 32.36, 33.44, 33.82, 36.64, 39.50, 41.24, 42.60,

43.52, 49.84, 52.59, 53.37, 66.07, 66.81, 109.66, 110.09,

110.84, 113.13, 125.96, 126.14, 126.68, 128.23, 128.47,

128.77, 128.99, 132.78, 133.56, 136.19, 137.09, 141.48,

146.38, 147.04, 151.11, 151.87, 157.22, 158.39, 164.56,

167.14, 169.00, 171.11, 171.98. MS (CI-NH₃): m/z (%)

=660 (10) [MH⁺+NH₃]. C₃₆H₄₃N₅O₆(641.8): calcd C

67.38, H 6.75, N 10.91; found C 65.98, H 6.87, N 11.03.

rac-2-[(2-Boc-aminoethyl)-(2-thymin-methyl-benzoyl)-

amino]-3,3-dimethyl-butyric acid-(cyclohexen-1-yl)-amide

6i. The title compound was prepared according to GP3

using 0.40 g (2.5 mmol) mono-Boc-ethylendiamine 4a,

0.15 g (2 mmol) pivalaldehyde, 0.65 g (2.5 mmol) 2-(thy-

min-1-yl)-methyl-benzoic acid 5h, and 0.21 g (2.0 mmol)

isocyanide 2b as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (dichloro-

methane:methanol, 95:5) to yield 0.56 g (52%) of a

colourless solid, mp: 164±166 ^ꢀC (dec.). ¹H NMR

(300 MHz, CDCl₃): (the title compound exists as a 90:10

mixture of rotamers in CDCl₃at room temperature) d

0.99, 1.15 (2s, 9H, CH±C(CH₃)₃), 1.32, 1.41 (2s, 9H, C±

(CH₃)₃), 1.56±1.65, 2.07±2.18 (2m, 8H, (CH₂)₄), 1.80,

1.83 (2s, 3H, thyminyl-CH₃), 2.91±3.96 (m, 4H), 4.82

(br, 1H), 5.00, 5.30, 5.51 (br, 2H, Ph-CH₂), 6.09 (br, 1H,

cyclohexenyl-CCH), 7.23±7.58 (m, 5H, thyminyl-H,

ar-H), 8.52 (br, 1H, cyclohexenyl-NH). MS (CI-NH₃):

m/z (%)=557 (25) [MH⁺+ NH₃]. C₂₈H₃₇N₅O₆

(539.30): calcd C 62.36, H 6.91, N 12.99; found C 62.31,

H 6.94, N 13.41.

rac-1-[(2-Boc-aminoethyl)-thyminacetyl-amino]-cyclo-

hexancarboxylic acid-(4-phenyl cyclohexen-1-yl)-amide

6g. The title compound was prepared according to

GP3 using 0.40 g (2.5 mmol) mono-Boc-ethylendiamine

4a, 0.20 g (2 mmol) cyclohexanone, 0.46 g (2.5 mmol) N-

1-carboxymethylthymine 5a, and 0.37 g (2.0 mmol) iso-

cyanide 2c as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (di-

chloromethane:methanol, 95:5) to yield 1.10g (90%) of

a colourless solid, mp: 115 ^ꢀC. ¹H NMR (300MHz,

CDCl₃): d 1.45 (s, 9H, Boc-CH₃), 1.4±2.4 (m, 16H, CH₂),

1.89 (s, 3H, T-Ac-CHC), 2.75 (m, 1H, CH-phenyl),

3.39, 3.56 (m, 4H, NCH₂CH₂), 4.62 (s, 2H, T-Ac-CH₂),

5.51 (m, 1H, Boc-NH), 6.03 (m, 1H, cyclohexenyl-

CCH), 6.98 (s, 1H, T-Ac-CHCCH₃), 7.87 (br, 1H,

NH), 9.68 (br, 1H, T-Ac-NH). ¹³C NMR (75 MHz,

2-[(2-Acetyl-aminoethyl)-(2-N⁴-Z-cytosin-methyl-benzoyl)-

amino]-phenyl-acetic acid-(4-tert-butyl-cyclohexen-1-yl)-

amide 6j. The title compound was prepared according

to GP3 0.25 g (2.5 mmol) mono-acetyl-ethylendiamine

4d, 0.21 g (2 mmol) benzaldehyde, 0.95 g (2.5 mmol) 2-

(N⁴-Z-cytosin-1-yl)-methyl-benzoic acid 5i, and 0.33 g

(2 mmol) isocyanide 2b as starting materials. The

resulting crude product was puri®ed by ¯ash chromato-

graphy (dichloromethane:methanol, 95:5) to yield 0.70 g

(48%) of a colourless solid (racemic mixture of two

diastereomers in a 50:50 ratio). ¹H NMR (300 MHz,

CDCl₃): d 0.82 (s, 9H, (CH₃)₃), 1.12±1.36, 1.70±2.31

1354

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

(2m, 10H, (CH₂)_3,(CH₃)₃±CH, CO±CH₃), 2.92±3.41 (m,

4H), 5.23±5.49 (m, 5H, Z-CH₂, Ph-CH₂, CH-Ph), 6.10

(br, 1H, cyclohexenyl-CCH), 7.28±7.94 (m, 16H, arH,

cytosine-H). ¹³C NMR (75 MHz, CDCl₃): d 23.16,

23.64, 25.45, 28.95, 28.95, 29.60, 27.12, 32.06, 38.27,

43.44, 67.67, 95.27, 114.27, 126.63, 127.42, 128.19,

128.59, 128.93, 129.25, 129.78, 132.46, 133.02, 134.07,

149.93, 168.33, 170.18. MS (CI-NH₃): m/z (%)=750

(15) [MH⁺+NH₃]. C₄₂H₄₇N₆O₆(731.87): calcd C

68.93, H 6.47, N 11.48; found C 68.96, H 6.37, N 11.31.

(10 mmol) benzaldehyde, and 1.56ml (12 mmol) triethyl-

amine were dissolved in 40 mL toluene and stirred for

24 h at room temperature. The solvent was evaporated

and the residue dissolved in 40 mL abs. MeOH. After

addition of 1.84 g (10 mmol) N-1-carboxymethylthy-

mine 5a and 1.64 g (10 mmol) isocyanide 2b the reaction

mixture was stirred for 48 h at room temperature. The

solvent was removed in vacuo and the crude product

puri®ed by ¯ash chromatography to yield 3.34 g (60%)

of a colourless solid (racemic mixture of two diaster-

eomers in a 60:40 ratio). ¹H NMR (300 MHz, CDCl₃): d

0.73±0.89, 1.29±1.61, 1.99±2.63 (3m, 9H, CH₂±COOEt,

(CH₂)₃, (CH₃)₃±CH), 0.91 (s, 9H, (CH₃)₃), 1.21 (m, 3H,

COO±CH₂±CH₃), 1.87 (s, 3H, thyminyl-CH₃), 3.47±3.79

(m, 2H, N±CH₂±CH₂±COOEt), 4.07 (m, 2H, COO±

CH₂±CH₃), 4.58, 4.83 (2d, 2H, T-CH₂), 5.71, 5.79, 5.83,

5.88 (4s, 1H, NCH), 6.02, 6.12, 6.29, 6.33 (4bs, 1H,

cyclohexenyl-CCH), 7.02 (2s, 1H, thyminyl-H), 7.28±

7.53 (m, 5H, arH). ¹³C NMR (75 MHz, CDCl₃): d

12.24, 14.01, 22.66, 23.62, 25.39, 27.12, 27.44, 28.92,

32.05, 32.23, 32.41, 32.72, 33.88, 34.02, 34.82, 41.00,

41.25, 41.41, 43.44, 46.61, 47.04, 48.32, 48.75, 50.56,

60.37, 60.73, 63.17, 63,71, 69.80, 110.37, 113.31, 126.60,

128.12, 129.11, 129.63, 129.70, 132.32, 133.67, 141.39,

151.17, 151.39, 164.52, 167.33, 167.67, 169.26, 171.15,

171.72. MS (CI-NH₃): m/z (%)=571 (15) [MH⁺

+NH₃]. C₃₀H₄₀N₄O₆(552.67): calcd C 65.17, H 7.29, N

10.14; found C 65.17, H 7.38, N 10.34.

rac-2-[(2-Benzyloxyethyl)-thyminacetyl-amino]-cyclo-

hexancarboxylic acid-(4-tert-butyl cyclohexen-1-yl)-

amide 6k. The title compound was prepared according

to GP3 using 0.38 g (2.5 mmol) O-benzyl ethanolamine

4e, 0.20 g (2 mmol) cyclohexanone, 0.46 g (2.5 mmol) N-

1-carboxymethylthymine 5a, and 0.33 g (2.0 mmol) iso-

cyanide 2b as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (di-

chloromethane:methanol, 95:5) to yield 0.94 g (81%)

of a colourless solid, mp: 234 ^ꢀC. H NMR (300 MHz,

1

CDCl₃): d 0.84 (s, 9H, C(CH₃)₃), 1.3±2.2 (m, 17H), 1.78

(s, 3H, T-Ac-CHC), 3.69 (m, 4H), 4.45±4.61 (m, 4H,

Bz-CH₂+T-Ac-CH₂), 6.01 (m, 1H, 4-tert-Bu-cyclohexenyl-

CCH), 7.25±7.39 (m, 6H, arH+T-Ac-CHCCH₃),

8.32 (br, 1H, NH), 9.01 (br, 1H, T-Ac-NH). ¹³C NMR

(75 MHz, CDCl₃): d 12.20, 22.17, 23.65, 25.24, 25.45,

27.15, 27.56, 32.07, 32.96, 41.29, 43.57, 50.76, 66.46, 68.59,

73.97, 110.16, 112.68, 127.95, 128.15, 128.48, 132.81,

137.64, 141.19, 150.98, 164.22, 170.49. MS (CI-NH₃): m/z

(%)=597 (10) [MH⁺+NH₃]. C₃₃H₄₆N₄O₅(578.8): calcd

C 68.49, H 8.01, N 9.68; found C 67.10, H 7.98, N 9.79.

2-[(2-Boc-aminoethyl)-thyminacetyl-amino]-acetic acid-4-

methoxy-2-nitro-phenylamide 7a. The title compound

was prepared according to GP5 using 0.32 g (2.00 mmol)

mono-Boc-ethylendiamine 4a, 0.06 g (2.00 mmol) para-

formaldehyde, 0.36 g (2.00 mmol) 4-methoxy-2-nitro-

phenylisocyanide 3a, and 0.37 g (2.00 mmol) N-1-

carboxymethylthymine 5a as starting materials and

puri®ed by chromatography to yield 0.68 g (64%) 7a as

an orange powder. ¹H NMR (300 MHz, DMSO-d₆,

rac-2-[(2-Ib-Aminophenyl)-thyminacetyl-amino]-biphenyl-

4-yl-acetic acid-(cyclohexen-1-yl)-amide 6l. The title

compound was prepared according to GP3 using 0.45 g

(2.5 mmol) mono-Ib-ortho-phenylendiamine 4f, 0.36 g

(2 mmol) 4-phenyl benzaldehyde, 0.46 g (2.5 mmol) N-1-

carboxymethylthymine 5a, and 0.21 g (2.0 mmol) iso-

cyanide 2a as starting materials. The resulting crude

product was puri®ed by ¯ash chromatography (di-

chloromethane:methanol, 90:10) to yield 0.65g (51%) of

.

rotamer ratio: ma.:mi.=64:36): d 1.38 (s, 0.64 9H,

.

Boc-CH₃, ma.), 1.43 (s, 0.36 9H, Boc-CH₃, mi.), 1.76

(s, 3H, T-CH₃), 3.01±3.62 (m, 4H, NCH₂CH₂, rot.),

.

3.84, 3.85 (2 s, 3H, ar-O-CH₃, rot.), 4.13 (s, 0.64 2H,

a colourless solid, mp: >250 ^ꢀC. H NMR (300 MHz,

NCH, ma.), 4.32 (s, 0.36 2H, NCH, mi.), 4.50 (s, 0.36

1

.

3

.

2H, T-Ac-CH₂, mi.), 4.69 (s, 0.64 2H, T-Ac-CH₂, ma.),

DMSO-d₆): d 1.21 (d, 3H, CH(CH₃)₂, J=6.6 Hz), 1.24

(d, 3H, CH(CH₃)₂, ³J=6.6 Hz), 1.50 (m, 4H, CH₂), 1.73

(s, 3H, T-Ac-CH₃), 2.08 (m, 4H, CH₂), 2.90 (m, 1H,

6.73 (s, 0.36 1H, Boc-NH, mi.), 6.96 (s, 0.64 1H, Boc-

NH, ma.), 7.21±7.38 (m, 2H, T-CHC, ar-H, rot.),

.

3

2

.

7.46±7.64 (m, 2H, ar-H, ar-H, rot.), 10.12 (s, 0.64 1H,

.

ar-NH, ma.), 10.39 (s, 0.36 1H, ar-NH, mi.), 11.27 (s,

CH(CH₃)₂, J=6.6 Hz), 3.92 (d, 1H, T-Ac-CH₂, J=

2

16.5 Hz), 4.00 (d, 1H, T-Ac-CH₂, J=16.5 Hz), 5.88 (s,

1H, NCH), 6.10 (s, 1H, cyclohexenyl-CCH), 6.7±8.3 (m,

14H, arH, T-Ac-CCH), 9.47 (s, 1H, NH), 11.22 (s, 1H,

NH), 11.32 (s, 1H, NH). ¹³C NMR (75 MHz, DMSO-d₆):

d 11.84, 19.39, 19.60, 21.22, 21.99, 23.51, 26.90, 35.32,

48.80, 65.66, 107.83, 111.54, 120.19, 122.63, 125.78,

126.25, 126.39, 127.05, 127.66, 128.84, 129.28, 130.10,

131.83, 133.29, 138.42, 138.85, 139.97, 142.01, 150.76,

150.99, 164.34, 167.28, 169.69, 170.02, 175.81. MS (CI-

NH₃): m/z (%)=651 (10) [MH⁺+NH₃]. C₃₇H₃₉N₅O₅

(633.6): calcd C 70.12, H 6.20, N 11.05; found C 70.49, H

6.24, N 11.07.

1H, T-NH). C₂₃H₃₀N₆O₉(534.5): calcd C 51.68, H 5.66,

N 15.72; found C 51.53, H 5.79, N 15.56.

2-[(2-Boc-aminoethyl)-(N⁴-Z-cytosinacetyl)-amino]-acetic

acid-4-methoxy-2-nitro-phenylamide 7b. The title

compound was prepared according to GP5 using

0.32 g (2.00 mmol) mono-Boc-ethylendiamine 4a, 0.06 g

(2.00 mmol) paraformaldehyde, 0.36 g (2.00 mmol)

4-methoxy-2-nitrophenylisocyanide 3a, and 0.61 g (2.00

mmol) N⁴-Z-N-1-carboxymethylcytosine 5c as starting

materials and puri®ed by chromatography to yield 0.83g

(64%) 7b as an orange powder, mp: 169 ^ꢀC (dec.). H

1

3-[(2-Ethoxycarbonylethyl)-thyminacetyl-amino]-phenyl-

acetic acid-(4-tert-butyl-cyclohexen-1-yl)-amide 6m. 1.54 g

(10 mmol) b-Alaninethylester-hydrochloride, 1.06 g

NMR (300 MHz, CDCl₃, rotamer ratio: ma.:mi.=83:

17): d 1.42 (s, 9H, Boc-CH₃), 3.25±3.35, 3.56±3.64 (2 m,

.

0.17 4H, NCH₂CH₂, mi.), 3.36±3.48, 3.65±3.76 (2 m,

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1355

.

0.83 4H, NCH₂CH₂, ma.), 3.85 (s, 3H, ar-O-CH₃), 4.16

using 0.32 g (2.00 mmol) mono-Boc-ethylendiamine 4a,

0.06 g (2.00 mmol) paraformaldehyde, 0.36 g (2.00

mmol) 4-methoxy-2-nitrophenylisocyanide 3a, and

0.60 g (2.00 mmol) 2-amino-6-benzyloxy-N-9-carboxy-

methylpurine 5f as starting materials and puri®ed by

chromatography to yield 0.41 g (32%) 7e as a yellow

powder, mp: 115 ^ꢀC. ¹H NMR (300 MHz, CDCl₃): d

1.38±1.49 (m, 9H, Boc-CH₃, rot.), 3.28±3.42, 3.55±3.70

(2 m, 4H, NCH₂CH₂, rot.), 3.82 (s, 3H, ar-O-CH₃),

.

(s, 0.83 2H, NCH, ma.), 4.50 (s, 0.17 2H, NCH, mi.),

.

Z

.

4.69 (s, 0.17 2H, C -Ac-CH₂, mi.) , 4.89 (s, 0.83 2H,

C^Z-Ac-CH₂, ma.), 5.22 , 5.77 (2 s, 3H, Z-CH₂-Ph, Boc-

NH, rot.), 7.19 (dd, 1H, ar-H), 7.23 (m, 1H, C^Z-

CHCH, rot.), 7.32±7.42 (m, 5H, Z-Ph), 7.60 (d, 1H,

ar-H), 7.68 (m, 1H, C^Z-CHCH, rot.), 8.25±8.38 (m,

1H, C^Z-NH, rot.), 8.43 (d, 1H, ar-H), 10.29±10.40 (m,

1H, ar-NH). ¹³C NMR (75 MHz, CDCl₃): d 28.34,

38.91, 39.55, 43.60, 48.88, 49.95, 52.14, 53.30, 55.89,

67.76, 79.85, 95.18, 108.78, 122.89, 124.48, 127.15, 128.14,

128.60, 135.09, 138.12, 149.88, 152.36, 155.53, 156.24,

162.99, 167.33, 167.87. C₃₀H₃₅N₇O₁₀(653.6): calcd C

55.13, H 5.40, N 15.00; found C 55.21, H 5.38, N 15.12.

4.12±4.40 (m, 2H, NCH, rot.), 4.73±5.18 (m, 3H, G^Bn

-

Ac-CH₂, Boc-NH, rot.), 5.44±5.85 (m, 2H, Bz-CH₂-Ph,

rot.), 5.96±6.15 (m, 2H, G^Bn-NH₂, rot.), 7.11 (dd, 1H,

ar-H), 7.28±7.50 (m, 5H, Bz-Ph), 7.55 (d, 1H, ar-H),

7.70 (s, 1H, G^Bn-CHN), 8.40 (d, 1H, ar-H), 10.29 (s,

1H, ar-NH). ¹³C NMR (75 MHz, CDCl₃): d 28.25,

38.63, 43.47, 48.69, 51.77, 55.78, 68.02, 79.85, 108.60,

114.54, 122.83, 124.08, 126.98, 127.90, 128.10, 128.27,

128.74, 137.71, 136.22, 140.31, 154.06, 155.36, 156.16,

159.27, 160.82, 167.14, 167.58. C₃₀H₃₅N₉O₈(649.7):

calcd C 55.46, H 5.47, N 19.40; found C 55.42, H 5.38,

N 19.31.

2-[(2-Boc-aminoethyl)-uracilacetyl-amino]-acetic acid-4-

methoxy-2-nitro-phenylamide 7c. The title compound

was prepared according to GP5 using 0.32 g (2.00 mmol)

mono-Boc-ethylendiamine 4a, 0.06 g (2.00 mmol) para-

formaldehyde, 0.36 g (2.00 mmol) 4-methoxy-2-nitro-

phenylisocyanide 3a, and 0.34 g (2.00 mmol) N-1-

carboxymethyluracil 5b as starting materials and pur-

i®ed by chromatography to yield 0.67 g (64%) 7c as an

2-[(2-Boc-aminoethyl)-(N²-Z-guaninacetyl)-amino]-acetic

acid-4-methoxy-2-nitro-phenylamide 7f. The title com-

pound was prepared according to GP5 using 0.32 g

(2.00 mmol) mono-Boc-ethylendiamine 4a, 0.06 g (2.00

mmol) paraformaldehyde, 0.36 g (2.00 mmol) 4-meth-

oxy-2-nitrophenylisocyanide 3a, and 0.69 g (2.00 mmol)

N²-Z-N-9-carboxymethylguanine 5e as starting materi-

als and puri®ed by chromatography to yield 0.27 g

(20%) 7f as a yellow powder, mp: 190 ^ꢀC (dec.). ¹H

NMR (300 MHz, CDCl₃): d 1.34, 1.44 (2 s, 9H, Boc-

CH₃, rot.), 3.21±3.32, 3.42±3.60, 3.68±3.77 (3 m, 4H,

NCH₂CH₂, rot.), 3.80 (s, 3H, ar-O-CH₃), 4.19, (2 s, 2H,

NCH, rot.), 4.89, 5.04, 5.08 (3 s, 2H, G^Z-Ac-CH₂, rot.),

5.21 (m, 2H, Z-CH₂-Ph), 5.44, 6.00, 6.08 (3 s, 1H, Boc-

NH, rot.), 7.11 (dd, 1H, ar-H), 7.31±7.39 (m, 5H, Z-Ph),

7.53 (m, 1H, ar-H, rot.), 7.70 (s, 1H, G^Z-CHN), 8.11,

8.31 (2 d, 1H, ar-H, rot.), 9.56, 9.87, 10.87 (3 s, 1H, G^Z-

NH, rot.), 10.20, 10.35 (2 s, 1H, ar-NH, rot.), 11.26,

11.31 (2 s, 1H, Z-NH, rot.). C₃₁H₃₅N₉O₁₀(693.7): calcd

C 53.68, H 5.09, N 18.17; found C 53.62, H 5.07, N

18.08.

1

orange powder. H NMR (300 MHz, CDCl₃, rotamer

ratio: ma.:mi.=55:45): d 1.40±151 (m, 9H, Boc-CH₃,

rot.), 3.29±3.93 (m, 4H, NCH₂CH₂, rot.), 3.87 (s, 3H,

.

ar-O-CH₃), 4.22 (s, 0.55 2H, NCH, ma.), 4.71 (s, 0.55

.

2H, T-Ac-CH₂, ma.), 4.14±4.96 (m, 0.45 4H, NCH, T-

Ac-CH₂, mi.), 5.16, 5.55 (2 m, 1H, Boc-NH, rot.), 5.70

(d, 1H, U-CCH), 7.19±7.28 (m, 2H, U-CHC, ar-H,

.

rot.), 7.62 (2 d, 1H, ar-H, rot.), 8.50 (d, 0.55 1H, ar-H,

.

ma.), 8.57 (d, 0.45 1H, ar-H, mi.), 8.91 (s, 0.45 1H, U-

.

NH, mi.), 9.10 (s, 0.55 1H, U-NH, ma.), 10.29 (s, 0.55

.

1H, ar-NH, ma.), 10.36 (s, 0.45 1H, ar-NH, mi.).

C₂₂H₂₈N₆O₉(520.5): calcd C 50.77, H 5.42, N 16.15;

found C 50.79, H 5.38, N 16.01.

2-[(2-Boc-aminoethyl)-(N⁶-Z-adeninacetyl)-amino]-acetic

acid-4-methoxy-2-nitro-phenylamide 7d. The title com-

pound was prepared according to GP5 using 0.32 g

(2.00 mmol) mono-Boc-ethylendiamine 4a, 0.06 g (2.00

mmol) paraformaldehyde, 0.36 g (2.00 mmol) 4-meth-

oxy-2-nitrophenylisocyanide 3a, and 0.65 g (2.00 mmol)

N⁶-Z-N-9-carboxymethyladenine 5d as starting materi-

als and puri®ed by chromatography to yield 0.94 g

2-[(2-Benzyloxyethyl)-thyminacetyl-amino]-acetic acid-4-

methoxy-2-nitro-phenylamide 7g. The title compound

was prepared according to GP5 using 0.30 g (2.00 mmol)

O-benzyl ethanolamine 4e, 0.06 g (2.00 mmol) para-

formaldehyde, 0.36 g (2.00 mmol) 4-methoxy-2-nitro-

phenylisocyanide 3a, and 0.37 g (2.00 mmol) N-1-car-

boxymethylthymine 5a as starting materials and puri®ed

by chromatography to yield 0.89 g (85%) 7g as a yel-

low powder, mp: 162 ^ꢀC (dec.). ¹H NMR (300 MHz,

DMSO-d₆, rotamer ratio:ma.:mi.=56:44): d 1.69 (s,

1

(69%) 7d as an orange powder. H NMR (300 MHz,

CDCl₃, rotamer ratio: ma.:mi.=55:45): d 1.39±1.48 (m,

9H, Boc-CH₃, rot.), 3.24±3.48, 3.57±3.91 (2 m, 4H,

NCH₂CH₂, rot.), 3.83 (m, 3H, ar-O-CH₃, rot.), 4.20,

4.24, 4.41 (3 s, 2H, NCH, rot.), 4.72, 4.95, 5.04 (3 s, 2H,

A^Z-Ac-CH₂, rot.), 5.21±5.28 (m, 2H, Z-CH₂-Ph, rot.),

5.35, 5.70 (s, m, 1H, Boc-NH, rot.), 7.12±7.20 (m, 1H,

ar-H, rot.), 7.30±7.40 (m, 5H, Z-Ph), 7.58±7.62 (m, 1H,

Z

.

ar-H, rot.), 8.10 (m, 1H, A -CHN, rot.), 8.44 (d, 0.55

.

1H, ar-H, ma.), 8.50 (d, 0.45 1H, ar-H, mi.), 8.60, 8.69

0.56 3H, T-CH₃, ma.), 1.75 (s, 0.44 3H, T-CH₃, mi.),

(m, 1H, A^Z-CHN, rot.), 8.92±9.20 (m, 1H, A^Z-NH,

3.55, 3.68 (2 s, 4H, NCH₂CH₂), 3.81, 3.82 (2 s, 3H, ar-

.

O-CH₃, rot.), 4.17 (s, 0.56 2H, NCH, ma.), 4.29, 4.32

.

rot.), 10.29 (s, 0.55 1H, ar-NH, ma.), 10.36 (s, 0.45 1H,

.

(2 s, 0.44 4H, NCH, CH₂-Ph, mi.), 4.50 (s, 2H, T-Ac-

ar-NH, mi.). C₃₁H₃₅N₉O₉(677.7): calcd C 54.94, H

5.21, N 18.60; found C 54.82, H 5.18, N 18.51.

.

CH₂), 4.74 (s, 0.56 2H, CH₂-Ph, ma.), 7.03 (s, 0.56 1H,

.

T-CHC, ma.), 7.19 (s, 0.44 1H, T-CHC, mi.), 7.21±

.

2-[(2-Boc-aminoethyl)-(2-amino-6-benzyloxy-N-9-purin-

acetyl)-amino]-acetic acid-4-methoxy-2-nitro-phenylamide

7e. The title compound was prepared according to GP5

7.33 (m, 6H, Ph, ar-H), 7.44 (d, 1H, ar-H), 7.59 (d, 0.44

.

1H, ar-H, mi.), 7.70 (d, 0.56 1H, ar-H, ma.), 10.05 (s,

.

0.56 1H, ar-NH, ma.), 10.28 (s, 0.44 1H, ar-NH, mi.),

.

1356

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

11.21 (s, 1H, T-NH). ¹³C NMR (75 MHz, DMSO-d₆): d

10.11, 45.43, 45.96, 46.22, 48.12, 49.40, 54.04, 65.93,

66.12, 70.35, 70.71, 106.53, 107.07, 118.50, 118.87,

122.02, 122.69, 124.72, 126.34, 125.49, 125.62, 126.28,

136.13, 139.85, 141.01, 149.22, 154.05, 154.43, 162.50,

165.32, 166.05. C₂₅H₂₇N₅O₈(525.5): calcd C 57.14, H

5.18, N 13.33; found C 57.28, H 5.21, N 13.14.

carboxymethylthymine 5a as starting materials and

puri®ed by chromatography to yield 0.41 g (41%) 7j as

an orange powder, mp: 115 ^ꢀC (dec.). ¹H NMR

(300 MHz, CDCl₃): d 1.42 (s, 9H, Boc-CH₃), 1.90 (s,

3H, T-CH₃), 3.20±3.51, 3.79±3.89 (2 m, 4H, NCH₂CH₂),

3.83 (s, 3H, ar-O-CH₃), 4.59, 4.80 (2 d, 2H, T-Ac-CH₂),

5.49 (s, 1H, Boc-NH), 5.77 (s, 1H, NCH), 7.00 (s, 1H,

T-CHC), 7.21 (dd, 1H, ar-H), 7.40±7.49 (m, 5H, Ph),

7.60 (d, 1H, ar-H), 8.59 (d, 1H, ar-H), 8.95 (s, 1H,

T-NH), 10.11 (s, 1H, ar-NH). ¹³C NMR (75 MHz,

CDCl₃): d 12.30, 28.39, 39.40, 45.51, 48.72, 55.89, 65.97,

79.92, 108.68, 110.70, 123.01, 123.93, 127.47, 129.57,

129.77, 129.88, 132.51, 137.57, 141.00, 150.97, 155.45,

155.92, 164.05, 167.99, 168.67. C₂₉H₃₄N₆O₉(610.6):

calcd C 57.04, H 5.61, N 13.76; found C 57.12, H 5.69,

N 13.59.

8-[(2-Boc-aminoethyl)-thyminacetyl-amino]-1,4-dioxaspiro-

(4.5)decan-8-carboxylic acid-4-methoxy-2-nitro-phenyl-

amide 7h. The title compound was prepared according

to GP5 using 0.32 g (2.00 mmol) mono-Boc-ethylendi-

amine 4a, 0.31 g (2.00 mmol) 1,4-cyclohexandione mono-

ethylenacetal, 0.36 g (2.00 mmol) 4-methoxy-2-nitro-

phenyl-isocyanide 3a, and 0.37 g (2.00 mmol) N-1-car-

boxymethylthymine 5a as starting materials and puri®ed

by washing the crude product twice with diethylether to

yield 1.09 g (83%) 7h as a yellow powder, mp: 230 ^ꢀC

(dec.). ¹H NMR (300 MHz, CDCl₃): d 1.43 (s, 9H,

Boc-CH₃), 1.63±1.70, 1.95±2.18, 2.34±2.40 (3 m, 8H,

(CH₂)₂C(CH₂)₂), 1.79 (s, 3H, T-CH₃), 3.35±3.47, 3.53±

3.62 (m, 4H, NCH₂CH₂), 3.85 (s, 3H, ar-O-CH₃), 3.93

(s, 4H, OCH₂CH₂O), 4.67 (s, 2H, T-Ac-CH₂), 6.69 (s,

1H, Boc-NH), 6.99 (s, 1H, T-CHC), 7.20 (dd, 1H, ar-

H), 7.55 (d, 1H, ar-H), 7.76 (s, 1H, T-NH), 8.10 (d, 1H,

ar-H), 9.48 (s, 1H, ar-NH). ¹³C NMR (75 MHz, CDCl₃/

DMSO-d₆): d 11.73, 27.97, 29.03, 30.76, 42.50, 49.11,

55.58, 63.63, 107.13, 108.21, 120.58, 125.97, 127.10,

141.50, 141.53, 150.84, 155.42, 164.25, 168.17, 171.20.

C₃₀H₄₀N₆O₁₁(660.7): calcd C 54.54, H 6.10, N 12.72;

found C 53.97, H 5.83, N 12.51.

rac-2-[(2-Boc-amino-1-methyl-ethyl)-thyminacetyl-amino]-

acetic acid-4-methoxy-2-nitro-phenylamide 7k. The title

compound was prepared according to GP5 using 0.35 g

(2.00 mmol) rac-1-Boc-amino-2-aminopropane 4h, 0.06g

(2.00 mmol) paraformaldehyde, 0.36 g (2.00 mmol) 4-

methoxy-2-nitro-phenylisocyanide 3a, and 0.37 g (2.00

mmol) N-1-carboxymethylthymine 5a as starting mate-

1

rials to yield 0.60 g (55%) 7k as an orange powder, H

NMR (CDCl₃, 300 MHz): d 1.31, 1.42 (2 d, 3H,

NCHCH₃, rot.), 1.50 (s, 9H, Boc-CH₃), 1.90 (s, 3H,

T-CH₃), 3.29±3.31 (m, 2H, NCH), 3.38±3.47 (m, 1H,

NCHCH₃), 3.85 (s, 3H, ar-OCH₃), 4.25, 4.36±4.82 (m,

5H, 2-H, T-Ac-CH₂, Boc-NH, rot.), 7.02, 7.09 (2 s, 1H,

T-CHC, rot.), 7.21 (dd, 1H, ar-H), 7.62, 7.66 (2 d, 1H,

ar-H, rot.), 8.45, 8.58 (d, 1H, ar-H), 8.61 (s, 1H, T-NH),

10.30, 10.38 (2 s, 1H, C-1-NH, rot.). C₂₄H₃₂N₆O₉

(548.6): calcd C 52.55, H 5.88, N 15.32; found C 52.32,

H 5.80, N 15.26.

8-[(2-Boc-aminoethyl)-thyminacetyl-amino]-1,4-dioxaspiro-

(4.5)decan-8-carboxylic acid-2-methoxy-4-nitro-phenyl-

amide 7i. The title compound was prepared according

to GP5 using 0.32 g (2.00 mmol) mono-Boc-ethylendi-

amine 4a, 0.31 g (2.00 mmol) 1,4-cyclohexandione mono-

ethylenacetal, 0.36 g (2.00 mmol) 2-methoxy-4-nitro-

phenyl-isocyanide 3b, and 0.37 g (2.00 mmol) N-1-car-

boxymethylthymine 5a as starting materials and pur-

i®ed by chromatography to yield 0.93 g (70%) 7i as a

rac-2-[(trans-2-Boc-aminocyclohexyl)-thyminacetyl-amino]-

acetic acid-4-methoxy-2-nitro-phenylamide 7l. The title

compound was prepared according to GP5 using 0.43 g

(2.00 mmol) mono-Boc-cyclohexylendiamine 4g, 0.06 g

(2.00 mmol) paraformaldehyde, 0.36 g (2.00 mmol) 4-

methoxy-2-nitro-phenylisocyanide 3a, and 0.37 g (2.00

mmol) N-1-carboxymethylthymine 5a as starting mate-

rials to yield 0.75 g (64%) 7l as a yellow powder, mp:

ꢀ

1

yellow powder, mp: 169 C (dec.). H NMR (300 MHz,

CDCl₃/DMSO-d₆): d 1.42 (s, 9H, Boc-CH₃), 1.59±1.69,

1.78±2.12, 2.23±2.35 (3 m, 8H, (CH₂)₂C(CH₂)₂), 1.74

(s, 3H, T-CH₃), 3.25±3.36, 3.49±3.57 (2 m, 4H, NCH₂

CH₂), 3.90 (s, 4H, OCH₂CH₂O), 3.99 (s, 3H, ar-O-

CH₃), 4.70 (s, 2H, T-Ac-CH₂), 6.88 (s, 1H, Boc-NH),

7.15 (s, 1H, T-CHC), 7.72 (d, 1H, ar-H), 7.80 (dd,

1H, ar-H), 8.22 (d, 1H, ar-H), 8.72 (s, 1H, ar-NH),

11.10 (s, 1H, T-NH). ¹³C NMR (75 MHz, CDCl₃/

DMSO-d₆): d 11.70, 27.94, 29.06, 30.75, 42.67, 49.04,

56.30, 63.67, 64.57, 64.87, 78.09, 105.06, 106.90, 108.26,

116.41, 118.85, 133.89, 141.34, 142.49, 148.40, 150.71,

155.67, 164.24, 169.05, 171.17. C₃₀H₄₀N₆O₁₁(660.7):

calcd C 54.54, H 6.10, N 12.72; found C 54.21, H 6.03,

N 12.85.

130 ^ꢀC (dec.). H NMR (300 MHz, DMSO-d₆, rotamer

1

.

ratio: ma.:mi.=55:45): d 1.31 (s, 0.55 9H, Boc-CH₃,

.

ma.), 1.35±1.45 (m, 0.45 9H, Boc-CH₃, mi.), 1.10±2.02

(m, 8H, (CH₂)₄), 1.78 (s, 3H, T-CH₃), 3.30±3.95 (m, 2H,

NCHCH, rot.), 3.82, 3.84 (2 s, 3H, ar-O-CH₃, rot.),

.

4.12±4.39 (m, 0.45 2H, NCH, mi.), 4.33 (s, 0.55 2H,

.

NCH, ma.), 4.48±4.82 (m, 0.45 2H, T-Ac-CH₂, mi.),

.

4.73, 4.91 (2 d, 0.55 2H, T-Ac-CH₂, ma.), 6.49±6.62

.

(m, 0.45 1H, Boc-NH, mi.), 6.92 (d, 0.55 1H, Boc-NH,

.

ma.), 7.03±7.24 (m, 0.45 1H, T-CHC, mi.), 7.12 (s,

.

0.55 1H, T-CHC, ma.), 7.31 (dd, 1H, ar-H), 7.47 (d,

.

0.55 1H, ar-H, ma.), 7.49±7.59 (m, 0.45 2H, ar-H, ar-

.

H, mi.), 7.72 (d, 0.55 1H, ar-H, ma.), 10.05 (s, 0.55

.

rac-2-[(2-Boc-aminoethyl)-thyminacetyl-amino]-2-phenyl-

acetic acid-4-methoxy-2-nitro-phenylamide 7j. The title

compound was prepared according to GP5 using 0.32 g

(2.00 mmol) mono-Boc-ethylendiamine 4a, 0.21 g (2.00

mmol) benzaldehyde, 0.36 g (2.00 mmol) 4-methoxy-2-

nitro-phenylisocyanide 3a, and 0.37 g (2.00 mmol) N-1-

1H, ar-NH, ma.), 9.93, 10.36, 10.46 (3 s, 0.45 1H, ar-

NH, mi.), 11.17±11.31 (m, 1H, T-NH, rot.). ¹³C NMR

(75 MHz, DMSO-d₆): d 12.20, 12.81, 24.70, 24.97, 28.45,

30.01, 32.40, 46.48, 48.48, 49.00, 50.33, 56.33, 60.18,

78.23, 107.94, 108.47, 109.28, 120.61, 121.23, 123.85,

125.21, 126.66, 141.53, 141.96, 142.14, 142.32, 151.29,

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1357

155.36, 156.06, 156.76, 164.71, 167.96, 168.53, 169.98.

C₂₇H₃₆N₆O₉(588.6): calcd C 55.09, H 6.16, N 14.28;

found C 55.18, H 6.12, N 14.11.

1-[(2-Etoc-aminoethyl)-thyminacetyl-amino]-cyclohexan-

carboxylic acid 8e. The title compound was prepared

according to GP4 using 0.70 g (1.25 mmol) 6e as starting

material. The resulting crude product was recrystallized

from Et₂O to yield 0.41 g (78%) of a colourless solid,

mp: 198 C (dec.). H NMR (300 MHz, DMSO-d₆): d

0.91 (t, 3H, Etoc-CH₃), 1.2±2.2 (m, 10H, CH₂), 1.76 (s,

3H, T-Ac-CHCCH₃), 3.2±3.4 (m, 4H), 4.03 (q, 2H,

Etoc-CH₂), 4.63 (s, 2H, T-Ac-CH₂), 7.21 (br, 1H, Etoc-

NH), 7.36 (s, 1H, T-Ac-CHCCH₃), 11.29 (s, 1H, T-

Ac-NH). ¹³C NMR (75 MHz, DMSO-d₆): d 11.87,

14.97, 22.55, 25.12, 28.15, 29.34, 32.23, 42.39, 49.18,

60.21, 108.20, 142.46, 151.34, 154.72, 164.76, 172.08.

MS (CI-isobutane): m/z (%)=426 (40) [MH⁺]. C₁₉H₂₈

N₄O₇(424.5): calcd C 53.77, H 6.65, N 13.20; found C

53.69, H 6.72, N 12.97.

2-[(2-Ib-Aminophenyl)-thyminacetyl-amino]-acetic acid-

4-methoxy-2-nitro-phenylamide 7m. The title compound

was prepared according to GP5 using 0.36 g (2.00 mmol)

mono-Ib-ortho-phenylendiamine 4f, 0.06 g (2.00 mmol)

paraformaldehyde, 0.36 g (2.00 mmol) 4-methoxy-2-

nitro-phenylisocyanide 3a, and 0.37 g (2.00 mmol) N-1-

carboxymethylthymine 5a as starting materials and

puri®ed by chromatography to yield 0.66 g (60%) 7m

as an orange powder, mp: 170 ^ꢀC (dec.). ¹H NMR

(300 MHz, CDCl₃/DMSO-d₆): d 1.29 (t, 6H, Ib-CH₃),

1.71 (s, 3H, T-CH₃), 2.69 (sept, 1H, Ib-CH), 3.80 (s, 3H,

ar-O-CH₃), 4.05±4.16 (2 d, 2H, NCH), 4.00, 4.77 (2 d,

2H, T-Ac-CH₂), 6.99 (s, 1H, T-CHC), 7.09±7.19 (m,

2H, ar-H, ar-H), 7.31±7.38 (m, 2H, ar-H, ar-H), 7.41 (d,

1H, ar-H), 7.70 (d, 1H, ar-H), 8.21 (d, 1H, ar-H), 10.22

(s, 1H, Ib-NH), 10.36 (s, 1H, ar-NH), 11.08 (s, 1H, T-

NH). ¹³C NMR (75 MHz, CDCl₃/DMSO-d₆): d 10.83,

18.13, 18.27, 34.23, 47.18, 52.27, 54.58, 107.82, 119.24,

121.64, 122.83, 123.43, 125.48, 127.53, 128.49, 129.48,

135.14, 139.85, 149.70, 155.13, 163.36, 166.27, 167.32,

175.12. C₂₆H₂₈N₆O₈(552.5): calcd C 56.52, H 5.11, N

15.21; found C 56.48, H 5.18, N 15.19.

ꢀ

1

1-[(2-Z-Aminoethyl)-thyminacetyl-amino]-cyclohexancar-

boxylic acid 8f. The title compound was prepared

according to GP4 using 0.25 g (0.39 mmol) 6f as starting

material. The resulting crude product was recrystallized

from Et₂O to yield 0.16 g (82%) of a colourless solid,

ꢀ

1

mp: 205 C (dec.). H NMR (300 MHz, DMSO-d₆): d

1.2±2.1 (m, 10H, CH₂), 1.74 (s, 3H, T-Ac-CHCCH₃),

3.2±3.5 (m, 4H), 4.68 (s, 2H, T-Ac-CH₂), 5.02 (s, 2H, Z-

CH₂), 7.26 (s, 1H, T-Ac-CHCCH₃), 7.35 (m, 5H,

arH), 11.12 (s, 1H, T-Ac-NH). ¹³C NMR (75 MHz,

DMSO-d₆): d 12.23, 22.97, 25.78, 28.15, 29.34, 42.39,

49.28, 60.21, 65.69, 108.06, 127.96, 128.04, 128.68,

137.34, 142.75, 151.36, 156.64, 164.78, 172.18. MS (CI-

isobutane): m/z (%)=488 (40) [MH⁺]. C₂₄H₃₀N₄O₇

(486.5): calcd C 59.25, H 6.22, N 11.52; found C 60.12,

H 6.34, N 11.89.

rac-2-[(2-Boc-aminoethyl)-thyminacetyl-amino]-4-ethoxy-

carbonyl-2-methyl-butyric acid-4-methoxy-2-nitro-phenyl-

amide 7n. The title compound was prepared according

to GP5 using 0.32 g (2.00 mmol) mono-Boc-ethylen-

diamine 4a, 0.29 g (2.00 mmol) ethyl-laevulinate, 0.36 g

(2.00 mmol) 4-methoxy-2-nitro-phenylisocyanide 3a,

and 0.37 g (2.00 mmol) N-1-carboxymethylthymine 5a

as starting materials to_ꢀyield 0.98 g (76%) 7n as an

1-[(2-Boc-aminoethyl)-thyminacetyl-amino]-cyclohexan-

carboxylic acid 8g. The title compound was prepared

according to GP4 using 0.50 g (0.94 mmol) 6g as starting

material. The resulting crude product was recrystallized

from dichloromethane to yield 0.35 g (82%) of a col-

1

orange powder, mp: 147 C (dec.). H NMR (300 MHz,

CDCl₃): d 1.25 (t, 3H, C(O)O±CH₂±CH₃), 1.41 (s, 9H,

Boc-CH₃), 1.60 (s, 3H, CCH₃), 1.84 (s, 3H, T-CH₃),

2.20±2.30, 2.39±2.53 (2 m, 4H, CCH₂CH₂), 3.40±3.77

(m, 4H, NCH₂CH₂), 3.85 (s, 3H, ar-O-CH₃), 4.12 (q,

2H, C(O)O-CH₂), 4.79 (s, 2H, T-Ac-CH₂), 5.38 (s, 1H,

Boc-NH), 6.91 (s, 1H, T-CHC), 7.21 (dd, 1H, ar-H),

7.61 (d, 1H, ar-H), 8.46 (d, 1H, ar-H), 8.65 (s, 1H, T-

NH), 10.29 (s, 1H, ar-NH). C₂₉H₄₀N₆O₁₁(648.7): calcd

C 53.70, H 6.22, N 12.96; found C 53.75, H 6.28, N

12.88.

ourless solid, mp: 185 ^ꢀC (dec.). H NMR (300 MHz,

1

DMSO-d₆, due to the existence of two rotamers in a

70:30 ratio several signals were doubled): d 1.41 (s, 9H,

Boc-CH₃), 1.2±2.05 (m, 10H, CH₂), 1.79 (s, 3H, T-Ac-

CHCCH₃), 3.2, 3.57 (2m, 4H), 4.35 (mi.), 4.64 (ma.)

(s, 2H, T-Ac-CH₂), 6.85 (ma.), 7.19 (mi.) (b, 1H, BocNH),

7.32 (ma.), 7.51 (mi.) (s, 1H, T-Ac-CHCCH₃), 11.18

(ma.), 11.29 (mi.) (s, 1H, T-Ac-NH). ¹³C NMR

(75 MHz, DMSO-d₆, due to the existence of two rota-

mers in a 70:30 ratio several signals were doubled): d

11.87, 21.42, 22.19, 24.85, 25.12, 28.15, 31.61, 41.98,

48.40, 48.86, 63.75, 64.90, 67.02, 78.02, 107.87, 108.30,

141.81, 142.33, 150.98, 155.70, 164.43, 167.19, 169.53,

173.68. MS (CI-isobutane): m/z (%)=454 (60) [MH⁺].

C₂₁H₃₂N₄O₇(452.5): calcd C 55.74, H 7.13, N 12.38;

found C 55.49, H 7.12, N 12.45.

rac-2-[(2-Boc-aminoethyl)-N⁶-Z-adeninacetyl-amino]-ortho-

chlorophenylacetic acid 8c. The title compound was pre-

pared according to GP4 using 0.30 g (0.42 mmol) 6c as

starting material. The resulting crude product was

recrystallized from dichloromethane to yield 0.21 g

(38%) of a colourless solid, mp: >102 ^ꢀC (dec.). ¹H

NMR (300 MHz, CDCl₃, due to the existence of two

rotamers in a 78:22 ratio several signals were doubled):

d 1.36 (ma.), 1.41 (mi.) (2s, 9H, Boc-CH₃), 3.1±3.4 (m,

4H), 5.19 (br, 1H, Boc-NH), 5.30 (m, 3H, 2H, Z-CH₂),

5.52 (m, 2H, A-Z-Ac-CH₂), 7.3±7.6 (m, 9H, ar-H), 7.98

(mi.), 8.17 (ma.) (2s, 1H, A-Z-Ac-NCH), 8.72 (s, 1H,

A-Z-Ac-NCH), 9.3 (br, 1H, COOH). MS (CI-iso-

butane): m/z (%)=639 (10) [MH⁺]. C₃₀H₃₂N₇O₇Cl

(638.1): calcd C 56.47, H 5.05, N 15.37; found C 56.49,

H 5.04, N 15.30.

2-[(2-Boc-aminoethyl)-2-thymine-methyl-benzoyl-amino]-

3,3-dimethyl-butyric acid 8i. The title compound was

prepared according to GP4 using 0.24 g (0.45 mmol) 6i

as starting material. The resulting crude product was

recrystallized from Et₂O to yield 0.11 g (47%) of a

colourless solid, mp: 116 ^ꢀC. ¹H NMR (300 MHz,

CDCl₃/DMSO-d₆): d 1.18 (s, 9H, t-Bu-CH₃), 1.21 (s,

1358

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

9H, Boc-CH₃), 1.84 (m, 3H), 3.49±3.81 (m, 4H), 4.50

(br, 1H, CH-t-Bu), 5.07±5.41 (m, 2H), 7.20±7.61 (m,

5H). ¹³C NMR (75 MHz, CDCl₃/DMSO-d₆): d 12.13,

28.17, 28.39, 36.22, 41.52, 47.42, 48.99, 60.42, 79.57,

110.95, 126.27, 126.97, 128.04, 129.11, 130.03, 134.02,

141.39, 151.50, 151.78, 155.67, 156.03, 164.81, 169.61,

172.42. MS (CI-isobutane): m/z (%)=517 (80) [MH⁺].

C₂₆H₃₆N₄O₇(516.6): calcd C 60.45, H 7.02, N 10.85;

found C 61.78, H 7.52, N 10.87.

48.81, 66.70, 67.42, 70.35, 70.77, 107.78, 107.89, 126.13,

126.36, 126.90, 126.99, 136.61, 136.70, 139.90, 140.02,

149.88, 163.41, 166.26, 169.07. C₁₈H₂₁N₃O₆(375.4):

calcd C 57.59, H 5.64, N 11.19; found C 57.75, H 5.48,

N 11.38.

rac-2-[(2-Boc-aminoethyl)-thyminacetyl-amino]-2-phenyl-

acetic acid 9j. The title compound was prepared

according to GP6 using 0.18 g (0.30 mmol) of the totally

protected monomer 7j as starting material to yield 0.11 g

(80%) 9j as a colourless solid, mp: 182 ^ꢀC (dec.). H

1

1-[(2-Benzyloxyethyl)-thyminacetyl-amino]-cyclohexan-

carboxylic acid 8k. The title compound was prepared

according to GP4 using 0.85 g (1.47 mmol) 6k as start-

ing material. The resulting crude product was recrys-

tallized from dichloromethane to yield 0.59 g (91%) of

a colourless solid, mp: 245 ^ꢀC (dec.). ¹H NMR

(300 MHz, DMSO-d₆): d 1.10±2.05 (m, 10H, CH₂), 1.72

(s, 3H, T-Ac-CHCCH₃), 3.35 (m, 2H, NCH₂), 3.71

(m, 2H, O-CH₂CH₂), 4.57 (s, 2H, T-Ac-CH₂), 4.76 (s,

2H, Bz-CH₂), 6.97 (s, 1H, T-Ac-CHCCH₃), 7.2±7.4

(m, 5H, ar-H), 11.29 (s, 1H, T-Ac-NH). ¹³C NMR

(75 MHz, DMSO-d₆): d 12.24, 22.56, 25.05, 31.93, 42.59,

49.40, 64.19, 69.89, 72.80, 108.21, 127.95, 128.11,

128.64, 138.48, 142.34, 151.28, 164.737, 167.76, 174.13.

MS (CI-NH₃): m/z (%)=445 (80) [MH⁺]. C₂₃H₂₉N₃O₆

(443.5): calcd C 62.29, H 6.59, N 9.47; found C 63.34, H

6.78, N 9.56.

NMR (300 MHz, CDCl₃/DMSO-d₆): d 1.39 (s, 9H, Boc-

CH₃), 1.85 (s, 3H, T-CH₃), 2.66±2.80, 3.00±3.15, 3.19±

3.41 (3 m, 4H, NCH₂CH₂), 4.74 (s, 2H, T-Ac-CH₂),

5.79 (s, 1H, NCH), 6.43 (m, 1H, Boc-NH), 7.26 (s, 1H,

T-CHC), 7.31±7.45 (m, 5H, Ph), 11.30 (s, 1H, T-NH).

¹³C NMR (75 MHz, CDCl₃/DMSO-d₆):

d 10.72,

26.82, 43.10, 46.85, 60.72, 77.20, 107.45, 126.94, 127.14,

128.08, 132.73, 140.21, 149.72, 154.30, 163.31, 166.41,

169.93. C₂₂H₂₈N₄O₇(460.5): calcd C 57.38, H 6.13, N

12.17; found C 57.23, H 6.03, N 12.35.

2-[(2-Ib-Aminophenyl)-thyminacetyl-amino]-acetic acid 9m.

The title compound was prepared according to GP6

using 0.17 g (0.30 mmol) of the totally protected mono-

mer 7m as starting material to yield 0.10 g (83%) 9m

as a colourless solid, mp: 215 ^ꢀC (dec.). ¹H NMR

(300 MHz, CDCl₃/DMSO-d₆): d 1.22 (2 t, 6H, Ib-

CH₃), 1.81 (s, 3H, T-CH₃), 2.73 (sept, 1H, Ib-CH), 4.18

(s, 2H, NCH), 3.99, 4.52 (2 d, 2H, T-Ac-CH₂), 7.14 (s,

1H, T-CHC), 7.20 (t, 1H, ar-H), 7.38±7.45 (m, 2H, ar-

H, ar-H), 8.21 (d, 1H, ar-H), 9.89 (s, 1H, Ib-NH), 11.21

(s, 1H, T-NH). ¹³C NMR (75 MHz, CDCl₃/DMSO-d₆):

d 10.65, 18.00, 34.11, 47.02, 49.99, 107.51, 121.71,

123.47, 127.52, 128.24, 129.64, 134.79, 139.83, 149.59,

163.16, 166.07, 170.78, 174.61. C₁₉H₂₂N₄O₆(402.4):

calcd C 56.71, H 5.51, N 13.92; found C 56.65, H 5.46,

N 13.23.

rac-2-[(2-Ib-Amino-phenyl)-thyminacetyl-amino]-biphen-

4-yl-acetic acid 8l. The title compound was prepared

according to GP4 using 0.35 g (0.55 mmol) 6l as starting

material. The resulting crude product was recrystallized

from dichloromethane to yield 0.20 g (66%) of a

colourless solid, mp: >250 ^ꢀC. ¹H NMR (300 MHz,

3

CDCl₃): d 1.21 (d, 6H, CH(CH₃)₂, J=6.6 Hz), 1.73 (s,

3H, T-Ac-CH₃), 2.91 (m, 1H, CH(CH₃)₂, J=6.6 Hz),

3

2

3.91 (d, 1H, T-Ac-CH₂, J=16.5 Hz), 4.00 (d, 1H, T-

2

Ac-CH₂, J=16.5 Hz), 5.86 (s, 1H, NCH), 6.7±8.5 (m,

15H, arH, T-Ac-CCH, COOH), 11.22 (s, 1H, T-Ac-

NH), 11.65 (s, 1H, NH-Ib). ¹³C NMR (75 MHz,

DMSO-d₆): d 11.82, 19.55, 35.15, 48.68, 64.99, 107.77,

114.05, 120.26, 122.57, 125.45, 125.88, 126.18, 126.38,

126.92, 127.62, 128.46, 128.83, 129.08, 129.18, 130.36,

131.85, 132.11, 132.78, 138.49, 138.67, 139.88, 141.96,

150.73, 164.29, 167.08, 173.92, 175.83. MS (CI-iso-

butane): m/z (%)=555 (100) [MH⁺]. C₃₁H₃₀N₄O₆

(554.6): calcd C 67.14, H 5.45, N 10.10; found C 67.18,

H 5.29, N 10.03.

rac-2-[(2-Ethoxycarbonyl-ethyl)-thyminacetyl-amino]-

phenyl-acetic acid-amide 10. 2.3 g (4.2 mmol) of the

vinyl amide 6m were dissolved in 50 mL abs. THF and

80 mL water and treated with 2 mL TFA. After stirring

the solution for 2 h at room temperature the solvent

was removed in vacuo and the crude product puri®ed by

¯ash chromatography to yield 1.12 g (64%) of a col-

ourless solid. ¹H NMR (300 MHz, CDCl₃/DMSO-d₆,

due to the existence of two rotamers in a 60:40 ratio

several signals were doubled): d 1.10 (dt, 3H, COO±

CH₂±CH₃), 1.79 (s, 3H, thyminyl-CH₃), 1.91, 2.50 (2m,

2H, CH₂±COOEt), 3.49 (m, 2H, N±CH₂±CH₂±COOEt),

3.91 (dq, 2H, COO±CH₂±CH₃), 4.66 (m, 2H, T-CH₂),

5.68, 5.98 (2s, 1H, NCH), 7.07±7.72 (m, 8H, thyminyl-

H, ar-H, CONH₂). ¹³C NMR (75 MHz, CDCl₃): d

11.88, 13.79, 32.01, 33.41, 48.18, 59.49, 59.75, 60.87,

61.64, 108.19, 128.00, 128.34, 128.42, 129.27, 135.29,

141.75, 141.92, 151.00, 164.42, 167.13, 167.42, 170.15,

170.32, 170.86. MS (CI-isobutane): m/z (%)=417 (40)

[MH⁺]. C₂₀H₂₄N₄O₆(416.43): calcd C 57.69, H 5.81, N

13.45; found C 57.76, H 5.78, N 13.44.

2-[(2-Benzyloxyethyl)-thyminacetyl-amino]-acetic acid 9g.

The title compound was prepared according to GP6

using 0.16 g (0.30 mmol) of the totally protected mono-

mer 7g as starting material to yield 0.08 g (71%) 9g

as a colourless solid, mp: 147 ^ꢀC. H NMR (300 MHz,

1

CDCl₃/DMSO-d₆, rotamer ratio: ma.:mi.=65:35): d

.

1.78 (s, 0.65 3H, T-CH₃, ma.), 1.85 (s, 0.35 3H, T-

.

CH₃, mi.), 3.59±3.72 (m, 4H, NCH₂CH₂), 4.09 (s, 0.65

.

2H, NCH, ma.), 4.28, 4.47, 4.51 (3 s, 0.35 6H, NCH,

.

T-Ac-CH₂, CH₂-Ph, mi.), 4.54 (s, 0.65 2H, T-Ac-CH₂,

.

ma.), 4.71 (s, 0.65 2H, CH₂-Ph, ma.), 6.80 (s, 0.35 1H,

.

T-CHQC, mi.), 7.10 (s, 0.65 1H, T-CHC, ma.),

7.27±7.39 (m, 5H, Ph), 11.24 (s, 1H, T-NH). ¹³C NMR

2-[(2-Boc-aminoethyl)-hydroxyacetyl-amino]-3,3-dimethyl-

butyric acid-4-methoxy-2-nitro-phenylamide 12. The title

(75 MHz, DMSO-d₆): d 10.79, 46.26, 46.34, 46.60, 46.86,

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1359

compound was prepared according to GP5 using 0.96 g

(6.00 mmol) mono-Boc-ethylendiamine 4a, 0.51 g (6.00

mmol) pivalaldehyde, 1.08 g (6.00 mmol) 4-methoxy-2-

nitrophenylisocyanide 3a, and 0.46 g (6.00 mmol) gly-

colic acid as starting materials and puri®ed by chroma-

tography to yield 2.38 g (82%) 12 as an orange solid,

Buchardt, O. Anti-Cancer Drug Design 1993, 8, 53. (c) Nielsen,

P. E.; Egholm, M.; Berg, R. H.; Buchardt, O. Anti-Cancer

Drug Design 1993, 11, 384. (d) Bonham, M. A.; Brown, S.;

Boyd, A. L.; Brown, P. H.; Bruckenstein, D. A.; Hanvey, J.

C.; Thomson, S. A.; Pipe, A.; Hassmann, F.; Bisi, J. E.; Froe-

ler, B. C.; Matteucci, M. D.; Wagner, R. W.; Noble, S. A.;

Babiss, L. E. Nucleic Acids Res. 1995, 23, 1197. (e) Good, L.;

Nielsen, P. E. Antisense and Nucleic Acid Drug Development

1997, 7, 431.

6. Demidov, V.; Potaman, V. N.; Frank-Kamenetskii, M. D.;

Buchardt, O.; Egholm, M.; Nielsen, P. E. Biochem. Pharmacol.

1994, 48, 1309.

7. Egholm, M.; Buchardt, O.; Nielsen, P. E.; Berg, R. H. J.

Am. Chem. Soc. 1992, 114, 1895.

8. Nielsen, P. E.; Haaima, G. Chem. Soc. Rev. 1997, 73.

9. (a) Hyrup, B.; Egholm, M.; Nielsen, P.E.; Wittung, P.;

Norden, B.; Buchardt, O. J. Am. Chem. Soc. 1994, 116, 7964.

(b) Puschl, A.; Sforza, S.; Haaima, G.; Dahl, O.; Nielsen, P. E.

Tetrahedron Lett. 1998, 39, 4707. (c) Gangamani, B. P.;

Kumar, V. A.; Ganesh, K. N. Biochem. Biophys. Res. Commun.

1997, 240, 778. (d) Goodwin, T. E.; Holland, R. D.; Jackson,

O. L.; Raney, K. D. Bioorg. Med. Chem. Lett. 1998, 8, 2231.

(e) Gildea, B. D.; Casey, S.; MacNeill, J.; Perry-O'Keefe, H.;

Sorensen, D.; Coull, J. M. Tetrahedron Lett. 1998, 39, 7255. (f)

Sforza, S.; Haaima, G.; Marchelli, R.; Nielsen, P. E. Eur. J.

Org. Chem. 1999, 197. (g) Nielsen, P. E.; Haaima, G. Chem.

Soc. Rev. 1997, 73.

mp: 61 ^ꢀC. H NMR (300 MHz, CDCl₃, rotamer ratio:

1

ma.:mi.=80:20): d 1.15 (s, 9H, Boc-CH₃), 1.31, 1.40 (2

s, 9H, tert.butyl-CH₃, rot.), 1.78 (s, br, 1H, OH), 3.02±

3.53, 3.68±3.82 (2 m, 5H, NCH₂CH₂, NCH), 3.89 (s,

3H, ar-O-CH₃), 4.30±4.50 (m, 2H, HO-Ac-CH₂, rot.),

.

4.85 (s, 0.80 1H, Boc-NH, ma.), 5.04 (s, 0.20 1H, Boc-

NH, mi.), 7.23 (dd, 1H, ar-H), 7.64 (d, 1H, ar-H), 8.40

.

(d, 0.80 1H, ar-H, ma.), 8.58 (d, 0.20 1H, ar-H, mi.),

.

10.23 (s, 0.80 1H, ar-NH, ma.), 10.35 (s, 0.20 1H, ar-

NH, mi.). ¹³C NMR (75 MHz, CDCl₃): d 28.20, 28.39,

28.68, 36.91, 37.13, 39.71, 40.27, 45.77, 46.47, 56.35,

60.90, 62.24, 67.04, 67.96, 80.18, 109.35, 110.65, 120.56,

122.93, 123.28, 124.95, 127.07, 127.49, 138.57, 139.21,

156.19, 167.64, 168.89, 174.99. MS (CI, NH₃): m/z

(%)=483 (13) [MH⁺], 427 (24) [MH⁺isobutene], 383

(17) [MH⁺isobutene CO₂], 315 (100) [MH⁺ar-

NH₂], 259 (80) [MH⁺ar-NH₂isobutene], 215 (19)

[MH⁺ar-NH₂isobutene CO₂]. C₂₂H₃₄N₄O₈(482.5):

calcd C 54.76, H 7.10, N 11.61; found C 54.68, H 7.12,

N 11.58.

10. Krotz, A. H.; Larsen, S.; Buchardt, O.; Eriksson, M.;

Nielsen, P. E. Bioorg. Med. Chem. 1998, 6, 1983.

11. Tsantrizos, Y. S.; Lunetta, J. F.; Boyd, M.; Fader, L. D.;

Wilson, M. C. J. Org. Chem. 1997, 62, 5451.

2-[(2-Boc-aminoethyl)-hydroxyacetyl-amino]-3,3-dimethyl-

butyric acid 13. The title compound was prepared

according to GP6 using 0.15 g (0.30 mmol) of the totally

protected monomer 12 as starting material to yield

0.09 g (90%) 13 as a colourless solid, mp 115 ^ꢀC (dec.).

¹H NMR (300 MHz, CDCl₃): d 1.12 (s, 9H, Boc-CH₃),

1.44 (s, 9H, tert.butyl-CH₃), 3.02±3.15, 3.21±3.38 (2 m,

4H, NCH₂CH₂), 3.90 (s, 1H, NCH), 4.70, 4.87 (2 d,

2H, HO-Ac-CH₂), 4.99 (s, 1H, Boc-NH). ¹³C NMR

(75 MHz, CDCl₃): d 26.56, 27.26, 36.95, 38.47, 47.80,

66.90, 68.32, 78.98, 155.33, 163.95. MS (CI, NH₃): m/z

(%)=333 (19) [MH⁺], 315 (4) [MH⁺H₂O], 277 (100)

[MH⁺isobutene], 259 (84) [MH⁺isobutene H₂O],

233 (20) [MH⁺isobutene CO₂], 215 (15) [MH⁺

isobutene CO₂H₂O]. C₁₅H₂₈N₂O₆(332.4): calcd C

54.20, H 8.49, N 8.43; found C 54.16, H 8.40, N 8.56.

12. Peyman, A.; Uhlmann, E.; Wagner, K.; Augustin, S.;

Breipohl, G.; Will, D. W.; Schafer, A.; Wallmeier, H. Angew.

Chem. 1996, 108, 2797. Peyman, A.; Uhlmann, E.; Wagner,

K.; Augustin, S.; Breipohl, G.; Will, D. W.; Schafer, A.;

Wallmeier, H. Angew. Chem. Int. Ed. Engl. 1996, 35, 2636.

13. (a) van der Laan, A.; Amsterdam, I.; Tesser, G. I.; van

Boom, J. H.; Kuyl-Yeheskiely, E. Nucleosides Nucleotides

1998, 17, 219. (b) Kuwahara, M.; Arimitsu, M.; Sisido, M. J.

Am. Chem. Soc. 1999, 121, 256. Lowe, G.; Vilaivan, T. J.

Chem. Soc., Perkin Trans. 1 1997, 555. (c) Jordan, S.;

Schwemler, C.; Kosch, W.; Kretschmer, A.; Stropp, U.;

Schwenner, E.; Mielke, B. Bioorg. Med. Chem. Lett. 1997, 6,

687. (d) Bergmeier, S. C.; Fundy, S. L. Bioorg. Med. Chem.

Lett. 1997, 24, 3135. (e) Fujii, M.; Yoshida, K.; Hidaka, J.;

Ohtsu, T. Bioorg. Med. Chem. Lett. 1997, 5, 637. (f) Howarth,

N. M.; Wakelin, P. G. J. Org. Chem. 1997, 62, 5441. (g) Die-

derichsen, U.; Schmitt, H. W. Eur. J. Org. Chem. 1998, 827.

14. Nielsen, P. E. Methods Enzymol. 1996, 267, 426.

15. (a) Ugi, I.; Kaufhold, G. Liebigs Ann. Chem. 1967, 709, 11.

(b) Keating, T. A.; Armstrong, R. W. J. Org. Chem. 1998,

63, 867. (c) Domling, A. Combinatorial Chemistry & High

Throughput Screening 1998, 1, 1.

References and Notes

1. (a) Uhlmann, E.; Payman, A. Chem. Rev. 1990, 90, 543.

(b) Englisch, U.; Gauss, D. Angew. Chem. 1991, 103, 629. Eng-

lisch, U.; Gauss, D. Angew. Chem. Int. Ed. Engl. 1991, 30, 613.

2. (a) Kool, E. T. Chem. Rev. 1997, 97, 1473. (b) Uhlmann, E.;

Peymann, A.; Will, D. W. Enzyclopedia of Cancer, Academic

Press, San Diego, CA, 1997; Vol. 1.

16. (a) Groger, H.; Hatam, M.; Kintscher, J.; Martens, J.

Synth. Commun. 1996, 26 3383. (b) Domling, A.; Richter, W.;

Ugi, I. Nucleosides Nucleotides 1997, 16, 1753. (c) Maison,

W.; Schlemminger, I.; Westerho, O.; Martens, J. Bioorg.

Med. Chem. Lett. 1999, 9, 581

17. Greene, T. W.; Wuts, P. G. M. Protective Groups in

Organic Synthesis, 2nd ed.; Wiley-Interscience: New York,

1991; pp 349±351.

3. (a) Egholm, M.; Berg, R. H.; Buchardt, O. Science 1991,

254, 1497. (b) Nielsen, P. E.; Egholm, M. Peptide Nucleic

Acids, Horizon Scienti®c: Wymondham, 1999.

18. Ugi, I. J. Prakt. Chem. 1997, 339, 499.

19. Keating, T. A.; Armstrong, W. J. Am. Chem. Soc. 1996,

118, 2574±2583.

20. (a) Barton, D. H. R.; Bowles, T.; Husinec, S.; Forbes, J.

E.; Llobera, A.; Porter, A. E. A.; Zard, S. Z. Tetrahedron Lett.

1988, 29, 3343. (b) Baldwin, J. E.; Yamaguchi, Y. Tetrahedron

Lett. 1989, 30, 3335.

4. (a) Eriksson, M.; Nielsen, P. E. Quart. Rev. Biophysics 1996,

29, 369. (b) Egholm, M.; Buchardt, O.; Christensen, L.; Beh-

rens, C.; Freier, S. M.; Driver, D.; Berg, R. H.; Kim, S. K.;

Norden, B.; Nielsen, P. E. Nature 1993, 365, 566. (c) Wittung,

P.; Nielsen, P. E.; Buchardt, O.; Egholm, M.; Norden, B.

Nature 1994, 368, 561.

5. (a) Nielsen, P. E.; Egholm, M.; Buchardt, O. Gene 1994,

149, 139. (b) Nielsen, P. E.; Egholm, M.; Berg, R. H.;

21. (a) Ugi, I.; Betz, W.; Fetzer, U.; Oermann, K. Chem. Ber.

1360

W. Maison et al. / Bioorg. Med. Chem. 8 (2000) 1343±1360

1961, 2814. (b) Ugi, I.; Fetzer, U.; Eholzer, U.; Knupfer, H.;

Oermann, K. Angew. Chem. 1965, 11, 492. Ugi, I.; Fetzer,

U.; Eholzer, U.; Knupfer, H.; Oermann, K. Angew. Chem.

Int. Ed. Engl. 1965, 4, 472.

22. Uhlmann, E.; Will, D. W.; Breipohl, G.; Peyman, A.;

Langner, D.; Knolle, J.; O'Malley, G. Nucleosides Nucleotides

1997, 16, 603±608.

23. (a) Hulme, C.; Peng, J.; Louridas, B.; Menard, P.; Kroli-

kowski, P.; Kumar, N. V. Tetrahedron Lett. 1998, 39, 8047. (b)

Hulme, C.; Peng, J.; Tang, S.-Y.; Burns, C. J.; Morize, I.;

Labaudiniere, R. J. Org. Chem. 1998, 63, 8021.

24. Ugi, I.; Rosendahl, F. K. Liebigs Ann. Chem. 1963, 666,

65±67.

N-protected PNA-monomer 8a was obtained from anilide 7a

by alkaline hydrolysis in 69% yield.

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Article Doi

Multicomponent synthesis of novel amino acid-nucleobase chimeras: aA versatile approach to PNA-monomers

DOI: 10.1016/S0968-0896(00)00066-3

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Full text of DOI:10.1016/S0968-0896(00)00066-3

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