Chemistry of the mycalamides: Antiviral and antitumour compounds from a New Zealand marine sponge. Part 6. The synthesis and testing of analogues of the C(7)-C(10) fragment

Article abstract of DOI:10.1039/a608168a

The key structural features associated with the potent cytotoxicity observed in the mycalamide, onnamide, pederin and theopederin series have been defined on the basis of structure-activity studies. A model pharmacophore structure has been proposed and selected examples, with modest bioactivity, synthesized.

Full text of DOI:10.1039/a608168a

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Chemistry of the mycalamides: antiviral and antitumour compounds
from a New Zealand marine sponge. Part 6.1–3 The synthesis and
testing of analogues of the C(7)–C(10) fragment
Andrew D. Abell,* John W. Blunt, Glenn J. Foulds and Murray H. G. Munro
Department of Chemistry, University of Canterbury, Christchurch, New Zealand
The key structural features associated with the potent cytotoxicity observed in the mycalamide, onnamide,
pederin and theopederin series have been defined on the basis of structure–activity studies. A model
pharmacophore structure has been proposed and selected examples, with modest bioactivity, synthesized.
activity. The product of deoxygenation at C(10) was 40 times
Introduction
less bioactive than 1, suggesting the crucial importance of the
C(10) centre to the activity. Kocienski et al.11 have also reported
that the C(10) epimer of mycalamide B (2) is some three orders
of magnitude less active than the parent compound. Further
support for the critical importance of the C(10) oxygen came
from studying the biological activity of the various onnamide
and theopederin derivatives that have been isolated by the
Fusetani group from Theonella sp. sponges.5b,6 Most notable
was the reported inactivity of an onnamide derivative lacking
oxygenation at C(10).5b
The aim of the current study was to synthesise and test, in
vitro against the P388 leukaemia cell line, simple analogues of
the C(7)–C(10) functionality of parents 1–3, i.e. compounds of
the general structure 4 where R1 to R4 could be variously alkyl
or aryl, and with defined stereochemistry at each of the two
stereogenic centres.
Mycalamides A 11 and B 2,2 pederin 3,4 the onnamides5 and the
theopederins6 are biologically active natural products charac-
terised by the presence of the O(1)–C(10) pederic acid subunit
(see structures 1–3 for atom numbering). The mycalamides,
onnamides and theopederins were isolated from marine
sponges while pederin, a potent insect toxin, was isolated from
a beetle (Paederus fuscipes). Considerable synthetic interest has
been generated in this class of compound due to its natural
scarcity, novel structure and potent biological activity. Total
syntheses of pederin,7,8 the mycalamides and onnamide A 9 have
been reported.
OH
RO
15
OH
O
MeO
O
H
Results and discussion
N
10
1
8
OMe
6
Synthesis
O
O
O
Two general synthetic routes were used to prepare the optically
active analogues 12, 13, 27–36, 42 and 43. The selection of R1 to
R4 was based initially on synthetic utility, then on aspects per-
taining to the actual structure of the mycalamides and finally
on aspects such as solubility. The method given in Scheme 1
CH2
1 R = H
2 R = Me
OH
R1
R1
ii
MeO
Ph
Ph
N
R2
OMe
R1
R2
CO2H
H
HN
15
OH
O
N
R2
OR3
1′
MeO
O
OMe
O
11
H
R4
2
5 R1 = OH
N
9 R2 = Me
10 R2 = Ph
1
8
10
i
6 R1 = OAc
OH
6
O
7 R1 = NHZ
O
OMe
8 R1 = NH-L-Ala-Z
iii
CH2
3
4
R1
R1
The biological activity of this class of compound is most
likely a consequence of inhibition of protein synthesis.10 We
recently reported extensive microscale structure–activity stud-
ies3 on 1 and 2 with a view to understanding the requirements
for biological activity. These experiments demonstrated that the
α-hydroxyamido acetal C(7)–C(10) functionality of 1 and 2 is
essential for the in vitro P388 anti-leukaemia activity. Some of
the more important structure–activity correlations from this
study can be summarised as follows. Acylation or alkylation of
the 7-OH group caused a 10–102-fold decrease in bioactivity as
compared to 1. Methylation of both the amide nitrogen and 7-
OH resulted in a 103-fold less bioactive derivative. Cleavage of
the C(8)–N(9) amide bond resulted in total loss of biological
H
H
N
Ph
N
R2
Ph
+
R2
OMe
1′
1′
2
2
O
O
OMe
R1
12
13
R2
a
b
c
OH
OH
NHZ
Ph
Me
Ph
d
NH-L-Ala-Z Ph
Scheme 1 Reagents and conditions: i, Ac2O, pyridine; ii, DCC, HOBT,
CH2Cl2; iii, NaBH4, PriOH
J. Chem. Soc., Perkin Trans. 1, 1997
1647

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involved a dicyclohexylcarbodiimide (DCC)-mediated coupling
of a suitable carboxylic acid 6–8 with methyl acetimidate 9, or
methyl benzimidate 10, to form a methyl N-acylimidate 11.
Subsequent reduction of 11 with a large excess of sodium boro-
hydride gave the desired compounds 12a–d and the correspond-
ing (1Ј)-epimers 13a–d. The epimers were separated by silica-
based radial chromatography. Similar methodologies have also
been applied by Kocienski et al.8 and Matsumoto and co-
workers12 in total syntheses of pederin. The reduction of 11
(where R1 = OAc) gave 12a/13a and 12b/13b as the isolated
products rather than the corresponding acetates. The starting
compound 9 was commericially available while 10 was prepared
by reaction of benzonitrile with methanol and gaseous hydro-
gen chloride.13 Compound 6 was prepared by acetylation of
(S)-3-phenylacetic acid 5 (Scheme 1, step i), while 7 and 8 were
commercially available.
The mixture of 12g and 13g was hydrolysed to give 12f and
13f, which were then separated by silica-based radial chrom-
atography. The (1Ј)-epimers 12e and 13e were also separately
hydrolysed to give 12a and 13a, respectively. This method gave
a 50% combined yield (from the acid 5) of 12a/13a. By com-
parison, the preparation of 12a/13a as detailed in Scheme 1 (via
the N-acylimidate 11) gave a 33% combined yield of 12a/13a
(from the acid 5).
In general, the methods detailed in Scheme 2 proved superior
to those given in Scheme 1 for the preparation of derivatives of
the type 4. In particular, the coupling of amides 15 and 16 with
α-chloro ethers 17–19, to form analogues of general structure 4,
gave typical yields ranging from 83 (for 12e/13e) to 52% (for
12h/13h). The corresponding two step procedure using 6–8
(Scheme 1) proved less satisfactory and gave typical yields ran-
ging from 54 (for 12d/13d) to 33% (for 12a/13a). Separation of
the mixtures of epimeric products 12 and 13, by silica-based
chromatography, resulted in a reduction in yield due to acid-
catalysed degradation of the amido acetal functionality. How-
ever, sufficient material was obtained for biological testing.
The starting amide 15, used in Scheme 2, was synthesized by
acetylation of 14, itself prepared by condensation of the α-
hydroxy acid 5 with acetone followed by reaction with ammonia
(Scheme 2, steps i–iii).14 Compound 16, which was used to pre-
pare 12h and 13h, was isolated as a decomposition by-product
of 12c and 13c on silica. The key α-chloro ethers 17–20 were
prepared from the corresponding aldehyde 23 by reaction with
gaseous hydrogen chloride and methanol (Scheme 3).15
The second method (Scheme 2) involved the reaction of a
primary amide, either 15 or 16, with an α-chloro ether (17, 18 or
R1
i,ii
iv
Ph
5
12e,g,h
13e,g,h
+
CONH2
14 R1 = OH
15 R1 = OAc
16 R1 = NHZ
R2
(ref. 14)
Cl
OMe
17 R2 = Ph
18 R2 = Me
19 R2 = Et
iii
Br
v
iv
14
H
R2
i R2 = Ph
+
12i
13i
17–20
Cl
ii R2 = Me,Et,Pri
O
O
O
OMe
20
23
Ph
CONH2
Scheme 3 Reagents and conditions: i, MeOH, HCl (g), EtCl, Ϫ60 ЊC;
ii, MeOH, HCl (g), Ϫ30 ЊC
21
The general method detailed in step iv in Scheme 2 was also
used to prepare a number of other derivatives of the general
structure 4. The reaction of 21 and 22 (prepared from 14 as
shown in Scheme 2) with 20 and 17 respectively, gave the deriva-
tives 12i/13i and 12j/13j as separable mixtures of epimers. These
compounds were prepared for structure–activity studies and in
an attempt to obtain a crystalline product suitable for X-ray
analysis (vide infra). A mixture of 12j and 13j (9:1 by 1H NMR
spectroscopy) was also prepared in 69% yield from a mixture of
O
iv
vi
14
12j
+
13j
O
O
17
O
Ph
CONH2
22
1
R1
R1
12a and 13a (9:1 by H NMR spectroscopy) (Scheme 2). The
H
N
H
N
enantiomers of 12a and 13a, compounds 30 and 28 respectively,
were synthesized as detailed in Scheme 4 using (R)-3-phenyl-
lactic acid 24 (cf. steps i–v in Scheme 2).
R2
Ph
R2
Ph
1′
1′
2
2
O
OMe
O
OMe
12
13
R1
R2
OR
OH
i,ii
Ph
Ph
CONH2
CO2H
(ref. 14)
a
e
f
OH
OAc
OH
Ph
Ph
Et
vii
vii
24
25 R = H
26 R = Ac
iii
iv
17
vi
g
h
i
OAc
NHZ
Et
OR
OR
Me
Pri
Ph
H
N
H
Ph
v
Ph
Ph
N
Ph
OMe
+
1′
1′
OCOC6H4Br-4
O-camphanyl
2
2
j
O
OMe
O
27 R = Ac
28 R = H
Scheme 2 Reagents and conditions: i, acetone, H2SO4, Ϫ10 ЊC; ii, NH3;
iii, Ac2O, pyridine; iv, Et3N, CH2Cl2, 0 ЊC; v, 4-BrC6H4COCl, DMAP,
Et3N, CH2Cl2; vi, (1S,4R)-camphanic chloride, DMAP, Pri2NEt,
CH2Cl2; vii, K2CO3, MeOH, H2O
29 R = Ac
30 R = H
v
Scheme 4 Reagents and conditions: i, acetone, H2SO4, Ϫ10 ЊC; ii, NH3;
iii, Ac2O, pyridine; iv, Et3N, CH2Cl2, 0–18 ЊC; v, K2CO3, MeOH, H2O
19) in the presence of an excess of triethylamine in dichloro-
methane at 0 ЊC. This procedure was used to prepare (1Ј)-
epimeric mixtures of 12e,g,h/13e,g,h. Silica-based radial chro-
matography was used to separate the (1Ј)-epimers 12e,h/13e,h.
The oxazolidinone-based examples 31–36 were synthesized
as mixtures of epimers by the direct reaction of 14 or 25 with
the α-chloro ethers 17 or 19, in the presence of gaseous hydro-
1648
J. Chem. Soc., Perkin Trans. 1, 1997

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R2
1′
R2
O
O
i
14
+
Ph
NH
Ph
NH
2
O
O
31 R2 = Ph
32 R2 = Et
33 R2 = Ph
34 R2 = Et
Ph
Ph
O
O
i
25
+
Ph
NH
Ph
NH
O
O
35
36
Scheme 5 Reagents and conditions: i, 17 or 19, CH2Cl2, Ϫ10 ЊC
gen chloride (Scheme 5). A related cyclisation of an α-hydroxy
amide with an aromatic or aliphatic aldehyde to give 1,3-
oxazolidin-4-ones has been reported.16
Fig. 1 X-Ray molecular structure of compound 13j with crystallo-
graphic numbering scheme
The glucosyl derivative 42 was synthesized by a DCC-
mediated coupling of the acid 5 with the glucopyranosyl amine
41 (Scheme 6, step v). The amine 41 was prepared 17–19 from -
Table 1 IC50 Values of derivatives against P388 cells
Configuration
Compound R1
R2
1Јa
2a
IC50/µg cmϪ3
OR
OAc
RO
AcO
OR
OR
OAc
OAc
ii
O
O
RO
(ref. 17)
12a
13a
12b
13b
12c
13c
12d
13d
12e
13e
12f
13f
12h
13h
12i
13i
12j
13j
28
OH
OH
OH
OH
NHZ
NHZ
NH-Ala-Z
NH-Ala-Z
OAc
OAc
OH
OH
NHZ
Ph
Ph
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
Et
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
S
R
R
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
R
R
S
S
S
S
R
R
S
S
52
>340
Br
37 R = H
38 R = Ac
i
39
>125
>188b
14
(ref. 17)
iii (ref. 18)
>188c
36
OR
OAc
RO
HN
HO
v
OR
OR
AcO
R
O
OAc
OAc
O
>125
101
>313
176
43
>375
>375
105d
105
42e
1′
2
Ph
iv
(ref. 19)
O
vi
40 R = N3
41 R = NH2
42 R = Ac
43 R = H
Et
Scheme 6 Reagents and conditions: i, Ac2O, H2SO4; ii, HBr in AcOH,
0–18 ЊC; iii, NaN3, DMF, 80 ЊC; iv, H2, PtO2, EtOAc; v, 5, DCC,
HOBT, CH2Cl2; vi, K2CO3, MeOH, H2O
Me
Me
Pri
Pri
Ph
Ph
Ph
Ph
Ph
Ph
Et
NHZ
OCOC6H4Br
OCOC6H4Br
O-camphanyl
O-camphanyl
OH
glucose 37 as detailed in Scheme 6. Hydrolysis of 42 then gave
43 (Scheme 6, step vi). The glucosyl derivatives 42 and 43 were
synthesized as compounds possessing the previously estab-
lished, biologically active (1ЈR)-configuration. As well as mod-
elling more closely the structural requirements of the mycal-
amide skeleton, cf. 1, it was also considered that the sugar
moiety might impart improved water solubility, which would be
of assistance in the in vitro cytotoxicity assay.
78e
27
102
57
37
57
47
8
12
30
OH
31
33
32
34
36
35
Et
Ph
Ph
42
43
OAc
OH
267
>375
Assignment of configuration
Compounds 12a–j and 13a–j were assigned the (1ЈR,2S)- and
(1ЈS,2S)-absolute configurations, respectively. The relative con-
figuration of the camphanate derivative 13j was determined
unambiguously by single crystal X-ray analysis (Fig. 1). The
absolute configuration of 13j, and hence its (1Ј)-epimer 12j,
followed from the known absolute configurations of 14 and
(1S,4R)-camphanyl chloride, which were used to prepare 12j
and 13j (Scheme 2). The absolute configuration of 12a, and
hence its (1Ј)-epimer 13a, was assigned on the basis that 12a
was converted into 12j (Scheme 2). Compounds 28 and 30 gave
identical NMR data, but opposite optical rotations, to the ref-
erence compounds 13a and 12a, respectively.
a
Atom numbering as shown in Schemes. b Activity obtained on 1:1
mixture of epimers. c Activity obtained on 3:1 mixture of epimers.
d Activity obtained on 17:3 mixture of epimers. e Activity obtained on
9:1 mixture of epimers.
tons labelled 1Ј and 2 (Scheme 5, non-systematic numbering)
of the oxazolidinones 31, 32 and 35, but not 33, 34 and 36,
was consistent with the assignment of configuration of these
derivatives.
Biological activity
The configurations of the other analogues given in Table 1
followed from a comparison of H NMR data. The methoxy
The analogues shown in Table 1 were each tested for in vitro
cytotoxicity against P388, a murine leukaemia cell line. IC50
values for each sample were determined, after a 72 h incubation
period, using an MTT endpoint.20
In general, compounds 12 with a (1ЈR,2S)-configuration
show significantly greater in vitro cytotoxicity than the corre-
sponding (1ЈS,2S)-derivatives 13, such that a (1ЈR)-config-
uration would appear favourable towards activity. Notable
exceptions were the parent natural products 1–3 [the equiv-
1
resonance of the (1ЈR,2S)-derivatives 12a–i, was in a character-
istic downfield position relative to the corresponding (1ЈS,2S)-
diastereoisomers 13a–i. The CHR1 resonance of 12a, 12b and
12f was also consistently 0.04–0.07 ppm downfield relative to
13a, 13b and 13f. However, the corresponding resonances for
12c and 12h (where R1 = NHZ) were upfield relative to those of
13c and 13h. An observed positive NOE between the ring pro-
J. Chem. Soc., Perkin Trans. 1, 1997
1649

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alent C(10) position is S] and 12f and 13f (see below for a dis-
cussion). The C(10) epimer of mycalamide B is reported to
be significantly less active than the parent natural product 2.11
An analysis of the data for 28 and 30 (Table 1), which possess
the alternative (2R)-configuration, also suggests that a (1ЈR)-
configuration, as in 28, is favoured over a (1ЈS)-configuration
(30) for cytotoxic activity. The (1ЈR)-compounds 12a and 28
show similar in vitro antitumour activity such that it seems that
there is no marked preference for either an (R)- or (S)-configur-
ation at position C(2). It is worth noting that the natural prod-
ucts 1–3 possess an (S)-configuration at the equivalent C(7)
centre. A preference for a (1ЈR)-configuration over a (1ЈS)-
configuration does not seem to be evident within the cyclic oxa-
zolidinone series 31–36, where the (1ЈS)- and (1ЈR)-compounds
(non-systematic numbering) show similar in vitro cytotoxicity.
A variety of R1 groups appear to be accommodated for the
induction of in vitro cytotoxicity. For example, the correspond-
ing acetates of 12a and 13a, compounds 12e and 13e, show
comparable activity. By comparison, acylation of the 7-hydroxy
group of 1 or 2 [analogous to C(2) in 12/13] results in com-
pounds with significantly decreased activity. The (1Ј)-epimeric
pairs 12c/13c, 12d/13d and 12h/13h were designed to give the
derivatives more peptide character. This was done since the
natural products (1–3), upon which the compounds in the cur-
rent study were modelled, exert their biological activity by
inhibiting protein biosynthesis. The most bioactive compounds
in this series, compounds 12c and 12d, show activities compar-
able to, or better than, 12a. Again a preference for a (1ЈR)-
configuration is noted (Table 1, 12c/13c and 12d/13d).
(S)-2-Acetoxy-3-phenylpropanoic acid 6
To a solution of (S)-3-phenyllactic acid 5 (106 mg, 0.64 mmol)
in dry pyridine (1 cm3) was added acetic anhydride (0.12 cm3,
1.27 mmol) and the mixture was stirred for 18 h at room temp.
Water (2 cm3) was added and the solution was extracted with
chloroform (3 × 5 cm3), dried and the solvent was evaporated to
give 6 (quant.) as a yellow oil which was not purified further. 1H
NMR Data were as previously reported.21
Preparation of compounds 12 and 13
The general methods A and B detailed below gave mixtures of
12 and 13 that were unstable to silica. However, for purposes
of biological testing, rapid silica-based radial chromatography
of the mixtures, where specified, gave samples of the separate
epimers with some loss due to decomposition.
Method A. Compound 6, 7 or 8 (typically 0.60 mmol), 1-
hydroxybenzotriazole (1 equiv.) and 1.5 equiv. of 10 (or the
hydrochloride salt of 9 and 1.5 equiv. of triethylamine) were
dissolved in dichloromethane (2.5 cm3) at 0 ЊC and the mixture
was stirred for 10 min. Dicyclohexylcarbodiimide (1 equiv.) was
added and the mixture was stirred for a further 10 min at 0 ЊC
and finally at 18 ЊC for 18 h. The reaction mixture was diluted
with more dichloromethane (5 cm3), filtered and the solvent was
evaporated to give 11, which was reduced without further purifi-
cation. The residue was redissolved in dry isopropyl alcohol (5
cm3), sodium borohydride (15 equiv.) was added and the sus-
pension was stirred at 0 ЊC for 2 h. Brine (5 cm3) was added and
the mixture was extracted with ethyl acetate (3 × 5 cm3). The
combined organic extracts were washed with water (5 cm3),
dried and evaporated to give 12a–d and 13a–d as mixtures.
Method B. Triethylamine (25 equiv.) and 17, 18, 19 or 20 (25
equiv.) were added to 15, 16, 21 or 22 (typically 0.30 mmol)
dissolved in dry dichloromethane (2.5 cm3) at 0 ЊC. The mixture
was then stirred for 18 h at 5 ЊC. The reaction mixture was
washed with water, dried and evaporated to give 12e,g–j and
13e,g–j as mixtures.
(1ЈR,2S)- and (1ЈS,2S)-2-Hydroxy-N-(1Ј-methoxy-1Ј-phenyl-
methyl)-3-phenylpropanamide 12a and 13a. The acid 6, freshly
prepared from 5 (96 mg, 0.58 mmol) as previously described,
was reacted with 10 according to general method A to give a
mixture of 12a and 13a (54 mg). Purification on a 1 mm silica
chromatotron plate eluting with diethyl ether–dichloromethane
(1:9 to 1:0) gave 13a (6 mg) [HRMS: found (M Ϫ Me)ϩ,
270.1125. C16H16NO3 requires 270.1130]; mp 104–105 ЊC; [α]D23
Ϫ92 (c 3.8, dichloromethane); νmax/cmϪ1 3406, 1684, 1504, 1497
and 1092; δH (CDCl3) 2.61 (1 H, d, J 4.9, OH), 2.96 (1 H, dd, J
14.0 and 8.5, CH2Ph), 3.27 (1 H, dd, J 14.0 and 4.2, CH2Ph),
3.37 (3 H, s, OMe), 4.32 (1 H, m, CHOH), 6.10 (1 H, d, J 9.3,
CHOMe), 7.00 (1 H, d, J 9.8, NH) and 7.30–7.38 (10 H, m,
ArH); δC(CDCl3) 40.8, 55.9, 72.9, 81.2, 125.8, 127.1, 128.6,
128.6, 128.8, 129.6, 136.5, 139.9 and 172.8; m/z (EI) 270
(Mϩ Ϫ Me, 15%), 253 (Mϩ Ϫ MeOH, 22), 121 (99) and 106
(100).
Further elution gave a second fraction (7 mg) containing a
mixture of 13a and 12a (3:2 by 1H NMR spectroscopy).
The final fraction gave 12a (9 mg) [HRMS: found
(M Ϫ Me)ϩ, 270.1128. C16H16NO3 requires 270.1130]; mp 66–
68 ЊC; [α]D23 Ϫ17 (c 3.6, dichloromethane); νmax/cmϪ1 3406, 1684,
1504, 1497 and 1090; δH (CDCl3) 2.96 (1 H, dd, J 13.8 and 8.1,
CH2Ph), 3.27 (1 H, dd, J 13.9 and 4.1, CH2Ph), 3.47 (3 H, s,
OMe), 4.45 (1 H, dd, J 8.3 and 3.9, CHOH), 6.12 (1 H, d, J 9.3,
CHOMe), 7.01 (1 H, d, J 9.3, NH) and 7.31 (10 H, m, ArH);
δC(CDCl3) 40.6, 56.1, 72.7, 81.1, 125.8, 127.1, 128.5, 128.5,
128.8, 129.6, 136.3, 138.8 and 172.9; m/z (EI) 270 (Mϩ Ϫ Me,
7%), 253 (Mϩ Ϫ MeOH, 17), 121 (77) and 106 (100).
Compounds 12a and 13a were also prepared by hydrolysing
separate samples of 12e (5 mg, 0.01 mmol) and 13e (4 mg, 0.01
mmol) in methanol and water (2.5 cm3 of a 9:1 mixture) with
K2CO3 (0.2 equiv.) at room temp. for 2 h. The mixtures were
evaporated and the residues were dissolved in dichloromethane
A change from R2 = Ph to Et appears to be tolerated,
although in this case, contrary to the other compounds given in
Table 1, a (1ЈS)-configuration seems to give the most potent in
vitro bioactivity (see compounds 12f and 13f, Table 1). It should
be noted that 13f and the parent natural products, compounds
1–3, possess the same relative configuration at this centre [(1ЈS)
in 13f and (10S) in 1–3]. The configurations at C(2) of 13f and
C(7) of 1–3 are both S. The introduction of a methyl group
at the R2 position resulted in compounds with significantly
reduced activity (see results for compounds 12b, 13b, 12h and
13h, Table 1). Finally, the glucosyl derivatives 42 and 43 show
less activity than the corresponding R2 = Et and Ph analogues
(Table 1).
Conclusion
Structure–activity studies on the mycalamide/pederin/onn-
amide skeleton (cf. 1–3) have established the key features which
are necessary or essential for the bioactivity observed across
this series of compounds. These structural requirements have
been summarised in structure 4. Examples of general structure
4 have been synthesized (Table 1) and shown to give modest
in vitro antitumour activity. The level of activity appears to
be more sensitive to changes at R2 than R1, and a (1ЈR)-
configuration is favoured.
Experimental
Mps were taken using a Reichert hot-stage microscope and are
uncorrected. Optical rotations were measured on a JASCO J-
20C recording spectropolarimeter and [α]D values are given in
units of 10Ϫ1 degrees cm2 gϪ1. IR Spectra were recorded on a
Shimadzu FTIR-8201PC spectrophotometer. 1H and 13C NMR
Spectra were recorded on Varian Unity and XL300 spectro-
meters, in CDCl3 solution, using Me4Si as an internal standard;
J values are given in Hz. Mass spectra were obtained using a
Kratos MS80RFA spectrometer. Radial chromatography was
performed on a chromatotron (Harrison and Harrison) using
Merck type 60 PF254 silica gel. Compounds 5, 7, 8, 9 and 24 are
commercially available. Compounds 10,13 14,14 17–2015 and
2514 were prepared by the general literature methods.
1650
J. Chem. Soc., Perkin Trans. 1, 1997

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(0.5 cm3). The organic solutions were washed with water (0.5
cm3), dried and evaporated to give white crystalline solids 12a
(4 mg, 90%) and 13a (4 mg, quant.).
(1ЈR,2S)- and (1ЈS,2S)-2-Hydroxy-N-(1Ј-methoxyethyl)-3-
phenylpropanamide 12b and 13b. The acid 6, freshly prepared
from 5 (100 mg, 0.60 mmol) as previously described, was
reacted with 9 according to general method A to give a mixture
of 12b and 13b (55 mg). Purification on a preparative silica
column eluting with methanol–water (92:5) gave three
fractions.
ArH), 7.72 (1 H, d, J 9.3, Phe-NH) and 8.23 (1 H, d, J 9.3,
CONH); δC(CDCl3, [2H6]DMSO) 17.2, 36.6, 49.9, 53.3, 54.5,
65.3, 80.2, 125.1, 125.4, 127.0, 127.1, 127.4, 128.4, 136.1, 138.2,
170.6 and 171.6.
(1ЈR,2S)- and (1ЈS,2S)-2-Acetoxy-N-(1Ј-methoxy-1Ј-phenyl-
methyl)-3-phenylpropanamide 12e and 13e. The amide 14 (87
mg, 0.53 mmol) was acetylated with acetic anhydride (0.15 cm3,
1.59 mmol) in pyridine (3 cm3) to give 1523 as a yellow oil
(quant.), which was not purified further. The amide 15 (0.53
mmol) was reacted with 17 according to general method B to
give a crude mixture of 12e and 13e. Repeated chromatography
on a 2 mm silica chromatotron plate eluting with ethyl acetate–
light petroleum mixtures gave a number of fractions.
The first fraction contained a mixture of 12b and 13b (11 mg,
1:1 by 1H NMR spectroscopy).
The second fraction contained a mixture of 12b and 13b (6
1
mg, 3:2 by H NMR spectroscopy); data for 13b (from the
The first fraction contained a mixture of 12e and 13e (21 mg,
1
mixture) δH (CDCl3) 1.30 (3 H, d, CHMe), 2.94 (1 H, m,
CH2Ph), 3.28 (1 H, m, CH2Ph), 3.24 (3 H, s, OMe), 4.05 (1 H, d,
OH), 4.36 (1 H, m, CHCO), 5.26 (1 H, m, CHOMe), 6.72 (1 H,
d, NH) and 7.28 (5 H, m, ArH).
The final fraction gave 12b as an oil (4 mg) [HRMS: found
(M Ϫ Me)ϩ, 208.0966. C11H14NO3 requires 208.0973]; δH -
(CDCl3) 1.26 (3 H, d, J 5.8, CHMe), 2.90 (1 H, dd, J 9.6 and
8.3, CH2Ph), 3.24 (1 H, m, CH2Ph), 3.30 (3 H, s, OMe), 4.41 (1
H, dd, J 8.3 and 3.4, CHOH), 5.25 (1 H, dd, J 9.7 and 5.8,
CHOMe), 7.03 (1 H, d, J 9.8, NH) and 7.25 (5 H, m, ArH); m/z
(EI) 208 (Mϩ Ϫ Me, 2%), 205 (Mϩ Ϫ H2O, 6), 191 (Mϩ Ϫ
MeOH, 80) and 91 (100).
(1ЈR,2S)- and (1ЈS,2S)-2-Benzyloxycarbonylamino-N-(1Ј-
methoxy-1Ј-phenylmethyl)-3-phenylpropanamide 12c and 13c.
The acid 7 (203 mg, 0.68 mmol) was reacted with 10 according
to general method A. The crude product was subjected to
repeated chromatography eluting with ethyl acetate–light pet-
roleum mixtures to give (S)-N-Z-phenylalaninamide22 16 (73
mg, 37%), further mixtures of 12c/13c (118 mg) and a sample of
12c (2 mg), mp 151–153 ЊC (HRMS: found Mϩ, 418.1886.
C25H26N2O4 requires 418.1893); δH (CDCl3) 3.08 (2 H, d, J 6.8,
CHCH2), 3.40 (3 H, s, OMe), 4.53 (1 H, m, CHCH2), 5.07 (2 H,
s, PhCH2O), 6.07 (1 H, d, J 9.7, CHOMe), 7.10–7.31 (15 H, m,
ArH) and 7.45 (1 H, d, J 9.3, NH); δC(CDCl3) 38.6, 55.8, 56.4,
66.8, 81.3, 125.7, 126.8, 127.8, 128.0, 128.1, 128.3, 128.4, 128.5,
129.2, 129.3, 136.2, 138.7, 155.9 and 171.4; m/z (EI) 418 (Mϩ,
5%), 403 (Mϩ Ϫ Me) and 386 (100).
Data for 13c (from the mixture) δH (CDCl3) 3.15 (2 H, d, J
6.8, CHCH2), 3.32 (3 H, s, OMe), 4.60 (1 H, m, CHCH2), 5.04
(2 H, s, PhCH2O), 6.09 (1 H, d, J 9.3, CHOMe) and 7.14–7.31
(15 H, m, ArH); δC(CDCl3) 38.3, 55.7, 56.2, 66.7, 81.4, 125.7,
126.7, 127.7, 127.9, 128.1, 128.2, 128.3, 128.4, 129.2, 136.1,
138.8, 155.9 and 171.5; m/z (EI) 403 (Mϩ Ϫ Me, 32%) and 386
(Mϩ Ϫ MeOH, 100).
(1ЈR,2S)- and (1ЈS,2S)-2-[(N-Benzyloxycarbonyl-L-alaninyl)-
amino]-N-(1Ј-methoxy-1Ј-phenylmethyl)-3-phenylpropanamide
12d and 13d. The acid 8 (50 mg, 0.13 mmol) was reacted with 10
according to general method A to give a mixture of 12d and 13d
(36 mg) which was purified on a 1 mm chromatotron plate elut-
ing with ethyl acetate–light petroleum (1:3 to 3:1) to give 12d
(9 mg) [HRMS: found (M Ϫ MeOH)ϩ, 457.1993. C27H27N3O4
requires 457.2002]; δH (CDCl3) 1.20 (3 H, d, J 7.1, CHMe), 3.12
(2 H, d, J 3.6, CHCH2), 3.30 (3 H, s, OMe), 4.17 (1 H, m,
CHMe), 4.76 (1 H, m, CHCH2), 4.92 (2 H, m, PhCH2O), 5.38
(1 H, d, J 5.8, Ala-NH), 6.05 (1 H, d, J 8.8, CHOMe), 6.88
(1 H, d, J 7.8, Phe-NH) and 7.15–7.31 (15 H, m, ArH);
δC(CDCl3) 18.1, 37.7, 51.0, 54.3, 55.8, 67.1, 81.6, 125.9, 125.9,
126.9, 127.0, 128.1, 128.3, 128.5, 128.6, 129.3, 136.1, 138.5,
171.1 and 172.3; m/z (EI) 457 (Mϩ Ϫ MeOH, 2%), 352 (4) and
91.0 (100).
9:1 by H NMR spectroscopy) which was crystallised from
ethyl acetate–light petroleum to give 12e (6 mg), mp 122–125 ЊC
[HRMS: found (M Ϫ Me)ϩ, 312.1233. C18H18NO4 requires
312.1236]; [α]D23 ϩ89 (c 5.3, dichloromethane); νmax/cmϪ1 3419,
1747, 1693, 1506, 1454, 1373 and 1220; δH (CDCl3) 2.07 (3 H, s,
COMe), 3.21 (2 H, dd, J 5.6 and 2.2, CH2Ph), 3.41 (3 H, s,
OMe), 5.49 (1 H, dd, CHOAc), 6.11 (1 H, d, J 9.8, CHOMe),
6.46 (1 H, d, J 9.7, NH) and 7.12–7.30 (10 H, m, ArH);
δC(CDCl3) 20.9, 37.5, 56.1, 74.2, 80.8, 125.7, 126.9, 128.3, 128.4,
128.4, 129.7, 135.9, 138.6, 149.7 and 169.3; m/z (EI) 312
(Mϩ Ϫ Me, 8%), 296 (Mϩ Ϫ OMe, 15), 237 (50) and 106 (100).
Further elution gave mixtures of 12e and 13e (81 mg).
Crystallisation of one such fraction from ethyl acetate–light
petroleum gave 13e (5 mg), mp 110–112 ЊC [HRMS: found
(M Ϫ Me)ϩ, 312.1234. C18H18NO4 requires 312.1236]; [α]D23 Ϫ25
(c 5.3, dichloromethane); νmax/cmϪ1 3419, 1747, 1693, 1506,
1454, 1373 and 1220; δH (CDCl3) 2.04 (3 H, s, COMe), 3.22 (2 H,
m, CH2Ph), 3.33 (3 H, s, OMe), 5.36 (1 H, m, CHOAc), 6.10 (1
H, d, J 9.2, CHOMe), 6.77 (1 H, d, NH) and 7.17–7.33 (10 H,
m, ArH); δC(CDCl3) 20.7, 37.5, 55.9, 74.5, 81.0, 123.6, 125.6,
126.9, 128.3, 128.4, 129.5, 135.9, 138.9, 149.6 and 169.3; m/z
(EI) 312 (Mϩ Ϫ Me), 296 (Mϩ Ϫ OMe, 8%), 252 (84) and 121
(100).
(1ЈR,2S)- and (1ЈS,2S)-2-Hydroxy-N-(1Ј-methoxypropyl)-3-
phenylpropanamide 12f and 13f. A mixture of 12g and 13g pre-
pared by method B (12 mg of a 1:1 mixture by 1H NMR spec-
troscopy) was hydrolysed in methanol and water (2.5 cm3 of a
9:1 mixture) with K2CO3 (0.2 equiv.) at room temp. for 2 h. The
mixture was evaporated and the residue was redissolved in
dichloromethane (2 cm3). The organic solution was washed
with water (2 cm3), dried and the solvent was evaporated to give
an oil (11 mg) which was chromatographed on a 1 mm silica
chromatotron plate eluting with ethyl acetate–light petroleum
(3:10) to give 13f as an oil (2 mg) [HRMS: found (M Ϫ Me)ϩ,
222.1125. C12H16NO3 requires 222.1130]; [α]D23 ϩ104 (c 0.2,
dichloromethane); νmax/cmϪ1 3400, 2972, 1680, 1301 and 1085;
δH (CDCl3, [2H5]pyridine) 0.91 (3 H, t, J 7.3, CH2Me), 1.57 (1 H,
m, CH2Me), 1.65 (1 H, m, CH2Me), 2.95 (1 H, dd, J 13.7 and
8.3, CH2Ph), 3.22 (3 H, s, OMe), 3.28 (1 H, m, CH2Ph), 4.38 (1
H, dd, J 8.3 and 3.9, CHOH), 5.03 (1 H, m, CHOMe), 6.98
(1 H, d, J 9.3, NH) and 7.21–7.30 (5 H, m, ArH); δC(CDCl3,
[2H5]pyridine) 9.0, 28.6, 41.1, 55.6, 72.7, 81.8, 126.7, 128.5,
129.6 and 137.5; m/z (EI) 222 (Mϩ Ϫ Me, 2%), 208
(Mϩ Ϫ C2H5, 13), 205 (Mϩ Ϫ MeOH, 64), 91 (63) and 73 (100).
Further elution gave mixtures of 12f and 13f and a sample
12f as an oil (2 mg) [HRMS: found (M Ϫ Me)ϩ, 222.1095.
C12H16NO3 requires 222.1130]; [α]D23 ϩ423 (c 0.2, dichlorometh-
ane); νmax/cmϪ1 3400, 2972, 1680, 1301 and 1085; δH (CDCl3,
[2H5]pyridine) 0.84 (3 H, t, J 7.3, CH2Me) , 1.48 and 1.65 (2 H,
m, CH2Me), 2.91 (1 H, dd, J 13.7 and 8.3, CH2Ph), 3.28 (1 H,
dd, J 13.7 and 3.4, CH2Ph), 3.31 (3 H, s, OMe), 4.46 (1 H, dd, J
8.3 and 3.4, CHOH), 5.03 (1 H, m, CHOMe), 6.95 (1 H, br s,
NH) and 7.18–7.33 (5 H, m, ArH); δC(CDCl3, [2H5]pyridine)
8.8, 28.2, 40.9, 55.5, 72.3, 81.7, 126.2, 128.1, 129.6, 137.9 and
174.3; m/z (EI) 222 (Mϩ Ϫ Me, 1%), 208 (Mϩ Ϫ C2H5, 4), 205
(27), 91 (36) and 73 (100).
Further elution gave 13d (21 mg) [HRMS: found (M Ϫ
MeOH)ϩ, 457.2005. C27H27N3O4 requires 457.2002]; δH (CDCl3,
[2H6]DMSO) 1.23 (3 H, d, J 7.3, CHMe), 3.01–3.15 (2 H, m,
CHCH2), 3.39 (3 H, s, OMe), 4.12 (1 H, m, CHMe), 4.71 (1 H,
m, Phe-CH), 5.05 (2 H, m, PhCH2O), 6.04 (1 H, d, J 9.3,
CHOMe), 6.86 (1 H, d, J 7.3, Ala-NH), 7.17–7.34 (15 H, m,
J. Chem. Soc., Perkin Trans. 1, 1997
1651

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(1ЈR,2S)- and (1ЈS,2S)-2-Acetoxy-N-(1Ј-methoxypropyl)-3-
phenylpropanamide 12g and 13g. The amide 15 (0.25 mmol),
prepared as described in the preparation of 12e and 13e, was
reacted with 19 according to general method B. Purification of
the crude product (49 mg) on a 1 mm silica chromatotron plate
eluting with ethyl acetate–light petroleum (1:5 to 1:3) gave a
mixture of 12g and 13g (12 mg, 1:1 by 1H NMR spectroscopy)
which could not be separated; δH (of the mixture; CDCl3) 0.78
and 0.83 (each 3 H, t, CH2Me), 1.42 and 1.57 (each 2 H, m,
CH2Me), 2.09 and 2.11 (each 3 H, s, COMe), 3.14 and 3.24
(each 3 H, s, OMe), 3.15–3.22 (m, CH2Ph), 4.99 (m, CHOMe),
5.35 and 5.40 (each 1 H, m, CHOAc), 6.10 (br m, NH) and
7.17–7.31 (m, ArH); δC(CDCl3) 8.8, 20.7, 20.9, 28.3, 28.5, 37.5,
37.6, 55.7, 55.9, 74.3, 74.4, 82.3, 127.0, 128.4, 128.4, 129.6,
129.6, 135.6, 135.7, 169.3 and 169.4.
(1ЈR,2S)- and (1ЈS,2S)-2-Benzyloxycarbonylamino-N-(1Ј-
methoxyethyl)-3-phenylpropanamide 12h and 13h. The amide
16, isolated from the preparation of 12c and 13c (61 mg, 0.21
mmol), was reacted with 18 according to general method B.
Purification of the crude product (38 mg) on a 1 mm silica
chromatotron plate eluting with ethyl acetate–light petroleum
(1:5 to 1:1) gave three fractions.
The first fraction gave 12h as a solid (18 mg) [HRMS: found
(M Ϫ MeOH)ϩ, 324.1474. C19H20N2O3 requires 324.1474]; mp
136–138 ЊC; [α]D23 Ϫ10 (c 0.1, dichloromethane); νmax/cmϪ1 3416,
3034, 1757, 1713, 1690 and 1497; δH (CDCl3, [2H5]pyridine) 1.12
(3 H, d, J 5.8, CHMe), 3.08 (2 H, d, J 7.4, CHCH2), 3.24 (3 H, s,
OMe), 4.47 (1 H, m, CHCH2), 5.08 (2 H, s, PhCH2O), 5.18 (1
H, m, CHOMe), 6.24 (1 H, d, J 7.4, BnOCONH) and 7.11–7.36
(10 H, m, ArH); δC(CDCl3, [2H5]pyridine) 20.9, 38.4, 55.1, 56.3,
66.5, 77.5, 126.6, 127.6, 127.8, 128.2, 128.3, 129.1 and 171.1;
m/z (EI) 324 (Mϩ Ϫ MeOH, 2%), 91 (100).
and 7.86 (2 H, m, ArH); m/z (EI) 403 [Mϩ(81Br) Ϫ MeOH,
3%], 401 [Mϩ(79Br) Ϫ MeOH, 4], 333 (9), 185 (95) and 183
(100).
Further elution gave fractions containing a mixture of 12i
and 13i (13 mg).
The final fraction contained a mixture of 12i and 13i (3 mg,
17:3 by 1H NMR spectroscopy) [HRMS: found (M Ϫ
MeOH)ϩ, 401.0633. C20H20NO379Br requires 401.0627]; data
for 12i (from the mixture) δH (CDCl3) 0.76 (3 H, d, J 6.9,
CHMe), 0.79 (3 H, d, J 6.4, CHMe), 1.68 (1 H, m, CHMe2),
3.22 (3 H, s, OMe), 3.33 (2 H, d, CH2Ph), 4.83 (1 H, dd, J 5.8
and 9.7, CHOMe), 5.64 (1 H, t, J 5.9, CHCH2), 5.97 (1 H, d, J
9.3, NH), 7.22–7.27 (5 H, m, ArH), 7.62 (2 H, m, ArH) and 7.84
(2 H, m, ArH); m/z (EI) 403 [Mϩ(81Br) Ϫ MeOH, 3%], 401
[Mϩ(79Br) Ϫ MeOH, 3], 333 (8), 185 (87) and 183 (85).
(1ЈR,2S)- and (1ЈS,2S)-2-[(1S)-Camphanyloxy]-N-(1Ј-meth-
oxy-1Ј-phenylmethyl)-3-phenylpropanamide 12j and 13j. A solu-
tion of (1S,4R)-camphanic acid (66 mg, 0.33 mmol) in thionyl
chloride (5 cm3) was refluxed for 2 h. Evaporation of the solvent
under reduced pressure gave an oil which was dissolved in
dichloromethane (1 cm3). The solution was added to a stirred
solution of 14 (24 mg, 0.15 mmol), 4-dimethylaminopyridine
(18 mg, 0.15 mmol) and diisopropylethylamine (28 µl, 0.16
mmol) in dichloromethane (1 cm3). After stirring for 18 h at
room temp. the reaction mixture was washed with water (2 cm3)
and dried. Evaporation under reduced pressure gave 22 (65 mg),
which was used without further purification.
Compound 22 (65 mg, 0.19 mmol) was reacted with 17
according to general method B. Purification of the crude prod-
uct (44 mg) by two passes through a 1 mm silica chromatotron
plate eluting with ethyl acetate–light petroleum (2:3) followed
by ethyl acetate–light petroleum (1:4 to 3:7) gave a mixture of
1
The second fraction contained a mixture of 12h and 13h (10
12j and 13j (14 mg, 3:2 by H NMR spectroscopy) [HRMS:
mg, 3:2 by 1H NMR spectroscopy).
found (M Ϫ OMe)ϩ, 434.1942. C26H28NO5 requires 434.1968];
data for 12j (from the mixture) δH (CDCl3, [2H5]pyridine) 0.71,
0.97 and 1.07 (each 3 H, s, camph-Me), 1.65 (1 H, m), 1.90 (2 H,
m), 2.33 (1 H, m), 3.16 (1 H, dd, J 14.6 and 8.3, CH2Ph), 3.33 (1
H, dd, J 14.6 and 4.6, CH2Ph), 3.39 (3 H, s, OMe), 5.52 (1 H,
dd, J 8.3 and 4.6, CHCO), 6.10 (1 H, d, J 9.3, CHOMe) and
7.19–7.37 (10 H, m, ArH); m/z (EI) 434 (Mϩ Ϫ OMe, 11%), 329
(5), 273 (82) and 131 (100).
The final fraction gave 13h (19 mg) [HRMS: found
(M Ϫ MeOH)ϩ, 324.1474. C19H20N2O3 requires 324.1474]; mp
158–160 ЊC; [α]D23 ϩ3 (c 2, dichloromethane); νmax/cmϪ1 3416,
3034, 1757, 1713, 1690 and 1499; δH (CDCl3, [2H5]pyridine) 1.23
(3 H, d, J 6.8, CHMe), 3.06 (2 H, d, J 6.8, CHCH2), 3.12 (3 H, s,
OMe), 4.55 (1 H, m, CHCH2), 5.06 (2 H, s, PhCH2O), 5.20 (1
H, m, CHOMe), 6.24 (1 H, d, J 7.8, BnOCONH), 7.16–7.30 (10
H, m, ArH) and 7.39 (1 H, d, J 8.7, CONH); δC(CDCl3, [2H5]py-
ridine) 21.0, 38.2, 55.1, 56.2, 66.6, 77.8, 126.6, 127.6, 127.8,
128.2, 128.2, 129.1, 155.8 and 166.1; m/z (EI) 324
(Mϩ Ϫ MeOH, 4%) and 91 (100).
(1ЈR,2S)- and (1ЈS,2S)-2-(4-Bromobenzoyloxy)-N-(1Ј-meth-
oxy-2Ј-methylpropyl)-3-phenylpropanamide 12i and 13i. To a
solution of amide 14 (55 mg, 0.33 mmol) and 4-dimethyl-
aminopyridine (61 mg, 0.50 mmol) in dichloromethane (2.5
cm3) was added triethylamine (92 µl, 0.66 mmol) and 4-
bromobenzoyl chloride (81 mg, 0.57 mmol). After stirring the
mixture at room temp. for 3 h the solvent was evaporated and
benzene (5 cm3) was added. The organic layer was washed with
2  aqueous HCl (3 cm3), saturated aqueous NaHCO3 (3 cm3)
and water (3 cm3), and dried. Evaporation under reduced pres-
sure gave 21 (117 mg) which was used without further purific-
ation; δH (CDCl3) 3.31 (2 H, m, CH2Ph), 5.60 (1 H, m, CHCH2),
5.77 (1 H, br s, NH), 6.00 (1 H, br s, NH), 7.23–7.29 (5 H, m,
ArH), 7.59 (2 H, m, ArH) and 7.82 (2 H, m, ArH).
The amide 21 was reacted with 20 according to general
method B to give a crude mixture of 12i and 13i (quant.). The
mixture was purified by two passes through a 1 mm silica chro-
matotron plate eluting with ethyl acetate–light petroleum
(3:50) followed by ethyl acetate–light petroleum (1:50) to
give 13i (1 mg) [HRMS: found (M Ϫ MeOH)ϩ, 401.0635.
C20H20NO379Br requires 401.0627]; δH (CDCl3) 0.75 (3 H, d, J
6.9, CHMe), 0.81 (3 H, d, J 6.4, CHMe), 1.68 (1 H, m, CHMe2),
3.16 (3 H, s, OMe), 3.34 (2 H, d, CH2Ph), 4.83 (1 H, dd, J 5.8
and 9.7, CHOMe), 5.60 (1 H, t, J 5.9, CHCH2), 5.93 (1 H,
d, J 9.3, NH), 7.22–7.28 (5 H, m, ArH), 7.62 (2 H, m, ArH)
Further elution gave a mixture of 13j and 12j which was
crystallised from ethyl acetate–light petroleum to give crystals
of 13j (11 mg) suitable for X-ray crystallography [HRMS:
found (M Ϫ OMe)ϩ, 434.1974. C26H28NO5 requires 434.1968];
δH (CDCl3, [2H5]pyridine) 0.76, 1.00 and 1.08 (each 3 H, s,
camph-Me), 1.60 (1 H, m), 1.76 (1 H, m), 1.87 (1 H, m), 2.26 (1
H, m), 3.17 (1 H, dd, J 14.4 and 8.5, CH2Ph), 3.30 (1 H, dd, J
14.2 and 5.4, CH2Ph), 3.42 (3 H, s, OMe), 5.41 (1 H, dd, J 8.4
and 5.4, CHCO), 6.11 (1 H, d, J 9.3, CHOMe), 7.17–7.32 (10
H, m, ArH) and 7.99 (1 H, d, J 9.3, NH); m/z (EI) 434
(Mϩ Ϫ OMe, 6%), 330 (7), 273 (70) and 131 (100).
1
A mixture (5 mg, 72%) of 12j and 13j (9:1 by H NMR
spectroscopy) was also prepared from a mixture (5 mg, 0.02
1
mmol) of 12a and 13a (9:1 by H NMR spectroscopy) using
(1S,4R)-camphanyl chloride as described for the preparation of
22 from 14.
(1ЈR,2R)- and (1ЈS,2R)-2-Acetoxy-N-(1Ј-methoxy-1Ј-phenyl-
methyl)-3-phenylpropanamide 27 and 29
The amide 25 (40 mg, 0.24 mmol) was acetylated with acetic
anhydride (69 µl, 0.73 mmol) in pyridine (3 cm3) to give 26 as a
yellow oil (quant.), which was not purified further. The amide
26 (0.24 mmol) was reacted with 17 according to general
method B (see preparation of 12/13). Purification of the crude
mixture (33 mg) on a 1 mm silica chromatotron plate eluting
with ethyl acetate–light petroleum (2:25 to 1:3) gave a mixture
of 27 and 29 (8 mg, 7:3 by 1H NMR spectroscopy) which was
recrystallised from ethyl acetate–light petroleum to give 27 (3
mg), mp 129–131 ЊC [HRMS: found (Mϩ Ϫ Me), 312.1233.
1652
J. Chem. Soc., Perkin Trans. 1, 1997

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C18H18NO4 requires 312.1236]; [α]D23 Ϫ37 (c 2.3, dichlorometh-
ane); δH and δC data identical to enantiomer 12e.
H, br s, NH) and 7.28 (5 H, m, ArH); δC(CDCl3) 7.3, 29.1, 37.9,
78.2 87.2, 126.7, 128.2, 129.7, 136.9 and 174.1; m/z (EI) 205
Further elution gave a fraction containing a mixture of 29
and 27 (7 mg, 8:2 by 1H NMR spectroscopy) which was
recrystallised from ethyl acetate–light petroleum to give 29 (3
mg), mp 111–113 ЊC [HRMS: found (M Ϫ Me)ϩ, 312.1234.
C18H18NO4 requires 312.1236]; [α]D23 ϩ24 (c 0.7, dichlorometh-
ane); δH and δC data identical to enantiomer 13e).
(Mϩ, 40%), 176 (Mϩ Ϫ C2H5, 78), 131 (73) and 91 (100).
(2S,5R)- and (2R,5R)-5-Benzyl-2-phenyl-1,3-oxazolidin-4-ones
35 and 36
Prepared as described for 31 and 33 using the amide 25 (40 mg,
0.24 mmol) and 17 (25 equiv.). Purification of the crude mixture
(141 mg) by flash silica chromatography, eluting with ethyl
acetate–dichloromethane (1:20 to 1:5) gave two fractions. The
first fraction contained a mixture of 36 and 35 (16 mg, 7:3 by
1H NMR spectroscopy). The second fraction gave 35 as an oil
(16 mg) (HRMS: found Mϩ, 253.1105. C16H15NO2 requires
253.1103); δH data identical to 31. The first fraction was further
purified on a 1 mm silica chromatotron plate eluting with ethyl
acetate–light petroleum (1:3 to 1:1) to give 36 as an oil (2 mg)
(HRMS: found Mϩ, 253.1102. C16H15NO2 requires 253.1103);
δH data identical to 33. Further elution gave more 35 (3 mg).
(1ЈR,2R)- and (1ЈS,2R)-2-Hydroxy-N-(1Ј-methoxy-1Ј-
phenylmethyl)-3-phenylpropanamide 28 and 30
The acetates 27 (2.3 mg, 0.007 mmol) and 29 (1.3 mg, 0.004
mmol) were separately hydrolysed (as described for 12e and 13e
in the preparation of 12a and 13a) to give 28 (1.7 mg, 84%) and
30 (0.7 mg, 60%), respectively. Compound 28, mp 62–64 ЊC
[HRMS: found (M Ϫ Me)ϩ, 270.1134. C16H16NO3 requires
270.1130]; [α]D23 ϩ21 (c 0.1, dichloromethane); δH and δC data
identical to enantiomer 12a. Compound 30, mp 99–101 ЊC
[HRMS: found (M Ϫ Me)ϩ, 270.1128. C16H16NO3 requires
270.1130]; [α]D23 ϩ76 (c 0.4, dichloromethane); δH and δC data
identical to enantiomer 13a.
(2S)-2-Hydroxy-3-phenyl-N-(2,3,4,6-tetra-O-acetyl-â-D-
glucopyranosyl)propanamide 42
A solution of the acid 517–19 (50 mg, 0.30 mmol), glucosylamine
41 (104 mg, 0.30 mmol), 1-hydroxybenzotriazole (42 mg, 0.30
mmol) and dicyclohexylcarbodiimide (61 mg, 0.30 mmol) in
dichloromethane (10 cm3) was stirred at room temp. for 5 d.
The mixture was filtered and evaporated to give the crude
amide 42 (quant.). Purification on a 1 mm chromatotron plate
eluting with ethyl acetate–light petroleum (1:1) gave 42 (87 mg,
59%), mp 172.5–174.5 ЊC (from ethyl acetate–light petroleum)
(HRMS: found MHϩ, 496.1810. C23H30NO11 requires
496.1820); [α]D23 ϩ46 (c 0.1, dichloromethane); νmax/cmϪ1 3052,
1756, 1225 and 1043; δH (CDCl3) 1.94, 2.02, 2.03, 2.07 (each 3
H, s, COMe), 2.78 (1 H, dd, J 13.6 and 8.5, CH2Ph), 2.86 (1 H,
d, J 4.8, OH), 3.18 (1 H, dd, J 13.7 and 2.9, CH2Ph), 3.82 (1 H,
m, H-5), 4.11 (1 H, m, H-6a), 4.31 (1 H, m, H-6b), 4.33 (1 H, m,
CHCO), 4.94 (1 H, t, J 9.5, H-2), 5.06 (1 H, t, J 9.5, H-4), 5.21
(1 H, t, J 9.2, H-1), 5.30 (1 H, t, J 9.3, H-3), 7.23–7.34 (4 H, m,
ArH) and 7.46 (1 H, m, ArH); δC(CDCl3) 20.5, 20.6, 40.3, 61.5,
68.0, 70.4, 72.6, 72.7, 73.6, 77.8, 127.0, 128.6, 129.5, 136.4,
169.5, 170.5 and 173.6; m/z (FAB) 496 (MHϩ, 53%) and 168
(100).
(2R,5S)- and (2S,5S)-5-Benzyl-2-phenyl-1,3-oxazolidin-4-ones
31 and 33
An excess of 17 (25 equiv.) was added to the amide 14 (93 mg,
0.56 mmol) in dichloromethane (5 cm3) and the mixture was
stirred at Ϫ10 ЊC for 18 h. The solution was washed with 10%
aqueous NaHCO3 (5 cm3) and water (5 cm3), dried and the
solvent was evaporated under reduced pressure to give a crude
mixture of 31 and 33 (141 mg). Purification on a 1 mm silica
chromatotron plate eluting with ethyl acetate–light petroleum
(2:3) gave a mixture of 31 and 33 (76 mg, 54%, 4:1 by 1H NMR
spectroscopy). Further purification on a 1 mm silica chroma-
totron plate eluting with ethyl acetate–light petroleum (1:9 to
1:0) gave 33 as an oil (19 mg) (HRMS: found Mϩ, 253.1102.
C16H15NO2 requires 253.1103); [α]D23 Ϫ17 (c 0.7, dichlorometh-
ane); νmax/cmϪ1 3429, 1756, 1728, 1278, 1247 and 1126;
δH (CDCl3) 3.13 (2 H, m, CH2Ph), 4.77 (1 H, m, CHCH2), 5.72
(1 H, d, J 2.4, NCH), 7.24–7.37 (10 H, m, ArH) and 7.86 (1 H,
br s, NH); δC(CDCl3) 37.6, 78.2, 87.8, 126.2, 126.8, 128.3, 128.7,
129.7, 129.7, 136.1, 138.3 and 166.4; m/z (EI) 253 (Mϩ, 76%),
106 (100).
Further elution gave 31 as an oil (11 mg) (HRMS: found Mϩ,
253.1105. C16H15NO2 requires 253.1103); [α]D23 Ϫ121 (c 0.1,
dichloromethane); νmax/cmϪ1 3430, 1730, 1498, 1462, 1313 and
1081; δH (CDCl3) 3.11 (2 H, m, CH2Ph), 4.59 (1 H, m, CHCH2),
5.96 (1 H, d, J 2.1, NCH), 7.03–7.07 (2 H, m, ArH), 7.18–7.36
(8 H, m, ArH) and 7.75 (1 H, br s, NH); δC(CDCl3) 37.4, 78.5,
87.1, 126.6, 127.0, 128.3, 128.5, 129.8, 129.9, 136.5, 137.5 and
174.5; m/z (EI) 253 (Mϩ, 25%), 147 (90) and 106 (100).
(2S)-2-Hydroxy-3-phenyl-N-(â-D-glucopyranosyl)propanamide
43
The amide 42 (37 mg, 0.08 mmol) and K2CO3 (2 mg, 0.02
mmol) were dissolved in methanol and water (4 cm3 of a 9:1
solution) and the mixture was stirred at room temp. for 1 h. The
methanol was removed under reduced pressure and the aque-
ous layer was washed with dichloromethane (3 × 5 cm3) and
evaporated to give 43 (24 mg, 96%) (HRMS: found MKϩ,
366.0960. C15H21NO7K requires 366.0955); δH (D2O) 1.77 (1 H,
s, OH), 2.84 (1 H, dd, J 14.2 and 7.8, CH2Ph), 3.02 (1 H, dd, J
14.1 and 4.9, CH2Ph), 3.25–3.77 (6 H, m, H-2–H-6), 4.36 (1 H,
dd, J 7.8 and 4.9, CHCO), 4.81 (1 H, d, J 9.3, H-1) and 7.16–
7.26 (5 H, m, ArH); m/z (FAB) 366 (MKϩ, 8%), 307 (10) and
153 (100).
(2R,5S)- and (2S,5S)-5-Benzyl-2-ethyl-1,3-oxazolidin-4-ones 32
and 34
Prepared as described for 31 and 33 using the amide 14 (124 mg,
0.73 mmol) and 19 (25 equiv.). Purification of the crude mixture
on a 1 mm silica chromatotron plate eluting with ethyl acetate–
dichloromethane (0:1 to 3:10) gave 34 as an oil (6 mg)
(HRMS: found Mϩ, 205.1103. C12H15NO2 requires 205.1103);
δH (CDCl3) 0.90 (3 H, t, J 7.5, Me), 1.60 (2 H, m, CH2Me), 3.05
(2 H, m, CH2Ph), 4.57 (1 H, m, CHCO), 4.85 (1 H, m, NCH),
6.46 (1 H, br s, NH) and 7.29 (5 H, m, ArH); δC(CDCl3) 7.2,
29.5, 37.8, 77.9, 87.7, 126.7, 128.3, 129.8, 136.5 and 176.0; m/z
(EI) 205 (Mϩ, 54%), 176 (Mϩ Ϫ C2H5, 49), 131 (87) and 91
(100).
Further elution gave a second fraction containing a mixture
of 32 and 34 (6 mg, 1:4 by 1H NMR spectroscopy).
The final fraction gave 32 as an oil (13 mg) (HRMS: found
Mϩ, 205.1106. C12H15NO2 requires 205.1103); δH (CDCl3) 0.87
(3 H, t, J 7.6, Me), 1.46 (2 H, m, CH2Me), 3.07 (2 H, m,
CH2Ph), 4.49 (1 H, m, CHCO), 5.10 (1 H, m, CHOMe), 6.88 (1
Crystal structure determination for 13j
Crystal data. C27H31NO6, M = 465.53, triclinic, a = 6.2953(13),
b = 12.667(3), c = 15.522(3) Å, α = 88.73(3), β = 86.45(3), γ =
85.19(3)Њ, V = 1230.9(4) Å3 [by refinement against setting
angles for 25 reflections with 106 ≤ 2θ ≤ 115Њ , λ = 1.541 84 Å,
T = 293(2) K], space group P1 (No. 1), Z = 2, Dx = 1.256 g cmϪ3
,
colourless needle 0.7 × 0.2 × 0.08 mm, µ(Cu-Kα) = 0.722
mmϪ1
.
Data collection and processing. Rigaku AFC four-circle dif-
fractometer, ω–2θ scans, graphite-monochromated Cu-Kα X-
radiation; 4056 reflections measured (5.7 ≤ 2θ ≤ 120.2Њ, ϩh, ±k,
±l); 3665 had F ≥ 4σ(F) and all 4056 were retained in all calcu-
lations. Three intensity standards, monitored every 150 reflec-
J. Chem. Soc., Perkin Trans. 1, 1997
1653

View Article Online
J. Chem. Soc., Perkin Trans. 1, 1994, 1025; Part 5: A. M. Thompson,
J. W. Blunt, M. H. G. Munro and N. B. Perry, J. Chem. Soc., Perkin
Trans. 1, 1995, 1233.
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5 (a) S. Sakemi, T. Ichiba, S. Kahmoto, G. Saucy and T. Higa, J. Am.
Chem. Soc., 1988, 110, 4851; (b) S. Matsunaga, N. Fusetani and
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tions, showed slight variations (1.3%). Corrections for absorp-
tion (min., 0.883; max., 1.000) were made using the ψ-scan
method.
Structure solution and refinement. Automatic direct meth-
ods24 (all non-H atoms). Full-matrix least-squares refinement 25
with all non-H atoms anisotropic; hydrogen atoms were intro-
duced at geometrically calculated positions and thereafter
allowed to ride on their parent atoms. The weighting scheme
2
2
2
w
Ϫ1 = [σ2(Fo ) ϩ (0.045P)2 ϩ 0.044P], P = ¹[MAX(Fo ,0) ϩ 2Fc ]
¯
³
gave satisfactory agreement analyses. Final R1 [F ≥ 4σ(F)] =
0.0282, wR2 (all data) = 0.102, S(F 2) = 1.12 for 621 refined
parameters and 3 restraints. An absolute structure (Flack 26
)
parameter refined to 0.3(2); no extinction correction was
10 N. S. Burres and J. J. Clement, Cancer Res., 1989, 49, 2935.
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Tetrahedron, 1988, 44, 7063; F. Matsuda, M. Yanagiya and
T. Matsumoto, Tetrahedron Lett., 1982, 23, 4043.
required; and the final ∆F synthesis showed no peaks above
±0.15 e ÅϪ3
.
Atomic coordinates, thermal parameters and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Perkin Trans. 1, 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature citation
and the reference number 207/108.
13 M. M. Endicott, E. Wick, M. L. Mercury and M. L. Sherrill, J. Am.
Chem. Soc., 1946, 68, 1299.
14 L. F. Audrieth and M. Sveda, Org. Synth., 1955, Coll. Vol. 3, 536.
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24 G. M. Sheldrick, Program for Crystal Structure Solution, University
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Acknowledgements
The authors acknowledge financial support from the New Zea-
land Foundation for Research, Science and Technology Public
Good Science Fund. We also thank Mrs G. Barns for providing
the biological assays, Mr B. M. Clark for the mass spectro-
metry, Professor W. Robinson for his assistance with the X-ray
crystallography, Andrew Thompson and Shane Blincoe for
carrying out some preliminary synthetic studies and Professor
Sir John Cornforth for some useful discussions.
25 G. M. Sheldrick, Acta Crystallgr., Sect. A, 1990, 46, 467.
26 International Tables for Crystallography, ed. J. A. Ibers and W. C.
Hamilton, vol. C, Kynoch Press, Birmingham, 1992.
References
1 Part 1: N. B. Perry, J. W. Blunt, M. H. G. Munro and L. K. Pannell,
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3 Part 3: A. M. Thompson, J. W. Blunt, M. H. G. Munro, N. B. Perry
and L. K. Pannell, J. Chem. Soc., Perkin Trans. 1, 1992, 1335; Part 4:
A. M. Thompson, J. W. Blunt, M. H. G. Munro and B. M. Clark,
Paper 6/08168A
Received 3rd December 1996
Accepted 25th February 1997
1654
J. Chem. Soc., Perkin Trans. 1, 1997