Design and synthesis of pyrrolidine-5,5-trans-lactams (5-oxo-hexahydro-pyrrolo[3,2-b]pyrroles) as novel mechanism-based inhibitors of human cytomegalovirus protease. 1. The α-methyl-trans-lactam template

Article abstract of DOI:10.1021/jm000078q

Mechanism-based inhibitors of human cytomegalovirus (HCMV) protease have been designed based on the pyrrolidine-5,5-trans-lactam ring system. New routes to the β-methyl-, desmethyl-, and α-methyl-pyrrolidine-5,5-trans-lactam templates have been developed

Full text of DOI:10.1021/jm000078q

4452
J . Med. Chem. 2000, 43, 4452-4464
Design a n d Syn th esis of P yr r olid in e-5,5-tr a n s-la cta m s
(5-Oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r oles) a s Novel Mech a n ism -Ba sed In h ibitor s
of Hu m a n Cytom ega lovir u s P r otea se. 1. Th e r-Meth yl-tr a n s-la cta m Tem p la te
Alan D. Borthwick,* S. J ane Angier,§ Andrew J . Crame, Anne M. Exall, Terry M. Haley,† Graham J . Hart,‡
Andrew M. Mason, Andrew M. K. Pennell, and Gordon G. Weingarten
Departments of Medicinal Chemistry 2, Molecular Cell Biology, Biomolecular Structure, and Enzyme Pharmacology, Glaxo
Wellcome Research and Development, Medicines Research Centre, Gunnels Wood Road, Stevenage Herts SG1 2NY, U.K.
Received February 22, 2000
Mechanism-based inhibitors of human cytomegalovirus (HCMV) protease have been designed
based on the pyrrolidine-5,5-trans-lactam ring system. New routes to the â-methyl-, desmethyl-,
and R-methyl-pyrrolidine-5,5-trans-lactam templates have been developed from 2,4-diamino-
butyric acid. ESI/MS studies have shown that these inhibitors can bind covalently and reversibly
to the viral enzyme in a time-dependent manner by a mechanism which is consistent with
acylation of HCMV δAla protease at the active site nucleophile Ser 132. SAR in this series of
pyrrolidine-5,5-trans-lactams has defined the relative stereochemisty of the methyl substituent
adjacent to the lactam carbonyl, the functionality on the lactam nitrogen, and the mechanism
of action of this novel series of serine protease inhibitors against the HCMV δAla protease.
Activity decreases on moving from the R-methyl to the desmethyl to the â-methyl series. This
selectivity is the opposite of that observed for these templates against the elastase and thrombin
enzymes. The activity against HCMV δAla protease is the greatest with inhibitors based on
the Cbz-protected R-methyl-5,5-trans-lactam template which have low micromolar activity
against the viral enzyme.
In tr od u ction
by two juxtapositioned histidine residues at positions
63 and 157. The substrate cleavage sites across all the
herpes virus family are unique and highly conserved:
Human herpes viruses cause a range of diseases:
HSV-1 (cold sores), HSV-2 (genital herpes), VZV (chicken
pox, shingles), and HCMV (retinitis, pneumonitis). The
current treatment of these diseases uses nucleoside
(acyclovir, ganciclovir) and phosphonate (foscarnet)
substrate analogues. Because of the toxicity associated
with foscarnet and ganciclovir, together with the emer-
gence of mutants resistant to acyclovir, there is a need
for a new class of antiherpes compounds based on a
novel mechanism.
Human herpes viruses encode a serine protease which
is essential for viral replication.1 The protease is part
of the scaffold around which the capsid of the virus is
built. The protease then cleaves the scaffold, which
enables viral DNA to be packaged into the capsid.
Inhibition of the protease blocks capsid formation and
hence viral replication. Mutation studies, reaction with
protease inhibitors, and recent X-ray structures indicate
that the herpes virus proteases are members of the
serine protease superfamily with little homology to the
human (chymotrypsin) and bacterial (subtilisin) serine
protease classes.1,2 The recent crystal structures of
HCMV protease3-6 show it to be a 7-stranded â-barrel
stabilized by surrounding R-helices; it exists as a dimer
of two of these units in the crystal structure. Moreover
it has a novel catalytic strategy for peptide cleavage,
where the serine nucleophile at position 132 is activated
1,2
the cleavage occurs between Ala/Ser and the consen-
sus sequence for HCMV is Val-Xxx-Ala V Ser. These
enzymes have become attractive molecular targets for
the design of novel antiviral drugs.2 The pyrrolidine-
5,5-trans-lactam serine protease inhibitors developed for
our elastase7,8 and thrombin9 projects are ideal starting
points for a chemical program aimed at developing
inhibitors of herpes protease, as they have the potential
to access all three specificity sites (S1′, S1, and S3).
These proven serine protease inhibitors also have other
advantages: they are novel and stable in plasma, their
activity in vivo has been demonstrated indicating that
these systems can have a favorable pharmacokinetic
profile, and the synthesis of the ring systems has been
established.
Our design of inhibitors was based on the trans-
lactam ring incorporating the natural substrate require-
ments of the consensus sequence of HCMV protease.
Hence the pyrrolidine-5,5-trans-lactam template A
(Scheme 1) with a methyl substituent alpha to the
lactam carbonyl (for access of the S1 site) became our
initial target, where variation of substituents on the
nitrogen atoms would allow us to access the S1′ and S3
sites. The initial exercise described in this publication
was to determine the stereochemistry of this substituent
for access of the S1 site, which is the major determinant
of specificity in serine proteases, the SAR of the func-
tionality on the lactam nitrogen, and the mechanism of
action of this novel series of serine protease inhibitors
against the HCMV protease.
* To whom correspondence should be addressed. Tel: +44 (0)1438
763422. E-mail: adb3028@glaxowellcome.co.uk.
§ Department of Molecular Cell Biology.
† Department of Biomolecular Structure.
‡ Department of Enzyme Pharmacology.
10.1021/jm000078q CCC: $19.00 © 2000 American Chemical Society
Published on Web 10/26/2000

Synthesis of Pyrrolidine-5,5-trans-lactams
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4453
Sch em e 1. trans-Lactam Template and Natural Substrate for HCMV Protease
Sch em e 2a
a
Reagents and conditions: (a) Cu (OAc)2, aq NaOH, 70 °C, 1-2 h, rt, pHf7-8, then CbzCl/dioxan/aq NaOH, 0 °C, then 1 h at rt; (b)
EDTA, aq HCl, 1.5 h, pHf4-5, then (Boc)2O/dioxan, pHf8, 40 h; (c) ClCO2Et, N-methylmorpholine, THF, -10 °C, then NaBH4/H2O; (d)
ClCOCOCl, DMSO, CH2Cl2, -70 °C, then Et3N at -50 °C; (e) (Ph)3PdCHCO2But added in situ, -50 °C; (f) LHMDS (0.25 equiv)/hexane,
TMEDA/toluene, rt; (g) LHMDS (4 equiv)/THF/HMPA, -78 °C, 30 min, then MeI titrated in; (h) aq TFA, 2 h, rt; (i) (PhO)2PON3, Et3N,
DMF, 23 h, rt; (j) aq TFA, 75 min, rt; (k) ButMgCl (3 equiv)/THF, <1 °C, 1 h, then 0 °C to rt, 45 min; (l) LHMDS (1.2 equiv)/THF, -78
°C, 30 min, then (Boc)2O (2.8 equiv)/THF, -78 °C; (m) LHMDS (1.3 equiv), THF/DMPU (4:1), MeI (2 equiv), -20 °C, or LHMDS (1.3
equiv), THF, MeI (10 equiv), -78 °C; (n) TFA, 35 min, rt.
Ch em istr y
diaminobutyric acid with CbzCl in the presence of Cu2+
followed by Boc-anhydride in the presence of EDTA
(ethylenediaminetetraacetic acid) to remove copper from
the first complex gave N-R-Boc-N-γ-Cbz-2,4-diaminobu-
tyric acid11 (1) in 74% overall yield. Attempts to reduce
the acid to the alcohol using diborane in THF failed.
However reduction of the mixed anhydride12 (formed
from the acid and ethyl chloroformate) with NaBH4/H2O
gave the alcohol 2 in 85% yield. Swern oxidation to form
The three templates to explore this stereochemistry
were synthesized from 2,4-diaminobutyric acid via the
protected 3-aminopyrrolidine-2-acetic acid ester7 (5)
(Scheme 2).
This is shorter than the previous route,7 which
contained some difficult chromatographic purification
steps, and the starting material is available in both
racemic and chiral forms. Bis-protection of D,L-2,4-

4454 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Borthwick et al.
Sch em e 3a
Sch em e 4a
a
Reagents and conditions: (a) ClCOCOCl, DMSO, CH2Cl2, -70
°C, then Et3N at -50 °C; (b) (Ph)3PdCHCO2But added in situ,
-50 °C.
the aldehyde followed by Horner-Emmons reaction of
tert-butyl diethylphosphonoacetate ((EtO)2P(O)CH2CO2-
But) on the isolated aldehyde resulted in a poor yield of
3. Attempts to form the aldehyde from the N-methoxy-
N-methylcarboxamide derivative of the carboxylic acid
followed by lithium aluminum hydride13 reduction also
resulted in poor yields. It was shown by NMR that the
aldehyde exists as the aminal at room temperature
(Scheme 3) and slowly decomposes in solution.
a
Reagents and conditions: (a) LHMDS (1.2 equiv)/THF, -78
°C, 30 min at 0 °C; (b) electrophile, -78 °C. *This reaction was
carried out using acetic anhydride and NaH.
the amino acid 11 with diphenyl phosphorazidate gave
only 15% of the cyclized unsubstituted trans-lactam 13
under a variety of conditions, in contrast to the â-methyl
series above. However an optimization exercise15 showed
that, after deprotection of 6 with TFA in 80% yield,
lactamization of ethyl ester 12 with ButMgCl gave the
unsubstituted trans-lactam 13 in 78% yield. Protection
of the desmethyl-5,5-trans-lactam 13 with Boc-anhy-
dride to give the tert-butyl ester 14 followed by ste-
reospecific methylation10 with methyl iodide (2 equiv)
in the presence of DMPU (1,3-dimethyl-3,4,5,6-tetrahy-
dro-2(1H)-pyrimidinone) at -20 °C gave 15, which on
deprotection with TFA gave the R-methyl-5,5-trans-
lactam 16 in 51% yield for the three steps.
The base of choice for introducing substituents onto
the lactam nitrogen was found to be LHMDS (1.2 equiv
in THF for 30 min at 0 °C and then adding the
electrophile at -78 °C) which was far superior in terms
of yield, ease of manipulation, and time required
compared to sodium hydride, which had been used
previously, and is compatible with a range of electro-
philes including acid chlorides, anhydrides, chloroform-
ates, and especially sulfonyl chlorides (Scheme 4).
Surprisingly with â-styrenesulfonyl chloride low yields
were seen with the desmethyl-5,5-trans-lactam and
R-methyl-5,5-trans-lactam ring systems compared to the
â-methyl-5,5-trans-lactam ring system. In part, this may
be due to the instability of any anion, generated under
equilibrium conditions, next to the lactam carbonyl in
the R-methyl-5,5-trans series relative to the â-methyl-
5,5-trans series, and the bulk of the electrophile. The
To avoid formation of the aminal, Swern conditions14
were used that generated the reactive aldehyde at -78
°C which then was reacted in situ at that temperature
with the milder Wittig reagent. These conditions re-
sulted in a high yield (70-85%) of exclusively the (E)-
R,â-unsaturated ester 3 in a one-pot sequence for the
twosteps.Addition oftheWittigreagent (Ph3PdCHCO2But)
at low temperature (-50 °C) to the Swern oxidation
mixture enables the aldehyde that is formed to be
captured immediately before it cyclizes to the aminal.
Similarly the phosphorane ethyl ester gave the unsatur-
ated ester 4. Cyclization of the R,â-unsaturated ester 3
with 0.25 equiv of LHMDS (lithium hexamethyldisi-
lazide) in the presence of TMEDA (tetramethylethyl-
enediamine) gave the major trans-substituted pyrroli-
dine 5 in 62% yield together with the 5,5-cis-lactam 7
in 13% yield, which resulted from the internal cycliza-
tion of the minor cis-substituted pyrrolidine product.
Similarly 4 gave 6 in 75% yield. Stereoselective methy-
lation10 of the tert-butyl ester 5 with methyl iodide
afforded predominantly the â-methyl isomer 8 (plus 10%
of R-methyl isomer) in 66% yield. The one-pot depro-
tection of the tert-butyl ester and the Boc-amine in 8
occurs in 98% yield to give the amino acid 9. Cyclization
of 9 with diphenyl phosphorazidate was achieved in 66%
yield to give the â-methyl-5,5-trans-lactam 10 plus 10%
of the R-methyl isomer 16 (Scheme 2) which were
readily separated by preparative HPLC. Deprotection
of 5 with TFA was quantitative; however, cyclization of

Synthesis of Pyrrolidine-5,5-trans-lactams
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4455
Sch em e 5a
chloride. A higher yield in the acylation reaction was
achieved using pivaloyl mixed anhydride17 (prepared
from para-methoxybenzyloxyacetic acid and pivaloyl
chloride) which in the desmethyl-5,5-trans-lactam series
gave the protected alcohol 36 from 13 as a white solid
in 65% yield. Deprotection of this product with DDQ
gave 37 in 75% yield (Scheme 5). Similarly prepared in
the R-methyl-5,5-trans-lactam series was the protected
alcohol 38 from 16 in 67% yield. Oxidative deprotection
of 38 with DDQ gave the alcohol 39 in 71% yield.
Resu lts a n d Discu ssion s
HCMV δAla protease formed by removing the internal
cleavage site (Ala 142/Ala 143) from the wild-type 28-
kb HCMV protease has been cloned and expressed in
E. coli.18 We have shown that this HCMV δAla protease
cleaves synthetic peptides (14-mers) based on the natu-
ral substrates,18 and this forms the basis of an HPLC-
based assay that has been developed and which allows
evaluation of potential inhibitors.19 The percent inhibi-
tion and IC50 values for the pyrrolidine-5,5-trans-
lactams (Tables 1-3) were determined using this HPLC
assay. Compounds were routinely assayed by determin-
ing percent inhibition after various periods of preincu-
bation. The results obtained give an idea of the ‘on’ rate
(acylation) and ‘off’ rate (deacylation) and the duration
of action of each compound. Determination of percent
inhibition using a range of inhibitor concentrations
enabled values for IC50 (the inhibitor concentration
giving 50% inhibition) to be determined.
â-Methyl-pyrrolidine-5,5-trans-lactams with Cbz pro-
tecting the pyrrolidine nitrogen and various electron-
withdrawing groups on the lactam nitrogen were only
weakly active. The best was the acetoxyacetyl derivative
17 (IC50 ) 805 µM; Table 1). Compounds in the des-
methyl-5,5-trans-lactam series (Table 2) are more active
than the corresponding â-methyl-5,5-trans-lactams. How-
ever the effects of various lactam nitrogen substituents
on protease activity are similar in the two series. The
acetoxyacetyl derivative 22 was best (IC50 ) 102 µM),
but the acyl compounds 23 and 37 and the protected
analogue 36 were also highly active. However, bulk
adjacent to the carbonyl in 28 or the ester in 14 is not
tolerated. Uniquely, the alkenes 24 and 27 retained good
activity after 24 h of preincubation. This may indicate
that the electron-deficient double bond is acting as a
Michael acceptor or picking up additional binding. The
lipophilic styrene and the PMB ether needed lengthy
preincubations to achieve maximum effect, possibly due
to insolubility.
With R-methyl-5,5-trans-lactams, a pattern similar to
the other two series is seen with a range of lactam
nitrogen substitutions (Table 3): the general trend in
activity against HCMV δAla protease has been found
to be acyl > ester > sulfonyl > carbamate. This is in
line with the electron-withdrawing ability of the trigonal
(sp2) substituents (which activates the lactam carbonyl
required for acylation of the active site serine) but not
the tetrahedral (sp3) sulfone, which indicates that the
latter’s stereochemistry is not so favored at this position
probably due to steric reasons. The acetoxyacetyl ana-
logue 29 is the most potent compound in any series (IC50
) 13 µM) and achieves maximum inhibition during 30
min, while the lipophilic styrene analogue 33 achieves
a
Reagents and conditions: (a) LHMDS (3 equiv)/THF, -78 °C,
then ClCOCH2OAc; (b) H2SO4 or enzymes; (c) LHMDS (3 equiv)/
THF, -78 °C, then ClCOCH2OPMB or LHMDS (1.2 equiv)/THF,
-78 °C, then (Me)3CCO2COCH2OPMB; (d) DDQ in H2O/CH2Cl2,
rt.
more hindered acetoxydimethylacetyl derivative 28 was
also formed in low yield. Also amides 40 and 41 were
prepared in 69% and 31% yields, respectively, by react-
ing the anion of the lactam with the required isocyanate.
Reacting the anion of 10 with chloroacetyl chloride and
with 4-acetylaminophenylsulfonyl chloride gave 42 and
43 in 38% and 5% yields, respectively.
The hydroxymethylacetyl derivative 34 was envisaged
as a crucial intermediate for attempts to mimic the
conserved serine at S1′ (Scheme 5). Attempted hydroly-
sis of the acetoxy group in 17 with base (KHCO3 or K2-
CO3) caused loss of the acetoxyacetyl group giving only
the unsubstituted lactam, while hydrolysis with acid or
a range of enzymes gave varying amounts of alcohol 34
(the best yield being 26%), unsubstituted lactam, and
starting material.
Other methods were investigated to prepare this
alcohol. The para-methoxybenzyl (PMB) analogue was
chosen as this group can be removed oxidatively avoid-
ing basic and acidic conditions. para-Methoxybenzyl-
oxyacetyl chloride was prepared16 and used crude with
lactam 10 to give the â-methyl-5,5-trans-lactam deriva-
tive 35 in 29% yield and then deprotected with DDQ to
give the required alcohol 34 in 86% yield. Attempts to
purify the crude para-methoxybenzyloxyacetyl chloride
by distillation resulted in decomposition of the acid

4456 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Ta ble 1. â-Methyl-pyrrolidine-5,5-trans-lactamsa
Borthwick et al.
compd
R
inhib at 15 min
max % inhib (h)
inhib at 24 h
protease IC50 (µM)
17
21
18
34
35
19
20
COCH2OCOMe
SO2CHdCHPh
COMe
COCH2OH
COCH2OCH2PhOMe
CO2Me
46.0
27.9
15.4
11.4
nt
61.2 (1)
34.9 (2)
39.8 (2)
21.4 (24)
nt
24.9
27.7
36.5
21.4
805
1800
7.9
15
17.8 (0.5)
19.4 (24)
0
19.4
SO2Me
a
[Compound] ) 500 µM for all tests except IC50 determinations; nt, not tested.
Ta ble 2. Desmethyl-pyrrolidine-5,5-trans-lactamsa
compd
R
inhib at 15 min
max % inhib (h)
inhib at 24 h
protease IC50 (µM)
22
23
37
36
24
27
25
26
40
28
14
COCH2OCOMe
COMe
COCH2OH
COCH2OCH2PhOMe
CO2CHdCH2
SO2CHdCHPh
CO2Me
SO2Me
CONHMe
COCMe2OCOMe
CO2CMe3
85.3
81.9
81.9
69
49.3
46
35.9
29.6
8.8
85.3 (0.08)
82.3 (1)
81.9 (0.25)
81.7 (1)
62 (0.5)
77 (2)
54.6 (0.5)
48.4 (1)
38 (2)
28.1
0
21.8
19.1
41
102
204
60
10.8
8.3
12.3
0
7.4
6.3
14.9 (4)
19.3 (4)
16.9
a
[Compound] ) 500 µM for all tests except IC50 determinations.
Ta ble 3. R-Methyl-pyrrolidine-5,5-trans-lactamsa
compd
R
inhib at 15 min
max % inhib (h)
inhib at 24 h
protease IC50 (µM)
29
30
31
32
33
39
38
43
42
41
COCH2OCOMe
COMe
CO2CHdCH2
SO2Me
SO2CHdCHPh
COCH2OH
COCH2OCH2PhOMe
SO2PhNHCOMe
COCH2Cl
96.6
97.7
73.8
48.8
43.9
96.1
90.3
48.9
10.0
3.2
96.6 (0.5)
97.9 (0.25)
96.5 (2)
0
8.2
13
110
48.9
22.1
90.7
0
17.9
71.0
60.9
0
59.7 (2)
90.7 (24)
97.0 (0.5)
97.3 (0.5)
74.6 (4)
63.4 (1)
9.2 (1)
200
32
CONHCH(CH3)2
a
[Compound] ) 500 µM for all tests except IC50 determinations.
maximum inhibition only after 24 h of preincubation.
Comparing the three templates (Table 4), potency is
seen to increase in the order â-methyl-5,5-trans-lactam
< desmethyl-5,5-trans-lactam < R-methyl-5,5-trans-
lactam for acetoxyacetyl, acetyl, and mesyl substituents
on the lactam nitrogen.
and thrombin, suggesting that selectivity may not be
too difficult to achieve.
Lon g Du r a tion of Action . Substitution on the
lactam nitrogen of our R-methyl-lactam template has
revealed three classes of inhibitors (Figure 1). These
include the acyl compounds 29 and 30 which reach their
maximum inhibition within e30 min and are turned
over by 24 h. The majority of our acyl-trans-lactams in
Tables 2 and 3 follow this pattern. The second group
33 (R ) SO2CHdCHPh; see Figure 1) is slower to reach
a maximum (1-24 h) and is turned over more slowly
(24-50 h). The third group includes 43 and 42 which
Selectivity in Com p a r ison to th e Ma m m a lia n
Ser in e P r otea ses. The best compounds from each
series were tested against thrombin and elastase (Table
5). While the R-methyl diastereomer is more active than
the â-methyl diastereomer for the viral enzyme, the
converse is true for the mammalian enzymes, elastase

Synthesis of Pyrrolidine-5,5-trans-lactams
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4457
% inhib @ 500 µM, IC (µM)
Ta ble 4. Comparison of trans-Lactam Templates
HCMV δAla protease inhib
COCH2OCOMe COMe
1800
R
CO2CHdCH2
SO2CHdCHPh
SO2Me
15%
46%
805
15%
-
-
28%
-
-
85%
97%
131
13
82%
98%
204
148
49%
74%
-
46%
44%
-
-
30%
49%
-
-
418
Ta ble 5. Protease Inhibitor Selectivity
covalent HCMV δAla protease/31 complex occurs during
a period of 30 min, with an Mav of 28 170 Da, a
difference of +344 Da with respect to the native pro-
tease. This is consistent with the acylation of the
enzyme by these trans-lactams. The enzyme gradually
turns over the compounds within a 21-h period. Thus
29 and 31 have been shown by ESI/MS studies to
acylate HCMV δAla protease in a reversible and cova-
lent fashion.
IC50 (µM)
compd
HCMV
thrombin
elastase
17, R1 ) â-Me
22, R1 ) H
29, R1 ) R-Me
805
131
13
24.2
6.2
0.71
7.58
9.08
Con clu sion s
>100
Mechanism-based inhibitors of HCMV protease have
been designed based on the novel pyrrolidine-5,5-trans-
lactam ring system. New synthetic routes to three of
these pyrrolidine-5,5-trans-lactam templates have been
developed from 2,4-diaminobutyric acid. The â-methyl
template has been synthesized in 8 stages in 13% yield,
the desmethyl template in 7 stages in 10% yield, and
the R-methyl template in 10 stages in 5% yield. The key
intermediate pyrrolidine 5 for these templates has been
synthesized in 32% yield in 5 stages from 2,4-diamino-
butyric acid.
The activity against HCMV δAla protease is the
greatest in the R-methyl series, and the best compound
is the acetoxyacetyl derivative 29 with an IC50 ) 13 µM.
Activity decreases on moving from the R-methyl to the
desmethyl to the â-methyl series. This selectivity is the
opposite of that observed for the elastase and thrombin
enzymes. For a range of lactam nitrogen substituents,
the general trend in activity against HCMV δAla
protease has been found to be acyl > ester > sulfonyl >
carbamate. This is in line with the electron-withdrawing
ability of the trigonal (sp2) substituents but not the
tetrahedral (sp3) sulfone, which indicates that the
latter’s stereochemistry is less favored at this position.
ESI/MS studies of the interaction of HCMV δAla
protease with the trans-lactams 29 and 31 have shown
that these inhibitors bind covalently and reversibly and
acylate HCMV δAla protease in a similar way, which
is consistent with acylation of HCMV δAla protease at
the active site nucleophile Ser 132.
reach a maximum inhibition in 4 and 1 h, respectively,
and both maintain that for 48 h. It is noteworthy that
both of the long-duration lactams 33 and 43 are more
sterically hindered than the carbonyl derivatives in the
first group because of the bulky tetrahedral sulfur on
the lactam nitrogen present in these sulfonyl deriva-
tives. This hinders approach of the catalytic serine,
which is shown by the longer time they take to reach
maximum inhibition (24 and 4 h, respectively) and
likewise hinders hydrolysis of the acylserine product,
which accounts for their longer duration of action. In
contrast the long duration of action of the halocarbonyl
derivative 42 is probably due to the alkylation of the
protease by this reactive functionality.
MS Ch a r a cter iza tion of th e Acyla tion of δAla
HCMV P r otease by P yr r olidin e r-Meth yl-5,5-tr a n s-
la cta m s. To investigate the mechanism of action of
these trans-lactams, the interaction of HCMV δAla
protease and inhibitors 29 and 31 has been studied by
liquid chromatography (LC) and electrospray ionization
mass spectroscopy (ESI/MS). Analysis of complexes
formed between HCMV δAla protease and the inhibitors
was conducted over a time course, enabling an assess-
ment of the speed and duration of the covalent modifi-
cation of the enzyme. Mass spectra were recorded after
incubations of 3 min and 0.5, 3, and 21 h (Chart 1). The
average molecular weight (Mav) of the unmodified
HCMV δAla protease was determined as 27 826 ( 2 Da.
The Mav’s of the complexes formed were consistent with
the addition of the complete inhibitor molecule to the
enzyme.
Exp er im en ta l Section
Gen er a l P r oced u r es. Melting points were obtained using
an Electrothermal digital melting point apparatus and are
uncorrected. All purifications by flash chromatography were
performed using Kieselgel 60, Merck 9385 silica gel. Monitor-
ing of reactions by TLC used Merck 60 F254 silica gel glass
backed plates (5 × 10 cm), eluted with mixtures of ethyl
This study indicates the maximum formation of a
covalent HCMV δAla protease/29 complex during a
period of 3 min, with an Mav of 28 200 Da, a difference
of +374 Da with respect to the native protease (Mav
)
27 826 Da). While for 31 the maximum formation of a

4458 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Borthwick et al.
F igu r e 1. Protease inhibition with respect to preincubation duration.
Ch a r t 1
acetate and cyclohexane, and visualized by UV light, followed
by heating with aqueous phosphomolybdic acid. Analytical
HPLC was run on a Hewlett-Packard 1090 HPLC instrument,
equipped with an Intersil M column ODS2. Standard condi-
tions were eluent system A (H2O, 0.1% H3PO4) and system B
(95% MeCN/H2O, 0.1% H3PO4): gradient 0% B 2 min, 0-100%
B 40 min, 100% B 10 min; flow rate ) 1 mL/min, λ ) 215 nm.
Retention times (tR) are given in minutes. LCMS was run on
a Hewlett-Packard 1050 instrument coupled with a Micromass
Platform II equipped with a Supelco ABZplus column. Stan-
dard conditions were eluent system A (H2O, 0.1% formic acid,
10 mmol ammonium acetate) and system B (MeCN, 0.05%
formic acid): gradient 100% A 0.7 min, 100% A-100% B 3.5
min, 100% B 3.5 min, 100-0% B 0.3 min; flow rate ) 1 mL/
sodium hydroxide solution (218 mL, 218 mmol) and a suspen-
sion of copper(II) acetate monohydrate (11.95 g, 59.83 mmol)
in water (135 mL) was added. The deep blue solution was
stirred at ca. 70 °C for 1.75 h before being allowed to cool to
room temperature. Then solid potassium hydrogen carbonate
was added to the solution to pH 7.4 and the mixture filtered.
The blue solution was cooled in an ice/water bath and diluted
with dioxan (400 mL). Benzyl chloroformate (18.65 mL, 130.6
mmol) was added to the stirred, cooled solution immediately
followed by 1 M aqueous sodium hydroxide (110 mL). The
mixture was stirred in an ice/water bath for 20 min and then
stirred at room temperature for 1 h before the precipitate was
collected by filtration, and then washed sequentially with
water, ethanol and diethyl ether and dried in vacuo to afford
the copper complex as a blue solid. Ethylenediaminetetraacetic
acid (12.58 g, 43.04 mmol) was suspended in 0.33 M hydro-
chloric acid (522 mL, 172 mmol) at room temperature. The
copper complex (24.4 g, 43.02 mmol) was added portionwise
to the vigorously stirred mixture over 30 min. After stirring
for another 1.5 h, 4 M aqueous sodium hydroxide was added
portionwise (over a period of 1 h) to the stirred mixture until
the mixture was at pH 4-5. Then after a further 30 min the
solid was collected by filtration, washed with water and dried,
in vacuo, for approximately 1 h at room temperature to afford
γ-Cbz-diaminobutyric acid, which was used without further
purification. The γ-Cbz-diaminobutyric acid was suspended in
1 M aqueous sodium hydroxide (120 mL, 120 mmol) and a
solution of di-tert-butyl dicarbonate (26.19 g, 120 mmol) in
dioxan (200 mL) was added. The pH of the reaction mixture
was maintained at pH 8 with the addition of 1 M aqueous
sodium hydroxide. The mixture was stirred at room temper-
min. All NMR spectra were run on
a Bruker 250-MHz
instrument generally as solutions in CDCl3 unless otherwise
stated. IR spectra were recorded on a Bio-rad FTS7 spectrom-
eter from thin films on NaCl plates, a KBr mix or solutions in
the solvent specified. Mass spectra were run on an Hewlett-
Packard electrospray 5989B instrument. Final organic solu-
tions were dried over MgSO4 before filtration and evaporation
using a Buchi rotavapor. Ambient temperature was 20 °C and
all compounds were produced as racemic mixtures. All solvents
used were Fisons analytical reagents except for pentane
(Aldrich Chemical Co.) and anhydrous THF (Fluka sureseal).
All other reagents were usually obtained from Aldrich, Fluka
or Lancaster. Elemental microanalyses were determined by
the Microanalytical Laboratory, GlaxoWellcome, Stevenage.
4-Ben zyloxycar bon ylam in o-2-ter t-bu toxycar bon ylam i-
n o-bu tyr ic Acid (1). d,l-2,4-Diaminobutyric acid dihydro-
chloride (20.78 g, 108.0 mmol) was dissolved in 1 M aqueous

Synthesis of Pyrrolidine-5,5-trans-lactams
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4459
ature for 24 h and the reaction monitored by TLC (n-butanol-
acetic acid-water, 4:1:1); if the reaction was incomplete
additional di-tert-butyl dicarbonate (3.76 g, 17.23 mmol) in
dioxan (16 mL) was added and the mixture stirred at room
temperature for a further 24 h. Then the reaction mixture was
mixed with ethyl acetate (250 mL) and acidified with 2 M
hydrochloric acid to pH 2. The phases were separated and the
aqueous one extracted with ethyl acetate (3 × 200 mL). The
organic phases were combined, washed with saturated brine
(2 × 150 mL) and the solvents then removed by evaporation.
The residue was treated with 1 M aqueous sodium hydroxide
solution (120 mL, 120 mmol), diluted with water (400 mL) and
washed with diethyl ether (3×, 300 mL). Then the aqueous
phase was mixed with ethyl acetate (200 mL) and acidified to
pH 1 using 2 M hydrochloric acid, the organic layer was
separated and the aqueous layer extracted with ethyl acetate
(2 × 200 mL). The combined ethyl acetate phase was dried,
filtered, evaporated and dried in vacuo at room temperature
to afford 1 as a pale orange foam: 1H NMR (CDCl3) δ 7.35 (s,
5H, C6H5), 6.2-6.4,5.6,5.4 (m, 2H, 2NH), 5.0-5.2 (m, 2H,
OCH2), 4.3-4.5 (m, 1H, NCHCO2H), 3.4-3.6, 3.0-3.4 (m, 2H,
CH2N), 2.0-2.2, 1.8-2.0 (m, 2H, CHCH2CH2), 1.45 (s, 9H,
t-BuO); MS (thermospray) m/z 353 (MH+); HPLC 99% (tR 23.7
min). Anal. (C17H24N2O6) C, H, N.
1.4-1.6 (m, 2H, CHCH2CH2), 1.5,1.45 (2s, 18H, 2t-BuO); HPLC
99.3% (tR 32.3 min). Anal. (C23H34N2O6) C, H, N.
(E)-6-Ben zyloxyca r bon yla m in o-4-ter t-bu toxyca r bon yl-
a m in o-h ex-2-en oic Acid Eth yl Ester (4). Compound 2 (12.6
g) was reacted with oxalyl chloride/dimethyl sulfoxide followed
by (ethoxycarbonylmethylene)triphenylphosphorane as de-
scribed for 3 to give 4 (10.71 g, 71%) as an oil: 1H NMR (CDCl3)
δ 7.40-7.30 (m, 5H), 6.86 (dd, 1H), 5.93 (dd, 1H), 5.42-5.28
(br, 1H), 5.12 (ABq, 2H), 4.72-4.60 (m, 1H), 4.50-4.32 (m,
1H), 4.19 (q, 2H), 3.60-3.30 (m, 1H), 3.15-2.98 (m, 1H), 2.00-
1.80 (m, 1H), 1.65-1.50 (m, 1H), 1.45 (s, 9H) and 1.28 (t, 3H);
TLC Rf 0.45 (2:3 ethyl acetate-cyclohexane); HPLC 98.7% (tR
11.25 min). Anal. (C21H30N2O6) C, H, N.
cis-2-Oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1,4-d ica r -
boxylic Acid 4-Ben zyl Ester 1-ter t-Bu tyl Ester (7) a n d
tr a n s-3-ter t-Bu toxyca r bon yla m in o-2-ter t-bu toxyca r bon -
ylm eth yl-p yr r olid in e-1-ca r boxylic Acid Ben zyl Ester (5).
To a solution of 3 (902 mg, 2.07 mmol) in anhydrous toluene
(12 mL), stirred under nitrogen at 21 °C, was slowly added 1
M LHMDS solution in hexane (1.03 mL, 1.03 mmol). The
yellow solution was stirred for 1.5 h, poured into saturated
aqueous ammonium chloride solution (50 mL) and the mixture
extracted twice with ethyl acetate (50 mL and 25 mL). The
combined organic phase was washed with saturated brine (50
mL), dried and evaporated to give a yellow oil (859 mg). The
crude oil was purified by flash chromatography eluting with
cyclohexane-ethyl acetate (4:1) to give 5 (557 mg, 62%) as a
white solid: mp 125-126 °C; IR (Nujol) νmax 3303, 1703, 1463
(3-Be n zyloxyca r b on yla m in o-1-h yd r oxym e t h yl-p r o-
p yl)ca r ba m ic Acid ter t-Bu tyl Ester (2). A solution of acid
1 (28.03 g, 79.54 mmol) in tetrahydrofuran (250 mL) was
cooled to -10 °C under nitrogen and 4-methylmorpholine (8.8
mL, 80.04 mmol) was added followed by the addition of ethyl
chloroformate (7.65 mL, 80.01 mmol) over 2 min. After stirring
for 8 min, a freshly prepared solution of sodium borohydride
(9.03 g, 241.6 mmol) in water (70 mL) was added dropwise
over a period of 12 min at -15 °C. After a further 5 min the
mixture was poured into water (1.5 L) and stirred for another
10 min at room temperature. The mixture was extracted with
ethyl acetate (3 × 500 mL) and the combined organic extracts
washed sequentially with 1 M hydrochloric acid (500 mL),
water (500 mL), saturated solution of sodium hydrogen
carbonate (500 mL) and saturated brine (500 mL), then dried,
filtered and evaporated. The crude residue, a colorless syrup,
was purified by flash chromatography using cyclohexane-
ethyl acetate (3:2) as eluent, to give 2 as a white solid (21.15
1
cm-1; H NMR (400 MHz, CDCl3) δ 7.40-7.28 (m, 5H, C6H5),
5.18-5.10 (m, 2H, PhCH2), 4.76-4.61 (broad signal, 1H, broad
signal, BocNH), 4.15-4.01 (m, 1H, CHNHBoc), 4.00-3.94 (m,
1H, CbzNCHCH2), 3.60-3.42 (m, 2H, CbzNCH2), 2.88 and 2.69
(2d, 1H, J ) 15.5 Hz, CHHCO2But), 2.40-2.30 (dd, 1H, J )
15.5, 9.5 Hz, CHHCO2But), 2.23-2.11 (m, 1H, CbzNCH2CHH),
1.94-1.82 (broad signal, 1H, CbzNCH2CHH), 1.44 (s, 18H, 2
× C(CH3)2); TLC Rf 0.38 (2:1 cyclohexane-EtOAc). Anal.
(C23H34N2O6) C, H, N.
Further elution with cyclohexane-ethyl acetate (2:1) gave
the cis-lactam 7 (97.7 mg, 13%): IR (CHBr2) νmax 1783, 1743,
1698 and 1419 cm-1; 1H NMR (DMSO-d6) δ 7.36 (s, 5H, C6H5),
5.08 (ABq, 2H, J ) 12.4 Hz, PhCH2), 4.58 (m, 1H, H-3a), 4.27
(m, 1H, H-6a), and 3.54 (m, 1H, H-2), 3.32 (m, 1H, H-2), 2.84
(m, 1H, H-6) and 2.45 (1H, m, H-6), 2.12 (m, 2H, H-3) 1.45 (s,
9H, C(CH3)2); 13C NMR (CDCl3) δ 172.6, 154.4, 249.7, 136.4,
128.6, 128.3, 128.2, 83.6, 67.4, 61.5, 53.0, 44.1, 39.1, 31.2, 28.2,
28.1, 27.9; MS (thermospray) m/z 261 (MH+ - Boc); TLC Rf
0.15 (2:1 cyclohexane-EtOAc). Anal. (C19H24N2O5) C, H, N.
g, 78%): IR (CHBr3) νmax 3431, 2973, 1704 cm-1 1H NMR
;
(CDCl3) δ 7.35 (s, 5H, C6H5), 5.55, 4.95 (m, 2H, 2NH), 5.0-5.2
(m, 2H, OCH2), 3.5-3.8 (m, 3H, HOCH2CH), 3.4-3.6, 2.9-
3.2 (m, 2H, CH2N), 2.5 (t, 1H, HO), 1.5-1.8 (m, 2H, CHCH2-
CH2), 1.45 (s, 9H, t-BuO); HPLC 98.9% (tR 23.25 min). Anal.
(C17H26N2O5) C, H, N.
tr a n s-3-ter t-Bu toxyca r bon yla m in o-2-eth oxyca r bon yl-
m eth yl-p yr r olid in e-1-ca r boxylic Acid Ben zyl Ester (6).
Compound 4 (12.2 g) was reacted with tetramethylethylene-
diamine followed by LHMDS as described for 3 to give 6 (8.49
(E)-6-Ben zyloxyca r bon yla m in o-4-ter t-bu toxyca r bon yl-
a m in o-h ex-2-en oic Acid ter t-Bu tyl Ester (3). A solution of
dimethyl sulfoxide (12.83 mL, 0.18 mol) in dichloromethane
(240 mL) was cooled to -70 °C under nitrogen. Oxalyl chloride
(13.3 mL, 0.15 mol) was added dropwise (care: evolution of
gas) and the solution stirred for 15 min while maintaining the
temperature at -60 to -70 °C. A solution of the alcohol 2 (23.7
g, 0.07 mol) in dichloromethane (200 mL) was added over 25
min at -65 °C. The reaction mixture was then stirred for 20
min during which time the temperature rose to -52 °C. The
reaction was recooled to -70 °C prior to the addition of
triethylamine (102 mL, 0.7 mol) at a rate which maintained
the temperature below -45 °C (∼10 min, exothermic), followed
by the addition of (tert-butoxycarbonylmethylene)triphenyl-
phosphorane (184 mg, 0.49 mmol), in one portion. The reaction
mixture was allowed to warm to 0 °C and then poured into a
mixture of saturated brine (1 L) and diethyl ether (1 L). The
organic phase was separated, dried (MgSO4) and then con-
centrated under reduced pressure. The crude residue was
purified by flash chromatography using (4:1f2:1), cyclohex-
ane-ethyl acetate as eluent to give 3 (27.3 g, 90%) as a white
1
g, 70%) as a white solid: mp 99-100 °C; H NMR (400 MHz,
CDCl3) δ 7.38-7.28 (m, 5H, C6H5), 5.17-5.10 (m, 2H, PhCH2),
4.75-4.60 (broad signal, 1H, BocNH), 4.18-3.97 (m, 4H,
CHNHBoc plus CbzNCHCH2 plus CO2CH2Me), 3.64-3.43 (m,
2H, CbzNCH2), 2.88 and 2.72 (2d, 1H, J )15.3 Hz, CHHCO2But),
2.55-2.41(m,1H,CHHCO2Et),2.23-2.11(m,1H,CbzNCH2CHH),
1.91-1.81 (broad signal, 1H, CbzNCH2CHH), 1.43 (s, 9H,
C(CH3)3), 1.27-1.18 (m, 3H, CH2CH3); MS (thermospray) m/z
407.4 (MH+); TLC Rf 0.8 (1:1 cyclohexane-EtOAc). Anal.
(C21H30N2O6) C, H, N.
r el-(2R,3S)-3-ter t-Bu t oxyca r b on yla m in o-2-((1R)-ter t-
bu toxycar bon yl-eth yl)pyr r olidin e-1-car boxylic Acid Ben -
zyl Ester (8). To a solution of ester 5 (2.00 g, 4.60 mmol) in
dry tetrahydrofuran (8 mL), stirred at -78 °C under nitrogen
was added 1 M LHMDS solution in tetrahydrofuran (20.0 mL,
20.0 mmol). The reaction mixture was stirred at -78 °C for
25 min, and then hexamethylphosphoric triamide (5 mL) was
added. After 10 min, iodomethane (0.33 mL, 5.3 mmol) was
added. Additional iodomethane (0.16 mL, 2.57 mmol) was
added after a further 28 min. The reaction mixture was stirred
at -78 °C for a further 25 min, quenched with saturated
aqueous ammonium chloride (68 mL), warmed to room tem-
perature and extracted with ethyl acetate (4×, 35 mL). The
solid: mp 113-116 °C; IR (CHBr3) νmax 3432, 1707, 1506 cm-1
;
1H NMR (CDCl3) δ 7.35 (s, 5H, C6H5), 6.75 (dd, J ) 15 Hz, 5
Hz, 1H, CHCHCH), 5.85 (dd, J ) 15 Hz, 1.2 Hz, 1H,
O2CCHCH), 5.4,4.6 (br, 2H, 2NH), 5.0-5.2 (m, 2H, OCH2), 4.4
(m, 1H, CHCHNH), 3.4-3.6, 2.9-3.1 (m, 2H, CH2N), 1.8-2.0,

4460 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Borthwick et al.
combined organic phase was dried, filtered and evaporated.
The crude residue was purified by flash column chromatog-
raphy eluting with 6:1 cyclohexane-EtOAc to yield 8 (1.42 g;
68%): mp 115-117 °C; IR (CHBr3) 3430, 1707 cm-1; 1H NMR
(CDCl3) δ 7.35 (m, 5H, C6H5), 5.16 (s, 2H, PhCH2), 4.54 (bs,
1H, NHBoc), 4.17 (m, 1H, CHN), 3.88 (d, J ) 7.0 Hz, 1H,
CHN), 3.60 (m, 1H, CHHNCbz), 3.39 (m, 1H, CHHNCbz), 2.73
(bd, 1H, COCHMe), 2.16 (m, 1H, CH2CH2CHNBoc), 1.83 (bs,
1H, CH2CH2CHNBoc), 1.42 (s, 18H, 2 x C(CH3)2), 1.17 (bs, 3H,
CH3); 13C NMR (CDCl3) δ 173.9, 155.6, 155.1, 128.9, 128.4,
67.3, 67.1, 66.5, 54.2, 53.3, 45.0, 43.6, 42.9, 30.9, 30.1, 28.7,
28.3, 14.4; MS (thermospray) m/z 449 (MH+). Anal. (C24H36N2O6)
C, H, N. Also eluted was the reverse Michael product (0.35 g,
17%). Spectral and chromatographic properties were identical
to those for 3.
After stirring for 35 min the solution was evaporated and the
resulting oil was dissolved in ethyl acetate (400 mL) and
washed with 2 M sodium hydroxide (3 × 200 mL), water (250
mL), brine (200 mL), dried (MgSO4) and evaporated and then
left under high vacuum for 24 h to give 12 as a golden oil (41.68
g, 92%): IR (KBr) νmax 3370, 1729, 1702 cm-1; 1H NMR (CDCl3)
δ 7.38 (m, 5H, C6H5), 5.14 (s, 2H, PhCH2), 4.12 (m, 2H, CH2-
CH3), 3.90 (br d, J ) 9.4 Hz, 1H), 3.65 (m, 1H) and 3.48
(m, 2H), (CH2CHNH2, CH2NCbz and CHNCbz), 2.98 (d, J )
16.3 Hz, 0.5H) and 2.77 (d, J ) 16.3 Hz, 0.5H) (EtOCOCHH),
2.31 (dd, J ) 10.0, 15.7 Hz, 1H, EtOCOCHH) 2.08 (m, 1H,
CH2CH2CHN2), 1.68 (m, 1H, CH2CH2CHNH2), 1.41 (s, 2H,
NH2), 1.26 (m, 3H, CH3); MS (Thermospray), m/z 307 (MH+),
613 (2M + H+); HPLC 89% (tR 14.27 min). Anal. (C16H22N2O4)
C, H, N.
r el-(2R,3S)-3-Am in o-2-((1R)-ca r boxyeth yl)p yr r olid in e-
1-ca r boxylic Acid Ben zyl Ester (9). To 8 (159 mg, 0.35
mmol) were added trifluoroacetic acid (1 mL) and water (0.04
mL), and the resulting solution stirred at room temperature
under nitrogen for 2 h. The reaction mixture was poured into
diisopropyl ether (50 mL) and a white solid was precipitated.
The supernatant liquid was decanted off and the solid dis-
solved in ethyl acetate (3 mL) and evaporated under reduced
pressure to give 9 as a white, hygroscopic foam (110 mg;
71%): 1H NMR (CDCl3) δ 8.13 (bs, 2H, NH2), 7.27 (s, 5H, C6H5),
5.15 (m, 1H, PhCH2), 4.92 (m, 1H, PhCH2), 4.44 (m, 1H,
CHNH2), 3.80 (m, 2H, CHHNCbz and CHNCbz), 3.37 (m, 1H
CHHNCbz), 2.45 (m, 1H) and 2.20 (m, 2H) (CH2CH2CHNBoc
and COCHMe), 1.12 (m, 3H, CH3); MS (thermospray) m/z 293
(MH+). Anal. (C24H36N2O6‚0.1EtOAc‚1.1TFA‚0.6H2O) C, H, N,
F.
tr a n s-5-Oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r -
boxylic Acid Ben zyl Ester (13). To the amino ester 12 (1.25
g, 4.1 mmol) in dry tetrahydrofuran (32 mL) under nitrogen
in an ice-salt bath was added dropwise 1 M ButMgCl solution
in tetrahydrofuran (13.1 mL, 13.1 mmol) over 15 min, keeping
the temperature <1 °C. The mixture was stirred at 0 °C for 1
h
and warmed to room temperature over 45 min, then
quenched with saturated aqueous ammonium chloride (30 mL)
while cooling in an ice bath. The phases were separated and
the aqueous phase diluted with water (30 mL) and extracted
with ethyl acetate (3 × 20 mL). The combined organic phase
was washed with water (30 mL) and brine (30 mL), dried and
evaporated to give the title compound as a crude, white solid.
This residue was purified by flash column chromatography
eluting with ethyl acetate to give the lactam 13 (833 mg, 78%)
as a white solid: mp 157-159 °C; IR (KBr) νmax 3277, 1699,
1690 cm-1; 1H NMR (CDCl3) δ 7.35 (m, 5H, C6H5), 5.99 (s, 1H,
NH), 5.12 (ABq, J ) 12.5 Hz, 2H, PhCH2), 3.87 (dd, 1H, J )
10.4 Hz, J ) 12.4 Hz, NCHHCH2), 3.71 (m, 1H, NCHHCH2),
3.34 (m, 2H, NCHCH2 and NCHCH2CO), 2.81 (m, 1H, CHH-
CO), 2.45 (m, 1H, CHHCO), 2.23 (m, 1H, NCH2CHH), 1.87
(m, 1H, NCH2CHH); 13C NMR (CDCl3) δ 179.5, 155.8, 136.2,
128.6, 128.2, 128.0, 67.2, 63.4, 60.5, 49.3, 39.6, 27.7; MS
(thermospray) m/z 261 (MH+), 278 (MNH4+); HPLC 99.5% (tR
18.56 min). Anal. (C14H16N2O3‚0.05CH2Cl2) C, H, N.
Alter n a tive P r ep a r a tion of 13. To a solution of the amino
acid 11 (35 mg, 0.088 mmol) in dichloromethane (12 mL),
stirred under nitrogen at room temperature, were added
triethylamine (65 µL, 0.44 mmol) and then 2-chloro-1-meth-
ylpyridinium iodide (79 mg, 0.308 mmol). The reaction mixture
was stirred for 66 h and then reduced in vacuo. The resulting
yellow oil was purified by flash column chromatography
eluting with ethyl acetate to yield 13 (9 mg, 41%), identical in
all respects with compound 13 prepared above.
r el-(3a S,6R,6a R)-6-Met h yl-5-oxo-h exa h yd r o-p yr r olo-
[3,2-b]p yr r ole-1-ca r boxylic Acid Ben zyl Ester (10). To a
solution of the amino acid 9 (302 mg, 0.714 mmol) in anhy-
drous DMF (73 mL), stirred at room temperature under
nitrogen, were added triethylamine (0.54 mL, 3.874 mmol) and
then diphenyl phosphorazidate (0.330 mL, 1.53 mmol). The
reaction mixture was stirred for 23 h, and then evaporated.
The crude residue was purified by flash column chromatog-
raphy eluting with ethyl acetate to yield 10 (128 mg, 65%) as
a white solid: mp 163-165 °C; IR (KBr) νmax 3200, 1704, 1702
1
cm-1; H NMR (CDCl3) δ 7.3-7.4 (s, 5H, C6H5), 6.08 (br, 1H,
NH), 5.25 (m, 1H, CHCH3), 5.14 (m, 2H; PhCH2), 3.92-3.68
(m, 2H, NCHHCH2 and NCHCH2), 3.28 (m, 1H, NCHHCH2),
3.03 (2d, J ) 10 Hz, 1H, NCHCHMe), 2.52 (m, 1H, CHMe),
2.21 (2t, J ) 6 Hz, 1H, NCH2CHH) and 1.80 (2t, J ) 10 Hz,
1H, NCH2CHH), 1.55-1.24 (br, 3H, Me); NOEs detected from
NCH2CHH toNCH2CHH,NCH,NCHH;NCH2CHH toNCH2CHH,
NCH, NCH, NH; CHMeCO to NCH; NCH to NCH2CHH; NCH
to NH, NCH2CHH, CHMeCO; NCHH to NCHH, NCH; NCHH
to NCHH, NCH2CHH; NH to NCH, NCH; COSY H1 NMR 2D
spectra as expected; 13C NMR (CDCl3) δ 154.6, 128.1, 127.8,
127.7, 70.1, 66.7, 58.1, 49.1, 44.5, 26.9, 13.4; MS (thermospray)
m/z 292 (MNH4+), 275 (MH+). Anal. (C15H18N2O3) C, H, N.
tr a n s-2-Oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1,4-d i-
ca r boxylic Acid 4-Ben zyl Ester 1-ter t-Bu tyl Ester (14).
To a solution of 13 (509 mg, 1.96 mmol) in tetrahydrofuran
(26 mL), stirred at -78 °C under nitrogen, was added 1 M
LHMDS solution in tetrahydrofuran (2.35 mL, 2.35 mmol). The
reaction mixture was stirred at -78 °C for 6 min and then
warmed rapidly to 0 °C. After a further 15 min, the reaction
mixture was cooled -78 °C and a solution of di-tert-butyl
dicarbonate (1.22 g, 5.11 mmol) in tetrahydrofuran (7 mL)
added. After 20 min, the reaction was quenched with saturated
aqueous ammonium chloride (85 mL), warmed to room tem-
perature and extracted with ethyl acetate (2 × 150 mL). The
combined organic phase was dried, filtered and evaporated.
The crude residue was purified by flash column chromatog-
raphy eluting with ethyl acetate-cyclohexane (3:7) to yield 14
(563 mg, 80%) as a white solid: mp 109-111 °C; IR (CDCl3)
tr a n s-3-Am in o-2-ca r boxym eth yl-p yr r olid in e-1-ca r box-
ylic Acid Ben zyl Ester (11). A solution of 5 (4.34 g, 10 mmol)
in 24/1 trifluoroacetic acid/water (25 mL) was stirred at room
temperature for 75 min and then poured into diisopropyl ether
(500 mL). The mixture was stirred at room temperature for a
further 45 min and the precipitate filtered, washed with
diisopropyl ether (150 mL) dissolved in methanol (100 mL) and
evaporated. The residue was dried in vacuo at room temper-
ature overnight to give a pale yellow foam (3.51 g, 89%): IR
(KBr) νmax 1712, 1671 cm-1; 1H NMR (CDCl3) δ 7.98 (bm, 6H,
C6H5 and OH), 5.02 (bm, 2H, PhCH2), 4.28 (m, 1H, CHNH2),
3.79 (m, 1H, CHCH2), 3.50 (m, 1H, NCHHCH2), 3.33 (m, 1H,
NCHHCH2), 2.98 (bd, 1H) and 2.18 (m, 3H) (NCH2CH2 and
CH2CO); MS (thermospray) m/z 279 (MH+); HPLC 95.9% (tR
11.40 min), 2.6% (tR 17.75 min). Anal. (C14H18N2O4‚1.0TFA‚
0.1MeOH‚0.1H2O) C, H, N, F.
1
nmax 1794, 1766, 1713 cm-1; H NMR (CDCl3) δ 7.36 (s, 5H,
C6H5), 5.12 (ABq, J ) 12.5 Hz, PhCH2), 3.85 (m, 1H, NCH-
HCH2), 3.73 (m, 1H, NCHHCH2), 3.47 (m, 1H, NCHCH2), 3.32
(m, 1H, NCHCHMe), 2.93 (m, 1H, CHHCO), 2.53 (m, 2H,
NCH2CHH and CHHCO), 2.02 (m, 1H, NCH2CHH), 1.53 (s,
9H, C(CH3)3); 13C NMR (CDCl3) δ 173.2, 134.7, 128.0, 127.7,
127.5, 82.8, 66.8, 62.8, 59.5, 48.1, 40.1, 28.2, 27.4; MS (ther-
mospray) m/z 378 (MNH4+), 361 (MH+); HPLC 99.74% (tR 27.65
min). Anal. (C19H24N2O5) C, H, N.
tr a n s-3-Am in o-2-eth oxyca r bon ylm eth yl-p yr r olid in e-1-
ca r boxylic Acid Ben zyl Ester (12). To the Boc-protected
compound 6 (60 g, 1 equiv, 0.148 mol) was added trifluoroacetic
acid (557 g, 376 mL, 33 equiv, 4.88 mol) at room temperature.

Synthesis of Pyrrolidine-5,5-trans-lactams
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4461
r el-(3S,3a R,6a S)-3-Met h yl-2-oxo-h exa h yd r o-p yr r olo-
[3,2-b]pyr r ole-1,4-dicar boxylic Acid 4-Ben zyl Ester 1-ter t-
Bu tyl Ester (15). To a solution of 14 (40.0 g, 110 mmol) in
tetrahydrofuran (500 mL), stirred at -78 °C under nitrogen,
was added 1 M LHMDS solution in tetrahydrofuran (143 mL,
143 mmol) keeping the temperature below -68 °C. The
reaction mixture was stirred at -78 °C for 15 min, and then
iodomethane (69 mL, 1.1 mol) was added dropwise. After 45
min, the reaction was quenched with saturated aqueous
ammonium chloride (500 mL) and warmed to room tempera-
ture. Water (300 mL) was added and then the aqueous phase
was extracted with ethyl acetate and the combined organic
phase was washed with water, brine, dried (MgSO4) and
evaporated to give a red-brown oil. The crude residue was
purified by flash column chromatography eluting with ethyl
acetate-cyclohexane (3:7) to yield 15 (28.6 g, 69%) as a yellow
foam: mp 89-91 °C; IR (KBr diffuse reflectance) νmax 1790,
mL), the organic phase was washed with saturated ammonium
chloride solution (20 mL) and the combined aqueous phase was
extracted with ethyl acetate (25 mL). The combined organic
phase was washed with water (25 mL) and then with saturated
brine (25 mL), dried and evaporated to give an oil which was
purified by flash column chromatography eluting with cyclo-
hexane-ethyl acetate (4:1) to give the title compound 17 (429
mg, 57%) as a solid: mp 107-109 °C. A sample was crystal-
lized from 2-propanol to give needles: mp 110-111 °C; IR
(CDCl3) νmax 1755, 1747, 1721, 1713, 1698 cm-1 1 NMR (CDCl3)
;
δ 7.37 (s, 5H, C6H5), 5.15 (s, 2H, CH2OAc), 5.09 (q, J ) 18 Hz,
2H, PhCH2), 3.7-3.9 (m, 2H, NCH2CH2), 3.48 (m, 1H,
NCHCH2), 3.07 (t, J ) 11 Hz, 1H, NCHCHMe), 2.70 (m, 2H,
NCH2CHH and CHMe), 1.95 (2t, J ) 11 Hz, 1H, NCH2CHH),
2.19 (s, 3H, OAc), 1.46 (br, 3H, CH3); TLC Rf 0.24 (cyclohex-
ane-ethyl acetate, 2:1). Anal. (C19H22N2O6) C, H, N.
P r ep a r a tion of 18-33, 35, 36, 38, 42, a n d 43. Using
essentially the same procedure as for the preparation of 17,
the following compounds listed in Scheme 5 were prepared
from 10, 13, or 16.
1
1763, 1717 cm-1; H NMR (CDCl3) δ 7.35 (s, 5H, C6H5), 5.13
(m, 2H, PhCH2), 3.88 (m, 1H, NCHHCH2), 3.70 (m, 2H,
NCHHCH2 and NCHCH2) and 3.45 (dd, J 3a,6a ) 11 Hz, J 6,6a
)
6.6 Hz, 1H, NCHCHMe), 3.07 (br m, 1H, CHMe), 2.51 (m, 1H,
NCH2CHH), 2.01 (m, 1H, NCH2CHH), 1.54 (s, 9H, C(CH3)3),
1.12 (bs, 3H, CH3); NOE Me f H6 (6%), Me f H3a (6%); 13C
NMR (CDCl3) δ 178.0, 156.1, 153.7, 129.1, 128.8, 128.6, 83.8,
68.0, 63.9, 59.2, 49.5, 43.7, 29.3, 28.4, 8.4; MS (thermospray)
m/z 375 (MH+); HPLC 97% (tR 28.75 min). Anal. (C20H26N2O5)
C, H, N.
r el-(3a S,6R,6a R)-4-Acet yl-6-m et h yl-5-oxo-h exa h yd r o-
p yr r olo[3,2-b]p yr r ole-1-ca r b oxylic a cid b en zyl est er
(18): derived from 10 and acetyl chloride to give 18 as a white
1
amorphous solid (68%); IR (CHBr3) νmax 1756, 1708 cm-1; H
NMR (CDCl3) δ 7.33 (s, 5H, C6H5); 5.15 (s, 2H, PhCH2), 3.80
(m, 2H, NCH2CH2), 3.45 (m, 1H, NCHCH2), 3.00 (t, J ) 11
Hz, 1H, NCHCHMe), 2.70 (m, 2H, NCH2CHH and CHMe),
2.47 (s, 3H, COCH3), 1.90 (2t, J ) 11 Hz, 1H, NCH2CHH),
1.42 (br, 3H, CH3); MS (thermospray) m/z 317 (MH+); TLC Rf
0.35, (cyclohexane-ethyl acetate, 7:3). Anal. (C17H20N2O4‚
0.25H2O) C, H, N.
Alter n a tive Con d ition s a t High er Tem p er a tu r e in th e
P r esen ce of DMP U. To a solution of 14 (180 mg, 0.5 mmol)
in tetrahydrofuran (2 mL) were added DMPU (400 µL) followed
by iodomethane (67 µL, 1 mmol). The mixture was stirred
under nitrogen, cooled to -20 °C and 1 M LHMDS solution in
tetrahydrofuran (0.55 µL, 0.55 µmol) was added. The mixture
was stirred at -20 °C for 10 min, then quenched at this
temperature by the addition of saturated aqueous ammonium
chloride (5 mL) and allowed to warm to room temperature.
The resulting mixture was partitioned between ethyl acetate
and water, the organic phase separated, dried (MgSO4) and
evaporated. The residue was purified by flash column chro-
matography eluting with ethyl acetate-cyclohexane (3:7) to
give a yellow foam (133 mg, 71%) identical in all respects with
15 prepared above.
r el-(3R,3a R,6a S)-3-Met h yl-2-oxo-h exa h yd r o-p yr r olo-
[3,2-b]p yr r ole-1,4-d ica r b oxylic a cid 4-b en zyl est er 1-
m eth yl ester (19): derived from 10 and methyl chloroformate
to give 19 (77%) as a white foam; IR (KBr) νmax 1800, 1766,
1718, 1708, 1702 cm-1; 1H NMR (CDCl3) δ 7.35 (s, 5H, C6H5),
5.1 (s, 2H, PhCH2), 3.9 (s, 3H, CO2Me), 3.9-3.7 (m, 2H, NCH2-
CH2), 3.5 (m, 1H, NCHCH2), 3.0 (t, J ) 11 Hz, 1H, NCH-
CHMe), 2.6 (m, 2H, NCH2CHH and CHMe), 2.0 (m, 1H,
NCH2CHH); MS(thermospray) m/z 350 (MNH4+), 333 (MH+);
HRMS calcd for
C
19H23N2O6 (MH+) 375.155612, found
375.155523; HPLC 98.5% (tR 24.68 min).
r el-(3a S,6S,6a R)-6-Met h yl-5-oxo-h exa h yd r o-p yr r olo-
[3,2-b]p yr r ole-1-ca r boxylic Acid Ben zyl Ester (16). To 15
(475 mg, 0.127 mmol) was added trifluoroacetic acid (1.6 mL),
and the resulting solution stirred under nitrogen at room
temperature for 35 min. The reaction mixture was then diluted
with toluene (60 mL) and evaporated. The crude residue was
dissolved in dichloromethane-diethyl ether (1:1) (60 mL) and
evaporated and the entire procedure repeated. The crude
residue was purified by flash column chromatography eluting
with ethyl acetate to yield 16 (316 mg, 91%): mp 169-170
r el-(3a S,6R,6a R)-4-Met h a n esu lfon yl-6-m et h yl-5-oxo-
h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic a cid ben -
zyl ester (20): derived from 10 and methanesulfonyl chloride
to yield 20 (68%) as a white foam; IR (KBr) νmax 1756, 1702
cm-1; 1H NMR (CDCl3) δ 7.3 (s, 5H, C6H5), 5.1 (s, 2H, PhCH2),
3.9-3.7 (m, 2H, NCH2CH2), 3.6 (m, 1H, NCHCH2), 3.3 (s, 3H,
SO2CH3), 3.1 (t, J ) 11 Hz,1H, NCHCHMe), 2.8 (m, 1H,
CHMe), 2.6 (m, 1H, NCH2CHH), 2.0 (m, 1H, NCH2CHH), 1.5
(bs, 3H, CH3); MS (thermospray) m/z 370 (MNH4+), 353 (MH+);
HRMS calcd for
353.117038; HPLC 94.9% (tR 25.13 min).
C
16H21N2O5S (MH+) 353.117119, found
°C; IR (CDCl3) νmax 3275, 1710, 1698, 1683 cm-1 1H NMR
;
(CDCl3) δ 7.35 (s, 5H, C6H5), 6.99 (bs, 1H, NH), 5.12 (ABq, J
) 12.5 Hz, 2H, PhCH2); 3.78 (br m, 1H, NCHHCH2), 3.60 (m,
3H, NCHHCH2, NCHCH2 and NCHCHMe), 2.88 (br m, 1H,
CHMe), 2.21 (m, 1H, NCH2CHH), 1.85 (m, 1H, NCH2CHH),
1.08 (br s, 3H, CH3); 13C NMR (CDCl3) δ 183.1, 155.4, 135.9,
128.3, 127.9, 127.7,67.0, 66.4, 55.8, 49.3, 41.8, 27.6, 7.2; MS
(thermospray) m/z 549 (2M + H+), 275 (MH+); HPLC 98.13%
(tR 19.82 min), 1.2% (tR 18.51 min). Anal. (C15H18N2O3‚
0.01EtOAc) C, H, N.
r el -(3a S ,6R ,6a R )-4-Ac e t o x y a c e t y l-6-m e t h y l-5-o x o -
h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic Acid Ben -
zyl Ester (17). To a solution of the lactam 10 (548 mg, 2 mmol)
in anhydrous tetrahydrofuran (20 mL) cooled to -78 °C under
nitrogen was added 1 M LHMDS solution in tetrahydrofuran
(3 mL, 3 mmol) over ca. 2 min. The solution was stirred at
-78 °C for 8 min, then at 0 °C for 30 min and then recooled to
-78 °C. Acetoxyacetyl chloride (0.54 mL, 5 mmol) was added
dropwise keeping the temperature below -70 °C and the
solution was stirred at -78 °C for 1 h. Saturated ammonium
chloride solution (20 mL) was added and the cooling bath was
removed. The mixture was extracted with ethyl acetate (50
r el-(3aS,6R,6aR)-6-Meth yl-5-oxo-4-(2-ph en yleth en esu lfo-
n yl)-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic a cid
ben zyl ester (21): derived from 10 and â-styrenesulfonyl
chloride to give 21 (64%) as a white solid; mp 199-201 °C; IR
(KBr) νmax 1755, 1712 cm-1; 1H NMR (CDCl3) δ 7.43 (m, 10H,
2 × C6H5), 7.70, 7.00 (2d, J ) 15.0 Hz, J ) 15.0 Hz, 2H, HCd
CH), 5.12 (s, 2H, CH2Ph), 3.80 (m, 2H, NCH2CH2), 3.52 (m,
1H, NCHCH2), 3.14 (t, J ) 10 Hz,1H, NCHCHMe), 2.68 (bm,
1H, CHMe), 2.59 (m, 1H, NCH2CHH), 2.09 (m, 1H, NCH2-
CHH), 1.42 (b, 3H, CH3); MS (thermospray) m/z 458 (MNH4+);
HPLC 96.52% (tR 31.65 min). Anal. (C23H24N2O5S‚0.05EtOAc)
C, H, N, S.
r el-(3a S,6R,6a R)-4-[(4-Me t h oxyb e n zyloxy)a ce t yl]-6-
m eth yl-5-oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r box-
ylic a cid ben zyl ester (35): derived from 10 and 4-methoxy-
benzyloxyacetyl chloride to give 35 (53 mg, 29%) as a solid;
mp 100-101 °C; IR (KBr) νmax 1751, 1710, 1698 cm-1; 1H NMR
(CDCl3) δ 7.37 (s, 5H, C6H5) 7.30 (d, 2H, J ) 8.0 Hz, 2,6-ArH),
6.87 (d, 2H, J ) 8.0 Hz, 3,5-ArH), 5.13 (s, 2H, PhCH2), 4.56
(q, 2H, J ) 12 Hz) and 4.60 (s, 2H) (CH2OCH2), 3.8 (s and m,
5H, OCH3, NCHHCH2 and NCHCH2), 3.45 (m, 1H, NCH-

4462 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Borthwick et al.
HCH2), 3.02 (t, J ) 11 Hz, 1H, NCHCHMe), 2.75 (m, 1H,
CH2CHH), 2.66 (m,1H, CHMe), 1.92 (2t, J ) 11 Hz, 1H, NCH2-
CHH), 1.42 (br, 3H, CH3); TLC Rf 0.13 (cyclohexane-ethyl
acetate, 1:1); MS m/z 470 (MNH4+). Anal. (C25H28N2O6‚
0.25H2O) C, H, N.
NCHCH2CO), 3.2-2.8 (bs, 1H, CHHCO), 2.7-2.5 (m, 2H,
NCH2CHH, CHHCO), 2.0 (m, 4H, OCOCH3, NCH2CHH), 1.7-
1.5 (m, 6H, CMe2); MS (thermospray) m/z 406 (MNH4+), 389
(MH+); HRMS calcd for C20H24N2O6 (MH+) 389.139961, found
389.141010; HPLC 89.52% (tR 27.48 min).
tr a n s-4-Acetoxya cetyl-5-oxo-h exa h yd r o-p yr r olo[3,2-b]-
p yr r ole-1-ca r boxylic a cid ben zyl ester (22): derived from
13 and acetoxyacetyl chloride to yield 22 (66%); IR (KBr) νmax
1754, 1712 cm-1; 1H NMR (CDCl3) δ 7.3 (s, 5H, C6H5), 5.2 (dm,
1H, COCH2O), 5.1 (s, 2H, PhCH2), 5.0 (dm, 1H, COCH2O), 3.9
(m, 1H, NCHHCH2), 3.8 (m, 1H, NCHHCH2), 3.6-3.4 (m, 2H,
NCHCH2 and NCHCH2CO), 3.2-2.9 (bs, 1H, CHHCO), 2.8-
2.6 (m, 2H, NCH2CHH, CHHCO), 2.2 (s, 3H, OCOCH3), 2.1
(m, 1H, NCH2CHH); MS (thermospray) m/z 378 (MNH4+), 361
(MH+); HRMS calcd for C18H21N2O6 (MH+) 361.139962, found
361.141020; HPLC 95.4% (tR 24.41 min).
tr a n s-4-[(4-Meth oxyben zyloxy)acetyl]-5-oxo-h exah ydr o-
p yr r olo[3,2-b]p yr r ole-1-ca r boxylic a cid ben zyl ester (36):
derived from 13 and 4-methoxyphenoxyacetylpivaloyl anhy-
dride17 to give 36 (65%) as a white solid; mp 114-115 °C; IR
1
(KBr) νmax 1756, 1722, 1712 cm-1; H NMR (CDCl3) δ 7.39-
7.25 (m, 2H, 3,5-ArH, and m, 5H C6H5), 6.88 (d, 2H, J ) 8.0
Hz, 2,6-ArH) 5.12 (q, 2H, J ) 12.0 Hz, CH2Ph), 4.59 (q, 2H, J
) 11.7 Hz, OCH2Ar), 4.54 (q, 2H, J ) 17.5 Hz, OdCCH2OCH2-
Ar), 3.81 (s, 3H, OCH3), 3.78 (m, 2H, NCH2CH2), 3.50 (m, 1H,
NCHCH2), 3.35 (m, 1H, NCHCH2CO), 2.92 (bm, 1H, CHHCO),
2.78 (m, 1H, NCH2CHH), 2.63 (m, 1H, CHHCO), 2.00 (m, 1H,
NCH2CHH); MS (electrospray) m/z 453 (MH+); HPLC 97.77%
(tR 28.90 min). Anal. (C24H26N2O6) C, H, N.
tr a n s-4-Acetyl-5-oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-
1-ca r boxylic a cid ben zyl ester (23): derived from 13 and
acetyl chloride to afford 23 (89%) as a white solid; mp 128-
r el -(3a S ,6S ,6a R )-4-Ac e t o x y a c e t y l-6-m e t h y l-5-o x o -
h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic a cid ben -
zyl ester (29): derived from 16 and acetoxyacetyl chloride to
give 29 (74%) as a white solid; mp 108-109 °C; IR (CDCl3)
132 °C; IR (KBr) νmax 2897, 1755, cm-1 1H NMR (CDCl3) δ
;
7.35 (m, 5H, C6H5), 5.15 (m, 2H, PhCH2), 3.9-3.6 (m, 2H,
NCHCH2 and NCHCHMe), 3.6-3.2 (m, 2H, NCH2CH2), 3.2-
2.8, 2.8-2.5 (m, 2H, CH2CO), 2.8-2.6, 2.1-1.7 (2m, 2H,
NCH2CH2), 2.5 (s, 3H, CH3); HPLC 99% (tR 23.4 min). Anal.
(C16H18N2O4) C, H, N.
νmax 1750, 1716, 1700 cm-1 1H NMR (CDCl3) δ 7.40 (s, 5H,
;
C6H5), 4.9-5.3 (m, 4H, PhCH2 and CH2OAc), 3.90 (m, 1H,
NCHHCH2), 3.78 (m, 1H, NCHCH2), 3.70 (m, 1H, NCHHCH2),
3.50 (m, 1H, NCHCHMe), 3.1 (bm, 1H, CHMe), 2.77 (m, 1H,
NCH2CHH), 2.20 (s, 3H, OAc), 2.00 (m, 1H, NCH2CHH), 1.15
(br, d J ) 21.3 Hz, 3H, CH3CH); TLC Rf 0.20 (cyclohexane-
EtOAc, 2:1). Anal. (C19H22N2O6) C, H, N.
tr a n s-2-Oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1,4-d i-
ca r boxylic a cid 4-ben zyl ester 1-vin yl ester (24): derived
from 13 and vinyl chloroformate to give 24 (34%) as a white
solid; mp 120-121 °C; IR (KBr) νmax 1809, 1733, 1715, 1702
1
cm-1; H NMR (CDCl3) δ 7.36 (s, 5H, C6H5), 7.21 (t, J ) 7.5
r el-(3a S,6S,6a R)-4-Acet yl-6-m et h yl-5-oxo-h exa h yd r o-
p yr r olo[3,2-b]p yr r ole-1-ca r boxylic a cid ben zyl ester (30):
derived from 16 and acetyl chloride to give 30 (89%) as a gum;
IR (KBr) νmax 1747, 1712, 1697 cm-1; 1H NMR (CDCl3) δ 7.37
(s, 5H, C6H5), 5.14 (q, J ) 11 Hz, 2H, PhCH2), 3.7 and 3.86
(m, 3H, NCH2CH2 and NCHCH2), 3.45 (dd, J ) 12 Hz, J )
7.5 Hz, 1H; NCHCHMe), 3.1 (bm, 1H, CHMe), 2.74 (dt, J ) 6
Hz, 1H, NCH2CHH), 2.46 (s, 3H, COCH3), 1.97 (2t, J ) 11
Hz, 1H, NCH2CHH), 1.14 (br, 3H, CH3CH); TLC Rf 0.32
(cyclohexane-ethyl acetate, 1:1). Anal. (C17H20N2O4‚0.25Et2O)
C, H, N.
Hz, 1H, CHdCH2), 5.12 (q, J ) 11 Hz, 2H, PhCH2), 4.68 (dd,,
J ) 7.5, 2 Hz, 1H and 4.99 dd, J ) 18, 2 Hz, 1H) (CHdCH2),
3.95-3.3 (m, 4H, NCH2CH2, NCHCH2 and NCHCH2CO), 3.00
and 2.64 (2m, 2H, CH2CO), 2.64 (m, 1H, NCH2CHH) and 2.09
(m, 1H, NCH2CHH); TLC Rf 0.33 (toluene-ethyl acetate-
acetic acid, 20:10:0.5). Anal. (C17H18N2O5) C, H, N.
tr a n s-2-Oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1,4-d i-
ca r boxylic a cid 4-ben zyl ester 1-m eth yl ester (25): derived
from 13 and methyl chloroformate to yield 25 (95%) as a white
foam; IR (KBr) νmax 1800, 1771, 1715, 1706 cm-1 1H NMR
;
(CDCl3) δ 7.4 (s, 5H, C6H5), 5.2 (s, 2H, PhCH2), 3.9 (s, 3H,
CO2Me), 3.9-3.8 (m, 1H, NCHHCH2), 3.8-3.7 (m, 1H, NCH-
HCH2), 3.6 (m, 1H, NCHCH2), 3.4 (m, 1H, NCHCH2CO), 3.2-
2.9 (bs, 1H, CHHCO), 2.7-2.6 (m, 2H, CHHCO, NCH2CHH),
2.10 (m, 1H, NCH2CHH); MS (thermospray) m/z 336 (MNH4+),
319 (MH+); HRMS calcd for C16H18N2O5Na (MH+) 341.111342,
found 341.111572; HPLC 95.4% (tR 22.12 min).
tr a n s-4-Meth an esu lfon yl-5-oxo-h exah ydr o-pyr r olo[3,2-
b]p yr r ole-1-ca r boxylic a cid ben zyl ester (26): derived from
13 and methanesulfonyl chloride to give 26 (67%) as a white
solid; mp 155-157 °C; IR (KBr) νmax 1750, 1712, 1702; 1H NMR
(CDCl3) δ 7.35 (m, 5H, C6H5), 5.01 (ABq, 2H, J ) 12.2 Hz,
CH2Ph), 3.88, 3.73, 3.58, 3.44 (4m, 4H, NCH2CH2, NCHCH2
and NCHCH2CO), 3.25 (s, 3H, CH3), 3.00 (m, 1H, CHHCO),
2.60 (m, 2H, CHHCO and NCH2CHH), 2.10 (m, 1H, NCH2-
CHH); MS (thermospray) m/z 339 (MH+), 356 (MNH4+); HPLC
99.7% (tR 22.91 min). Anal. (C15H18N2O5S‚0.05C6H12) C, H, N,
S.
r el-(3S,3a R,6a S)-3-Met h yl-2-oxo-h exa h yd r o-p yr r olo-
[3,2-b]p yr r ole-1,4-d ica r boxylic a cid 4-ben zyl ester 1-vi-
n yl ester (31): derived from 16 and vinyl chloroformate to
give 31 (78%) as an oil; IR (KBr) νmax 1805, 1735, 1710, 1697
1
cm-1; H NMR (CDCl3) δ 7.35(s, 5H, C6H5), 7.23 (dd, 1H, J )
15, 7.5 Hz, OCHdCH2), 5.13 (q, J ) 12 Hz, 2H, PhCH2), 5.00
(dd, J ) 15, 2.5 Hz, 1H) and 4.68 (dd, J ) 7.5, 2.5 Hz, 1H,
OCHdCH2), 4.0-3.64 (m, 3H, NCH2CH2 and NCHCH2), 3.52
(dd, J ) 11 Hz, J ) 7.5 Hz, 1H, NCHCHMe), 3.2 and 3.02 (br
d, 1H, CHMe), 2.62 (2t, J ) 6 Hz, 1H, NCH2CHH), 2.05 (2t, J
) 12 Hz, 1H, NCH2CHH), 1.15 (br, 3H, CH3CH); TLC Rf 0.54
(cyclohexane-ethyl acetate, 1:1). Anal. (C18H20N2O5‚0.25Et2O)
C, H, N.
r el-(3a S,6S,6a R)-4-Met h a n esu lfon yl-6-m et h yl-5-oxo-
h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic a cid ben -
zyl ester (32): derived from 16 and methanesulfonyl chloride
to give 32 (80%) as a white solid; IR (KBr) νmax 1745, 1712,
1705 cm-1; 1H NMR (CDCl3) δ 7.35 (s, 5H, C6H5), 5.33 (q, J )
12 Hz, 2H, PhCH2), 4.0-3.75 (m, 2H, NCH2CH2), 3.67 (m, 1H,
NCHCH2), 3.57 (dd, J ) 10 Hz, J ) 6 Hz, 1H, NCHCHMe),
3.25 (s, 3H, OCH3), 3.0 (br, 1H, CHMe), 2.58 (dt, J ) 11 Hz,
1H, NCH2CHH), 2.08 (2t, J ) 6 Hz, 1H, NCH2CHH), 1.15 (br,
3H, CH3CH); TLC Rf 0.25 (cyclohexane-ethyl acetate, 1:1).
Anal. (C16H20N2O5S‚0.2CH2Cl2) C, H, N, S.
tr a n s-5-Oxo-4-(2-ph en yl-(E)-eth en esu lfon yl)-h exah ydr o-
p yr r olo[3,2-b]p yr r ole ca r boxylic a cid ben zyl ester (27):
derived from 13 and â-styrenesulfonyl chloride to give 27 (7%)
as a white foam; IR (KBr) νmax 1755, 1712 cm-1 1H NMR
;
(CDCl3) δ 7.42 (m, 10H, 2 × C6H5), 6.99, 7.70 (2d, 2H, J )
18.7 Hz, HCdCH), 5.11 (AB q, 2H, J ) 12 Hz, CH2Ph), 3.89,
3.72, 3.50 (3m, 4H, NCH2CH2, NCHCH2 and NCHCH2CO),
2.93, 2.61 (2m, 2H, CH2CO), 2.61, 2.16 (2m, 2H, NCH2CH2);
MS (thermospray) m/z 444 (MNH4+); HPLC 86.68% (tR 29.66
min) and 12.34% (tR 31.65 min). Anal. (C22H22N2O5S‚0.3CH2-
Cl2) C, H, N, S.
r el-(3a S,6S,6a R)-6-Met h yl-5-oxo-4-(2-p h en yl-(E)-et h -
en esu lfon yl)-h exahydr o-pyr r olo[3,2-b]pyr r ole-1-car boxylic
a cid ben zyl ester (33): derived from 16 and â-styrenesulfonyl
chloride to give 33 (22%) as a light brown solid; mp 128-132
1
°C; IR (KBr) νmax 1753, 1709, 1450, cm-1; H NMR (CDCl3) δ
tr a n s-4-Acet oxyisob u t yr yl-5-oxo-h exa h yd r o-p yr r olo-
[3,2-b]p yr r ole-1-ca r boxylic a cid ben zyl ester (28): derived
from 13 and 2-acetoxyisobutyryl chloride to yield 28 (35%);
1H NMR (CDCl3) δ 7.4 (s, 5H, C6H5), 5.1 (d, 2H, PhCH2), 3.9-
3.7 (m, 2H, NCH2CH2), 3.55 (m, 1H, NCHCH2), 3.35 (m, 1H,
7.6-7.3 (m, 10H, 2 × C6H5), 7.7, 7.0 (d, J ) 15 Hz, 2H,
SO2CHdCH), 5.2 (m, 2H, PhCH2), 4.0-3.5 (m, 4H, NCH2CH2,
NCHCH2 and NCHCHMe), 3.3-2.9 (m, 1H, CHMe), 2.7-2.5,
2.3-2.0 (m, 2H, NCH2CH2), 1.1 (br s, 3H, CH3); HPLC 95%
(tR 30.55 min). Anal. (C23H25N2O5S‚0.3EtOAc) C, H, N.

Synthesis of Pyrrolidine-5,5-trans-lactams
J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23 4463
r el-(3aS,6S,6aR)-4-Ch lor oacetyl-6-m eth yl-5-oxo-h exah y-
d r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic a cid ben zyl ester
(42): derived from 16 and chloroacetyl chloride to give 42 (38%)
as a yellow gum; IR (KBr) νmax 2874, 1751, 1712 cm-1; 1H NMR
(CDCl3) δ 7.35 (s, 5H, C6H5), 5.17 (d, J ) 13 Hz, 1H, PhCH2),
5.09 (d, J ) 13 Hz, 1H, PhCH2), 4.67 (d, J ) 16 Hz, 1H, CH2-
Cl), 4.56 (d, J ) 16 Hz, 1H, CH2Cl), 4.0-3.4 (m, 4H, NCH2-
CH2, NCHCH2 and NCHCHMe), 3.4-2.9 (m, 1H, CHMe),
2.85-2.7, 2.1-1.9 (m, 2H, NCH2CH2), 1.4-1.0 (br, 3H, CH3);
MS (thermospray) m/z 368/369 (Cl, MNH4+); HPLC 94% (tR
27.43 min). Anal. (C17H17ClN2O4‚0.1CHCl3) C, H, N.
r el-(3a S,6S,6a R)-4-(4-Acetyla m in oben zen esu lfon yl)-6-
m eth yl-5-oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r box-
ylic a cid ben zyl ester (43): derived from 16 and N-acetyl-
sulfanilyl chloride to afford 43 (5%) as a white solid; IR (KBr)
νmax 1703, 1590, 1529 cm-1; 1H NMR (CDCl3) δ 7.95, 7.7 (d, J
) 9 Hz, 2H, ArH), 7.5 (s, 1H, NH), 7.3 (s, 5H, C6H5), 5.17 (d,
J ) 13 Hz, 1H, PhCH2), 5.08 (d, J ) 13 Hz, 1H, PhCH2), 4.0-
3.4 (m, 4H, NCH2CH2, NCHCH2 and NCHCHMe), 3.2-2.7 (m,
1H, CHMe), 2.75-2.55, 2.3-2.0 (m, 2H, NCH2CH2), 2.25 (s,
3H, COCH3), 1.0-0.8 (br, 3H, CH3); MS (thermospray) m/z 472
(MH+), 489 (MNH4+); HRMS (ESP) calcd for C23H26N3O6S
(MH+) 472.154233, found 472.152869; HPLC 99% (tR 28.12
min).
cm-1; 1H NMR (CHCl3) δ 7.36 (m, 5H, C6H5), 5.14 (ABq, 2H, J
) 12.0 Hz, CH2Ph), 4.60 (dABq, 2H, J ) 4.0 Hz, J ) 19.0 Hz,
CH2OH), 3.98-3.65, 3.53 (2m, 4H, NCH2CH2, NCHCH2 and
NCHCHMe), 3.10 (bm, 1H, CHMe), 3.05 (t, 1H, J ) 5 Hz, OH),
2.77, 2.06 (2m, 2H, NCH2CH2), 1.17 (bs, 3H, CH3); MS
(thermospray) m/z 333 (MH+); HPLC 97.78% (tR 21.59 min).
Anal. (C17H20N2O5‚0.15C6H12) C, H, N.
tr a n s-4-Met h ylca r b a m oyl-5-oxo-h exa h yd r o-p yr r olo-
[3,2-b]p yr r ole-1-ca r boxylic Acid Ben zyl Ester (40). To a
solution of compound 13 (50 mg, 0.192 mmol) in tetrahydro-
furan (10 mL) under nitrogen was added sodium hydride (11
mg, 60% dispersion in mineral oil, 0.288 mmol). The mixture
was stirred at room temperature for 5 min and then reacted
with methyl isocyanate (0.017 mL, 0.288 mmol). The mixture
was stirred for 1.5 h, quenched with saturated aqueous
ammonium chloride solution (20 mL) and the mixture ex-
tracted with ethyl acetate (4 × 10 mL). The combined organic
layer was separated and washed with brine (30 mL), dried,
filtered and evaporated. The crude residue, a clear syrup was
purified by flash column chromatography eluting with cyclo-
hexane-ethyl acetate (1:2) to yield 40 (42 mg, 69%) as a white
1
solid: IR (KBr) νmax 1728, 1698, 1548 cm-1; H NMR (CDCl3)
δ 7.7 (br s, 1H, NH), 7.4 (s, 5H, C6H5), 5.15 (d, J ) 13 Hz, 1H,
PhCH2), 5.10 (d, J ) 13 Hz, 1H, PhCH2), 4.0-3.0 (m, 4H,
NCH2CH2, NCHCH2 and NCHCH2CO), 2.89 (d, J ) 5 Hz, 3H,
CH3N), 3.2-2.8, 2.8-2.6 (br m, 2H, CH2CO), 2.8-2.6, 2.2-
2.0 (m, 2H, NCH2CH2); MS (thermospray) m/z 318 (MH+);
HPLC 97% (tR 21.98 min). Anal. (C16H18N3O4) C, H, N.
r el-(3aS,6S,6aR)-4-Isopr opylcar bam oyl-6-m eth yl-5-oxo-
h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic Acid Ben -
zyl Ester (41). Compound 16 was reacted with isopropyl
isocyanate as described for 40 to give 41 (31%) as a white
r el-(3a S ,6S ,6a R )-4-[(4-Me t h oxyb e n zyloxy)a ce t yl]-6-
m eth yl-5-oxo-h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r box-
ylic a cid ben zyl ester (38): derived from 16 and 4-methoxy-
phenoxyacetylpivaloyl anhydride17 to give 38 (67%) as a white
1
wax; mp 87-89 °C; IR (KBr) νmax 1746, 1720, 1711 cm-1; H
NMR (CDCl3) δ 7.36 (m, 5H C6H5), 7.32 (d, 2H, J ) 8 Hz, 3,5-
ArH), 6.88 (d, 2H, J ) 8 Hz, 2,6-ArH), 5.13 (q, 2H, J ) 11.5
Hz, CH2Ph), 4.59, 4.53 (m, 4H, OdCCH2OCH2Ar), 3.81 (s, 3H,
OCH3), 3.95-3.63 (m, 3H, NCH2CH2 and NCHCH2), 3.47 (dd,
1H J ) 7, 12 Hz, NCHCHMe), 3.07 (bm, 1H, CHMe), 2.78,
2.00 (2m, 2H, NCH2CH2), 1.13 (bs, 3H, CH3); MS (electrospray)
m/z 453 (MH+); HPLC 98.86% (tR 30.06 min). Anal. (C25H28N2O6)
C, H, N.
solid: IR (KBr) νmax 3330, 1728, 1714, 1694 cm-1 1H NMR
;
(CDCl3) δ 7.7 (br s, 1H, NH), 7.36 (s, 5H, C6H5), 5.15 (q, J )
12 Hz 2H, PhCH2), 3.45 (dd, J ) 12 Hz, J ) 7.5 Hz, 1H,
NCHCHMe) and 4.06-3.6 (m, 4H, (Me)2CH, NCH2CH2 and
NCHCH2), 2.95 and 3.2 (br d, 1H, CHMe), 2.72 (2t, J ) 5.5
Hz 1H, NCH2CHH), 2.05 (2t, J ) 11 Hz, 1H, NCH2CHH),
1.05-1.3 (br s and d, J ) 7 Hz 9H, CH3CH and (CH3)2CH);
TLC Rf 0.31 (cyclohexane-ethyl acetate, 1:1); MS (thermo-
spray) m/z 360 (MH+). Anal. (C19H25N3O4‚0.2C6H12) C, H, N.
Bioch em ica l Assa y. Compounds were dissolved in DMSO
and added at a concentration of 500 µM to reaction mixtures
containing 6.65 µM HCMV δAla protease in 85 mM HEPES/
NaOH buffer, pH 7.5, containing 0.17 mM EDTA, 8.5 mM
NaCl, 1.7 mM dithiothreitol and 25.5% (v/v) glycerol. The final
concentration of DMSO present in assays was 2% (v/v).
Routinely, mixtures were incubated at 37 °C for 15 min, prior
to addition of 1 mM substrate (RESYVKASVSPEAA), and then
incubated for a further 15 min. For time-course experiments,
incubation times of 0, 0.25, 0.5, 1, 2, 3, 6, 24 and 48 h were
used prior to substrate addition. Reactions were stopped by
the addition of TFA (1% v/v final concentration), and the extent
of peptide substrate cleavage was determined by reverse-phase
HPLC using a C8 column and an acetonitrile gradient in 0.1%
(v/v) TFA. Products were quantified by comparison of peak
areas with calibration plots generated using peptide solutions
of known concentration.
r el-(3a S ,6R ,6a R )-4-H yd r oxya ce t yl-6-m e t h yl-5-oxo-
h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic Acid Ben -
zyl Ester (34). To a solution of the 4-methoxybenzyloxy ether
35 (42 mg, 0.093 mmol) in dichloromethane (2 mL) were added
water (0.1 mL) and DDQ (25 mg, 0.11 mmol). The resulting
mixture was stirred for 2 h, more DDQ (12 mg, 0.05 mmol)
was added and stirring continued for a further 1.25 h when
another portion of DDQ (10 mg, 0.045 mmol) and more
dichloromethane (1 mL) were added. The reaction mixture was
stirred for a total of 23 h before the pink solid was filtered off
and washed with dichloromethane. The filtrate was concen-
trated and purified by flash chromatography eluting with
cyclohexane-ethyl acetate (2:1) to give the title compound 34
(26.5 mg, 86%) as a white solid: mp 124-125 °C; IR (KBr)
ν
max 3500, 1754, 1746, 1731, 1711, 1692 cm-1; 1H NMR (CDCl3)
δ 7.37 (s, 5H, C6H5), 5.15 (s, 2H, PhCH2), 4.01 (m, 2H, CH2-
OH), 3.83 (m, 2H, NCHHCH2 and NCHCH2), 3.08 and 3.5 (s
1H, OH and m, 2H, NCHCHMe and NCHHCH2), 2.77 (m, 2H,
NCH2CHH and CHMe), 1.97 (m, 1H, NCH2CHH), 1.45 (br, 3H,
CH3); TLC Rf 0.17 (cyclohexane-ethyl acetate, 1:1). Anal.
(C17H20N2O5) C, H, N.
Ack n ow led gm en t. We are grateful for analytical
and spectroscopic assistance from Pat McDonough, Sean
Hindley, and Andy D. Roberts. We also thank Cathy
Van Wely and Vanessa Hotham for the HCMV δAla
protease assays.
tr a n s-4-H yd r oxya cet yl-5-oxo-h exa h yd r o-p yr r olo[3,2-
b]p yr r ole-1-ca r boxylic Acid Ben zyl Ester (37). Compound
36 was reacted with DDQ as described for 34 to give 37 (63%)
as a white gum: IR (KBr) νmax 3480 (OH), 1758, 1712, 1695
cm-1; 1H NMR (CDCl3) δ 7.35 (m, 5H, C6H5), 5.13 (ABq, 2H, J
) 12.0 Hz, CH2Ph), 4.61 (dm, 2H, CH2OH), 3.82, 3.54, 3.40
(3m, 4H, NCH2CH2, NCHCH2 and NCHCH2CO), 3.05 (t, 1H,
J ) 5 Hz, OH), 2.99, 2.67 (2bm, 2H, CH2CO), 2.77, 2.06 (2m,
2H, NCH2CH2); MS (thermospray) m/z 319 (MH+), 336
(MNH4+); HPLC 96.44% (tR 19.81 min). Anal. (C16H18N2O5‚
0.2C6H12‚0.1EtOAc) C, H, N.
r el-(3a S ,6S ,6a R )-4-H yd r oxya c e t yl-6-m e t h yl-5-oxo-
h exa h yd r o-p yr r olo[3,2-b]p yr r ole-1-ca r boxylic Acid Ben -
zyl Ester (39). Compound 38 was reacted with DDQ as
described for 34 to give 39 (71%) as a white wax: mp 130-
132 °C; IR (KBr) νmax 3495 (broad) (OH), 1748, 1712, 1695
Refer en ces
(1) Gibson, W.; Welch, A. R.; Hall, M. R. T. Assemblin, a herpesvirus
serine maturational proteinase and a new molecular target for
antivirals. Perspect. Drug Discov. Des. 1994, 2, 413-426.
(2) (a) Holwerda, B. C. Herpesvirus proteases: targets for novel
antiviral drugs. Antiviral Res. 1997, 35, 1-21. (b) Qiu, X. Y.;
Abdelmeguid, S. S. Human Herpes Proteases. In Proteases of
Infectious Agents; Dunn, B. M., Ed.; Academic Press: San Diego,
1999; Chapter 3, pp 93-115. (c) Waxman, L.; Darke, P. L. The
herpes proteases as targets for antiviral chemotherapy. Antiviral
Chem. Chemother. 2000, 11, 1-22.

4464 J ournal of Medicinal Chemistry, 2000, Vol. 43, No. 23
Borthwick et al.
(3) Chen, P.; Tsuge, H.; Almassy, R. J .; Gribskov, C. L.; Katoh, S.;
Vanderpool, D. L.; Marbosiak, S. A.; Pinko, C.; Matthews, D.
A.; Kan, C. C. Structure of the Human Cytomegalovirus Protease
Catalytic Domain Reveals a Novel Serine Protease Fold and
Catalytic Triad. Cell 1996, 86, 835-843.
(4) Tong, L.; Qian, C. G.; Massariol, M. J .; Bonneau, P. R.;
Cordingley, M. G.; LaGace, L. A. A New Serine-Protease Fold
Revealed by the Crystal Structure of Human Cytomegalovirus
Protease. Nature 1996, 383 (N6597), 272-275.
role) and Stereoselective Alkylation of the Strained Pyrrolidine-
5,5-Trans-Lactam Ring System. Synth. Lett. 2000, 504-508.
(11) Richman, S. J .; Goodman, M.; Nguyen, Thi M. D.; Schiller, P.
W. Synthesis and Biological activity of linear and cyclic en-
kephalins modified at the Gly3-Phe4 amide bond. Int. J . Pept.
Protein Res. 1985, 25, 648-662.
(12) Kokotos, G. A. Convenient One-Pot Conversion of N-Protected
Amino Acids and Peptides into Alcohols. Synthesis 1990, 249-
252.
(5) Qiu, X. Y.; Culp, J . S.; Dilella, A. G.; Hellmig, B.; Hoog, S. S.;
J anson, C. A.; Smith, W. W.; Abdelmeguid, S. S. Unique Fold
and Active Site in Cytomegalovirus Protease. Nature 1996, 383
(N6597), 275-279.
(6) Shieh, H. S.; Kurumbail, R. G.; Stevens, A. M.; Stegeman, R.
A.; Sturman, E. J .; Pak, J . Y.; Wittwer, A. J .; Palmier, M. O.;
Wiegand, R. C.; Holwerda, B. C.; Stallings, W. C. Three-
Dimensional Structure of Human Cytomegalovirus Protease.
Nature 1996, 383 (N6597), 279-282.
(7) Macdonald, S. J . F.; Belton, D. J .; Buckley, D. M.; Spooner, J .
E.; Anson, M. S.; Harrison, L. A.; Mills, K.; Upton, R. J .; Dowle,
M. D.; Smith, R. A.; Molloy, C. R.; Risley, C. Syntheses of trans-
5-Oxo-hexahydro-pyrroles[3,2-b]pyrroles and trans-5-Oxo-hexahy-
dro-furo[3,2-b]pyrroles (Pyrrolidine trans-Lactams and trans-
Lactones): New Pharmacophores for Elastase Inhibition. J . Med.
Chem. 1998, 41, 3919-3922.
(8) Dowle, M. D.; Finch, H.; Harrison, L. A.; Inglis, G. G. A.;
J ohnson, M. R.; Macdonald, S. J . F.; Shah, P.; Smith, R. A. WO
9736903 A1 971009P.
(9) Pass, M.; Abu-Rabie, S.; Baxter, A.; Conroy, R.; Coote, S. J .;
Craven, A. P.; Finch, H.; Hindley, S.; Kelly, H. A.; Lowdon, A.
W.; McDonald, E.; Mitchell, W. L.; Pegg, N. L.; Procopiou, P. A.;
Ramsden, N. G.; Thomas, R.; Walker, D. A.; Watson, N. S.; J hoti,
H.; Mooney, C. J .; Tang, C.-M.; Thomas, P. J .; Parry S.; Patel,
C. Thrombin Inhibitors based on [5,5] Trans-Fused Indane
Lactams. Bioorg. Med. Chem. Lett. 1999, 9, 1657-1662.
(10) Borthwick, A. D.; Crame, A. J .; Davies, D. E.; Exall, A. M.;
J ackson, D. L.; Mason, A. M.; Pennell, A. M. K.; Weingarten, G.
G. Stereoselective Synthesis of R-Methyl and â-Methyl 5,5-
Pyrrolidine-Trans-Lactam (5-Oxo-hexahydro-pyrrolo[3,2-b]pyr-
(13) Nahm, S.; Weinreb, S. Tetrahedron Lett. 1981, 22, 3815-3818.
Fehrentz, J . A.; Castro, B. Synthesis 1983, 676-678.
(14) Ireland, R. E.; Norbeck, D. W. Application of the Swern Oxidation
to the Manipulation of Highly Reactive Carbonyl Compounds.
J . Org. Chem. 1985, 50, 2198-2200.
(15) Borthwick, A. D.; Crame, A.; Pennell, A.; Mason, A.; Exall, A.
An Improved Synthesis of the Pyrrolidine-5,5-Translactam Ring
System. Tetrahedron Lett. 1999, 40, 3061-3062.
(16) Kanazawa, A. M.; Denis, J .-N.; Greene, A. E. Direct, stereose-
lective synthesis of the protected paclitaxel (taxol) side chain
and high-yield transformation to paclitaxel. J . Chem. Soc., Chem.
Commun. 1994, 22, 2591-2592.
(17) Askin, D.; Reamer, R. A.; J oe, D.; Volante, R. P.; Shinkai, I. A
Mechanistic Study of the FK-506 Tricarbonyl System Rear-
rangement: Synthesis of C.9 Labeled FK-506. Tetrahedron Lett.
1989, 30, 6121-6124.
(18) Haley, T. M.; Angier, S. J .; Borthwick, A. D.; Montogomery D.
S.; Purivs, I. J .; Smart, D. H.; Bessant, C.; Van Wely, C.; Hart,
G. J . Investigation of the Covalent Modification of the Catalytic
Triad of Human Cytomegalovirus Protease by Pseudo-reversible
â-Lactam Inhibitors and a Peptide Chloromethyl ketone. J . Mass
Spectrom. 1998, 33, 1246-1255.
(19) Borthwick, A. D.; Weingarten, G. G.; Haley, T. M.; Tomaszewski,
M.; Wang, W.; Hu, Z.; Bedard, J .; J in, H.; Yeun, L.; Mansour, T.
S. Design and Synthesis of monocyclic â-lactams as Mechanism-
Based inhibitors of Human Cytomegalovirus Protease. Bioorg.
Med. Chem. Lett. 1998, 8, 365-370.
J M000078Q