Synthesis of clarithromycin ketolides chemically modified at the unreactive C10-methyl group

Article abstract of DOI:10.1016/j.bmc.2017.02.041

Chemoselective substitutions in the C10-methyl group of erythromycin A ketolides is reported. The C10-methyl group in the clarithromycin derived substrate 10,11-anhydro-O⁶-methyl-descladinosylerythromycin was activated by conversion into an allyl acetate and thereafter to the corresponding allylic cyanide. Both the allylic acetate and the cyanide reacted with carbonyldiimidazole and ammonia to afford a C11,C12-cyclic carbamate with concurrent elimination of the allylic function to yield a methylene α,β-unsaturated ketone. Conjugate addition with amines resulted in stereoselective C–N bond formation between the terminal methylene carbon and the amino nitrogen. Carbylation in the methylene group was effected under Stille conditions for cross-coupling with Pd-catalysis. With anion stabilized nucleophiles, such as a sodium salt of a malonate, stereoselectivity was observed in the formation of the 10-substituent. Stereoselective cycloaddition with trimethylsilyldiazomethane afforded a spirane where the C10 carbon of the macrolide skeleton had become a quaternary spirocarbon. Antibacterial in vitro data for a selected group of compounds against strains of respiratory pathogens S. pneumoniae and S. aureus are reported. Most of the compounds tested showed improved activities over CLA as a reference compound against efflux resistant S. pneumoniae as well as against efflux and inducibly resistant strains of S. aureus.

Full text of DOI:10.1016/j.bmc.2017.02.041

Accepted Manuscript
Synthesis of clarithromycin ketolides chemically modified at the unreactive
C10-methyl group
Hany Fakhry Anwar, Mioara Andrei, Kjell Undheim
PII:
S0968-0896(16)31079-3
DOI:
http://dx.doi.org/10.1016/j.bmc.2017.02.041
BMC 13571
Reference:
Bioorganic & Medicinal Chemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
2 November 2016
8 February 2017
11 February 2017
Please cite this article as: Anwar, H.F., Andrei, M., Undheim, K., Synthesis of clarithromycin ketolides chemically
modified at the unreactive C10-methyl group, Bioorganic & Medicinal Chemistry (2017), doi: http://dx.doi.org/
10.1016/j.bmc.2017.02.041
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1
Synthesis of clarithromycin ketolides chemically modified at the unreactive C10-
methyl group
Hany Fakhry Anwara, Mioara Andreia and Kjell Undheimb*
aC10 Pharma AS, Oslo, Norway
bDepartment of Chemistry, University of Oslo, N-0315 Oslo, Norway
Abstract: Chemoselective substitutions in the C10-methyl group of erythromycin A
ketolides is reported. The C10-methyl group in the clarithromycin derived substrate 10,11-
anhydro-O6-methyl-descladinosylerythromycin was activated by conversion into an allyl
acetate and thereafter to the corresponding allylic cyanide. Both the allylic acetate and the
cyanide reacted with carbonyldiimidazole and ammonia to afford a C11,C12-cyclic
carbamate with concurrent elimination of the allylic function to yield a methylene α,β-
unsaturated ketone. Conjugate addition with amines resulted in stereoselective C-N bond
formation between the terminal methylene carbon and the amino nitrogen. Carbylation in
the methylene group was effected under Stille conditions for cross-coupling with Pd-
catalysis. With anion stabilized nucleophiles, such as a sodium salt of a malonate,
stereoselectivity was observed in the formation of the 10-substituent. Stereoselective
cycloaddition with trimethylsilyldiazomethane afforded a spirane where the C10 carbon of
the macrolide skeleton had become a quaternary spirocarbon. Antibacterial in vitro data
for a selected group of compounds against strains of respiratory pathogens S. pneumoniae
and S. aureus are reported. Most of the compounds tested showed improved activities over
CLA as a reference compound against efflux resistant S. pneumoniae as well as against
efflux and inducibly resistant strains of S. aureus.
Keywords: Antibacterials, in vitro MIC data, syntheses, C10-aminomethyl-3-ketolides,
NCS acetoxylation, allylic substitutions, stereoselectivity.
e-mail: kjell.undheim@kjemi.uio.no
Telephone: 47 22 85 55. 21

2
1. Introduction
Erythromycin A is a major antibiotic macrolide. The macrolide structure has been
subjected to a number of chemical modifications over the years to improve its
physicochemical properties and antibacterial profiles. All positions in the macrolactone
scaffold, except for the 10-position, had been chemically modified when our work on
chemical modifications was started.1,2 The low chemical reactivity of the C10-methyl
group may in part be ascribed to its position in an electronically non-activated site in the
macrocyclic ring. Some modifications of the 10-position, however, had been effected by
genetic engineering techniques that afforded 10-desmethylerythromycin A, 10-ethyl and
10-hydroxy macrolides.3,4 Quaternization at C10 had been effected by intramolecular 1,3-
dipolar cycloaddition in a C10-C11 unsaturated macrolide, the product being a tricyclic
derivative.5 The generically produced macrolides possessed moderate antibacterial activity
including the 10-desmethyl analogue. Recently, considerable efforts have been reported
on development of methods for total syntheses of desmethyl macrolide antibiotics
including 4,8,10-tridesmethyl telithromycin and 4,10-didesmethyl telithromycin.6,7,8 In
general, it appears that the synthetic 10-desmethyl macrolides were inferior to
telithromycin as antibacterial agents.6 We were interested in structural modifications
which could lead to an increase in the size of the 10-substituent. The substrate for the
chemical transformation was to be a clarithromycin derivative where the 10-methyl group
was to be chemically modified. Part of this work has been presented in preliminary
publications.1,2 The target compounds were 3-ketolides, modified as cyclic 11,12-
carbamate 6-methoxyerythromycin derivatives where the 11,12-cyclic carbamate linkage
occupies the positions of the two hydroxyl groups in erythromycin A.9,10
From work on the development of erythromycin drugs it appears that side-chains in
positions other than the macrolide 10-position have variable and significant influence on
the activity of the ketolides. A reference is made to the drug telithromycin which has aza-
hetaryls spaced from the lactone ring structure via short alkyl or allyl linkages attached to
the carbamate nitrogen.11-13 In our work the emphasis has been on functionalization of the
10-methyl group for making available products which may serve as intermediates for
subsequent introduction of pharmacophoric side-chains extending from the 10-position.
In the macrolide scaffold, the 10-position is expected to be only weakly polarized.
Consequently, the C10-methyl group may show relatively low reactivity towards chemical
transformations. We wanted to increase the polarizability of the C10-methyl group by
working with unsaturated intermediates, in particular with C10-C11 double bond
structures. In this manner allylic properties will be conferred onto the methyl group.

3
2. Results and discussion
The target molecules are 3-ketolides with a modified methyl substituent in the C10-
position, strucures A in Fig. 1. Ketolides are available from erythromycin macrolides by
selective removal of the O3-sugar (L-cladinose moiety) and oxidation of the resultant
hydroxyl compound to a corresponding oxo compound. Ketolides in general show
relatively good acid stability and antibacterial potency against bacteria which may be
resistant to macrolides.9
Fig. 1 Structural relationships between clarithromycin and targeted 10-substituted 3-
ketolides.
Reactions leading to transformations of the C10-methyl group in the erythromycin
scaffold are shown in Scheme 1. In clarithromycin, the O6-methyl analogue of
erythromycin, the methoxy function may be regarded as a protected 6-hydroxy group.
Various alkyl, aryl or acyl groups attached to the oxygen would be eligible for the
protecting function in general provided these groups can be removed after the synthetic
operations have been completed. Protection of the 6-OH group in erythromycin is
necessary to avoid chemical interference in the series of transformations to be carried out.
The 9-methylene ketolide 3 was the substrate for most of the chemical transformations
(Scheme 1). It is available from clarithromycin after transformations we have in part
previously reported.1

4
Scheme 1. Reagents and conditions; (i) CDI, NaH, 0 oC to rt 17 h; (ii) NH3(aq), MeCN,
THF, rt, 48 h; (iii) (a) NaH, THF, 0 oC; (b) CDI, rt, 17 h; (iv) NH3(aq), MeCN, THF, rt, 17
h.
The allylic acetate 1 was reacted with carbonyldiimidazole (CDI) in the presence of
sodium hydride (NaH) in THF. The reaction occurs at the 12-hydroxyl group to afford the
12-acylimidazolyl intermediate 2 in 60% yield. Treatment of the latter with aqueous
ammonia in acetonitrile led to a two-step transformation, presumably by initial formation
of a corresponding urethane followed by cyclization in a stereoselective manner by
analogy to the methodology developed by Baker.14
In a similar manner, the allylic azide 4 can be an intermediate in the preparation of
compound 3. We have previously reported a synthesis of the azide 4 involving a cyanide
substitution of the allylic acetate function in compound 1.1 Treatment of the sodium salt of
azide 4 with carbonyldiimidazole afforded the 12-acylimidazolyl azide 5. The cyanide
function was expelled when the cyanide 5 was cyclized in a reaction with ammonia to
afford the target compound 3.
The stereochemistry in the cyclic carbamate formation in the applied protocol was
originally established by NMR spectroscopy.14 Subsequently, this methodology has gained
wide application and in some cases the stereochemical outcome has been verified by
single crystal X-ray analysis.6,10, 15 In cyclizations shown in Scheme 1, however, the
internal Michael addition reaction resulted in acetate or cyanide eliminations rather than
protonation at C-10. The product was a novel 10-methylene derivative 3.

5
For comparison, C12-vinyl ketolides have been prepared from the natural C12-methyl
group in the erythromycin core. The C12-vinyl macrolides are described as active
antibacterial agents against respiratory pathogens.16
Dipolar addition between amines and 10-methylene substrates has been used to
achieve C-N bond formation. The C10-hinged methylene group in structure 3 is part
of an electron deficient α,β-unsaturated carbonyl system which will react with
heteroatom nucleophiles. In Scheme 2, amine addition reactions in refluxing THF
afford C10-aminomethyl products 6. Benzylamine was a good nucleophile in the
conjugated amine addition to afford 6a. Phenethylamine reacted in the same manner
to yield 6b. Pyridine-3-amine has a π-deficient system with deactivation of the
amino group; the yield of 6c was 16%. The furyl-2-amine and the thienyl-2-amine
are π-excessive systems and afforded the furyl derivative 6d and the thienyl
derivative 6e in high yields. The ester group in compounds 6 was cleaved by
methanolysis at room temperature to provide the corresponding hydroxy compounds
7. Only one stereoisomer at the epimeric C10-carbon was observed. The product
was identified by its diagnostic signal in 1H NMR from H-11 which resonated as
a singlet at ca 3.9 ppm (3.82, 3.91 and 3 x 3.93 ppm) and was therefore assigned
the (R)-configuration) 7.
In the 10-methylene substrate
3
, which has no vicinal H-10, the H-11 proton
resonated as a singlet at 3.87 ppm. In the analogous methylene compounds 21 and
23 (Scheme 5), H-11 resonated as a singlet at 3.70 ppm and 3.82 ppm,
respectively. In closely related clarithromycin derivatives, it has been observed
that the vicinal H-11 proton in the (10
singlet in the (10
)-isomer.14 The stereochemistry at C10 arising from adduct
formation of the 10-methylene substrate and the added nucleophile will depend
on structural features as well as on experimental conditions. Epimerization
changes may favor formation of either the (10 )- or the (10
)-epimer.10,15 The
natural (10 )-isomer is thermodynamically more stable than its (10 )-isomer.
The same stereochemical course of the reaction is assumed in the formation of
the other members in the amine family of adducts The reactivity will also be
S)-isomer resonated as a doublet, but as a
R
3
R
S
R
S
6.
affected by the nucleophilicity of the amino nitrogen. Thus aniline failed to form
adducts under the conditions used with alkylamines. Non-bonded interactions are
also important. With secondary
Shifting the methyl group to the
for adduct formation affording the product
was obtained after deprotection of the adduct
N
-methylbenzylamine, adduct formation failed
-benzyl carbon, however, gave an active amine
in 55% yield. The target compound
in methanol in high yield.
.
α
8
9
8

6
R1(CH2)nNH
R1(CH2)nNH
O
O
O
NH
O
NH
O
NH
O
(i)
NMe2
O
OMe
O
(ii)
NMe2
O
OMe
O
O
OMe
O
OAc
OH
OAc
NMe2
O
O
O
O
O
O
O
O
O
O
O
O
7a
R1 = Ph, n = 1
(48%)
6a
3
7b ( 45 % overall)
7c (72%)
7d (85%)
6b R1 =Ph, n = 2
R1 = 3-picolylamino n = 1 (16%)
6c
6d R1 = 2-furyl, n = 1
6e R1 = 2-thienyl, n = 1
(58%)
7e (32% overall)
PhCH(Me)NH
O
PhCH(Me)NH
O
O
O
NH
O
NH
O
OMe
O
OMe
O
OH
OAc
NMe2
NMe2
O
O
(iii)
(iv)
O
3
O
O
O
O
O
9 (86%)
8 (55%)
Scheme 2. Reagents and conditions: (i) R1(CH2)nNH2, THF, reflux, 48 h; (ii) MeOH, rt,
o.n.; (iii) PhCH(Me)NH2, THF, reflux, 60 h; (iv); MeOH, rt, o.n.
The allylic acetate 10 was the substrate for introduction of unsaturated functions into the
C10-methyl group. Palladium mediated transcoupling reactions under Stille
conditions with the acetate 10 produced carbylation (Scheme 3). The tin reagent
delivered a phenyl, phenylethynyl or a phenylethenyl group. Either N-
methylpyrrolidone (NMP) or DMF was the solvent. Transfers to the acetoxy carbon
afford substitution products 12. The Stillemethodology is highly compatible with our
macrolides. If members of theproducts were to beselected for clinical studies, the
methodology for transcoupling may be adapted to the Suzukiconditions because
organoboranes are generally considered to be acceptable reagentsfor compounds
prepared for clinical studies.
The 2´-hydroxy group in transcoupled products 11 (Scheme 3) was protected as
acetate 12 by reactions with acetic anhydride and trimethylamine. Chemoselective
oxidation under the Dess-Martin periodinane (DMP) conditions afforded the 3-
ketolides 13. For cyclic carbamate formation (15), carbonyldiimidazole (CDI), was

7
used under basic conditions. Treatment of the initial product 14 with aqueous
ammonia afforded the cyclic carbamates 15. Subsequent deacetylation of the product
in methanol solution at room temperature yielded target compound 16.
Scheme 3. Reagents and conditions (i) (a) Bu3SnPh, Pd2dba3.CHCl3, NMP, 90 oC, o.n., (b)
Bu3SnR1, Pd2dba3.CHCl3, DMF, 80-90 oC, o.n.; (ii) Ac2O, NEt3, CH2Cl2, rt, 17 h; (iii)
DMP, CH2Cl2, rt, 3 h; (iv) CDI, NaH, THF, 0 oC, 20 h; (v) NH3(aq), MeCN, THF, rt, 48 h;
(vi) MeOH, rt, 14 h.
The product 16a was a mixture of the two C10-epimers. Separation or partial separation
could be effected by flash chromatography. The minor isomer in 1H NMR showed H-11 as
a doublet at 3.76-3.80 ppm. The 1H NMR signal for H-11 signal for the major isomer was
not resolved due to overlap with other signals (3.67-3.74; 3.72-3.78 ppm). Based on the
doublet in the minor product this isomer is assigned the (10S)-configuration. The major
isomer has the (10R)-configuration. The isomer distribution in 16b was close to 1:1. The

8
first eluted epimer on chromatography showed the H-11 signal as a singlet at 3.97 ppm
and therefore this product was assigned the (10R)-configuration. The isomer distribution
in 16c was also about 1:1, but separation of the epimers was not achieved.
Adduct formation using stabilized carbanion chemistry with sodium salts of diethyl
malonate, malononitrile or ethyl 3-oxo-3-phenylpropanoate afforded the products 17 in
Scheme 4. The substrate was the cyclic 11,12-carbamate 3. Acetyl deprotection of the
adduct 17 by methanolysis yielded 18. Adduct formation using N-benzyl-2-amino-2-
cyanoacetamide proceeded in the same manner to afford adduct 19. Subsequent
methanolysis furnished the target compound 20. The stereochemistry at the epimeric C10-
center is uncertain. The one-proton signal in the region 3.8-4.3 ppm appeared as a doublet
with coupling constant close to 7 Hz. The coupling constant is higher than reported for a
(10S)-isomer. In these reactions strongly basic conditions are used which may well lead to
epimerizations in favor of the (10S)-epimer. Alternatively, the highly polar substituents
may have changed the conformational preferences in the products which may affect the 1H
NMR signals. The structures of the products have tentatively been drawn in the (10R)-
epimeric form.

9
Scheme 4. Reagents and conditions: (i) R1CH2R2, NaH, THF, 0 oC to rt; (ii) MeOH, rt,
o.n., BnNHCOCH2CN, NaH, THF, 0 oC to rt.
In Scheme 1 it was shown that formation of the urethane ring in compound
the substrate 10-acetoxymethyl-2 ´-acetyl-12 -acylimidazolyl-10,11-anhydro-
10-desmethyl- was achieved in
6-methyl-3-oxodescladinosylerythromycin
3 from
O
O
O
A
38% yield using aqueous ammonia. The corresponding reaction with benzylamine
as a nucleophilic primary amine afforded the cyclic urethane 21 in 43% yield
(Scheme 5). Another urethane 23 in Scheme 5 has a 10-methylene substituent.
Neither compound has a proton at the C10-carbon. Accordingly, H-11 in the 1H
NMR resonated as singlets at 3.70 and 3.82 ppm, respectively. In addition
reactions with the smaller methylamine molecule, the reaction proceeded largely
past cyclization. A second step involved conjugate addition and thereby formation
of the diamine 22 as the major product.
Preparation of the 10-N-(methylbenzylamino)methyl amine 23 (Scheme 5) failed
in an attempted conjugate addition reaction between the methylene substrate 23
and benzylmethylamine. By a different approach, a synthetic path was developed
towards reductive N-benzylation using benzaldehyde and sodium
tri(acetoxy)borate. The major product from the diamine substrate 22 was formed
by elimination of methylamine to afford the 10-methylene derivative 22 (77%).
The minor product was the tertiary amine 24 (10%). In the 1H NMR spectra the
products 22
,
24 and 25 contained H-11 as a singlet at 3.7 ppm, 2x3.82 ppm,
)-epimer configuration.
respectively. They have been assigned the (10
R
Conjugated addition of benzylamine to the methylene derivative 23 afforded the
diamino adduct 25 in 57% yield after reflux with excess of benzylamine in THF
for 60 h. The proton NMR signal for H-11 resonated as a doublet at 4.01 ppm
with a coupling constant
have occurred.
J = 6.1 Hz. Epimerization to the (10S)-configuration may

10
Scheme 5. Reagents and conditions: (i) BnNH2, THF, MeCN, rt, 40 h; (ii) MeOH, rt, 24
h; (iii) MeNH2 (40%), THF, MeCN, rt, 60 h; (iv) PhCHO, NaB(OAc)3, THF, rt, 22 h; (v)
(v) BnNH2, THF, reflux, 60 h; (vi) TMSCHN2, CH2Cl2, 0 oC-rt, 72 h.
The C10-carbon can be transformed into a quaternary spirocarbon by [3+2] by
dipolar cycloaddition reactions. In the case presented in Scheme 6 the reagent is
trimethylsilyldiazomethane. The reaction with substrate
3 was effected in
dichloromethane at 0 oC. The reaction was slow. After 48 hours a product with

11
expected properties was isolated in 33% yield. With electron deficient alkenes the
nucleophilic diazoalkene adds to the more electrophilic -carbon of the alkene.
The initially formed 3 -4,5-dihydropyrazole is unstable and is isomerized to 1
4,5-dihydropyrazole. The slow cycloaddition reactions may be caused by
significant non-bonded interactions from the -substituents of the macrolide core.
β
H
H-
β
Therefore the cycloaddition is postulated to be stereoselective yielding spirane 26
as an intermediate. A subsequent elimination reaction affords the final product 27
H-11 in 27 has no vicinal protons for coupling and resonates as a singlet at 3.56
.
ppm. Only one singlet is seen for H-11 in support of an epimerically pure product.
Two NH signals are present as singlets at 5.50 ppm and 6.33 ppm in accordance
with structure 27. The product is tentatively assigned structure 27
.
TMS
O
N
O
N
NH
O
OMe
O
NH
O
OAc
O
OMe
O
OAc
O
NMe2
NMe2
O
(i)
O
O
HN
O
O
O
O
3
26
N
O
HN
NH
O
O
OMe
OAc
NMe2
O
O
HN
O
O
27 (33%)
Scheme 6. Reagents and conditions: (i) TMSCHN2, CH2Cl2, 0 oC-rt, 72 h.
3. Antibacterial activity
Selected ketolides have been tested for in vitro activity against strains of respiratory
pathogens from Streptococcus pneumonia and Staphylococcus aureus. Clarithromycin was
the reference standard macrolide. The data obtained are shown in Table 1. The compounds
tested have been arranged into groups according to their structures and assigned an entry
number. Square brackets show the number of these compounds in the synthetic schemes.

12
Table 1. In vitro activity of selected C10-substituted ketolides against different strains of
the respiratory pathogens S. pneumoniae and S. aureus. Minimum inhibitory concentration
(MIC) value are given in micrograms per milliliter.
R1
O
O
N
O
N
R1
R2
HN
O
N
O
O
NH
O
O
O
Entry
Entry
Entry
27
(8) [
(1) [ ] R1 = H
6a
1
2
3
(3) [ ] R = NHCH2Ph, R = H
]
]
R1 = CH2Ph
6c
1
2
21
(2) [
(4) [ ] R = NHCH2(pyridin-3-yl, R = H
1
2
25
(5) [ ] R = NHCH2Ph, R = Me
1
2
12a
(6) [
(7) [
] R = Ph, R = H
1
2
17a
] R = CH(CO2Et)2, R = H
Entry
S. pneumoniae
S. aureus
ATTC4961 BAA1402 3914 BAA1407 ATCC29213 BAA976 BAA977 ND048910
M (mef) MLS MLS (mef+erm) M (mef) iMLS (erm) cMLS (erm)
CLA 0.015
2
2
>16
>8
0.125
32
64
64
2
>64
64
2
>64
>64
64
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
1
128 >64
<0.07 0.125 2
<0.007 <0.007 2
64
64
64
1
0.25
1
0.5
2
1
>64
>64
>64
>64
>128
>128
0.015 0.06
4
4
0.25
0.25
0.06
0.06
1
<128 64
16
32
16
0.5
2
16
32
0.5
2
0.5
64
>64
128
64
16
0.125 4
0.25
2
0.25 16
The in vitro antibacterial activity values in Table 1 are minimum inhibitory
concentrations (MIC) in (µg/mL) as determined by the broth microdilution method.17 The
parent compound in this investigation was the 10-methylene derivative in entry (1). The
MIC values show that the parent compound (1) was less active than reference compound
clarithromycin. Activity was markedly increased for the more lipophilic N-carbamoyl
benzylated homologue (2). The entry group (3) – (7) shows compounds where the C10-
substituent has been changed from the unsaturation of the methylene group to a saturated
and substituted methyl group. The benzylamino derivative in entry (3) was one of the most
active compounds. Activity was lower after methylation of its carbamoyl nitrogen, entry
(5). Substitution of the benzyl group in (3) with the corresponding basic pyridine moiety,

13
as in entry (4), had little effect on MIC values. The highly polarized carbonyl derivative,
the diester in entry (6) has a similar activity profile as clarithromycin. Even the 10-spiro
compound in entry (8), had MIC values which did not differ significantly from the figures
for clarithromycin.
In summary, the activity values against S. pneumoniae ATTC as well as against S. aureus
ATCC 29213 are similar or slightly inferior to the values for the reference agent CLA.
Most of the compounds, however, showed improved activities against efflux resistant S.
pneumonia BAA1402 M(mef) as well as against inducibly resistant strains of S. aureus
BAA976 M(mef), and some improvement towards BAA977 iMLS(erm).
The remaining target compounds in the synthetic schemes have not been tabulated
because the MIC values were similar to the values given in the Table 1.
4. Conclusion
In conclusion, we describe synthetic methodology for preparation of ketolides which are
substituted regioselectively in the C10-methyl group. In most cases the substituted methyl
group is generated with the same stereochemistry as in the original substrate. The
clarithromycin derived substrate 10,11-anhydro-O6-methyl-descladinosylerythromycin
was used in the chemical preparations. Both N-C and C-C bond formations are exclusively
at the exocyclic methylene carbon in a C11-C12-cyclic carbamate which is generated in
reaction with carbonyldiimidazole and ammonia or primary amines. Dipolar conjugate
additions were used to achieve stereoselective aminations. Carbon substituents were
introduced by Pd-catalyzed cross coupling reactions or by stabilized anionic carbon
nucleophiles. Dipolar cycloaddition reactions will afford adducts where the C10-carbon
becomes the quaternary carbon in the respective spirane. Highly pharmacophoric
functions as described in literature,11-13 can be introduced at the C10-position by chemical
methodology readily adapted from the present work.
The in vitro MIC values against strains of the respiratory pathogens S. pneumoniae and S.
aureus showed antibacterial potencies and profiles are close to the values of
clarithromycin. Together with improved activities against efflux resistent S. pneumonia
BAA1402 M(mef) as well as against inducibly resistant strains of S. aureus BAA976
M(mef) and some improvement towards BAA977 iMLS(erm).

14
5. Experimental
1H NMR spectra were recorded in CDCl3 or DMSO at 300 MHz with Bruker DPX 300.
13C NMR spectra were recorded at 75 MHz. Chemical shifts are reported in ppm using
CHCl3 (7.24 ppm) and CDCl3 (77 ppm) as references. In DMSO the references were 2.49
ppm for 1H NMR and 39.5 ppm for 13C NMR. Mass spectra were recorded at 70 eV. The
spectra are represented as m/z (% relative intensity). Electrospray spectra were obtained
with a Micromass QTOF 2 W spectrometer with electrospray ionization quadrupole time
of flight. Melting points are uncorrected.
The reactions were performed under an inert atmosphere except for the N-oxidation of the
macrolides. THF was distilled from sodium/benzophenone. Dichloromethane and
triethylamine were distilled from calcium hydride. Merck silica gel 60 (230-400 mesh)
was used for flash chromatography.
In vitro antibacterial activities: The in vitro minimal inhibitory concentrations (MICs) in
µg/mL have been determined by standard broth microdilution methodology.17
10-Acetoxymethyl-2´O-acetyl-10,11-anhydro-10-desmethyl-O6-methyl-3-oxo-
descladinosylerythromycin A (1)
10-Acetoxymethyl-2´O-acetyl-10,11-anhydro-10-desmethyl-O6-methyl-
descladinosylerythromycin A1 (1.50 g, 2.30 mmol) was dissolved in dichloromethane (40
mL) and Dess-Martin periodinane reagent (1.40 g, 3.10 mmol) was added. The reaction
mixture was stirred at room temperature for 3 h before the mixture was concentrated under
reduced pressure. The residual material was dissolved in ethyl acetate, the solution washed
with dilute KOH (pH adjusted to 10-11), with brine and dried (MgSO4). The crude
product was a white solid with mp 172-174 oC; yield 0.93 g (87%). Spectroscopic and
spectrometric data are available.1
10-Acetoxymethyl-2´O-acetyl-12O-acylimidazolyl-10,11-anhydro-10-desmethyl-O6-
methyl-3-oxodescladinosylerythromycin A (2)
10-Acetoxymethyl-2´O-acetyl-10,11-anhydro-10-desmethyl-O6-methyl-3-
oxodescladinosylerythromycin A (1) (0.333 g, 0.496 mmol) was dissolved in THF (4 mL)
and the solution cooled to 0 oC before NaH (0.036 g, 1.49 mmol) was added. A solution
of carbonyldiimidazole (0.221 g, 1.4 mmol) in THF (2 mL) was added dropwise over 5
min to the reaction mixture which was stirred for 17 h, cooled to 0 oC and the reaction
quenched with aqueous sodium bicarbonate. The product was extracted into ethyl acetate,
washed with water (pH 10-11), with brine and dried (Na2SO4). The crude product was a
white solid; yield 0.227 g (60%). The crude product was pure according to NMR and was

15
used as such in the next step without further purification. Spectroscopic and spectrometric
data are available.1
2´O-Acetyl-11N,12O-cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-10-
methylene-3-oxodescladinosylerythromycin A (3)
Ammonia(aq) (0.2 mL) was added to a solution of 10-acetoxymethyl-2´O-acetyl-12O-
acylimidazolyl-10,11-anhydro-10-desmethyl-O6-methyl-3-oxodescladinosylerythromycin
A (2) (0.127 g, 0.166 mmol) in acetonitrile (2 mL) and THF (0.2 mL). The reaction
mixture was stirred at room temperature for 24 h and concentrated under reduced pressure.
The residual material was dissolved in ethyl acetate, the solution washed with dilute KOH
(pH adjusted to 10-11), with brine and dried (MgSO4). The solution was evaporated and
the residual material subjected to flash chromatography on silica gel. Elution was with
acetone:hexane, initial ratio 2:1, and then 1:1.The product was a white solid with mp 142-
145 oC; yield 0.042 g (38%). Spectroscopic and spectrometric data are available.1
2´O-Acetyl-12O-acylimidazolyl-10,11-anhydro-10-azidomethyl-10-desmethyl-O6-
methyl-3-oxodescladinosylerythromycin A (5).
NaH (0.006 g, 0.200 mmol) was added to a solution of 2´O-acetyl-10,11-anhydro-10-
azidomethyl-10-desmethyl-O6-methyl-3-oxodescladinosylerythromycin A (4)1 (0.044 g,
0.067 mmol) in THF (2 mL) at 0 oC. A solution of carbonyldiimidazole (CDI) in THF (1
mL) was added dropwise over 5 min. The resultant solution was stirred at room
temperature for 17 h, cooled to 0o C before being quenched with sodium bicarbonate,
extracted with ethyl acetate, the organic extracts washed with water (pH 10-11), with brine
and dried (MgSO4). The crude product was a white solid, yield 0.050 g (59%). HRMS
[Na+]: M 769.3760. Calc. for C36H54N6O11: 769.3742. The crude product was used in the
subsequent step without further purification.
2´O-Acetyl-11N,12O-cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-10-
methylen-3-oxodescladinosylerythromycin A (3) available from the azide 4.1
Ammonia(aq) (0.2 mL) was added to a solution of 2´O-acetyl-12O-acylimidazolyl-10,11-
anhydro-10-azidomethyl-10-desmethyl-O6-methyl-3-oxodescladinosylerythromycin A
(4)1 (0.07 mmol) in acetonitrile (2 mL) and THF (0.2 mL). The mixture was stirred at
room temperature for 17 h. The reaction mixture was concentrated under reduced pressure
and the residual material was dissolved in ethyl acetate. The solution was washed with
water/KOH (pH adjusted to 10-11), with brine and dried (MgSO4). The solution was
evaporated and the residual material subjected to flash chromatography on silica gel using

16
acetone .hexane, initially 2:1, then 1:1. The product was an off-white solid; yield 0.026 g
(60%). HRMS [Na+]: M 653.4. Spectra were the same as spectra for the originally
produced compound 8.1
10-Benzylaminometyl-10N,12O-cyclocarbamate-10-deshydroxy-10-
desmethyl-O6-methyl-3-oxodescladinosylerythromycin A (7a).1
10-(2-Phenylethaneaminomethyl)-10,12-cyclocarbamate-10-deshydroxy-10-
desmethyl-O6-methyl-3-oxodescladinosylerythromycin A (7b).
A solution of phenethylamine (0.093 mL, 0.73 mmol) and 2'O-acetyl- 11,12-
cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-10-methylen-3-
oxodescladinosylerythromycin A (3) (0.12 g, 0.18 mmol) in THF (15 mL) was heated
under reflux for 24 h. More phenethylamine (0.090 mL, 0.71 mmol) was added and the
mixture heated for another 24 h. The solution was concentrated at reduced pressure, and
the residual material extracted with ethyl acetate, the solution washed with NaHCO3, with
brine, the solution dried (MgSO4) and the solvent distilled off. The residual product 6b
was a yellow oil. The adduct 6b was dissolved in methanol (5 mL) and the solution
stirred at room temperature for 24 h. The solvent was evaporated, and the product
subjected to flash chromatography on silica gel using CH2Cl2:MeOH:NH3 90:10:2. Flash
chromatography was repeated using CH2Cl2:MeOH:NH3(aq) 92:6:1. The title compound
7b was a white solid; yield 0.06 g (45%). HRMS (Electrospray, H+): M 732.4448. Calcd.
for C39H62N3O10:
M 732.4435. 1H NMR (300 MHz; CDCl3): δ 0.88 (3H, t, J = 7.3 Hz,
CH3), 1.07 (3H, d, J = 7.0 Hz, CH3), l.21-1.31 (1-OH, m), 1.39 (3H, d, J = 6.8 Hz, CH3),
1.48 (3H, s, CH3), 1.51-1.61 (2H, m), 1.61-1.77 (2H, m), 1.86-1.96 (lH, m), 2.28 (6H,
s, N(CH3)2), 2.42-2.52 (1H, m), 2.55-2.62 (1H, m), 2.70 (3H, s, OCH3), 2.70-2.88
(5H, m), 2.90-2.99 (3H, m), 3.15-3.20 (1H, m), 3.51-3.58 (2H, m), 3.80 (lH, q,
Hz), 3.93 (lH, s), 4.17 (lH, d, =7.8 Hz), 4.34, (1H, d, = 7.3 Hz), 5.07 (lH, dd,
10.0, 2.6 Hz), 5.60 (1H, s, NH), 7.14-7.22 (3H, m, Ar), 7.27-7.31 (2H, m, Ar); 13C
J =6.8
J
J
J =
NMR (75 MHz; CDC13): δ 10.6 (CH3), 13.8 (CH3), 14.4 (CH3), 16.2 (CH3), 17.6 (CH3),
19.5 (6-CH3), 21.2 (CH3), 22.6, 28.2, 36.0, 39.S, 40.2 (N(CH3)2), 44.3, 44.5, 47.7, 47.8,
49.2, 51.2, 51.S, 57.S, 65.9, 69.S, 70.3, 76.3, 78.0, 78.6, 83.9, 103.6, 126.2, 128.4, 128.7,
139.7(C), 157.8 (C), 169.3(C), 204.6 (C), 217.5 (C).
10-(3-Picolylaminomethyl)-11N,12O-cyclocarbamate-11-deshydroxy- 10-desmethy1-
O6- methyl-3-oxodescladinosylerythromycin A (7c)
A solution of 3-picolylamine (0.127 g, 1.17 mmol) and 2'O-acetyl- 11,12-
cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-10-methylen-3-oxo-

17
descladinosylerythromycin A (3) (0.192 g, 0.294 mmol) in THF (18 mL) was heated at
reflux for 24 h. Another portion of 3-picolylamine (0.127 g, 1.17 mmol) was added and
the mixture heated for another 24 h. The solution was concentrated at reduced pressure,
and the residual material extracted with ethyl acetate, the solution washed with aq.
NaHCO3, with brine and dried (MgSO4). The solution was evaporated and the residual
material was subjected to flash chromatography on silica gel using
CH2Cl2:MeOH:NH3(aq) 90:4:1. The product 6c was a white solid 0.035 (16%). The
product 6c (0.02 g, 0.026 mmol) was stirred in methanol (1.5 mL) at room
temperature for 24 h, the solvent evaporated, and the product subjected to flash
chromatography on silica gel using CH2Cl2:MeOH:NH3(aq) 90:5:1. The title compound
7c was a white solid; yield 0.013 g (72%). HRMS (Electrospray, H+): M 719.4236. Calcd
for C37H58N4O10: M 719.4231. 1H NMR (300 MHz; CDCl3): δ 0.85 (3H, t, J = 7.3 Hz,
CH3), 1.15 (3H, d, J = 7.0 Hz, CH3), l.21-1.32 (1OH, m), 1.37 (3H, d, J = 6.8 Hz, CH3),
1.46 (3H, s, CH ), 1.51-1.59 (2H, m), 1.60-1.69 (2H, m), 1.86-1.94 (lH, m), 2.25 (6H,
3
s, N(CH3)2, 2.30-2.52 (2H, m), 2.61 (3H, s, 6-OCH3), 2.88-3.03 (SH, m), 3.06-3.19
(2H, m), 3.50-3.56 (2H, m), 3.70 (1H, brs) 3.77 (1H, q, J = 6.8 Hz), 3.82 (lH, s), 4.15
(1H, d,
7.19-7.25 (IH, m, Ar), 7.55-7.59 (1H, m, Ar), 8.45-8.49 (2H, m, Ar); 13C NMR (75
MHz; CDCl3): 10.5 (CH3), 13.9 (CH3), 14.4 (CH3), 163 (CH3), 17.8 (CH3), 19.5 (CH3),
J =7.8 Hz), 4.30 (1H, d, J= 7.3 Hz), 5.07-5.08 (IH, m), 5.63 (lH, s, NH),
δ
21.1 (CH3), 22.6, 28.1, 39.6, 40.2, (N(CH3)2), 44.4, 47.6, 47.8, 49.2, 51.2, 51.9, 57.5,
65.8, 69.5, 70.2, 76.3, 77.2, 78.0, 78.7, 83.8, 103.6, 123.3, 134.9 (C), 135.7, 148.6,
149.5, 157.7 (C), 169.3(C), 204.5 (C), 216.9 (C).
10-(Furan-2-yl)methylamino)methyl)-11N,12O-cyclocarbamate-11-deshydroxy-10-
desmethyl-O6-methyl-3-oxo-descladinosylerythromycin A (7d)
A solution of (furan-2-yl)methanamine (0.09 mL, 0.92 mmol) and 2'O-acetyl-11N-
12O- cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-10-methylen-3-oxo-
descladinosylerythromycin A (3) (0.15 g, 0.23 mmol) was heated in THF (12 mL) at
reflux for 28 h. More (furan-2-yl)methanamine (0.045 mL, 0.46 mmol) was added
and the mixture was heated for another 30 h. The solution was concentrated at
reduced pressure, and the residual material was extracted with ethyl acetate (3x15
mL), the organic solution washed with aqueous NaHCO3, with brine and dried over
(MgSO4). The solvents were distilled off and the residual solid subjected to flash
chromatography on silica gel using CH Cl :MeOH:NH
100:10:2. The product 6d
3(aq)
2
2
was a white solid; yield 0.10 g (58%). The adduct 6d (50 mg) was dissolved in
methanol (2 mL) and stirred at room temperature for 24 h before the solvent was

18
evaporated, and the residual product was subjected to flash chromatography on silica
gel using CH2Cl2:MeOH:NH3 92:8:2. The title compound 7d was a white solid; yield
0.40 g (85%). HRMS (Electrospray, H+): M 708.4078. Calcd for C36H58N3O11: M
708.4071. 1H NMR (300 MHz; CDCl3): δ 0.86 (3H, t, J = 7.4 Hz, CH3), 1.18-1.31
(14H, m), 1.37 (3H, d, J = 6.8), 1.49 (3H, s, CH3), 1.57-1.70 (4H, m), 1.72-1.80 (1H,
m), 1.85-1.95 (1H, m), 2.27 (6H, s, N(CH3)2), 2.40-2.50 (lH, m), 2.62 (3H, s), 3.00
(2H, s), 3.03-3.07 (1H, m), 3.17-3.20 (1H, m), 3.52-3.55 (lH, m), 3.79 (1H, q,
6.8 Hz), 3.87-3.90 (2H, m), 3.93 (lH, s), 4.15 (1H, d, = 7.8 Hz), 4.32 (1H, d,
7.3 Hz), 5.06 (1H, dd, = 10.0, 2.6 Hz), 5.60 (1H, brs), 6.85-6.83 (2H, m), 7.17
(1H, dd, 10.6 (CH3) , 13.9, (CH3)
=5.1, 1.2 Hz); 13C NMR (75 MHz, CDCl3):
J =
J
J =
J
J
δ
14.5 , 16.3 , 18.0 , 19.6 (CH3), 21.2 (CH3), 22.7, 28.3, 39.7, 40.3 (CH3)x2, 44.4, 44.6,
47.3, 47.8, 49.1, 49.2, 51.3, 57.6, 66.0, 69.5, 70.3, 76.4, 78.1, 78.8, 84.0, 103.7,
124.5, 125.0, 126.7, 143.5 (C), 157.8(C), 169.4 (C), 204.7 (C), 217.3 (C).
10-(Thiophen-2-yl)methylaminomethyl)-11N,12O-cyclocarbamate-11-deshydroxy-
10-desmethyl-06-methyl-3-oxodescladinosylerythromycin A (7e)
A solution of (thiophen-2-yl)methanamine (0.11 g, 0.97 mmol) and 2'O-acetyl-
11N,12O- cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-10-methylene-3-
oxo-descladinosyl- erythromycin A (3) (0.16 g, 0.24 mmol) was heated in THF (12
mL) under reflux for 28 h. Another portion of (thiophen-2-yl)methanamine (0.10 g,
0.88 mmol) was added and the mixture was heated for another 30 h. The solution was
concentrated at reduced pressure, the residual material extracted with ethyl acetate
(3x15 mL), the solution washed with NaHCO3, with brine and then dried over
(MgSO4). Finally the solvents were removed in vacuo. The residual solid 6e was
subjected to flash chromatography on silica gel using CH2Cl2:MeOH:NH3(aq)
90:10:2 to furnish 6e as a white solid. The adduct 6e was dissolved in methanol and
the solution stirred (2 mL) for 24 h. The solvent was evaporated, and the product
was subjected to flash chromatography on silica gel using actone:hexane 1.5:1. The
title product 7e was a white solid; yield 0.06 g (32%). HRMS: (Electrospray, H+): M
724.3856. Calcd for C36H58N3O10S: M 724.3842; 1NMR (300 MHz; CDCl3): δ 0.86
(3H, t, J = 7.4 Hz, CH3), 1.18-1.31 (14H, m), 1.37 (3H, d, J = 6.8 Hz, CH3), 1.49 (3H,
s, CH ), 1.57-1.70 (4H, m), 1.72-1.80 (lH, m), 1.85-1.95 (1H, m), 2.27 (6H, s,
3
N(CH3)2), 2.40-2.50 (lH, m), 2.62 (3H, s), 3.00 (2H, s), 3.03-3.07 (lH, m), 3.17-
3.20 (1H, m), 3.52-3.55 (1H, m), 3.79 (1H, q,
(1H, s), 4.15 (1H, d, = 7.8 Hz), 4.32 (lH, d,
J
= 6.8 Hz), 3.87-3.90 (2H, m), 3.93
= 7.3 Hz), 5.06 (1H, dd, 10.0,2.6
5.1,1.2 Hz). 13C NMR (75
J
J
J =
Hz), 5.60 (1H, brs), 6.85-6.83 (2H, m), 7.17 (1H, dd, J =

19
MHz; CDCl3): δ 10.6 (CH3), 13.9 (CH3), 14.5 (CH3), 16.3 (CH3), 18.0 (CH3), 19.6
(CH3), 21.2 (CH3), 22.7 (CH3), 28.3(CH3), 39.7(CH3), 40.3 (CH3)x2, 44.4, 44.6,
47.3, 47.8, 49.1, 49.2, 51.3, 57.6, 66.0, 69.5, 70.3, 76.4, 78.1, 78.8, 84.0, 103.7,
124.5, 125.0 126.7, 143.5 (C), 157.8 (C), 169.4 (C), 204.7 (C), 217.3 (C).
10-(N-1-Phenylethan-1-yl)aminomethyl-11
N,12O-cyclocarbamate-11-
deshydroxy-10-desmethyl-
O
6-methyl-3-oxodescladinosylerythromycin A (9)
A solution of 1 phenylethan-1-amine (0.13 mL, 0.96 mmol) and 2'O-acetyl-
11N,12O- cyclocarbamate-11-deshydroxy-l0-desmethyl-06-methyl-l0-methylen-3-oxo-
descladinosylerythromycin A (3) (0.15 g, 0.24 mmol) was heated under reflux for 28
h. Another portion of phenylethan-1-amine (0.07 mL, 0.48 mmol) was added and the
mixture was heated for an additional 30 h. The solution was concentrated at reduced
pressure, and the residual material was extracted with ethyl acetate, the extract
washed with NaHCO3, and brine before being dried over (MgSO4). The solvents were
removed at reduced pressure. The residual solid was subjected to flash
chromatography on silica gel using CH2Cl2:MeOH:NH3(aq) 90:5:1. The product 8
was a white solid; yield 0.1 g (55%). The 2'O-acetyl adduct 8 (25 mg) was dissolved
in methanol (2 mL) and the solution stirred at room temperature overnight. The
solvent was evaporated, and the product was subjected to flash chromatography on
silica gel using CH2Cl2:MeOH:NH3(aq) 90:10:2. The title product 9 was a white
solid; yield 0.02 g (86%). HRMS (Electrospray, H+): M 732.4448. Calcd for
C39H62N3010: M 732.4435. 1H NMR (300 MHz; CDCl3):
δ 0.85 (3H, t, J =7.3 Hz, CH3),
1.07 (3H, d, J = 7.0 Hz, CH ), 1.15-1.31 (15H, m), 1.32-1.34 (3H, m), 1.50 (3H, s,
3
CH3), 1.60-1.80 (4H, m), 1.80-1.90 (1H, m), 2.26 (6H, s, N(CH3)2), 2.61 (lH, d, J =
11.9 Hz), 2.70-2.77 (2H, m), 2.88-2.91 (1H, m), 3.04-3.09 (lH, m), 3.14-3.20 (2H,
m), 3.46-3.53 (1H, m), 3.54-3.57 (1H, m), 3.79 (1H, t, J = 5.7 Hz), 3.88 (1H, d, J =
5.7 Hz), 4.16 (1H, d, J = 7.7 Hz), 4.32 (lH, d,
J =7.3 Hz), 5.04 (1H, m), 5.55 (1H,
d, J = 16.0 Hz), 7.19-7.25 (3H, m, Ar), 7.27-7.29 (2H, m. Ar).
10,11-Anhydro-10-benzyl-10-desmethyl-O6-methyldescladinosylerythromycin A
(11a)
Tris(2-furyl)phosphine (0.011 g, 0.044 mmol) and Pd2dba3.CHCl3 (0.011 mg, 0.011
mmol) were added to a deoxygenated solution of 10-acetoxymethyl-10,11-anhydro-10-
desmethyl-O6-methyldescladinosylerythromycin A (10)1 (0.280 g, 0.44 mmol) in NMP (4
mL) under argon, and the solution heated at 50 oC for 10 min to generate the catalyst
system. Subsequently, a solution of tributyl(phenyl)tin (0.28 mL, 0.88 mmol) in NMP (1
mL) was added and the resulting mixture was heated at 90 oC overnight. The solvent was

20
removed at reduced pressure, the residue extracted into ethyl acetate, the organic solution
shaken with aqueous NaHCO3, with brine, dried over MgSO4, evaporated and the residual
material subjected to flash chromatography on silica gel using CH2Cl2:MeOH:NH3
(90:10:2). The product was a white solid; 0.140 g (48%). HRMS (Electrospray, H+): M
648.4107. Calcd for C36H59N1O9: :M 648.4111; 1H NMR (300 MHz; CDCl3): δ 0.88 (t,
3H, 14-CH3), 1.02 (d, 3H, 4-CH3), 1.20-2.20 (23H, m, overlapped signals,), 2.23 (6H, s,
N(CH3)2), 2.50-2.68 (1H, m), 2.70-2.81 (1H, m), 3.03 (3H, s, OCH3), 3.15-3.22 (2H, m),
3.48-3.52 (1H, m), 3.90 (5H, s), 3.98-4.00 (2H, d, CH2C6H5), 4.06 (1H, brs, 3-H), 4.45-
4.49 (1H, d, 1’-H), 4.88-4.94 1H, (dd, 13-H), 6.49 (1H, s, 11-H), 7.07-7.25 (5H, m, H-ar);
13C NMR (75 MHz, CDCl3): 7.6, 10.4, 15.5, 16.2, 20.3, 20.7, 20.8, 21.3, 28.2, 31.5, 36.5,
36.7, 38.5, 44.2, 44.3, 48.0, 65.5, 69.7, 70.5, 74.1, 77.7, 79.1, 80.95, 92.35, 106.8, 125.9,
128.2, 128.5, 140.0, 140.7, 142.3, 176.7 (1-C=O), 207.1 (9-C=O).
10,11-Anhydro-10-desmethyl-O6-methyl-10-phenylpropynyldescladinosyl-
erythromycin A (11b)
Tris(2-furyl)phosphine (0.047 g, 0.20 mmol) and Pd2dba3.CHCl3 (0.048 mg, 0.046 mmol)
were added to a deoxygenated solution of 10-acetoxymethyl-10,11-anhydro-10-
desmethyl-O6-methyldescladinosylerythromycin A (10)1 (1.25 g, 2.0 mmol) in DMF (10
mL) under argon and the solution heated at 50 oC for 10 min to generate the catalyst
system. Subsequently, a solution of tributyl(phenylethynyl)tin (1.17 g, 1.05 mL, 3.0
mmol) in DMF (3 mL) was added and the resulting mixture was heated overnight at 80 oC.
The solvent was removed at reduced pressure, the residue extracted into ethyl acetate, the
solution shaken with aqueous NaHCO3, with brine, dried over MgSO4, evaporated and the
residual material subjected to flash chromatography on silica gel using
CH2Cl2:MeOH:NH3 (aq) 93:7:2 as eluent system. The product was a white solid material
0.630 g (47%). HRMS (Electrospray, H+): M 672.4128. Calcd for C38H58N1O9 : M
672.4111 ; 1H NMR (300 MHz; CDCl3): 0.82-0.89 (3H, t, 14-CH3), 0.99-1.02 (3H, d, 4-
CH3), 1.18-2.20 (23H, m, overlapped signals), 2.21[6H, s, N(CH3)2], 2.50-2.68 (1H, m),
2.70-2.81 (1H, m,), 3.06 (3H, s, OCH3), 3.09-3.97 (6H, m, overlapped signals), 4.45-4.49
(1H, d), 4.68-4.70 (1H, d, 1’-H), 4.90-4.95 (1H, dd, 13-H), 6.48 (1H, s, 11-H), 7.20-7.33
(5H, m, H-arom).
10,11-Anhydro-10-desmethyl-O6-methyl-10-phenylpropenyldescladinosyl-
erythromycin A (11c)
Tris(2-furyl)phosphine (0.047g, 0.20 mmol) and Pd2dba3.CHCl3 (0.048 mg, 0.046 mmol)
were added to a deoxygenated solution of 10-acetoxymethyl-10,11-anhydro-10-
desmethyl-O6-methyldescladinosylerythromycin A (10)1 (1.25 g, 2.0 mmol) in DMF (10

21
mL) under argon and the solution heated at 50 oC for 10 min to generate the catalyst
system. Subsequently, a solution of tributyl(styryl)tin (1.15 g, 3.0 mmol) in DMF (3 mL)
was added and the resulting mixture was heated overnight at 80 oC. The solvent was
removed at reduced pressure, the residue extracted into ethyl acetate, the solution shaken
with aqueous NaHCO3, with brine, dried over MgSO4, evaporated and the residual
material subjected to flash chromatography on silica gel using CH2Cl2:MeOH:NH3
(95:5:2). The product was a white solid 0.800 g (59%). HRMS (Electrospray, H+): M
674.4262. Calc. for C38H60N1O9 : M 674.4268 ; 1H NMR (300 MHz; CDCl3): δ 0.82-1.82
(25H, overlapped signals), 1.88 (1H, s), 1,70-1.73 (1H, m), 2.21 [6H, s, N(CH3)2], 2.45-
2.49 (1H, m), 2.68-2.73 (1H, m), 3.06 (3H, s, OMe), 3.18-3.24 (2H, m), 3.50-3.56 (3H, m,
overlapped signals), 3.82 (1H, s), 3.91 (1H, s), 4.00-4.05 (1H, m), 4.46-4.49 (1H, d),
4.66-4.68 (1H, dd), 4.87-4.90 (1H, dd), 6.11-6.18 (1H, m), 6.33-6.38 (1H, d), 6.51 (1H, s),
7.10-7.35 (5H, m, C6H5); 13C NMR (75 MHz, CDCl3): δ 7.5, 10.4, 15.4, 16.1, 20.3, 20.6,
20.7, 21.3, 28.2, 29.6, 39.6, 36.7, 38.4, 40.2, 44.3, 48.1, 65.5, 69.7, 70.4, 74.1, 77.8, 79.0,
81.0, 92.2, 106,8, 126.0, 127.1, 128.4, 128.5, 130.7, 137.2, 139,7, 142.8, 176.7, 206.6.
2`O-Acetyl-10,11-anhydro-10-benzyl -10-desmethyl-O6-methyldescladinosyl-
erythromycin A (12a)
A solution of 10,11-anhydro-10-benzyl-10-desmethyl-O6-methyl-
descladinosylerythromycin A (11a) (0.455 g, 0.7 mmol), triethylamine (0.196 mL, 1.4
mmol) and acetic acid anhydride (0.132 mL, 1.4 mmol) in dichloromethane (7 mL) was
stirred at room temperature for 17 h. The reaction mixture was concentrated under reduced
pressure and the product was extracted into ethyl acetate, the solution washed with
NaHCO3, brine and dried (MgSO4). The solution was evaporated and the residual material
subjected to flash chromatography on silica gel using CH2Cl2:MeOH:NEt3 90:7:2. The
product was a white solid; yield 0.32 g, 66%. HRMS (Electrospray, H+): M 690.4223.
Calcd for C38H60N1O10 : M 690.4217 ; 1H NMR (300 MHz; CDCl3): δ 0.89-0,95 (6H, m),
1.1 (3H, d, 4-CH3), 1.20-2.20 (19H, m, overlapped signals), 2.02 (3H, s, OAc), 2.22 (6H,
s, N(CH3)2), 2.69-2.72 (1H, m), 2.86 (3H, s, OCH3), 3.00-3.17 (3H, m), 3.48-3.53 1H, m),
3.70-3.72 (1H, q), 3.85 (1H, d), 4.07-4.13 (2H, m), 4.31 (1H, d), 4.67-4.73 (1H, dd), 4.89-
4.93 (1H, dd, 13-H), 6.67 (1H, s, 11-H), 7.07-7.25 (5H, m, H-arom); 13C NMR (75 MHz,
CDCl3): 8.1, 10.5, 15.6, 16.3, 20.3, 21.1, 21.2, 21.3, 21.4, 30.0, 32.0, 36.8, 36.9, 38.1,
40.7, 44.3, 48.6, 64.3, 69.3, 71.9, 77.0, 79.5, 79.5, 79.6, 89.1, 103.0, 126.0, 128.2, 128.4,
139.8, 141.7, 142.0, 170.2, 175.9, 207.1 (9-C=O).

22
2`O-Acetyl-10,11-anhydro-10-desmethyl-O6-methyl-10-phenylpropynyl-
descladinosylerythromycin A (12b)
A solution of 10,11-anhydro-10-desmethyl-O6-methyl-10-phenylpropynyl-
descladinosylerythromycin A (11b) (0.610 g, 0.88 mmol), triethylamine (0.24 mL, 1.76
mmol) and acetic acid anhydride (0.16 mL, 1.76 mmol) in dichloromethane (12 mL) was
stirred at room temperature for 17 h. The reaction mixture was concentrated under reduced
pressure and the product was extracted into ethyl acetate, the solution washed with
NaHCO3, brine and dried (MgSO4). The solution was evaporated and the residual material
subjected to flash chromatography on silica gel using CH2Cl2:MeOH:TEA 95:5:2. The
product was a white solid; yield 0.47 g (75%). HRMS (Electrospray, H+): M 714.4233.
Calcd for C40H60N1O10 : M 714.4217 ; 1H NMR (300 MHz; CDCl3): δ 0.85-0.94 (6H, m,
6H), 1.18-2.00 (23H, m, overlapped signals), 2.07 (3H, s, OCH3), 2.20 (6H, s, N(CH3)2,
2.48-2.61 (2H, m), 3.14 (3H, s, OCH3), 3.09-3.97 (6H, m, overlapped signals), 4.61-4.71
(3H, m), 5.00-5.03 (1H, dd, 13-H), 6.3 (1H, s11-H), 7.20-7.33 (5H, m, H-ar); 13C NMR
(75 MHz, CDCl3): δ 7.9, 10.5, 15.5, 16.3, 17.1, 20.1, 21.1, 21.2, 21.2, 21.4, 30.0, 37.1,
37.3, 38.8, 40.7, 44.3, 48.7, 64.2, 69.2, 71.9, 73.9, 77.3, 79.4, 80.2, 87.8, 102.8, 123.3,
127.8, 128.2, 131.5, 138.4, 141.7, 170.2, 175.9, 205.6 (9-C=O).
2`O-Acetyl-10,11-anhydro-10-desmethyl-O6-methyl-10-phenylpropenyl-
descladinosylerythromycin A (12c)
A solution of 10,11-anhydro-10-desmethyl-O6-methyl-10-phenylpropenyl-
descladinosylerythromycin A (11c) (1,00 g, 1.48 mmol), triethylamine (0.416 mL, 2.96
mmol) and acetic acid anhydride (0.28 mL, 2.96 mmol) in dichloromethane (20 mL) was
stirred at room temperature for 17 h. The reaction mixture was concentrated under reduced
pressure and the product was extracted into ethyl acetate, the solution washed with
NaHCO3, brine and dried (MgSO4). The solution was evaporated and the residual material
subjected to flash chromatography on silica gel using CH2Cl2:MeOH:NEt3 95:5:2. The
product was a white solid; yield 0.850 g (80%). HRMS (Electrospray, H+): M 716.4379.
Calcd for C40H62N1O10 : M 716.4373. 1H NMR (300 MHz; CDCl3): δ 0.82-2.03 (27H,
overlapped signals), 2.06 (3H, s, OAc), 2.19 (6H, s, N(CH3)2), 2.59-2.65 (3H, m), 3.06
(3H, s, OCH3), 3.07-3.11 (1H, m), 3.49-3.54 (3H, m, overlapped signals), 3.83-3.86 1H,
(m), 3.87-3.88 (1H, d), 4.63-4.72 (2H, m), 4.90-4.97 (1H, dd), 6.05-6.18 (1H, m), 6.29-
6.37 (1H, d), 6.47 (1H, s), 7.16-7.25 (5H, m, C6H5). 13C NMR (75 MHz, CDCl3): δ 7.9,
10.5, 15.6, 16.3, 20.2, 21.0, 21.1, 21.1, 21.4, 29.9, 30.1, 36.9, 37.17, 4.88, 40.7, 44.3, 48.6,
53.4, 64.2, 69.2, 71.9, 73.8, 77.2, 79.3, 80.2, 88.9, 102.9 126.0, 127.1, 128.2, 128.4, 130.8,
137.3, 140.9, 142.3, 170.2, 175.9, 206.6.

23
2`O-Acetyl-10,11-anhydro-10-benzyl -10-desmethyl-O6-methyl-3-oxodescladinosyl-
erythromycin A (13a)
2`O-Acetyl-10,11-anhydro-10-benzyl-10-desmethyl-O6-methyl-
descladinosylerythromycin A (12a) (0.300 g, 0.435 mmol) was dissolved in
dichloromethane (4 mL) and Dess–Martin periodinane reagent (0.258 g, 0.60 mmol) was
added. The reaction mixture was stirred at room temperature for 3 h before the mixture
was concentrated under reduced pressure. The residual material was dissolved in ethyl
acetate, the solution washed with aqueous NaOH (pH adjusted to 10–11), with brine and
dried (MgSO4). The crude product was subjected to flash chromatography on silica gel
using acetone:hexane 1.5:1. The product was a white solid; yield 0.200 g (64%). HRMS
1
(Electrospray, H+): M 688.4066. Calcd for C38H58N1O10 : M. 688.4060 ; H NMR (300
MHz; CDCl3): δ 0.89-0.95 (6H, m), 1.1 (3H, d, 4-CH3), 1.20-2.20 (17H, m, overlapped
signals), 2.02 (3H, s, OAc), 2.22 (6H, s, N(CH3)2), 2.69-2.72 (1H, m), 2.86 (3H, s, OCH3),
3.00-3.17 (3H, m), 3.48-3.53 (1H, m), 3.70-3.72 (1H, q), 3.85 (1H, d), 4.07-4.14 2H, (m,),
4.30-4.34 (1H, d), 4.67-4.72 (1H, dd), 4.89-4.94 (1H, dd, 13-H), 6.67 (1H, s, 11-H), 7.07-
7.24 (5H, m, H-Ar); 13C NMR (75 MHz, CDCl3): δ 10.8, 14.0, 15.0, 18.5, 21.0, 21.3,
22.4, 22.6, 30.0, 30.4, 32.3, 38.6, 40.6, 47.4, 50.4, 51.2, 63.4, 69.1, 71.5, 73.9, 78.3, 79.9,
81.4, 101.7, 125.9, 128.2, 128.4, 140.09, 142.5, 169.7, 169.8, 206.8 (9-C=O).
2`O-Acetyl-10,11-anhydro-10-desmethyl-O6-methyl-3-oxo-10-phenylpropynyl-
descladinosylerythromycin A (13b)
2`O-Acetyl-10,11-anhydro-10-desmethyl-O6-methyl-10-phenylpropynyl-
descladinosylerythromycin A (12b) (0.43 g, 0.60 mmol) was dissolved in
dichloromethane (5 mL) and Dess–Martin periodinane reagent (0.356 g, 0.84 mmol) was
added. The reaction mixture was stirred at room temperature for 3 h before the mixture
was concentrated under reduced pressure. The residual material was dissolved in ethyl
acetate, the solution washed with water/NaOH (pH adjusted to 10–11), with brine and
dried (MgSO4). The crude product was subjected to flash chromatography on silica gel
using CH2Cl2:MeOH:NH3(aq.) 95:5:1. The product was a white solid; yield 0.300 g
(70%). HRMS (Electrospray, H+): M 712.4081. Calcd for C40H58N1O10 : M 712.4060 ; 1H
NMR (300 MHz; CDCl3): δ 0.83-2.20 (26H, m, overlapped signals), 2.01 (3H, s, OAc),
2.22 (6H, s, N(CH3)2), 2.69-2.72 (1H, m), 2.78 (3H, s, OCH3), 3.00-3.17 (2H, m), 3.53-
3.89 (4H, m), 4.08-4.13 (2H, m), 4.30-4.34 (1H, d), 4.65-4.71 (1H, dd), 4.96-5.00 (1H, dd,
13-H), 6.60 (1H, s, 11-H), 7.21-7.35 (5H, m, H-arom); 13C NMR (75 MHz, CDCl3): δ
10.8, 14.0, 15.1, 17.3, 18.8, 20.9, 21.3, 22.4, 22.5, 26.9, 30.3, 34.6, 40.6, 40.7, 47.3, 50.1,
51.1, 63.5, 69.1, 71.5, 73.9, 78.3, 80.7, 80.9, 81.2, 88.2, 101.8, 123.2, 127.7, 128.1, 131.5,
142.7, 169.5, 169.7, 205.3 (9-C=O).

24
2`O-Acetyl-10,11-anhydro-10-desmethyl-O6-methyl-3-oxo-10-phenylpropenyl-
descladinosylerythromycin A (13c)
2`O-Acetyl-10,11-anhydro-10-desmethyl-O6-methyl-10-phenylpropenyl-
descladinosylerythromycin A (12c) (0.800 g, 1.12 mmol) was dissolved in
dichloromethane (10 mL) and Dess–Martin periodinane reagent (0.664 g, 1.56 mmol) was
added. The reaction mixture was stirred at room temperature for 3 h before the mixture
was concentrated under reduced pressure. The residual material was dissolved in ethyl
acetate, the solution washed with dilute NaOH (pH), adjusted to pH 10–11 and dried
(MgSO4). The crude product was subjected to flash chromatography on silica gel using
CH2Cl2:MeOH:NH3 95:5:2. The product was a white solid; yield 0.610 g (75%). HRMS
(Electrospray, H+): M 714.424. Calcd for C40H60N1O10 : M 714.4217 ; 1H NMR (300 MHz;
CDCl3): δ 0.82-2.03 (22H, overlapped signals), 1.99 (3H, s, OAc), 2.00-2.20 (2H, m),
2.21 (6H, s, N(CH3)2), 2.60-2.63 (3H,m), 2.81 (3H, s, OCH3), 2.96-3.13 (3H, m), 3.40-
3.56 (3H, m), 3.69-3.71 (1H, m), 4.09-4.12 (1H, d), 4.30-4.33 (1H, d), 4.66-4.69 (1H, m),
4.91-4.96 (1H, dd), 6.15-6.21 1H, (m), 6.31-6.37 (1H, d), 6.66 (1H, s), 7.22-7.26 (5H, m,
C6H5).
2`O-Acetyl-12O-acylimidazolyl-10,11-anhydro-10-benzyl-10-desmethyl-O6-methyl-3-
oxodescladinosylerythromycin A (14a)
The ketolide (13a) (0.620 g, 0.90 mmol) was dissolved in THF (8 mL) and the solution
cooled to 0 oC before NaH (60%, 0.053 mg, 1.35 mmol) was added. A solution of
carbonyl diimidazole (0.364 g, 2.25 mmol) in THF (2 mL) was added dropwise over 5
min to the reaction mixture. The solution was stirred at room temperature for 20 h before
the mixture was cooled to 0 oC, quenched with NaHCO3, extracted with ethyl acetate, the
extracts washed with NaHCO3, with brine and dried (MgSO4). The solution was
evaporated and the product was purified by flash chromatography on silica gel using
acetone/hexane 1.5:1. The product was a white solid; yield 0.210 g (29%). HRMS
(Electrospray, H+): M 782.4236. Calcd for C42H60N3O11 : M 782.4227 ; 1H NMR (300
MHz; CDCl3): δ 0.89-1.82 (28H, overlapped signals), 1.99 (3H, s, OAc), 2.19 6H, (s,
N(CH3)2), 2.51-2.60 (1H, m), 2.83 (3H, s, OCH3), 3.01-3.11 (1H, m), 3.20-3.23 (1H, m),
3.31-3.42 (1H, m), 3.67-3.74 (2H, m, overlapped signals), 3.88-3.96 (1H, d), 4.08-4.12
(2H, m), 4.30-4.34 (1H, d), 4.67-4.69 (1H, dd), 5.61-5.66 (1H, dd, 13-H), 6.82-7.23 (7H,
m, overlapped signals, Har, Himid., 11-H), 7.80 (1H, s, Himid.).
2`O-Acetyl-12O-acylimidazolyl-10,11-anhydro-10-desmethyl-O6-methyl-3-oxo-10-
benzenepropynyldescladinosylerythromycin A (14b)

25
The ketolide (13b) (0.250 g, 0.35 mmol) was dissolved in THF (5 mL) and the solution
cooled to 0 oC before NaH (60%, 0.028 mg, 0.7 mmol) was added. A solution of carbonyl-
diimidazole (0.170 g, 2.25 mmol) in THF (2 mL) was added dropwise over 5 min to the
reaction mixture. The solution was stirred for 20 h at room temperature. The reaction
mixture was cooled to 0 oC, quenched with NaHCO3, diluted with ethyl acetate, washed
with NaHCO3, with brine and dried (MgSO4). The solution was evaporated and the
compound (14b) was purified by flash chromatography on silica gel using acetone/hexane
2:1. The product was a white solid; yield 0.120 g (42%). HRMS (Electrospray, H+): M
806.4241. Calcd for C44H60N3O11: M 806.4227 ; 1H NMR (300 MHz; CDCl3): δ 0.89-1.82
(26H, overlapped signals), 1.99 (3H, s, OAc), 2.21 (6H, s, N(CH3)2), 2.51-2.60 (1H, m),
2.72 (3H, s, OCH3), 2.97-3.29 (2H, m), 3.53-3.89 (3H, m, overlapped signals), 4.11-4.15
(1H, m), 4.33-4.37 (1H, d), 4.69-4.76 (1H, dd), 5.66-5.71 (1H, dd, 13-H), 6.93-7.19 (7H,
m, overlapped signals, Har, Himid., 11-H), 8.04 (1H, s, Himid).
13C NMR (75 MHz, CDCl3): δ
1.9, 10.4, 13.8, 15.0, 17.9, 18.6, 20.4, 20.9, 21.3, 22.5, 25.6, 30.3, 40.6, 47.5, 50.3, 51.0,
63.6, 68.0, 69.2, 71.5, 78.6, 80.9, 83.8, 85.5, 116.3, 117.0, 123.0, 127.6, 127.8, 130.6,
131.4, 136.8, 137.7, 139.2,146.0, 168.9, 169.7 (9-C=O and 3-C=O, not seen).
2`O-Acetyl-12O-acylimidazolyl-10,11-anhydro-10-desmethyl-O6-methyl-3-oxo-10-
phenylpopenyl-descladinosylerythromycin A (14c)
The ketolide (13c) (0.600 g, 0.84 mmol) was dissolved in THF (10 mL) and the solution
cooled to 0 oC before NaH (60%, 0.050 mg, 1.26 mmol) was added. A solution of
carbonyl diimidazole (0.34 g, 2.1 mmol) in THF (3 mL) was added dropwise over 5 min
to the reaction mixture. The solution was stirred at room temperature for 20 h. The
reaction mixture was cooled to 0 oC, quenched with NaHCO3, diluted with ethyl acetate,
washed with NaHCO3, with brine and dried (MgSO4). The solution was evaporated and
the product was purified by flash chromatography on silica gel using acetone:hexane 2:1.
The product was a white solid; yield 0.200 g (29%). HRMS (Electrospray, H+): M
808.4393. Calcd for C44H62N3O11: M 808.4384 .
2`O-Acetyl-10-benzyl-11N,12O-cyclocarbamate-11-deshydroxy-10-desmethyl-O6-
methyl-3-oxo-descladinosylerythromycin A (15a)
Ammonia(aq) (0.3 mL) was added to a solution of 2`O-acetyl-12O-acylimidazolyl-10,11-
anhydro-10-benzyl-10-desmethyl-O6-methyl-3-oxo-descladinosylerythromycin A (14a)
(0.150 g, 0.192 mmol) in acetonitrile (3 mL) and THF (0.3 mL) and the mixture stirred at
room temperature for 48 h. The mixture was concentrated under reduced pressure and the
residual material was dissolved in ethyl acetate. The solution was washed with dilute
NaOH (pH adjusted to 10–11), with brine and the solution dried (MgSO4). The solution

26
was evaporated and the residual material subjected to flash chromatography on silica gel
using acetone:hexane 3:2. The product was a white solid, mixture of 2 diastereomers (2:1).
Isolation of pure isomers failed; yield 0.063 g (45%). The product was used in the next
reaction step as a mixture of diastereomers. HRMS (Electrospray, H+): M 731.4132
Calcd for C39H59N2O11: M 731.4118 .
2`O-Acetyl-11N,12O-cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-3-oxo-
10-benzenepropynyl-descladinosylerythromycin A (15b)
Ammonia(aq) (0.3 mL) was added to a solution of 2`O-acetyl-12O-acylimidazolyl-10,11-
anhydro-10-desmethyl-O6-methyl-3-oxo-10-benzenepropynyldescladinosylerythromycin
A (14b) (0.100 g, 0.124 mmol) in acetonitrile (3 mL) and THF (0.3 mL) and the mixture
stirred at room temperature for 48 h. The reaction mixture was concentrated under reduced
pressure and the residual material was dissolved in ethyl acetate. The solution was washed
with dilute NaOH (pH adjusted to 10–11), with brine and dried (MgSO4). The solution
was evaporated and the residual material subjected to flash chromatography on silica gel
using acetone:hexane 1.5:1. The product was a white solid, mixture of 2 diastereomers
(1:1); isolation of pure isomers failed; yield 0.060 g (64%). The the diastereomeric
product was used in the next reaction step. HRMS (Electrospray, H+): M 755.4138
Calcd for C41H59N2O11: M 755.4118 .
2`O-Acetyl-11N,12O-cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-3-oxo-
10-benzenepropenyl-descladinosylerythromycin A (15c)
Ammonia(aq) (0.3 mL) was added to a solution of 2`O-acetyl-12O-acylimidazolyl-10,11-
anhydro-10-desmethyl-O6-methyl-3-oxo-10-benzenepropenyl-descladinosylerythromycin
A (14c) (0.200 g, 0.24 mmol) in acetonitrile (3 mL) and THF (0.3 mL) and the mixture
stirred at room temperature for 48 h. The reaction mixture was concentrated under reduced
pressure and the residual material was dissolved in ethyl acetate. The solution was washed
with dilute NaOH (pH adjusted to 10–11), with brine and dried (MgSO4). The solution
was evaporated and the residual material subjected to flash chromatography on silica gel
using acetone:hexane 2:1. The product was a white solid which was obtained as a mixture
of 2 diastereomers (1:1); isolation of pure isomers failed; yield 0.085 g (49%). The
product was used in the next reaction as a mixture of diastereomers. HRMS (Electrospray,
H+): M 757.4299. Calcd for C41H61N2O11 757.4299.
10-Benzyl-11N,12O-cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-3-oxo-
descladinosylerythromycin A (16a)

27
Methanol (2 ml) was added to the cyclic carbamate (15a) (0.063 g, 0.086 mmol) and the
mixture stirred at room temperature overnight. The methanol was removed under reduced
pressure and the crude product was purified by flash chromatography on silica gel using
CH2Cl2: MeOH: NH3 90:5:2. Partial separation of pure diastereomers was achieved:
The major isomer: 20 mg. HRMS (Electrospray, H+): M 689.4026. Calcd for
C37H57N2O10: M 689.4013 ; 1H NMR (300 MHz; CDCl3): δ 0.45-0.48 (3H, d), 0.82-2.03
(28H, overlapped signals), 2.22 (6H, s, N(CH3)2), 2.31-2.60 (1H, m), 2.77 (3H, s, OCH3),
2.81-3.65 (4H, m, overlapped signals), 3.67-3.74 (2H, m, overlapped signals), 3.72-3.78
(2H, m), 4.04-4.08 (1H, d, 5-H), 4.24-4.27 (1H, d, 1’-H), 4.98-5.04 (1H, dd, 13-H), 6.62
(1H, s, NH), 7.02-7.19 (5H, m, H-Ar); 13C NMR (75 MHz, CDCl3): δ 10.7, 14.9, 15.9,
17.4, 18.2, 20.4, 21.2, 22.5, 28.3, 31.7, 39.8, 40.3, 41.8, 48.7, 50.3, 51.3, 58.6, 60.6, 65.7,
69.5, 70.2, 77.7, 78.6, 79.5, 86.2, 104.1, 126.5, 128.5 (4 x Car), 139.8, 158.6, 169.9, 204.9,
214.6.
The minor isomer: 10 mg. HRMS (Electrospray, H+): M 689.4023. Calcd for C37H57N2O10
: M 689.4013 ; 1H NMR (300 MHz; CDCl3): δ 0.00-0.03 (3H, d), 0.82-2.03 (28H,
overlapped signals), 2.21 (6H, s, N(CH3)2), 2.31-2.60 (1H, m), 2.63 (3H, s, OCH3), 2.96-
3.07 (4H, m, overlapped signals), 3.40-3.64 (2H, m, overlapped signals), 3.76-3.80 (1H,
d), 4.08-4.12 (3H, m), 4.27-4.30 (1H, d, 1’-H), 5.09-5.16 (1H, dd, 13-H), 5.59 (1H, s,
NH), 7.02-7.23 (5H, m, Har).
11N,12O-Cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-3-oxo-10-
phenylpropynyl-descladinosylerythromycin A (16b)
Methanol (2 ml) was added to the cyclic carbamate (15b) (0.060 g, 0.079 mmol) and the
mixture stirred at room temperature overnight. The methanol was removed under reduced
pressure and the crude product was purified by flash chromatography on silica gel using
CH2Cl2: MeOH: NH3 93:7:2. Pure diastereomers were isolated.
The first isomer: 23 mg. HRMS (Electrospray, H+): M 713.4019. Calcd for
C39H57N2O10 713.4013 ; 1H NMR (300 MHz; CDCl3): δ 0.80-1.75 (25H, overlapped
signals), 1.86-2.02 1H, (m,), 2.23 (6H, s, N(CH3)2), 2.37-2.49 (1H, m), 2.63 (4H, s+m),
2.73-2.77 (2H, d), 2.98-3.19 (3H, m, overlapped signals), 3.40-3.63 (2H, m, overlapped
signals), 3.78-3.84 (1H, q), 3.97 (1H, s), 4.14-4.18 (1H, d, 5-H), 4.30-4.34 (1H, d, 1’-H),
5.04-5.09 (1H, dd, 13-H), 5.61 (1H, s, NH), 7.24-7.36 (5H, m, H-Ar);
The second isomer: 20 mg. HRMS (Electrospray, H+): M 713.4023. Calcd for
C39H57N2O10: 713.4013 ; 1H NMR (300 MHz; CDCl3): δ 0.80-1.75 (25H, overlapped

28
signals), 1.86-2.02 (1H, m, 1H), 2.24 (6H, s, N(CH3)2), 2.39-2.49 (1H, m), 2.78 (3H, s),
2.79-2.85 (3H, m), 3.00-3.07 (2H, m), 3.12-3.18 (1H, m), 3.45-3.56 (2H, m, overlapped
signals), 3.61-3.63 (1H, m), 3.76-3.86 (1H, q), 4.14-4.16 (1H, d, 5-H), 4.26-4.30 (1H, d,
1’-H), 4.96-5.02 (1H, dd, 13-H), 5.32 (1H. s, 1H), 7.24-7.36 5H, (m, 5H, H-Ar).
11N,12O-Cyclocarbamate-11-deshydroxy-10-desmethyl-O6-methyl-3-oxo-10-
benzenepropenyl-descladinosylerythromycin A (16c)
Methanol (2 ml) was added to the cyclic carbamate (15c) (0.073 g, 0.096 mmol) and the
mixture stirred at room temperature overnight. The methanol was removed under reduced
pressure and the crude product was purified by flash chromatography on silica gel using
CH2Cl2: MeOH: NH3(aq) 90:10:2. A mixture of diastereomers was isolated; yield 50 mg
(53%).
10-(2,2-Bis(ethoxycarbonyl)ethan-1-y1)-11N,12O-cyclocarbamate-11-deshydroxy-
6-methyl-3-oxodescladinosylerythromycin A
10 desmethyl-
0
(18a
)
The ketolide 3 (0.12 g, 0.18 mmol)) was dissolved in THF (6 mL) and the solution cooled
to 0 °C before NaH (60%, 0.01 g) was added. Diethyl malonate (0.07 mL, 0.45 mmol)
was added dropwise over 5 min to the reaction mixture. The solution was stirred at room
temperature for 23 h, the reaction mixture cooled to 0 °C, NaHCO3 added, the mixture
extracted with ethyl acetate (3x15 mL), the extracts washed with brine, dried (MgSO4)
and the solution evaporated. The residual material was subjected to flash
chromatography on silica gel using CH2Cl2:MeOH:NH3(aq) 90:10:2. The product 17a
was white solid; yield 0.058 (39%). Compound 17a (0.04 g) was dissolved in methanol
(2 mL) and the solution stirred at room temperature for 24 h. The solvent was distilled
off and the residual material was subjected to flash chromatography on silica gel using
actone:hexane 3:2. The title compound 18a was a white solid; yield 0.03 g (79%).
18a: HRMS (Electrospray, H+): M 771.4289. Calcd for C38H64N2O14: M 771.4279. 1H
NMR (300 MHz; CDCl3): δ 0.87 (3H, t, J = 7.4 Hz, CH3), 1.02 (3H, d, J = 7.0 Hz, CH3),
1.18-1.32 (16H, m), 1.37 (3H, d, J = 6.8 Hz, CH3), 1.50-1.60 (2H, m), 1.66 (3H, s),
1.67-1.73 (2H, m) , 1 . 8 9 - 1 9 4 ( 2 H , m ) , 2 . 2 2 - 2 . 2 5 ( 1 H , m ) , 2 . 2 6 ( 6 H , s ,
N ( C H 3 ) 2 , 2.64 (3H, s), 3.02-3.19 (4H, m), 3.52-3.60 (2H, m), 3.79 (1H, q, J = 6.8 Hz ),
4.09-4.24 (6H, m), 4.33 (1H, d, J = 7.3 Hz), 5.08 (1H, dd, J = 9.8, 2.7 Hz), 5.36 (lH,
brs). 13C NMR (75 MHz; CDCl3): δ10.7 (CH3), 12.8 (CH3), 13.9 (CH3), 14.0 (CH3), 14.5
(CH3), 16.1 (CH3), 17.7 (CH3), 19.6 (CH3), 21.2 (CH3), 22.8, 26.0, 28.3, 39.1, 40.2
(CH3)x2, 41.7, 44.4, 47.5, 49.2, 49.6, 51.4, 57.68, 6.69, 61.9, 65.9, 69.5, 70.2, 76.1,

29
78.1, 78.2, 84.5, 103.5, 157.9 (C), 168.5 (C), 169.1 (C), 169.4 (C), 204.8 (C), 216.8
(C).
10-(2,2-Biscyanoethan-1-yl)-11N,12O-cyclocarbamate-11-deshydroxy-10-desmethyl-06-
methyl-3-oxodescladinosylerythromycin A (18b)
The ketolide 3 (0.15 g, 0.22 mmol) was dissolved in THF (5 mL) and the solution cooled to
0 °C before NaH (60%, 0.01 g) was added. Malononitrile (0.06 g, 0.90 mmol) was added
dropwise over 5 min to the reaction mixture. The solution was stirred at room temperature
for 23 h before the reaction mixture was cooled to 0 °C and NaHCO3 added. The mixture
was extracted with ethyl acetate (3x15 mL), washed with brine and dried (MgSO4). The
solution was evaporated and the residual material was subjected to flash
chromatography on silica gel using CH2Cl2:MeOH:NH3(aq) 90:10:2. The product 17b
was a white solid; yield 0.12 g (73%). Compound 17b was stirred in a methanol solution (2
mL) at room temperature for 24 h. The solvent was evaporated, and the residual material
was subjected to flash chromatography on silica gel using CH2Cl2:MeOH:NH3(aq) 90:10:2.
The title compound 18b was a white solid; yield 0.085 g (90%). HRMS (Electrospray, H+):
M 677.3779. Calcd for C34H53N4O10: 677.3761. 1HNMR (300 MHz; CDCl3): δ 0.92 (3H, t,
J = 7.8 Hz, CH3), 1.00 (3H, d, J = 7.1 Hz, CH3), 1.18-1.30 (13H, m), 1.44 (3H, d, J = 7.1
Hz, CH3), 1.49 (2H, s), 1.60-1.80 (3H, m), 1.90-2.00 (l H, m), 2.26 [6H, s, N(CH 3)2], 2.40-
2.51 (3H, m), 2.74-2.76 (IH, m), 2.85 (3H, s), 2.86-2.96 ( l H, m), 3.15-3.21 ( l H, m), 3.33-
3.38 (1H, m), 3.47-3.50 (1H, m), 3.77-4.02 (3H, m), 4.30 ( l H, d, J = 7.3 Hz), 4.85-4.99
(1H, m), 5.98 (1H, brs). 13C NMR (75 MHz; CDCl3): δ 10.3 (CH3), 14.6 (CH3), 14.5 (CH3),
16.9 (CH3), 18.0 (CH3), 19.7 (CH3), 20.6 (CH3), 21.3, 25.5, 28.5, 36.1 (CH3), 39.2, 40.3
(CH3)x2, 42.9, 43.9, 49.1, 50.6, 50.9, 58.9, 62.4, 65.6, 69.5, 70.3, 78.8, 79.4, 85.3, 104.1,
119.9, 149.6 (C), 152.1 (C), 170.7 (C), 208.6 (C).
10-(2-Benzoyl-2-ethoxycarbonylethan-1-yl)-11N,12O-cyclocarbamate-11-
deshydroxy-10-desmethyl-O6-methyl-3-oxodescladinosylerythromycin A (18c)
The ketolide 3 (0.20 g, 0.30 mmol) was dissolved in THF (13 mL) and the solution
cooled to 0 °C before NaH (60%, 0.02 g) was added. Ethyl 3-oxo-3-
phenylpropanoate (0.13 mL, 0.76 mmol) was added dropwise over 5 min to the
reaction mixture. The solution was stirred at room temperature for 23 h. The
reaction mixture was cooled to 0 °C and NaHCO3 added. The mixture was extracted
with ethyl acetate (3x15 mL), the extracts washed with brine and dried (MgSO4).
The organic solution was evaporated and the residual material was subjected to
flash chromatography on silica gel using CH2Cl2:MeOH:NH3(aq) 90:5:1.The