Carbon and oxygen analogs of penicillin

In accordance with this invention, it has been found that carbon and oxygen analogs of 6.beta.-aminopenicillanic acid and biologically active derivatives thereof can be formed from esters of 6-oxopenicillanic acid. For example, 6.beta.-phenoxyacetoxypenicillanic acid -- an oxygen analog of penicillin V and 6.beta.-phenoxyacetylmethylpenicillanic acid -- a carbon analog of penicillin V, may be formed from an ester of 6-oxopenicillanate. The ester of 6-oxopenicillanic acid is formed by a diiospropyl carbodiimide/dimethyl sulfoxide oxidation of the corresponding ester of 6.alpha.-hydroxypenicillanic acid. The oxygen analogs are formed by reducing the ester of 6-oxopenicillanic acid to the corresponding 6.beta.-hydroxypenicillanate and then forming the desired analog by acylation. The carbon analogs are formed by a Wittig reaction of the ester of 6-oxopenicillanic acid with a suitable acylmethylenetriphenylphosphorane followed by saturation of the newly formed double bond and removal of the protective ester group.

BACKGROUND OF THE INVENTION 
1. Introduction 
This invention relates to derivatives of penicillin and more particularly 
to carbon and oxygen analogs of 6-aminopenicillanic acid and biologically 
active derivatives thereof. 
2. Description of the Prior Art 
In U.S. Pat. No. 3,159,617, there is taught the first commercial synthesis 
6-aminopenicillanic acid and penicillin derivatives based thereon. A vast 
number of derivatives of the 6-aminopenicillanic acid may be formed by 
introduction of various groups into the amino group of the acid. Thus, 
acyl groups, isocyanates, isothiocyanates, halogen compounds, 
methylisoureas, ethylene oxide, ethylene imine, and the like have been 
introduced into the amino group of the 6-aminopenicillanic acid to form 
both biologically active and biologically inactive derivatives. 
Many of the derivatives of 6-aminopencillanic acid, especially those 
derivatives formed by acylation have become useful drugs. For example, 
ampicillin and carbenicillin have broadened the spectra of activity to 
include use against certain Gram-negative organisms while methicillin 
shows good activity against certain resistant staphylococci. 
In an effort to find new biologically active derivatives of 
6-aminopenicillanic acid, attempts have been made to modify the same by 
methods in addition to introduction of new groups into the amino group. 
Thus, stimulated by the elucidation of the structure of the 
cephalosporins, there have been attempted modifications of the 
thiazolidine moiety of 6-aminopenicillanic acid. This is especially true 
since cephalosporins are not readily available from nature and most of the 
drugs used today are converted from penicillins. Thus, much effort has 
been concentrated on the investigation of possible transformations of the 
thiazolidine ring to the dihydrothiazine ring without any concomitant 
change of the chemically sensitive .beta.-lactam moiety. These efforts are 
described by D. H. R. Barton and T. G. Sammes, Proc. R. Soc. Lond. B, 179, 
345 (1971). 
Other attempts have been made to modify 6-aminopenicillanic acid through 
modification of the .beta.-lactam moiety, but such attempts are relatively 
few and are focused on the variations on the substituents or 
stereochemistry of the C-6 carbon in the penam system. Primarily, four 
types of modifying reactions are reported, namely acylation, 
epimerization, alkylation and diazotization. 
One successful example of the epimerization reaction is reported by G. E. 
Gutowski, Tet. Lett., 1970, 1779 and 1863. However, this penicillin having 
the epimerized C-6 substituent is devoid of any biological activity. With 
regard to alkylation at the C-6 position, most attempts have been to 
introduce an .alpha.-alkyl group based upon earlier predictions that the 
introduction of an .alpha.-methyl group at the C-6 position might enhance 
antibiotic activity. Both direct and indirect .alpha.-hydroxyalkylation of 
the penicillin nucleus at C-6 with benazldehyde and formaldehyde is 
reported by R. Riner and P. Zeller, Helv Chim. Acta 51, 1905 (1968). These 
derivatives and other .alpha.-alkylated derivatives show some biological 
activity, but both show substantially less activity than the well known 
penicillin G. Deamination of 6-aminopenicillanic acid by sodium nitrite in 
mineral acid proceeds with the inversion at C-6 resulting in the C-5 and 
C-6 protons being trans-oriented in the product. When the reaction is run 
in the presence of a halo acid, a 6-.alpha.-halo product is obtained. 
Deamination of 6-aminopenicillanic acid by sodium nitrite with oxygen 
acids is reported by T. Hauser and H. P. Sigg, Helv, Chim, Acta, 50, 1327 
(1967). With such oxygen acids, 6.alpha.-hydroxypenicillanic acid is 
isolated as the benzyl ester which may then be transformed to the 
.alpha.-oxygen analog 6-.alpha.-phenoxyacetoxypenicillanic acid, the 
.alpha.-oxygen analog of penicillin V. This material shows no biological 
activity. 
SUMMARY OF THE INVENTION 
The present invention is based upon the discovery that though the 
aforementioned ester of 6.alpha.-hydroxypenicillanic acid is biologically 
inactive, it can be transformed to an ester of 6-oxopenicillanic acid 
which latter ester can be transformed to carbon and oxygen analogs of 
6-.beta.-aminopenicillanic acid. These analogs are biologically active as 
are the derivatives of these analogs. 
The ester of the 6-oxopenicillanic acid is formed by diisopropyl 
carbodiimide/dimethyl sulfoxide oxidation of the corresponding, 
biologically inactive, ester of 6.alpha.-hydroxypenicillanic acid. The 
oxygen analogs are formed by reducing the ester of the 6-oxopenicillanic 
acid to the corresponding 6 .beta.-hydroxypenicillanate and then to the 
desired derivative by a reaction such as acylation in a manner analogous 
to the acylation of 6-aminopenicillanic acid. The carbon analogs are 
formed by a Wittig reaction of an ester of 6-oxopenicillanic acid with a 
suitable acylmethylenetriphenylphosphorane followed by saturation of the 
newly formed double bond and removal of the protective ester group.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As noted above, 6-.alpha.-hydroxypenicillanic acid is formed by deamination 
of 6 .beta.-aminopenicillanic acid with sodium nitrite and certain acids 
such as perchloric acid or sulfonic acid according to the process of 
Hauser and Sigg, ibid. The 6.alpha.-hydroxypenicillanic acid, which is 
biologically inactive, is isolated as an ester. Preferably, the benzyl 
ester is formed by reaction with phenyldiazomethane, though any other 
ester providing a pharmaceutically useful blocking group may be used 
provided the group is readily removed. Using the benzyl ester for purposes 
of illustration only, this ester of 6.alpha.-hydroxypenicillanic acid is 
then oxidized to benzyl 6-oxopenicillanate by diisopropylcarbodiimide in 
dimethylsulfoxide according to the procedures described by K. E. Pfitzner 
and J. G. Moffatt, Journal of the American Chemical Society, 85, 3027, 
(1963). It is this material which is the starting material for the 
formation of carbon and oxygen analogs of 6 .beta.-aminopenicillanic acid 
and the biologically active derivatives thereof. 
As noted above, the aforesaid reaction for the formation of the benzyl 
6-oxopenicillanate may be used for the formation of other esters of 
6-oxopenicillanic acid and in this respect, for purposes of this 
invention, the general formula for the ester of the 6-oxopenicillanic acid 
is as set forth below: 
##STR1## 
where R' represents a pharmaceutically useful or readily removable 
protective group. Such groups include (1) alkyl, cycloalkyl, aryl, alkaryl 
and aralkyl as illustrated by methyl, benzyl and 
.beta.,.beta.,.beta.-trichloroethyl, (2) phenacyl with or without 
substitution on the ring such as p-methoxyphenacyl and 
2,5-dimethoxyphenacyl, (3) salts such as sodium, potassium, 
N-ethylpiperidine and dicyclohexylamine and (4) organo silicon groups such 
as trimethyl silyl. It should be understood that some of the aforesaid 
groups may be more difficult to remove than others, but most are groups 
heretofore used as protective groups in analogous reactions of penicillins 
and are removed in accordance with recognized procedures dependent upon 
the particular group involved. 
The aforesaid ester of 6-oxopenicillanic acid (I) is the starting material 
for the formation of the oxygen analogs of 6 .beta.-aminopenicillanic acid 
and the derivatives thereof. The principles of the reaction scheme for the 
formation of the oxygen analog as well as derivatives thereof are 
illustrated in the following reaction chart. In the specific example 
referred to in this chart, there is described for purposes of illustration 
only, the production of the oxygen analog of penicillin V 
(phenoxymethylpenicillin) from benzyl 6-oxopenicillanate: 
##STR2## 
In the above reaction sequence, the benzyl 6-oxopenicillanate (II) is 
reduced to benzyl 6 .beta.-hydroxypenicillanate (III) with potassium 
borohydride. This material shows biological activity which is quite 
unexpected as it is the epimer of the corresponding benzyl 
6-.alpha.-hydroxypenicillanate which shows no biological activity. Though 
not shown in the reaction chart, this material can be transformed to 6 
.beta.-hydroxypenicillanic acid by hydrogenolysis over a palladium 
catalyst to remove the benzyl group and give the free acid as represented 
by the following formula: 
##STR3## 
This material is the oxygen analog of 6 .beta.-aminopenicillanic acid and 
is also biologically active. 
Following further in the above reaction chart, the benzyl 6 
.beta.-hydroxypencillanate (III) is phenoxyacetylated to give benzyl 6 
.beta.-phenoxyacetoxypencillanate (IV). Hydrogenolysis over a palladium 
catalyst to remove the benzyl group gives the free acid (V) which material 
is considered to be the oxygen analog of penicillin V. In proceeding from 
the benzyl 6-oxopenicillanate, it should be noted that it was not 
necessary to go through the oxygen analog 6 .beta.-hydroxypencillanic acid 
(VI) though this may be done, if desired. 
From the foregoing reaction chart, it can be seen that organic acid 
radicals can be introduced into the hydroxyl group of the benzyl 6 
.beta.-hydroxylpenicillanate (III) or 6 .beta.-hydroxylpenicillianic acid 
(VI), as illustrated by the phenoxyacetylation step in a manner analogous 
to the reactions of the amino group of 6-aminopenicillanic acid. A wide 
variety of acyl groups can be introduced into the hydroxyl group thus 
making it possible to produce a wide variety of oxygen analogs of 
penicillin. In this respect, typical acylating agents include for example, 
formyl, acetyl, phenylacetyl, phenoxyacetyl, carbomethoxy, carbobenzyloxy, 
p-nitrocarbobenzyloxy, carbophenoxy, p-chlorocarbophenoxy, 
methanesulfonyl, benzylsulfonyl, p-chlorobenzylsulfonyl, phenylsulfonyl, 
p-aminophenylsulfonyl or N, N-pentamethylenesulfonyl. Although the 
halides, especially chlorides and bromides, or anhydrides of the acid 
group to be introduced into the 6 .beta.-hydroxypenicillanic acid are 
particularly suitable, other acylating agents may also be used. Such 
acylating agents include mixed anhydrides, acid azides, lactones, 
particularly .beta.-lactones, "activated esters" such as thiol esters and 
phenolic esters, carboxylic acids with carbodiimides or alkoxyacetylenes, 
thiolactones, particularly .beta.-thiolactones, and acylated enols. 
Other groups can also be introduced into the hydroxy group of 
6.beta.-penicillanic acid to provide additional types of penicillin 
analogs by means of such reagents as: isothiocyanates, for example, 
phenylisothiocyanate and ethylisothiocynate, to convert the hydroxy group 
to a substituted thioncarbonate, reactive halogen compounds, such as 
triphenylmethyl chloride which forms the trityl ether derivative; 
methylisourea which converts the hydroxyl group to an isourea group; 
ethylene oxide and ethyleneimine, which add to the hydroxyl group with 
ring opening and others known to the art. Further exemplification of the 
above and, additional groups can be found by reference to Naylor, Proc. R. 
Soc. Land, B 179, pp. 357-367, 1971, wherein the reactions of 
6-aminopenicillanic acid are described in detail. 
With further reference to the above reaction scheme, it should be noted 
that the free acid 6 .beta.-phenoxyacetoxypenicillanic acid (V) can be 
esterified in conventional manner to further alter the structure of the 
derivatives such as by formation of the methyl ester by reaction with 
diazomethane. Thus, by selection of the appropriate acylating agent for 
reaction with the benzyl 6 .beta.-hydroxypenicillanate (IV) and by 
selection of an appropriate material to react with the free acid (V) or by 
a combination of such reactions with the oxygen analog 6 
.beta.-hydroxypenicillanic acid (VI), a multitude of derivatives of the 
oxygen analogs can be formed having the formula: 
##STR4## 
where R' is as above defined and R" may be selected from the group of (1) 
organic carboxylic radicals such as phenylacetyl, phenoxyacetyl, 
2,6-dimethoxybenzoyl, .alpha.-carboxyphenylacetyl, 
.alpha.-aminophenylacetyl and tyrosyl, (2) an organic carbonic acid 
radical such as carbomethoxy, carbobenzyloxy and carbo 
.beta.,.beta.,.beta.-trichloroethoxy, and (3) an organic sulfonic acid 
radical. 
The ester of 6-oxopenicillanic acid (I) is also the starting material for 
the formation of the carbon analogs in accordance with the invention. 
These carbon analogs are formed by a Wittig reaction of the ester with an 
acylmethylenetriphenylphosphorane of the formula: 
EQU (C.sub.6 H.sub.5).sub.3 P.dbd.CHR.sub.1 (VIII) 
where R.sub.1 is selected from the group consisting of H and R" where R" is 
as defined above. The formation of Wittig reagents is described in Organic 
Reactions, 14, pp. 270-490. 
The principles for the reaction scheme for the formation of the carbon 
analog as well as derivatives thereof are illustrated in the following 
reaction chart. In the specific example referred to in the chart, there is 
described for purposes of illustration only, the production of the carbon 
analog of penicillin V (phenoxymethylpenicillin) from 
benzyl-6-oxopenicillanate. 
##STR5## 
In the above reaction sequence, the benzyl 6-oxopenicillinate (II) is 
subjected to a Wittig reaction with a 
phenoxyacetylmethylenetriphenylphosphorane (IX) to give benzyl 6 
.beta.-phenoxyacetylmethylenepenicillanate (X). It is suspected that the 
product is a mixture of geometrical isomers and the saturated isomers are 
obtained by hydrogenation over platinum oxide. The 6 
.beta.-phenoxyacetylmethylpenicillanic acid (XII) is obtained by 
hydrogenolysis of the benzyl 6 .beta.-phenoxyacetylmethylpenicillanate 
(XI) over palladium on charcoal. This material is the carbon analog of 
penicillin V. 
With respect fo the 6.beta.-phenoxyacetylmethylpenicillanic acid (XII) the 
acid radical is reactive and can be used to form additional derivatives. 
Moreover, since there is the possibility for selection for substitution on 
the 6-C position dependent upon the selection of the Wittig reagent, a 
derivative of a carbon analog of 6 .beta.-aminopenicillanic acid can be 
formulated having the following general formula: 
##STR6## 
where R' and R" are as defined above. 
The carbon analog of 6-aminopenicillanic acid may be formed by the 
following reaction sequence: 
##STR7## 
The above free acid (XVI) is the carbon analog of 6-aminopenicillanic 
acid. It can be reacted such as by esterification to form derivatives 
corresponding to the formula: 
##STR8## 
where R.sup.1 is as above defined. 
The following examples will help to illustrate the invention with more 
particularity. 
Benzyl 6.alpha.-hydroxypenicillanate 
This compound was prepared by the method of Hauser and Sigg. The crude 
product was recrystallized in benzene; mp 162.degree.-163.degree. (lit. 
157.degree.-160.degree.); .alpha..sub.D.sup.25 = +200.degree. (c=0.62, 
MeOH) (lit. +191.degree. (c=0.53, MeOH); ir and nmr spectra are identical 
to those published. 
Benzyl 6-oxopenicillanate 
Pfitzner and Moffatt's DMSO oxidation method, ibid, was employed to 
transform the benzyl 6.alpha.-hydroxypenicillanate to benzyl 
6-oxopenicillanate. Thus, benzyl 6.alpha.-hydroxypenicillanate (9 g, 29.30 
mmol) was dissolved in 120 ml dimethyl sulfoxide. Pyridine (2.37 ml, 29.30 
mmol) and trifluoroacetic acid (1.10 ml, 14.65 mmol) were added. To the 
stirred solution, N, N.sup.1 -diisopropylcarbodiimide (11.30 g, 87.90 
mmol) was added slowly and the stirring continued for 17 hours. Distilled 
water (23 ml) was added dropwise to the stirred reaction mixture to 
consume the excess carbodiimide. The resulting mixture was filtered to 
remove the solid N,N.sup.1 -diisopropylurea. To the filtrate was added 800 
ml benzene, and the solution was washed with three 800 ml portions of 
water to remove dimethyl sulfoxide. The resulting benzene solution was 
dried over anhydrous sodium sulfate. After evaporation of benzene, the 
yellow residual oil partly solidified when stored in vacuum. It contains 
54% of benzyl 6-oxopenicillanate as determined by the formation of its 
cyanohydrin. This crude product was used without purification in the 
subsequent transformations. 
However, pure benzyl 6-oxopenicillanate can be isolated by two successive 
column chromatographic separations. First, 4 g crude reaction product were 
chromatographed on a silicic acid column (200 g) which was eluted with an 
excess methylene chloride (1400 ml) to remove most of the diisopropylurea 
and other contaminants. Then the eluting solvent was changed to 1:4 
Et.sub.2 O/CH.sub.2 Cl.sub.2 to wash out the partially purified benzyl 
6-oxopenicillanate (2.59). 
The product (1 g) was further purified on a second column of silicic acid 
(50 g) using 1:25 Et.sub.2 O/CH.sub.2 Cl.sub.2 as eluent. Fractions (8 ml) 
were collected and checked by TLC. Fractions 31 to 50 were combined and 
the solvent evaporated. The residual yellow oil solidified after 
evaporation at 1 mm Hg to give 0.5 g of the benzyl 6-oxopenicillanate; 
R.sub.f = 0.19 (1:25 Et.sub.2 O/CH.sub.2 Cl.sub.2); [.alpha.].sub.D.sup.25 
= +186.degree. (c = 0.92, C.sub.6 H.sub.6); ir (film, cm.sup.-1) 1830, 
1780, 1735; nmr (DCCl.sub.3, ppm) 7.40 (s, 5H), 5.85 (s, 1H), 5.30 (s, 
2H), 4.87 (s, 1H), 1.55 (s, 3H), 1.48 (s, 3H). 
Anal. Calcd for C.sub.15 H.sub.15 NO.sub.4 S (305.40): C, 59.10; H, 4.96; 
N, 4.59; S, 10.50. found C, 58.97; H, 5.07; N, 4.53; S, 10.60. 
Benzyl 6.beta.-hydroxypenicillanate 
To a cooled, stirred solution of crude benzyl 6-oxopenicillanate (8.15 g, 
14.48 mmol) in 470 ml 1:1 methanol/ethanol was added a cold solution of 
potassium borohydride (0.85 g, 15.75 mmol) in 570 ml 50% aqueous ethanol. 
After two minutes, 1 N hydrochloric acid was added to bring the pH of the 
solution to 2. The solution was extracted twice with methylene chloride 
and the combined extracts were washed once with 5% sodium bicarbonate 
solution, once with water, dried over anhydrous sodium sulfate, and 
evaporated at reduced pressure. The resulting yellow oil was 
chromatographed on a silicic acid column eluted with 1:4 Et.sub.2 
O/CH.sub.2 Cl.sub.2 to isolate benzyl 6 .beta.-hydroxypenicillanate which 
was recrystallized from benzene-pentane to yield 2.80 g (63%); mp 
97.degree.; [.alpha.].sub.D.sup.25 = +222.degree. (c = 0.87, MeOH); ir 
(KBr, cm.sup.-1) 3420, 1780, 1725; nmr (DCCl.sub.3, ppm) 7.36 (s, 5H), 
5.56 (d, 1H, J = 4), 5.20 (s, 2H), 5.22-4.98 (q, 1H, J = 4 and 11), 4.50 
(s, 1H), 3.40-3.20 (d, br, 1H, J = 11), 1.65 (s, 3H), 1.50 (s, 3H). 
Anal. Calcd for C.sub.15 H.sub.17 O.sub.4 NS (307.40): C, 58.80; H, 5.20; 
N, 4.60; S, 10.40. Found: C, 58.73; H, 5.32; N, 4.48; S, 10.20. 
Benzyl 6.beta.-phenoxyacetoxypenicillanate 
Benzyl 6.beta.-hydroxypenicillanate (1.26 g, 4.11 mmol) was 
phenoxyacetylated in methylene chloride (120 ml) with phenoxyacetyl 
chloride (0.97 g, 5.71 mmol) and triethylamine (0.77 ml, 5.56 mmol) for 3 
hours. Excess reagents were removed by washing with 1 N potassium 
bicarbonate and water. Evaporation of the solvent yielded a yellow oil, 
1.90 g. Purification by chromatography on silicic acid eluted with 1:50 
Et.sub.2 O/CH.sub.2 Cl.sub.2 gave a pale yellow oil; 1.55g (85%); R.sub.f 
= 0.43 (1:50 Et.sub.2 O/CH.sub.2 Cl.sub.2); [.alpha.].sub.D.sup.25 = 
+210.degree. (c = 1.06, CHCl.sub.3); ir (film, cm.sup.-1) 1780, 1740, 
1600, 1500; nmr (DCCl.sub.3, ppm) 7.35 (s, 5H), 7.40-6.70 (m, 5H), 
5.60-5.60 (q, 2H, J = 4), 5.25 (s, 2H), 4.70 (s, 2H), 4.55 (s, 1H), 1.60 
(s, 3H), 1.45 (s, 3H). 
Anal. Calcd for C.sub.23 H.sub.23 O.sub.6 NS (441.39); C, 62.75; H, 5.27; 
N, 3.19; S, 7.26. Found: C, 62.50; H, 5.40; N, 3.12; S, 7.46. 
6.beta.-Phenoxyacetoxypenicillanic acid 
Benzyl 6.beta.-phenoxyacetoxypenicillanate (0.81 g, 1.84 mmol) dissolved in 
120 ml ethyl acetate was hydrogenated over 10% palladium on charcoal (4 g) 
for 11 hours at room temperature and 1 atm. pressure. The resulting 
mixture was filtered to remove the catalyst and the filtrate was extracted 
twice with 50 ml portions of cold 1N potassium bicarbonate solution. The 
combined aqueous extracts were washed once with ether and cooled to 
0.degree.. Ether was added and the stirred mixture was acidified to pH 2 
by slow addition of concentrated hydrochloric acid (12N). The ether layer 
was separated and the aqueous layer was extracted three times with ether. 
The organic phase was then washed once with distilled water, dried over 
anhydrous sodium sulfate and evaporated to yield a pale yellow oil, 0.53 
g. This oil was obtained as a white solid, 0.48 g, after freeze drying 
from benzene. The product absorbed moisture readily from the air and after 
attempted recrystallization, the yellow oil was recovered. TLC showed two 
spots with heavy tailing, R.sub.f = 0.50 and 0.22 (1:4 Et.sub.2 O/CH.sub.2 
Cl.sub.2); ir (CH.sub.2 Cl.sub.2, cm.sup.-1) 3620, 3440, 1790, 1765, 1745, 
1720, 1595, 1490, nmr (DCCl.sub.3, ppm) 8.90 (s, 2H), 7.50-6.80 (m, 8H), 
5.90-5.60 (q, 2H, J = 4), 5.35-5.25 (m, br, 0.5H). 
The singlet at 4.70 ppm is believed to be the .alpha.-protons of 
phenoxyacetic acid which is present as a side-product of hydrogenolysis. 
From the integration, the ratio of 46a to phenoxyacetic acid is 2 to 0.9. 
Potassium Salt 
The free acid formed above (0.22 g, 0.63 mmol) was dissolved in a mixture 
of 10 ml ethyl ether and 20 ml distilled water. The stirred mixture was 
triturated with 0.1 N potassium hydroxide solution at 0.degree. to pH 7.5 
as indicated by a pH meter. The aqueous phase was separated and washed 
once with ethyl ether. The solution was reduced at room temperature to 
about 8 ml and freeze dried to give a white solid, 0.26 g. The salt was 
insoluble in benzene, chloroform, ethyl ether, ethyl acetate, acetone, and 
tetrahydrofuran. Recrystallization from acetone-water failed and the 
substance was recovered by freeze drying; mp 180.degree.; ir (KBr, 
cm.sup.-1), 3540-3040, 1770-1720, 1590; nmr of the salt in D.sub.2 O 
showed weak signals for the compound among other impurity signals (ppm) 
7.60-6.90 (m, 9H), 5.90-5.60 (q, 2H), 4.90 (s, 1.5H), 4.80 (s, strong 
water peaks with side bands), 4.47 (s, 2 H), 4.32 (s, 1H), 2.73 (s, 2H), 
2.30 (s, 3.6H), 1.60-1.55 (d, 6H), 1.30 (s, 6.2H). The compound exhibits 
low bacteriostatic endpoints (in mcg. of active material per ml) for 
pneumoniae (5% serum), Streptococcus pyogenes (5% serum), and 
Staphylococcus aureus. 
Methyl 6 .beta.-phenoxyacetoxypenicillanate 
Crude potassium 6 .beta.-phenoxyacetoxypenicillanate (0.27 g, 0.69 mmol) 
was reconverted to the free acid by acidifying the aqueous solution 
covered with ethyl ether at 0.degree. with N hydrochloric acid. Worked up 
as described above, 0.23 g (95%) free acid was obtained as an oil which 
was then methylated with diazomethane in ether solution to give 0.24 g 
yellow oil. After separation by a silicic acid column eluted with 1:25 
Et.sub.2 O/CH.sub.2 Cl.sub.2, methyl phenoxyacetate was isolated from 
early fractions as a colorless oil, 0.08 g; ir (film cm.sup.-1) 1755, 
1600, 1495, 1440, 1290, 1200, 1090; nmr (DCCl.sub.3, ppm) 7.50-6.85 (m, 
5H), 4.65 (s, 2H), 3.80 (s, 3H). 
The later fractions gave 0.15 g of methyl 6 
.beta.-phenoxyacetoxypenicillanate as a colorless oil which was 
rechromatographed to give 0.12 g (48%); R.sub.f = 0.46 (1:25 Et.sub.2 
O/CH.sub.2 Cl.sub.2); [.alpha.].sub.D.sup.25 = +268.degree. (c = 0.97, 
CHCl.sub.3); ir (film, cm.sup.-1) 1790, 1740, 1600, 1495, 1310, 1210, 
1170; nmr (DCCl.sub.3, ppm) 7.50-6.85 (m, 5H), 5.90-5.65 (q, 2H, J=3.5), 
4.80 (s, 2H), 4.55 (s, 1H), 3.80 (s, 3H), 1.60 (s, 3H), 1.50 (s, 3H). 
Anal. Calcd for C.sub.17 H.sub.19 O.sub.6 NS (365.39): C, 58.65; H, 5.25; 
N, 3.84; S, 8.79. 
Found: C, 58.50; H, 5.47; N, 3.79; S, 8.85. 
6.beta.-Hydroxypenicillanic acid and methyl ester 
Benzyl 6 .beta.-hydroxypenicillanate (1.31 g, 4.27 mmol) was dissolved in 
150 ml ethyl acetate and hydrogenated over 10% palladium on charcoal 
(2.5g) for 24 hours at room temperature. The hydrogen pressure was 
maintained at 50 psi for the first 2 hours. At the end of the reaction 
period, it had fallen to 42.5 psi. The free acid was isolated as described 
for the preparation of 6 .beta.-phenoxyacetoxypenicillanic acid to give 
0.61 g (66%) of a white solid. From the organic layer, 0.44 g (34%) of 
benzyl 6 .beta.-hydroxypenicillanate was recovered. The white solid thus 
obtained had mp 130.degree. (dec. begins); ir (KBr, cm.sup.-1) 3560-2480, 
1775, 1725; nmr in acetone-d.sub.6 showed broad peaks at (ppm) 5.60-5.10, 
4.45, 3.90-3.60, 1.80-1.65, 1.40-1.25. Methylation of the 6 
.beta.-hydroxypenicillanic acid (0.41 g, 1.90 mmol) with diazomethane in 
ethyl ether gave the methyl ester as an oil. Purification with a silicic 
acid column eluted with 1:4 Et.sub.2 O/CH.sub.2 Cl.sub.2 gave 45b as a 
colorless oil, 1.12 g (27%); R.sub.f = 0.48 (1:4 Et.sub.2 O/CH.sub.2 
Cl.sub.2); [.alpha.].sub.D.sup.25 = +153.degree. (c = 1.30, CHCl.sub.3); 
ir (film, cm.sup.-1) 3420, 1785, 1740, 1440, 1290, 1210; mnr (DCCl.sub.3, 
ppm) 5.65-5.58 (d, 1H, j = 4), 5.30-5.05 (q, br, 1H, J = 4 and 11), 4.50 
(s, 1H), 3.80 (s, 3H), 3.35-3.15 (d, br, 1H, J = 11), 1.70 (s, 3H), 1.55 
(s, 3H). 
Anal. Calcd for C.sub.9 H.sub.13 O.sub.4 NS (231.26): C, 47.25; H, 5.67; N, 
6.06; S, 13,85. Found: C, 47.44; H, 5.79; N, 5.89; S, 13.96. 
The bacteriostatic endpoint for the methyl ester in mcg. of active ester 
per ml is 32 for Staphylococcus aureus (10.sup.-4 dilution) and 16 for K 
pneumoniae (10.sup.-4 dilution). 
Wittig reagents 
Carbobenzyloxymethylenetriphenylphosphorane, 
benzoylethylenetriphenylphosphorane, and 
phenoxyacetylethylenetriphenylphosphorane were prepared by the action of 
sodium hydroxide on the readily accessible triphenylalkylphosphonium 
chlorides. Phenylacetylmethylenetriphenylphosphorane was made by the 
method of Bestmann and Arnason, ibid, using phenyl phenylacetate and 
methylenetriphenylphosphorane. 
1-Chloro-3-phenoxyacetone 
To a stirred solution of diazomethane (ca 6 g = 0.141 mmol) in ethyl ether 
(400 ml) was added over 2 hours at 1.degree.-3.degree. phenoxyacetyl 
chloride (11.95 g = 0.07 mole) dissolved in ethyl ether (50 ml). The 
mixture was stirred at the same temperature for 2 more hours and was 
allowed to stand overnight at room temperature. Then 5.5 N hydrochloric 
acid (25 ml, 0.137 moles) was added with stirring over 110 min. at 
16.degree.-20.degree.. After the mixture was stirred for an additional 4 
hours, the layers were separated and the ether layer was washed with three 
80 ml portions of water and dried over anhydrous sodium sulfate. Removal 
of the solvent gave the crude product as a yellow oil, 13 g (100%); ir 
(film, cm.sup.-1) 1740, 1595, 1495, 1240; nmr (DCCl.sub.3, ppm) 7.40-6.70 
(m, 5H), 4.60 (s, 2H), 4.25 (s, 2H). This product was used without 
purification to prepare phenoxyacetylmethyltriphenylphosphonium chloride. 
Phenoxyacetylmethyltriphenylphosphonium Chloride 
1-Chloro-3-phenoxyacetone (13 g, 0.07 mole) dissolved in 20 ml chloroform 
was mixed with a solution of triphenylphosphine (19.7 g, 1 eq) in 30 ml 
chloroform at room temperature. The mixture was swirled for 5 minutes and 
benzene (20 ml) was added. A white crystalline compound appeared when most 
of the solvents had been evaporated. The product was collected by suction 
and washed with benzene. Second and third crops were collected by 
evaporation of the washings. The total yield was 23 g (73%); sublimation 
without melting at 90.degree.; ir (KBr, cm.sup.-1) 3450-3280, 2770, 1720, 
1595, 1585, 1485, 1435, 1220, 1110, 1030; nmr (DCCl.sub.3, ppm) 8.20-6.80 
(m, 22H), 5.30 (br, 2H). 
Phenoxyacetylmethylenetriphenylphosphorane 
Phenoxyacetylmethyltriphenylphosphonium chloride (10 g, 22.40 mmol) was 
suspended in 250 ml water with a few crystals of phenolphthalien added as 
an indicator. Sodium hydroxide (5%) was added dropwise until the 
vigorously stirred mixture turned pink. The white solid was collected, 
washed with water, and dried in a desicator, weight 9 g (98%); mp 
127-128.5; ir (KBr, cm.sup.-1) 1595, 1580, 1540, 1480, 1435, 1400, 1225, 
1105, 1045, 870; nmr (DCCl.sub.3, ppm) 7.90-6.90 (m, 21H), 4.53 (s, 2H). 
Wittig reaction 
6-OPA benzyl ester benzyl-6-oxopenicillanate was refluxed in benzene with 
1.2 equivalents of each of the above Wittig reagents for 40 hours. The 
yellow solution turned dark brown. The resulting black oil from 
evaporation of solvent was fractionated with a silicic acid column eluted 
with 1:25 Et.sub.2 O/CH.sub.2 Cl.sub.2. A brown oil containing the adduct 
was obtained. Treatment of the adduct in methylene chloride with activated 
charcoal and rechromatography on silicic acid eluted with 1:50 Et.sub.2 
O/CH.sub.2 Cl.sub.2 yielded a yellow, oily product. 
Benzyl-6-benzoylmethylenepenicillanate 
This compound was isolated as a yellow oil in 64% yield; R.sub.f = 0.75 
(1:50 Et.sub.2 O/CH.sub.2 Cl.sub.2); ir (film, cm.sup.-1) 1770, 1740, 
1690, 1635, 1595, 1450; nmr (DCCl.sub.3, ppm) 8.07-7.30 (m, 11H), 6.12 (d, 
1H, J = 1), 5.22 (s, 2H), 4.60 (s, 1H), 1.60 (s, 3H), 1.45 (s, 3H). 
Benzyl-6-phenoxyacetylmethylenepenicillanate 
This compound was isolated as a yellow oil in 62% yield; R.sub.f = 0.65 
(1:25 Et.sub.2 O/CH.sub.2 Cl.sub.2); [.alpha.].sub.D.sup.25 = +279.degree. 
(c = 1.20, CHCl.sub.3); ir (film, cm.sup.-1) 1775, 1735, 1715, 1595, 1490; 
nmr (DCCl.sub.3, ppm) 7.40-6.70 (m, 11H), 6.05 (d, 1H, J = 1), 5.15 (s, 
2H), 4.70 (s, 2H), 4.65 (s, 1H), 1.55 (s, 3H); 1.40 (s, 3H). 
Anal. Calcd for C.sub.24 H.sub.23 NO.sub.5 S (437.51): C, 65.95; H, 5.30, 
N, 3.20; S, 7.32 Found: C, 65.77; H, 5.40; N, 3.31; S, 7.41. 
Hydrogenation of Benzyl 6-benzoylmethylenepenicillanate 
Benzyl 6-benzoylmethylenepenicillanate (0.92 g, 2.26 mmol) was hydrogenated 
in the presence of 1.6 g platinum oxide in 100 ml ethyl acetate for 10 
hours at room temperature and 1 atm pressure. After filtration through 
celite cake, the filtrate was still brown in color owing to the colloidal 
platinum particles. It was treated with activated charcoal and evaporated 
to yield a yellow oil (0.75 g) which was fractionated with a silicic acid 
column eluted with 1:50 Et.sub.2 O/CH.sub.2 Cl.sub.2 to give benzyl 
6-benzoylmethylpenicillanate. 
Benzyl 6-benzoylmethylpenicillanate 
Early fractions from the column gave the major component which was shown by 
nmr to be a mixture of cis and trans isomers of benzyl 
6-benzoylmethylpenicillanate (51c), weight 0.45 g (48.5%); R.sub.f = 0.45 
(1:50 Et.sub.2 O/CH.sub.2 Cl.sub.2). In an attempt to separate the cis and 
trans isomers, the yellow oil was rechromatographed on silicic acid eluted 
with 1:50 Et.sub.2 O/CH.sub.2 Cl.sub.2 and the collected fractions were 
checked by nmr. Integrations showed that one early fraction had a 
cis/trans ratio of 2 to 1 and for a later fraction, it was 19:3. Nmr 
spectrum for a 19:7 cis/trans mixture (relative integration values are 
shown, ppm) 8.05-7.20 (m, 97, aromatic protons), 5.70 (d, 6.6, J = 4.5, 
C-5 protons of the cis isomer), 5.20 (s, 17.5, benzylic protons), 5.10 (d, 
2.4, J = 1.5, C-5 proton of the trans isomer), 4.52 (s, 2.4, C-3 proton 
of the trans isomer), 4.48 (s, 6.6, C-3 proton of the cis isomer), 
4.30-3.25 (m, 26, C-6 protons and protons to the ketone function), 
1.60-1.40 (d over d, 54, gemdimethyl protons); ir (film, cm.sup.-1) 1770, 
1740, 1680, 1600, 1450. 
Anal. Calcd for C.sub.23 H.sub.23 NO.sub.4 S (409.49): C, 67.50; H, 5.66; 
N, 3.42; S, 7.82. Found: C, 67.70; H, 5.71; N, 3.36; S, 7.76. 
Benzyl 6-phenoxyacetylmethylpenicillanate 
Benzyl 6-phenoxyacetylmethylenepenicillanate (2.65 g, 6.07 mmol) was 
hydrogenated in the presence of platinum oxide (4.3 g) in 200 ml ethyl 
acetate for 5 hours at room temperature and 1 atm. pressure. Colloidal 
platinum particles were removed by treating with activated charcoals as 
described in the preparation of benzyl 6-benzoylmethylpenicillanate. After 
separation with silicic acid column eluted with 1:10 Et.sub.2 O/CH.sub.2 
Cl.sub.2, three portions were collected. The first portion, as shown by 
nmr spectrum, was a mixture of cis/trans isomers of a ratio of 4 to 1; 
weight 0.75 g, 29% yield. The second portion was the pure cis isomer, 
weight 0.02 g, 3% of the total yield of the saturation products. The third 
portion was 
2,2-dimethyl-3-carbobenzyloxy-6-phenoxyacetylmethyl-7-oxo-2,3,4,7-tetrahyd 
ro-1,4-thiazepine (52d), weight 0.20 g, 7.5% yield; ir (film, cm.sup.-1) 
3310, 1735, 1625, 1600, 1550-1500, 1200, 910; nmr (DCCl.sub.3, ppm) 
7.35-6.40 (m, 12H), 5.20 (s, 2H), 4.70 (s, 2H), 4.32-4.25 (d, 1H, J = 5), 
3.73-2.92 (q, 2H, J = 16), 1.45 (s, 3H), 1.38 (s, 3H). The cis isomer, 
namely benzyl 6 .beta.-phenoxyacetylmethylpenicillanate is a pale yellow 
oil; R.sub.f = 0.75 (1:10 Et.sub.2 O/CH.sub.2 Cl.sub.2); 
[.alpha.].sub.D.sup.25 = +148.degree. (c = 0.46, CHCl.sub.3); ir (film, 
cm.sup.-1) 1770, 1735, 1595, 1490; nmr (DCCl.sub.3, ppm) 7.50-6.80 (m, 
10H), 5.65 (d, 1H, J = 4.2), 5.20 (s, 2H), 4.60 (s, 2H), 4.45 (s, 1H), 
4.30-3.85 (m, 1H), 3.25-3.12 (d, 2H, J = 8), 1.58 (s, 3H), 1.42 (s, 3H). 
Anal. Calcd for C.sub.24 H.sub.25 NO.sub.5 S (439.52): C, 65.60; H, 5.74 N, 
3.19; S, 7.28. Found: C, 65.40; H, 5.90; N, 3.12; S, 7.40. 
6 .beta.-Phenoxyacetylmethylpenicillanic acid 
Hydrogenolysis of benzyl 6-phenoxyacetylmethylpenicillanate to give 6 
.beta.-phenoxyacetylmethylpenicillanic acid was carried out as described 
for the preparation of 6 .beta.-phenoxyacetoxypenicillanic acid. Starting 
with a sample of benzyl 6 .beta.-phenoxyacetylmethylpenicillanate (0.35 g, 
0.80 mmol) containing 8:1 cis/trans isomers, the product obtained was pure 
cis compound as shown by nmr spectrum. The free acid when isolated can be 
purified by recrystallisation. 
Thus the acid was first dissolved in methylene chloride which is then 
replaced by benzene. The benzene solution is chilled to give 0.12 g (43%) 
white crystals; mp 101.5.degree.-102.degree.; [.alpha.].sub.D.sup.25 = 
+217.degree. (c = 0.62 CHCl.sub.3); ir (KBr, cm.sup.-1) 3440, 1785, 1765, 
1750, 1730, 1720, 1700, 1595, 1490, 1225; nmr (DCCl.sub.3, ppm) 11.15 (s, 
1H), 7.50-6.85 (m, 5H), 5.65 (d, 1H, J = 4.5), 4.65 (s, 2H), 4.50 (s, 1H), 
4.30-3.95 (m, 1H), 3.35-3.20 (d, 2H, J = 8), 1.65 (d, 6H). 
Anal. Calcd for C.sub.17 H.sub.19 NO.sub.5 S (349.39): C, 58.50; H, 5.49; 
N, 4.02; S, 9.16. Found: C, 58.73; H, 5.47; N, 3.93; S, 9.11. 
The bacteriostatic endpoint in mcg of active material per ml is 1 for D 
pneumoniae (5% serum), 2 for Streptococcus pyogenes (5% serum) and 32 for 
Staphylococcus aureus (10.sup.-4 dilution).