[CPC]

Hallo,
I have had a nice discussion with DAN and I have been able to do the cyclization reaction using thiourea.
Now, I go a further step in practicing the synthesis of cefotaxime (a laboratory task at university).
I followed the procedure in Synthesis, 1992, 11, 1160-1164 which was extracted from the paper and attached here (File name: MAEM+7-ACA procedure). As I can see that the approach proceeds through 2 steps.
1. Protecting MAEM with trityl chloride.
2. Acylating 7-ACA by the protected MAEM.
The product does not look the one described at the end of the reported procedure.
I got a mixture containing a component having a similar Rf to that of 2-mercaptobenzothiazol released as the  result of the substitution reaction of MAEM with any nucleophile (please have a look through the file MAEM+7-ACA TLC).
I have conducted a separation with an aid of column chromatography and I could get that component as a pure crystalline solid having a m.p. of 177-179oC which is also in the range for that of 2-mercaptobenzothiazol (176-178oC).
Nevertheless, this compound does not appear to be 2-mercaptobenzothiazol. The IR does not fit and the molecular weigh revealed from the MS fits the formula of 2-mercaptobenzothiazol neither (see the files MAEM+7-ACA IR and MAEM+7-ACA MS)
I still have no ideas what compound this solid should be responsible for. Could any one help with some suggestions?
Thank you very much in advance.
CPC

[orgopete]

I don't know what you have, but I just note the MW (563) is close to the ketone rather than oxime ether of your starting thioester.

[CPC]

You are right it is close to the ketone.
But how come that we have that ketone? Is there a possibility for the oxime ether to be converted to the corresponding ketone?

[CPC]

Hi,
thank you for the information.
Could you please be so kind as to give me the address of the article in ACS?
I would appreciate that much.
Best regards,
CPC

[CPC]

I would like to add here a notice that the product I have mentioned might not be the ketone even though the MW does fit the formula. It is because of the fact that the IR does not show the signals responsible for the ketone functional group.
CPC