Rearrangement Morin

Sila-Morin-Rearrangement of Penicillin Sulfoxides to Cephalosporins... 

The reaction is unusual in that sulfoxides processing an a-hydrogen atom normally undergo a Pummerer reaction under these conditions to form the acetoxy sulfide. The reaction can be compared with the Morin rearrangement of penicillin sulfoxide to cephalosporins.121... 

Other references related to the Morin rearrangement are cited in literature. ... 

The method of choice for the epimerisation of 6-aminopenicillanic acid at the 5-position was developed by Stjepan P. Kukolja at Eli Lilly. [44,45] It consists of treating adequately protected derivatives with chlorine or suUuryl chloride, with the objective of selectively cleaving the bond between C-5 and S. Tin(II) chloride is then used for recyclisation. The mixture of epimers can be purified by flash chromatography. The ring expansion follows according to the so-caUed Morin rearrangement. [46,47] First, the sulfur is oxidised to sulfoxide with m-chloro-perbenzoic acid, and this is then heated in DMF to 100 °C in presence of catalytic amounts ofp-toluene-sulfonic acid. 

The second approach (Scheme 3.40) was based on the fact that the target compound 129 might be easily obtained from its (7k)-epimer 135 by any of the methods devised to convert (6k,7S)-cephems, available from various total syntheses to the naturally configured ones [91]. Sulfide precursor on oxidation by m-chloroperoxybenzoic acid (mCPBA) afforded sulfoxide 130 that underwent an acid-catalyzed Morin rearrangement to produce cephem 131. As in the first approach, dephthaloylation of cephem 131 using hydrazine hydrate afforded amine 132. The subsequent acylation with phenoxylacetic acid in the presence of DCC then produced amide 133 in good yield. Crude acid obtained by debenzylation... 

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