Benzyl derivatives salt analysis

The electrospray ionization mass spectrometry (ESI-MS) analysis of the incubation between porcine pancreatic elastase (PPE) and the tert-butylammonium salt of clavulanic acid 54 (R1 = R2 = H) at time points of between 3 min and 5h revealed that there were no mass increments relative to PPE. However, when the benzyl derivative 54 (R1 = Bn, R2 = H) was used, a peak was observed at 26187 Da after 3 min, which corresponded to the formation of an initial acyl-enzyme complex. The intensity of the peak decreased significantly and two clear additional peaks at 25 968 and 25 967 Da appeared after 5 min, which corresponded to adducts with mass increments at 77 and 88 Da, respectively. The intensities of both peaks decreased after 60 min and almost disappeared after 5 h. The corresponding />-nitrobenzyl ester 54 (R1 = CH2PhN02, Rz = H) showed similar results except that the formation of adducts appeared slightly faster <2000T5729>. 

FIGURE 1,12. (a) Chemical formula and (b) stereoview of the potassium salt of the benzyl derivative of the antibiotic penicillin. This crystallographic analysis established this chemical formula of penicillin showing that it contained, unexpectedly, a / -lactam (four-membered) ring. Circles representing atoms S, large stippled 0, small stippled N, small black C, small white K+, very small black hydrogen atoms omitted. 

N,N-disubstituted benzylamine (65) was allowed to react in a high-dilution Dieckmann cyclization to give the ketoester (66) (88%), which displayed a typical transannular interaction [Eq. (23)]. Conversion into the perchlorate salt produced a bicyclic structure (67). Hydrogenation of 67 gave the de-benzylated salt (68) in 69% yield. The stereospecificity of this reaction probably arises from cis-addition of the hydrogen atoms from the less hindered side of the likely intermediate iminium salt (69). The free base derived from 68 was reduced to give ( )-isoretronecanol (22) (53%) with an isomeric purity of 98%, as determined by GLC analysis. 

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