Functionalised pyrrolidinones derived from (S)-pyroglutamic acid by cycloaddition reactions

Functionalised bicyclic tetramates derived from cysteine as antibacterial agents

“…oxazolomycin 54,55 and pramanicin 56 ), the synthesis of a pyroglutamate-tetramate hybrid system was also examined. This was achieved by condensing pyroglutaminol 31, 57 prepared by the literature procedure, 58,59 with terephthalaldehyde by reflux in toluene using a Dean-Stark apparatus to give a mixture of products 32 and 33 in 1:2.4 ratio (Scheme 10); the lactam-functionalized aldehyde 33 was isolated by column chromatography as a single diastereomer, whose stereochemical assignment was in agreement with previous reports on N,O-acetal formation of 31 with benzaldehyde. 60,61 Aldehyde 33 was in turn converted to the desired bicyclic tetramate ester 34a in the usual way, which was converted to carboxamide 34b with 1-adamantylamine.…”

Diastereospecific synthesis of (S,S)‐2‐substituted‐4,4‐diphenyl‐3, 1‐oxazabicyclo[3.3.0]octanes

“…[15]. The stereo-chemistry of the products was confirmed by NOE experiments [3]. For example, the NOE difference spectrum of product 5a shows that the hydrogen atoms located at C2 and C5 have a cis relationship.…”

Synthesis of Mimics of Pramanicin from Pyroglutamic Acid and Their Antibacterial Activity

“…51 Oxidative elimination, by treatment of 4a-e with hydrogen peroxide using a standard protocol, gave enones 5b-e (Table 1) effectively, with the exception of 4a which gave epoxide 6a directly. Noteworthy was the relative stability of enones 5b-e; it had been earlier found that related ester enones were highly prone to dimerisation under basic conditions, [43][44][45][46] but this proved not to be a problem with these amide equivalents, except on standing over extended periods or on purification via silica gel column chromatography. reagents when pyridine was used; when a more basic amine (Et 3 N) was used, the 1 H NMR spectrum of the reaction crude mixture was complex.…”