Hydrates lactams

In general, electron-releasing groups (e.g. —NH2, —OH) diminish or prevent covalent hydration by decreasing the electron deficiency in the nucleus. This diminution becomes ineffective if a new kind of stabilizing resonance is facilitated by the substituent, e.g. the urea-type resonance and the 4-aminopyridine-type resonance in 2- and 6-hydroxypteridine, respectively. The reluctance of the anions of these substances to form hydrates is attributed to the stable benzenoid system, e.g. 42, in the anhydrous anion compared with the predominantly lactam form of the neutral species, e.g. 43. 

Reductive alkylation has been used to prepare a-amino acids suitable for lactam formation and further elaboration. In a single step a carbobenzyloxy group was removed, and alkylation with glyoxylic acid hydrate was achieved (18). 

The detailed mechanism of inhibition of TEM-2 (class A) enzyme with clavulanate has been established (Scheme 1) [23,24], The inhibition is a consequence of the instability of the acyl enzyme formed between the /1-lactam of clavulanate and the active site Ser-70 of the enzyme. In competition with deacylation, the clavulanate acyl-enzyme complex A undergoes an intramolecular fragmentation. This fragmentation initially provides the new acyl enzyme species B, which is at once capable of further reaction, including tautomeriza-tion to an entity C that is much less chemically reactive to deacylation. This species C then undergoes decarboxylation to give another key intermediate enamine D, which is in equilibrium with imine E. The imine E either forms stable cross-linked vinyl ether F, by interacting with Ser-130 or is converted to the hydrated aldehyde G to complete the inactivation. 

Lactams are cyclic amides that have several features in common with their ester counterparts (lactones). As with lactones, the ring opening of lactams should be regarded as hydration rather than hydrolysis, since lactams,... 

Penicillins have several properties that are characteristic of /i-lactam antibiotics. They are obtained in relatively pure form as off-white, tan, or yellow freeze-dried or spray-dried solids that are usually amorphous. Alternatively they are sometimes obtained as crystalline solids, often as hydrates. Penicillins do not usually have sharp melting points, but decompose upon heating to elevated temperatures. Most natural members have a free carboxyl group and commercial preparations are generally either supplied as salts, most frequently as sodium salts, or in zwitterionic form as hydrates, e.g.. amoxicillin trihydrate. The acid strength of the carboxyl group in aqueous solution varies from pAT = 2.73 for oxacillin to p= 3.06 for carbenicillin. 

Being very strong bases, organometallic compounds are capable to start the polymerization (7, 12, 30, 51, 62). If organomagnesium compounds are used, the interaction of magnesium cations with lactam anions can probably reduce the dissociation of the salt analogous the basic character is certainly weakened in lactam complexes formed by addition of hydrated oxides of Ti, Zr, Hf, Th or Ce (48). 

A large number of compounds used as catalysts in acid-ion lactam polymerization are known. These include alkalis, alkali-earth metals, hydrates, Grignard reagents, lithium oxide, various hydroxides and carbonates, sulfates, halides, sodium zincate, alkaline salts of different acids, i.e., compounds that cause the formation of lactam acid ion in the reactive medium. The mechanism of polymerization in the presence of sodium-lactam- salt compounds is largely known. 

The lactones 81 and 82 on heating with hydrazine hydrate gave rise to the diazepinones 83 and 84, respectively.68 Treatment of 83 and 84 with glacial acetic acid and sodium nitrite caused loss of a nitrogen atom with formation of a lactam.68 This loss of a nitrogen has been noted above for other 1,2-diazepines and appears to be a fairly general reaction under a variety of conditions. A somewhat more complex quinobenzodiazepine has also been prepared.69... 

X-ray crystal results on cjiiosine itself ° (anhydrous and mono-hydrate), its complexes with different partners,cytidine, and cytidine 2, 3 -cyclic phosphateall indicate its existence in the lactam-amine form (2). In a number of crystals the cytosine ring is protonated, invariably at In cytosine 5-acetic acid half of the molecules... 

A photochemical technique for the synthesis of iV-acyl-imines has been reported. Photolysis of the azido-ketone (78) in the presence of pyridine or NEts yielded the AT-acyl-imine (79) which was hydrated to (80a) on alumina or sulphonic acid ion-exchange resin. Irradiation of (78) in MeOH afforded (80b), (79) being an intermediate. Catalytic reduction of (79) furnished the lactam (81). In refluxing... 

Both models mentioned have been used to investigate the simultaneous influence of electronic excitation and solvation (hydration) on the tautomeric equilibrium in the first two excited states of 2- and 4-oxopyri-dine tautomers (2a), (2b) and (3a), (3b). The relative stabilization energies A a,b( ) in the first two excited electronic states of the tautomers in question are given with the available experimental data in Table VIII. Comparison with experimental data can only be done for the second excited state (the appropriate experimental data for the first n - 7r state are not available). In the case of 2-oxopyridine the value of Af2a,2b( ) is estimated to be equal to -(5.4-11.7) kJ mole-1 from shifts of the absorption bands of the lactim and lactam tautomers of 2-oxopyridine and the... 

Reaction of a lactam with dimorpholinophosphoric chloride gives an O-substituted derivative which is susceptible to reaction at ambient temperature with acethydrazide. It is not necessary to isolate the intermediate. A lactam thiocarboiiyl and its ring-nitrogen are annulated on heating the compound first with hydrazine hydrate and then with trimethyl orthoacetate. 

An acetyl group and an adjacent lactam thiocarbonyl react with hydrazine hydrate to form a fused pyrazole. 

Despite the ample evidence presented above for the steric structure of cocaine, it seemed worth while to have a direct proof of the relationship of N to Cj-COOR. This has been realized by hydration of. AT-cyano-wor-cocaine (XXXIV) into JV -carbamyl-nor-cocaine followed by ring closure to yield the lactam of JV -carbamyl-Mor-ecgonine... 

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