Cyclic lactams

Starting with the cyclic lactams, by the hydrolytic polymerization method, three... 

The AB polyamides are made from either >-amino acids or cyclic lactams, derivatives of the oj-amino acids (Table 3.1). In these polymers, the amino and acid groups are inherently balanced and the polymer also contains one amino and one acid endgroup. There are a number of different routes available for polymerizing these AB-type polyamides ... 

Another method is to start with lactams. The cyclic lactams have a lower melting temperature compared to co-ammo acids and are therefore more easily purified and easier to handle. e-Caprolactam has a melting temperature of 69°C and can be transported in the molten state in heated tanks. The energy consumption of the lactam polymerization is also low as little water is added by the polymerization process and therefore there is little to evaporate. 

Cyclic esters, ring-opening polymerization of, 85-87 Cyclic lactams, 174 Cyclic oligoesters, 31 Cyclic oligomers, 63, 542 formation of, 39... 

We have previously seen how cyclic lactams can be synthesized by installing a protected amine in one of the Ugi or Passerini components, followed by cyclization onto the isocyanide-derived amide, taking advantage of the particular reactivity of convertible isocyanides. The same type of compounds can be accessed through nucleophilic attack of the amine onto an ester moiety, suitably installed as additional function into another component. This strategy has been widely used for the preparation of diketopiperazines 104 (Fig. 22), a typical privileged structure, starting with... 

During the synthesis of 436, Muraoka and colleagues produced the diazobi-cyclo[4.3.1]decane 435 via the classical ring expansion (equation 184). Huisgen-White rearrangement of the cyclic lactam leads to 436, a key synthetic intermediate for piperidine alkaloids. 

The third major method for achieving difunctionality involves the ring-opening polymerization of a cyclic monomer, typified for example by the synthesis of polyamides from cyclic lactams. Reactions of this type proceed by chain-reaction mechanisms but yield polymers more typical of step-reactions, in that they contain functional groups within the chain. 

Fermentation methods for synthesis and resolution Reaction with cyclic lactam intermediates Reaction with glycine and aldolase Fractional crystallization... 

Nuclear Overhauser effect (NOE) experiments clarified the preference of the cis-trans-geometry in solution for cyclic lactams 19. For 19a-c, X-ray geometries (Section 14.10.3.1) retain in solution, and NOEs were observed between the methylene protons next to the ring carbonyl and the NCH2 protons, whereas no such NOE was observed in 19d <2002CC2656>. 

Another general method for the introduction of a nitrogen atom into a macrocyclic skeleton is via the Beckmann reaction. Rearrangement of cyclotridecanone oxime led to cyclic lactam, which was reduced to amine by lithium aluminium hydride (LAH). Further substitution yielded 14-membered mutuporamine <1999TL5401>. Dieckmann condensation was used for the preparation of 14-membered aza ketone 15 <1999JA2919>, but no experimental details were given. 

Cyclic lactams do not normally form hydrazones or other derivatives typical for ketone carbonyl groups. However, 2-methyl-3(2//)-pyridazinone when treated with formylhydrazine and triethyl-oxonium fluoroborate afforded the hydrazone (93) which undergoes oxidative coupling to form azo dyes. Oximes of 4(lH)-pyridazinones are also claimed to exist. ... 

SYNS AMINOCAPROIC LACTAM 6-AAflNOHEXAN -OIC ACID CYCLIC LACTAM 2-AZACYCLOHEPTAN-ONE 6-CAPROLACTAM co-CAPROLACTAM (MAK)... 

Irradiation of spiro oxaziridines gives rise to various cyclic lactams as summarized in Table 1. 

Table 1 Irradiation of spiro oxaziridines to cyclic lactams...

In a very early example, Freidinger et al. developed a series of cyclic lactams that stabilized j8- and y-turn structures in linear peptides (Fig. 15.8). This strategy was applied to determine conformations of LH-RH that are consistent with the turn structure permitted by the constraint. For example, the 3-amin-olactam (18)was used to mimic a p-turn conformation. When inserted in LH-RH, com-... 

Scheme 1 Formation of Cyclic Lactam Peptides on a Solid Supportl l...

Lactam polymerization comprises the conversion of a cyclic lactam unit into a linear one without the formation of any new chemical bonds. The term polymerizability involves both the thermodynamic feasibility and a suitable reaction path to convert the cyclic monomer into a linear polymer. Sometimes, a slight confusion arises when the term polymerizability is used as a synonym for both the rate of polymerization and the thermodynamic instability of the lactam. Due to the reversible nature of the polymerization of most lactams, eqns. (1)—(3), their polymeriz-abilities cannot be expressed in terms of the rate of polymerization only, but the rate of both polymerization and monomer reformation must be compared. 

Substituents affect both the heat and entropy of polymerization, mainly through conformational effects [58—61]. Steric repulsions between substituents as well as between atoms of the monomer unit and substituents usually do not change the enthalpy of the cyclic lactam. Only... 

Both phenylacetic and 3-phenylpropionic acids (120) easily undergo the Schmidt reaction under the standard conditions using sulfuric acid, giving the corresponding amines (121). 4-Phenylbutyric acid (122), however, produces the cyclic lactam (123), in addition to the sulfonated amine (124). Replacement of sulfuric acid with polyphosphoric acid again affords the lactam (123) mainly, together with 3-phenylpropylamine (125) as a minor product. In the rearrangement of S-phenylpentanoic acid (126), only the sulfonated amine (127) is obtained, as shown in Scheme 24. 

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