Macro-Heterocycles

The cyclization reactions discussed here either involve the intramolecular reaction of a donor group D with an acceptor group A or a cyclizing dimerization of two molecules with two terminal acceptors and two donors. A polymerization reaction will always compete with cyclization. For macrolides see p. 146 and p. 319 — 329. 

The intramolecular cyclization can be favored by (i) high dilution techniques, (ii) the action of a template which farces the reacting ends together, and (iii) stepwise condensations. 

---

The genus Mackinlaya (Arali tce ie) on the other hand yielded quinazolines of a type not previously encountered, such as 37 52], accompanied by a base (38) with a macro heterocyclic ring that appears to be biosynthetically related to the quinazoline types 53]. 

PF foams offer to the construction industry a useful combination of physical and flammability characteristics. They generate low levels of smoke in most fire tests. It was reported that a cupric complex of a macro heterocyclic compound is an effective stabiliser for thermo-oxidative decomposition of PF foams above 200 °C. An amount of 0.25-5.0 pph permits significant decrease of ignitability [178]. 

Situations are known when demetallation results in the formation of a macro-heterocyclic organic compound which is unstable in the metal-free state. This is the case, for instance, when [Ni(L15)](C104)2 interacts with aqueous NaCN [51] (Eq. 1.7). 

Startg. cyclic sulfonium perchlorate heated at 90° with l,8-diazabicyclo[5.4.0]-undec-7-ene in toluene cw-product. Y 67% (and 7% rran -isomer). - S-Macro-heterocyclics by repetition of this 2,3-sigmatropic shift s. E. Vedejs and J. P. Hagen, Am. Soc. 97, 6878 (1975). 

Chalinidae 300-320 300-320 Adocia, Chalinula, Haliclona, Reniera Acetylenic derivatives, macro-heterocycles, triterpenes, sulfated meroterpenes, isonitriles, aromatic carotenoids, atypical sterols, long-chain phenols, pyridine derivatives, S/N heterocycles, cyclic peptides, sulfated derivatives... 

Niphatidae 140-150 160-180 Amphimedon, Cribochalina, Niphates Acetylenic derivatives, macro-heterocycles, cyclopropanic fatty acids, S/ P sterols, isonitriles, isothiocyanates, pyridine derivatives (3-alkyl pyridinium), merosesquiterpenes... 

Petrosidae 360-380 500-520 Petrosia, Strongylophora, Xestospongia (= Neopetrosia) Acetylenic derivatives, macro-heterocycles, ve long-chain fatty acids (>4°C), brominated fatty acids, atypical sterols (cyclopropanes, polyhydroxylated, sulfated), atypical glycerol ethers, meroterpenes, aromatic derivatives... 

---