Cyclic backbone

The presence of the cyclic backbone in ligands of this type makes a substantial contribution to their metal-ion complexing ability even though coordination involves donors which are not directly incorporated in the ring fragment. The origins of the enhanced stability of the metal-containing species may be considered to reflect the operation of an indirect macrocyclic effect (see Chapter 6) in these systems. 

When the lactone function of such bicyclic systems is consumed in a ring opening reaction, the main carbohydrate cyclic backbone is maintained in the product, unlike aldonolactones. Selected recent examples will be given in this section. 

It has been proposed that simple non-carbohydrate analogues containing the carboxylate and the acetylamino groups attached to a cyclic backbone spacer would be suflSdent to generate lead compoimds for further elaboration as NA inhibitors. The spacer would need to orient correctly these groups as found in bound DANA. It has been also required thad such compounds adopt a planar structure near the carboxylate to mimic the transition state and be able to present additional side-chain functionality for interaction with other conserved amino acid residues in the sialic acid binding site. 

Cyclic backbone side-chain cyclic backbone-backbone, backbone to C- or N-terminal... 

Sasai s group [13] developed a series of bisnitrogen ligands with fused hetero spiro cyclic backbones, including spiro bis(isoxazoline) 11 and 12, spiro isoxazole-isoxazoline 13, spiro bis(oxazoline) 14, spiro bis(pyrazole) 15, and spiro bis(isoxazole) 16 (Figure 3). Ligands 11 [14] and 13 [15] exhibited excellent reactivity and enantioselectivity in the Pd-catalyzed oxidative cyclization reactions. 

Peptidic p-tum mimetics are generally based on cyclic backbone mimetics (e.g. replacing the turn hydrogen bond by a covalent bond) or by introducing one or several unusual amino acids, which constrain the backbone in P-tum conformations. Synthetic approaches to non-peptidic turn mimetics can be grouped into two classes 1) external P-turn mimetics, and 2) internal P-turn mimetics. ... 

The conformation of uncomplexed antamanide is entirely different from that of the alkali metal ion complexes. Not only is the cyclic backbone elongated and flattened, but sequences 4,5,6 and 9,10,1 turn inside-out so that the... 

The lower hydroxyl number reduces formulation cost, by reducing the required isocyanate, but it does not compromise important physical properties due to its higher functionality from the sucrose-based cyclic backbone built into the polyol. The quantity of catalyst required to promote the desired reaction profile is less than would be required with polyols with no amine in the backbone. 

Copolymerizations of ethylene and/or propylene with nonconjugated dienes using various metallocene catalysts are a useful method to synthesize polyolefins with cyclic backbones. 

By reaction of [Cu(en)(o-phda)] or [Cu(l,3-pn)(o-phda)] + (o-phda = o-phenylenediamine) with bromomalondialdehyde, macrocyclic systems [Cu(L260)l and [Cu(L261)], combining aliphatic and aromatic diamine residues in the cyclic backbone, were synthesised (Eq. 2.156) [301, 305]. 

Porphyrins are the most widespread macrocyclic compounds in nature. Synthetic porphyrins, which can be obtained in good yields from quite cheap raw materials by simple technology, are also of interest. Substances containing the porphin nucleus as a cyclic backbone are usually referred to as porphyrins (Eq. 2.216) [231]. 

The routes shown above are suitable only for the synthesis of symmetric 14-membered macrocyclic systems containing four phosphorus atoms in a cyclic backbone, but a general method for the synthesis of tetraphosphacycloalkanes containing 14-16 units in a ring has been reported [9], The compounds L1208-L1215 have been synthesised by this technique (Eq. 5.4). 

Azacrown ethers L1543-L1545, containing a hydrazine fragment in the cyclic backbone, were obtained in the presence of Na+ or K+ following Scheme 6-13 [179, 180]. 

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