Macrocyclic amides

Macrocyclic amides and esters containing the 2,6-dipicolinate subunit. . 241... 

Comba et al. reported structural properties (in the solid state and in solution) and molecular modeling studies on a dicopper(II) complex (545) (SP) of a macrocyclic amide ligand.443 In 1993... 

An extremely versatile and simple synthesis of macrocyclic amide complexes has been based on the reactivity of JV-acylisatin compounds (Scheme 32).170 The template reaction occurs very readily as a result of the increase in electrophilicity of the carbonyl groups in the a-keto esters and... 

Metathesis reactions may be intramolecular and ring-closing diene metathesis (RCM, implicated in Scheme 1.13, see Chapter 12) allows disconnections in retro-synthetic analysis otherwise of little use. The normal disconnection of the macrocyclic amide in Scheme 1.13 would be at the amide but, because of the ready reduction of alkenes to alkanes, the alternative disconnection now becomes a viable option. And since any of the C—C linkages could be formed by RCM, such a disconnection allows far greater synthetic flexibility than the conventional disconnection at the functional group. 

The range and versatility of amide anion binding hosts is very extensive. Macrocyclic amides have also been reported, such as 4.42 which forms a remarkable sandwich compound with sulfate in the solid state. Sulfate binding is enhanced by protonation of the tertiary amine groups and the host is thus a hybrid between amide and ammonium binding sites. The triethylbenzene scaffold has been used to prepare... 

Figure 12.8.2(a) shows the molecular structure of Na4Mg2(TMP)6(C6H4), in which the N atom of each tetramethylpiperidinide is bonded to two metal atoms to form a cationic 12-membered (Na-N-Na-N-Mg-N-h ring. The mixed metal macrocyclic amide acts as a host that completely encloses a 1,4-deprotonated benzenediide guest species whose naked carbon atoms are each stabilized by a covalent Mg-C bond and a pair of Na- C n interactions. 

Of course, the peptides [55] and peptide alkaloids [48, 56] belong to the field of macrocyclic amides, as well. The cytotoxic ulicyclamide 58, for example, can be prepared in very diluted solution from the open-chained penta-peptide by reaction with diphenylphosphorazidate in DMF/triethylamine in high yield. 

Macrocyclic amides as anion receptors based on directed hydrogen-bonding interactions 03CCR(240)101. 

A further variant of this method using bismalonate tetraester allows the preparation of bis-macrocyclic amides (64) <84IC39I7>, which can be then reduced with in diglyme to the corresponding bismacrocyclic amine (65) (Scheme 7) <86102671,87JCS(D)263i>. 

The macrocyclic amide linked cobalticinium receptor (18) has recently been prepared (Scheme 3) and its crystal structure elucidated (Figure 3). 

A series of optically active macrocyclic amides, such as 74 (Fig. 18), consisting of one or more units of 70, have been prepared [63]. A modest level of asymmetric induction using 74 as the catalyst for the addition reaction between aromatic aldehydes and diethylzinc was observed. 

In one of the crystal forms of the acetate structure of 20, however, a sandwich-like, 2 1 complex is formed (Figure 8d) when [nBu4N]+ is the counterion, while a simple 1 1 complex is formed in the presence of [(CH3)4N]+. In the sandwich complex, each oxygen atom of the carboxy-late group is H-bonded to the host via four NH- O bonds (Figure 8d). In the 1 1 complex of 20 with acetate, the acetate hovers above the macrocyclic cavity, much like the chloride structure, with four H-bonds to the macrocyclic amides (Figure 8e). The anion is also coordinated by an H-bond to an axial water molecule, an occurrence that is frequently seen in complexes with anions. 

Fig. 4 Dimeric macrocyclic amides from hexa-O-methylsucrose.

An efficient method for the conversion of iV>alkyl-lactams into the corresponding thiolactams, involving treatment with R3O+BF4- followed by NaSH, is reported. Twenty-four-membered macrocyclic amides containing phenylalanine and leucine units have been obtained. A total synthesis of the natural product bastadin-6, which has a 28-membered lactam ring, has been described, and total syntheses of ( )-maysine and ( >ma5dansinol are reported. ... 

Biidged calix[4]arenes (e.g. calixcrowns) normally have Ctv symmetry. This is also observed for the macrocyclic amides 20 obtained by reaction of t-butylceilix[4]arene-l,3-diacidchlorides with various diamines, including ethylene-diamine [26]. MA -Dimethylethylenediamine, however, leads to a cyclic amide with C2 symmetry, which is obviously caused by the steric demands of this rather rigid bridge. 

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