Synthesis, X-ray and conformational studies of novel tetrazole-containing macrocycles: 4,13-dioxa-1,7,8,9,17,18,19,20-octaazatricyclo[14.2.1.1(7,10)]icosa-8,10(20),16(19),17-tetraene and 4,14-dioxa-1,7,8,9,10,18,19,20-octaazatricyclo[15.2.1.0(7,10)]icosa-8,10,17(20),18-tetraene

Alkylation of 1,5-bis(tetrazol-5-yl)-3-oxapentane by 2,2'-dichlorodiethyl e ther under conditions of high dilution led to two isomeric crown-like macro cycles: 4,13-dioxa-1,7,8,9,17,18,19,20-octaazatricyclo[14.2.1.1(7,10)]icosa -8,10(20),16(19),17-tetraene 2 and 4,14-dioxa-1,7,8,9,10,18,19,20-octaazatr icyclo[15.2.1.0(7,10)]icosa-8,10,17(20),18-tetraene 3. The crystal structur es of both compounds were determined. In the crystalline state, macrocycle 2 exists in syn-form with a symmetry near C-s, whereas macrocycle 3 has onl y C-1 symmetry. The latter was observed to adopt two different conformation s in the crystalline state. An AM1 conformational analysis of macrocycle 2 revealed 30 different conformations, one of which is similar to the observe d crystal structure.