The facile, high-yielding synthesis of a series of macrocycles 7a−k in 75−100% yield is reported.The transformation of these compounds to their carboxymethylated analogues 8a−k in 75−90%yield and subsequent gadolinium complexes 9a−k provides a series of homologous neutralparamagnetic contrast agents (PCAs) with tunable lipophilicity. Alkylated cationic intermediates6a−k are prepared in yields of 72−94% from glyoxal adduct of cyclen (5) and slight excesses ofalkyl iodides. The methodology is selective for monoalkylation and amenable to large-scale synthesis.