Abstract
Two new groups of cholane-peptoid hybrid macrocycles were produced by implementing novel combinations of the MiB methodology. Steroid-based hybrid macrolactams including heterocycle and aryl moieties were obtained by utilizing cholanic dicarboxylic acids and diamines in a bidirectional double Ugi-Four-Component (Ugi-4CR) based macrocyclization protocol. Alternatively, N-substituted cyclocholamides were produced from a cholanic pseudo-amino acid by an Ugi-4CR-based cyclooligomerization approach. Both types of macrocycles are steroid-peptoid hybrid macrocycles containing exocyclic peptidic chains. These novel frameworks are a result of the use of bile acids bifunctionalized with carboxylic and amino functionalities as bifunctional building blocks of the Ugi-MiB approach.
Highlights
Macrocycles incorporating the cholanic skeleton have proven successful as host compounds in molecular and ion pair recognition studies [1,2,3,4]
We have recently developed a new macrocyclization approach termed multiple multicomponent macrocyclizations including bifunctional building blocks (MiBs) [16,17,18]
N-substituted cyclocholamides were achieved by an unidirectional Ugi-MiB approach based on the acid/amine combination
Summary
Macrocycles incorporating the cholanic skeleton have proven successful as host compounds in molecular and ion pair recognition studies [1,2,3,4]. It is known that the appropriate binding of a guest to a Molecules 2007, 12 synthetic receptor is a result of the presence of the proper recognition elements, and of their relative disposition in space and the three-dimensional shape of the overall interaction [5] In this sense, molecules such as steroids with well-defined, preorganized architectures are amenable to the design of macrocyclic hosts wherein conformational freedom can be kept under close control [1,2,3,4]. Different types of bile acid-based macrocycles have been reported to be useful for the encapsulation of metal cations, anions or biologically relevant molecules such as sugars and amino acids These macrocycles can be integrated into two main types of compounds, i.e., the oligomeric and the hybrid steroidal macrocycles. Examples of this widely explored type of macrocycles are the well-known cholaphanes [1], as well as other steroid-aryl [3,4,12], steroid-peptide [13,14] and steroid-polyether hybrids[3, 4,15]
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