The folding of linear molecular species within biology into more complex architectures is critical in dictating their overall function as it results in the presentation of functionality in a very precise way within three-dimensional space. This complex relationship between structure and function has inspired chemists to design their own minimalistic scaffolds, known as foldamers, 1 with the purpose of uncovering functions that are inextricably linked to this higher order structure. These goals are diverse and range from peptidomimetics 2 through to catalysis 3 and molecular recognition systems. Understandably, owing to the elegance with which nature can combine a relatively simple set of just twenty amino acids and fashion them towards a vast range of structures and functionalities, a great deal of focus has been on novel peptidic foldamers. This ranges from peptoids 5 through to homologated amino acids -particularly b-, 6 and g-systems. These unnatural sequences have advantages over naturally occurring a-peptides in that the secondary structures formed are more predictable, and -critically for any therapeutic application -resistant to metabolism and proteolysis. Within these peptidic foldamers, heteromeric sequences consisting of aand homologated amino acids in a 1:1 ratio have gained considerable attention. First modelled by Hofmann and co-workers, these systems can form a diverse array of novel helices as reported in a series of in silico papers. Such helices are described as being "mixed" -and have the potential for hydrogen bonds to alternately point into forward and backward directions along the sequence, in contrast to helices with unidirectional hydrogen bonds. Among the various possible 1:1 heteromers of a-amino acids with higher homologated amino acids, a,band a,g-hybrid peptides predominate the literature. -for example by the groups of Gopi, 8a,8b,13 Tomasini, and recently our own, where we described a highly stable 10/12-helix made from a cis-cyclopentyl-g-amino acid. d-Amino acid heteromers on the other hand, also proposed by Hofmann and co-workers, have received far less attention despite their broad predicted range of helices, with the only examples coming from the same report, and from Gervay-Hague and co-workers. These hybrid systems are of particular interest, because an a,d-dipeptide corresponds to an a-amino acid trimer unit and has the potential to replace this in peptides and proteins. We were particularly drawn to the most stable of these proposed by Hofmann -the H13/11 system -because according to his modelling, the a-residues appeared to be embedded within the helix, whilst the d-residues occupy the perimeter (Figure ). We anticipated that this arrangement would provide a highly defined binding pocket that could be exploited for catalysis, whereby the a-residues might provide the functionality and the d-residues the steric environment.