Pergamon Tetrahedron Letters 40 (1999) 3025-3028 TETRAHEDRON LETTERS Synthesis and Chirai Recognition Properties of L-Ala-Crown(3)-L-Ala Capped 13-Cyciodextrin Roberto Corradini, Giuseppe Buccella, Gianni Galaverna, Arnaldo Dossena, and Rosangela Marchelli* Dipartimento di Chimica Organica e lndustriale, University of Parma-Parco Area delle Scienze, 1-43100 Parma (Italy) Received 2 December 1998; accepted 9 February 1999 Abstract The synthesis and full spectroscopic characterization (IR, 1D and 2D TOCSY and ROESY NMR, MS) of a novel capped 13-cyciodextrin bearing a 6A,6D-dideoxy-N,N'-3,6,9-trioxa-undecanoyl-(L,L)-bis-alanyl bridge are described. The chiral recognition properties of the product towards Dns-amino acids have been examined by capillary electrophoresis. © 1999 ElsevierScienceLtd. All rights reserved. Keywords: CaPlmd-Cyclodextrins; Chiral Discrimination;Dansyl-Amino Acids. Capillau, Electrophoresis Owing to their ability to distinguish between size and shape and to their intrinsic chirality, cyclodexlrins (CDs) have been used as efficient molecular and chiral selectors in analytical applications, Ill especially in GC, I21 HPLC [3] and C E [41 analyses. Selective functionalization of CDs with different groups generally improved the recognition properties by increasing the asymmetry and allowing for more specific interactions between the host and the guest such as hydrogen bonding, electrostatic interactions and metal coordination, lsl Recently, cyclodextrins capped with chiral moieties have been proposed as enzyme models (three-dimensional CDs). In particular, a 13-CD capped with the cyclic dipeptide L-hystidyl-L- hystidyl was synthesized and its complexing ability towards the copper(lI) ion examined. [61 Furthermore, a trehalose capped I3-CD has been synthesized as the first example of an extended cavity with a sugar moiety. I71 Whether or not the capping of CDs with chiral or achiral bridges will enhance the enantioselectivity has not been studied to our knowledge. Here, we report the synthesis and the enantiomeric recognition ability of the new capped 6A,6D-dideoxy-N,N'-3,6,9-trioxa-undecanoyl-(L,L)-bis-alanyl-13-CD: L-AIa-Crown(3)-L-Ala- 13-CD (1) (Fig. 1). Our aim was that of obtaining a water soluble selector to be used as an additive to the buffer in capillary electrophoresis. The bridge had already been used by us as a chiral selector in GC for the enantiomeric discrimination of alkyl esters of TFA-amino acids. 181. Recently, we have performed very good enantiomeric separation of Dns-amino acids by CE with two positively charged histamine-functionalized I3-CDs. [91 A model was devised to account for the chiral separation in which the inclusion mode of the Dns-moiety was opposed to that generally assumed for an unmodified 13-CD. In order to verify the inclusion mode of the dansyl-amino acids in the case in which only one side of the CD cavity is accessible to the 0040-4039/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S0040-4039(99)00315-9