Molecular clefts chiral

There are a number of examples of chiral molecular clefts. Among the most interesting are those introduced by Wilcox and coworkers, which involve derivatives of Troger s base. Such systems were used as hosts for various guests and as tools for the evaluation of edge-face interactions between n systems. Related molecular clefts are known. 

Design and application of molecular tweezers, particularly those that are chiral and those that can bind multiple n systems within their clefts, are only beginning to be explored. Molecular tweezers and other molecular clefts have the potential to dimerize to produce molecular... 

As shown in Table 1.1, oxaziridine (29b) is a superior reagent for sulfide oxidation, compared to (28b). Values of ee up to 95% were obtained. The two chlorines of (29b) are crucial for the enantioselection (see entries 1, 2 and 5, 6 in Table 1.1). Chiral oxaziridines are now commercially available. A mechanism has been proposed for the electrophilic attack on sulfur. In the present case preferred transition states I and II were postulated. Rl and Rs are large and small groups, respectively. The steric influence seems to be of major importance, presumably because of a molecular cleft defined by a chlorine atom and the phenylsulfonyl... 

In the transition state for the asymmetric Claisen rearrangement of allyl vinyl ether 7c with (J )-ATBN 5a, the one conformation of the ether substrate is the matched system for the Cj-symmetric molecular cleft of the chiral aluminum reagent 9, which gives the (S)-product (Fig. 2.3). Increased enantioselectivity using... 

Crossley et al. (95JCS(CC)1077) covalently linked two tetraarylporphyrins through the methanodiazocine bridge of TB to prepare well-defined chiral cleft-containing molecules 36 and 37a,b (Figure 8), whose molecular recognition properties could be... 

The cleft of Troger s bases provides only limited sueeess in supramoleeular applieations, however, their well-defined structures were used as armatures for aligning further functionality in order to provide receptors for molecular and chiral recognition. That goal was achieved with scaffold-type derivatives 19, 20, 24 (cf. 18) and by embedding Troger s bases in macrocycles that were called trogerophanes (21-23, 25) (Fig. 3). 

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