A thiodipeptide carrier system is shown to be effective at enabling a range of covalently bound molecules, including benzyl, benzoyl and ibuprofen conjugates, to be transported via the intestinal peptide transporter PepT1, demonstrating its potential as a rational drug delivery target.

N‐Benzoylamides of 2,2,6,6‐tetramethylpiperidine are not ortholithiated by organolithium compounds but instead undergo nucleophilic addition of the organolithium compound to the aromatic ring in the manner of a conjugate addition. The resulting dearomatised enolates may be protonated or alkylated, and yield substituted cyclohexadienes in yields of up to 76%. Deprotection of the piperidine ring is possible under acidic conditions. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Poles apart: The relative orientation of a pair of functional groups—amides in this case—can be controlled by the choice of the substituent that lies between them. Groups which are effectively cylindrically symmetrical (Me, Cl) allow direct interaction between the dipoles of the amides and induce an anti orientation, whereas polar groups (OCOR, OSO2R, SO2R) interact with the dipole of both amides to yield a syn orientation (see picture).

Benzamides whose nitrogen atom is part of a 2,2,6,6-tetramethylpiperidine ring are dearomatised by alkyllithiums, which attack them regioselectively to yield, after electrophilic quench, substituted cyclohexadienes.

Dreierbeziehung: Die relative Orientierung zweier funktioneller Gruppen – hier Amide – lässt sich über die Wahl des Substituenten zwischen ihnen steuern. Bei Gruppen mit effektiv zylindrischer Symmetrie (Me, Cl) können die Dipole der Amide direkt wechselwirken, was eine anti‐Orientierung zur Folge hat, während polare Gruppen (OCOR, OSO2R, SO2R) mit den Dipolen beider Amide wechselwirken und so eine syn‐Orientierung bewirken (siehe Bild).