Fmoc-D-aspartic acid

We synthesized fifteen oligopeptides consisting of Asp or Glu conjugated with a fluorescent probe, 9- fluorenylmethylchloroformate (Fmoc). In the in vitro binding assay to putative hydroxyapatite (HA), the affinities of these conjugates depended only on the number of amino acid residues, not on their optical characters (L or D) or their species (Asp or Glu). In an in vivo experiment involving a single i.v. injection of Fmoc-D-Asp oligopeptides into mice, peptides consisting of over six Asp residues were selectively distributed to the bone. Then, we synthesized estradiol-17 beta-succinate-(L-Asp)6 [E2-(L-Asp)6] and studied its pharmacokinetic characteristics and its antiosteoporotic effects on ovariectomized (OVX) mice. Although the distribution volume of E2-(L-Asp)6 was significantly smaller than that of E2, E2-(L-Asp)6 was selectively distributed in the bone after i.v. injection and gradually decreased during 7 days. E2-(L-Asp)6 effectively prevented OVX-induced bone loss, without altering the uterine weight, in the dosage range of 0.

We have synthesized (acyloxy)methyl ketone inactivators of papain, cathepsin B, and interleukin-1beta conversion enzyme (ICE) that interact with both the S and S' subsites. The value of k(inact)/K(i) for these inactivators is strongly dependent on the leaving group. For example, Z-Phe-Gly-CH(2)-X is a poor inactivator of papain when X is OCOCH(3) (k(inact)/K(i) = 2.5 M(-)(1) s(-)(1)) but becomes a potent inactivator when X is OCO-L-Leu-Z (k(inact)/K(i) = 11 000 M(-)(1) s(-)(1)). Since these leaving groups have similar chemical reactivities, the difference in potency must be attributed to interactions with the S' sites. The potency of the leaving group correlates with the P' specificity of papain. Similar results are also observed for the inactivation of cathepsin B by these compounds. A series of inactivators with the general structure Fmoc-L-Asp-CH(2)-X were designed to inactivate ICE. No inhibition was observed when X was OCOCH(3). In contrast, ICE is inactivated when X is OCO-D-Pro-Z (k(inact)/K(i) = 131 M(-)(1) s(-)(1)).

In the past few years affinity capillary electrophoresis (ACE) has proven to be a powerful tool to study molecular interactions. In ACE the change in electrophoretic mobility between a free and a complexed ligand with a receptor dissolved in the background electrolyte is observed. It provides an accurate way to calculate binding or dissociation constants and, when coupled to mass spectrometry, it forms a promising method to analyze solution-based combinatorial libraries. We report a model study on the macrocyclic antibiotic vancomycin using a 36-component library of tetrapeptides of the type 9-fluorenylmethoxycarbonyl (Fmoc)-L-Asp-L-Asp-D-Xaa-D-Xaa. The mass spectrometry conditions were optimized by fine-tuning the background electrolyte and sheath flow composition to achieve optimal sensitivity in the negative ionization mode. Different types of capillaries were also evaluated on their potential to screen combinatorial libraries. The library components that show the strongest interaction were identified.

Various 3-substituted chiral 1,2,4-oxadiazole-containing Fmoc-beta(3)- and -alpha-amino acids were synthesized from Fmoc-(l or d)-Asp(OtBu)-OH and Fmoc-l-Asp-OtBu, respectively, in three steps (i.e., condensation of an aspartyl derivative with differentially substituted amidoximes, formation of the 1,2,4-oxadiazole, and cleavage of the tert-butyl ester). These compounds represent new series of nonnatural amino acids, which could be used in combinatorial synthesis. A simple protocol has been developed to generate the 1,2,4-oxadiazole ring. Indeed, common methods resulted in cleavage of the Fmoc group or required long reaction times. We found that sodium acetate in refluxing ethanol/water (86 degrees C) was a convenient and efficient catalyst to promote conversion of Fmoc-amino acyl amidoximes to 1,2,4-oxadiazoles, and this procedure proved to be compatible with Fmoc protection. It is shown that these compounds can be prepared without significant loss of enantiomerical purity.