Synthesis of a .BETA.-Tetrapeptide Analog as a Mother Compound for the Development of Matrix Metalloproteinase-2-Imaging Agents

Abstract

Matrix metalloproteinases (MMPs) comprise a family of enzymes that degrade the basement membrane and extracellular matrix, thus contributing to tissue remodeling and cell migration. 1,2) Numerous studies have demonstrated the various roles of MMPs in pathological processes associated with cancer and atherosclerosis, making MMPs potential targets for diagnosis using noninvasive imaging.3,4) Among MMPs, MMP-2, which degrades a major component of the basement membrane, has been studied extensively and shown to be involved in tumor invasion and metastasis, 5,6) and atherosclerotic plaque rupture. 7,8) For in vivo imaging of MMP-2 activity, we and others used a cyclic decapeptide, cCTTH-WGFTLC (cCTT), as the mother compound because of the clinical and radiopharmaceutical utility of peptide radiopharmaceuticals.9-11) The cyclic decapeptide cCTT was screened as a selective gelatinase (especially MMP-2) inhibitor using phage display technology. Koivunen et al. showed that cyclic decapeptides containing the amino acid sequence His-TrpGly-Phe (HWGF) exhibited selective inhibition toward MMP-2 and MMP-9 activities while a liner peptide containing the HWGF sequence had little inhibitory activity. 10) In tumor-bearing mice, however, both radiolabeled cCTTs exhibited low accumulation in MMP-2-positive tumors. They considered the poor stabilities of these peptides in vivo as one of the causes of low tumor accumulations. Our previously designed compound, 111In-labeled diethylenetriaminepentaacetic acid (DTPA)-conjugated cCTT, showed a good correlation between its tumor accumulation and MMP-2 activity in the tumor, but the accumulations in MMP-2-expressing tumors were relatively low. 11)Oligomers of b-amino acids, b-peptides, have emerged as a promissing class of peptidomimetics. [13][14][15] It is recognized that one of their important characteristics is to form stable secondary structures with as few as four b-amino acid residues. Furthermore, they are entirely stable against proteolytic degradation in vivo. Gademann et al. synthesized a linear b-tetrapeptide analog, Ac-b 3 -HThr-b 2 -HLys-b 3 -HTrp-b 3 -HPhe-NH 2 , to mimic a somatostatin (cyclic 14-mer) in its binding to the human somatostatin receptors, which is known to rest upon a turn containing the amino acid sequence PheTrp-Lys-Thr.16) The turn of the linear b-tetrapeptide analog which has the retro-sequence, is comparable to that of the cyclic a-peptide both in size and orientation of the side chains, although the amide bonds are reversed. These findings led to the design of a linear b-tetrapeptide analog, H-b-His-OH (1), as a downsized derivative to mimic cCTT. In the present study, b-tetrapeptide (1) was prepared by solution-phase synthesis techniques and its inhibitory effect on MMP-2 activity was compared with that of cCTT. To investigate the validity of the drug design, the linear a-tetrapeptides, H-His-Trp-Gly-Phe-OH (2) and H-PheGly-Trp-His-OH (3), were also prepared for comparison (Fig. 1). Results and DiscussionIn general, the preparation of b-amino acids ca...

Synthesis of Aminomethylene-gem-bisphosphonates Containing an Aziridine Motif: Studies of the Reaction Scope and Insight into the Mechanism

“…1 H NMR (400 MHz, CDCl 3 ): δ 8.03 (s, 1H, NH), 7.65 (d, J = 7.5 Hz, 1H, CHAr), 7.43–7.28 (m, 6H), 7.21 (t, J = 7.5 Hz, 1H, CHAr), 7.15–7.07 (m, 1H, CHAr), 7.03 (s, 1H, CHAr), 5.10 (s, 2H, CH 2 Ph), 5.04 (br s, 1H, NH), 4.16–3.95 (m, 1H, CH), 3.68 (ddd, J = 15.4, 9.7, 4.2 Hz, 2H, CCH 2 CH), 3.03 (d, J = 6.8 Hz, 2H, CH 2 OH). Data in accordance with the literature. , …”

Peptide-Based Selective Inhibitors of Matrix Metalloproteinase-Mediated Activities

“…Mukai et al found that H-β 3 -Phe-β-Ala-β 3 -Trp-β 3 -His-OH inhibited MMP-2 with an IC 50 value of 225 µM, in comparison to CTT IC 50 of 212 µM (as determined herein) [31]. Linear α-tetrapeptide had no significant contribution towards MMP inhibition, with an IC 50 value of >1 mM [31]. While H-β 3 -Phe-β-Ala-β 3 -Trp-β 3 -His-OH has a similar affinity for MMP-2 as CTT, the new class of β-tetrapeptide is smaller in size and generally more stable, thereby enhancing its accumulation in target tissues.…”

“…The linear β-tetra peptide H-β 3 -Phe-β-Ala-β 3 -Trp-β 3 -His-OH was designed to mimic CTT. Mukai et al found that H-β 3 -Phe-β-Ala-β 3 -Trp-β 3 -His-OH inhibited MMP-2 with an IC 50 value of 225 µM, in comparison to CTT IC 50 of 212 µM (as determined herein) [31]. Linear α-tetrapeptide had no significant contribution towards MMP inhibition, with an IC 50 value of >1 mM [31].…”

Improved enzymatic syntheses of valuable β-arylalkyl-β-amino acid enantiomers

“…Allylbenzene, 4-phenylbut-1-ene and Meldrum's acid were from Aldrich. (2,4,acetic acid was from Matrix Scientific. The solvents were of the highest analytical grade.…”

“…Racemic b-lactams (±)-3 and (±)-4 were prepared by the addition of chlorosulfonyl isocyanate to allylbenzene (1) or 4-phenylbut-1ene (2), respectively, according to known literature methods. 19b,24 (±)-3 and (±)-4 (6.0 mmol) were then refluxed with 22% HCl/EtOH (15 mL) for 8 h, after which the solvent was evaporated off, resulting in the corresponding b-amino ester hydrochlorides (±)-5•HCl and (±)-6•HCl, which were immediately treated with aqueous K 2 CO 3 to afford (±)-5 and (±)-6, as oils.…”