Chemistry: natural resins or derivatives; peptides or proteins; – Peptides of 3 to 100 amino acid residues – Synthesis of peptides
Reexamination Certificate
1998-12-18
2002-04-23
Low, Christopher S. F. (Department: 1654)
Chemistry: natural resins or derivatives; peptides or proteins;
Peptides of 3 to 100 amino acid residues
Synthesis of peptides
C530S332000, C530S335000, C530S336000, C530S337000, C530S342000, C530S343000, C530S345000, C436S085000, C436S091000, C436S092000
Reexamination Certificate
active
06376649
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for the synthesis of &agr;-hydroxy-&bgr;-amino acid and amide derivatives, and methods of using these intermediates in the synthesis of a variety of more complex peptidyl &agr;-ketoamides and &agr;-hydroxy-&bgr;-amino carboxylic acid derivatives.
BACKGROUND AND INTRODUCTION TO THE INVENTION
&agr;-Hydroxy-&bgr;-aminocarboxylic acid and amide derivatives are found in a variety of natural products and pharmaceutical substances. Subunits incorporating the &agr;-hydroxy-&bgr;-aminocarboxylic acid motif have been termed “norstatine” derivatives, and serve as key intermediates for the synthesis of the general class of P
1
-&agr;-ketocarboxylic transition-state inhibitors of serine or cysteine proteases. Such inhibitors are finding increasing applications in medicine for the treatment of a diverse array of disease states including thrombosis, cancer, and osteoporosis. Towards this end, &agr;-hydroxy-&bgr;-aminocarboxylic acid, ester and amide derivatives serve an important role as the most common precursors for the preparation of these &agr;-keto-carboxylic-acid-incorporating drug candidates.
Electrophilic &agr;-dicarbonyl compounds are regarded as interesting and highly reactive functional arrays which are capable of undergoing a myriad of transformations. Such chemical properties can be exploited in novel and therapeutically useful ways by strategically incorporating these reactive &agr;-ketocarboxylic moieties into a peptidic or peptidomimetic matrix. The &agr;-keto-carbonyl group is highly electropositive due to the presence of the adjoining electron-withdrawing amide functionality. Hence, it is highly reactive towards conventional biological nucleophiles encountered at the catalytic triad of a protease active site, including hydroxyl, thiol, and amino nucleophiles.
A prototypical serine protease substrate for which a suitable inhibitor is to be designed is Compound 1-1, depicted in FIG.
1
A. The target site for this protease is composed of four amino acid residues: P
3
, P
2
, P
1
, P
1
′. In this and the derived ketoamide inhibitor structure 1-2, the notation P
1
, P
2
, . . . P
n
denotes the position of a peptide residue relative to the scissile bond which is defined as P
1
-P
1
′ of the substrate undergoing cleavage (Schechter and Berger,
Biochem. Biophys. Res. Commun.
1967, 27: 157-162).
Upon entering and docking into the active site of a serine or cysteine protease, the peptidic or peptidomimetic backbone portion P
n
. . . P
n
′ of target inhibitor 1-2 provides an array of important contact points which are stabilizing and energetically favorable. Such key geometric, hydrophobic, and electrostatic interactions help to bind the inhibitor to the protease, while the strategically positioned P
1
&agr;-ketoamide function serves to inactivate the protease via formation of a slowly reversible covalent bond with the critical serine hydroxyl or cysteine thiol functions at the S1 site. The formation of such tetrahedral intermediates effectively ties up and, therefore, deactivates the active site, ultimately leading to inhibition of the enzyme.
Due to the highly stereospecific nature of several critical interactions at the enzyme active site, the relative and absolute stereochemistry of both P
1
-&agr;- and &bgr;-positions has a profound effect on the overall biological activity and selectivity profiles of the target drugs, e.g. protease inhibitors, into which these motifs are incorporated. As a result, the stereospecific synthesis of these classes of compounds has received increasing attention over the past decade.
Several prominent examples have recently emerged that illustrate the variety and importance of the &agr;-hydroxy-&bgr;-aminocarboxylic acid and amide derivatives (see
FIGS. 1B
to
1
D). For instance, the natural product paclitaxel (Taxol®), a potent anticancer drug, features a biologically essential C-13 N-benzoyl-3-phenylisoserine side chain esterified to a secondary alcohol function.
FIG. 1B
depicts the N-benzoyl-3-phenylisoserine side chain. The natural product bestatin (structure depicted in FIG.
1
C), also an &agr;-hydroxy-&bgr;-amino amide derivative, is reported to possess anticancer, immune response modifier, as well as amino-peptidase B (AP-B), leucine aminopeptidase (LAP), and prolyl endopeptidase (PEP) enzyme inhibitory activities. Amastatin (structure depicted in FIG.
1
D), a related peptidic natural product, is reported to demonstrate amino-peptidase A (AP-A) and leucine aminopeptidase enzyme inhibitory properties.
&agr;-Hydroxy-&bgr;-amino amide derivatives also are useful inhibitors of aspartyl proteases (see FIG.
2
A). The promising synthetic HIV protease inhibitor Kynostatin (2-2) (Mimoto, et al.,
Chem. Pharm. Bull.
40(8): 2251-2253 (1992)) which incorporates an allophenylnorstatine (Apns) (2-1) moiety, is an &agr;-hydroxy-&bgr;-amino amide derivative. Some synthetic renin inhibitors (2-4 and 2-5) feature the related cyclohexylnorstatine (Chns) residue (2-3) (see
FIG. 2B
) (Iizuka, et al.,
J. Med. Chem.
33: 2707-2714 (1990); Dhanoa, et al.,
Tetrahedron Letters,
33(13): 1725-1728 (1992)). In the HIV and renin inhibitors, the &agr;-hydroxy-&bgr;-aminocarboxylic, or “norstatine”, residue is employed as a hydroxymethyl carbonyl peptide bond isostere, which in turn serves as the P
1
-transition state mimic of peptide hydrolysis.
Inhibition of thrombin, a key terminal serine protease in the blood coagulation cascade, has been the subject of recent intensive investigation. Within the &agr;-hydroxy-&bgr;-amino ester group of compounds (3-1), the thrombin inhibitor BMS 181316 incorporates a P
1
-lysine derived &agr;-hydroxy-&bgr;-aminoester residue (3-2) (see FIG.
3
A). (Iwanowicz et al.,
Bioorganic
&
Medicinal Chemistry Letters,
2(12); 1607-1612 (1992)).
A variety of electrophilic P
1
-transition state compounds have been discovered and developed for use as thrombin inhibitors. From this general family of inhibitors, &agr;-ketoamide derivatives have figured prominently with regard to outstanding inhibitory potency. Such peptidomimetic inhibitors have been efficacious both in vitro and in vivo, for example, in animal models of small vein thrombosis and deep vein thrombosis (DVT). By elaboration of &agr;-hydroxyhomoarginine precursors (3-3 of FIG.
3
B), a series of P
1
-ketoargininamide derivatives were prepared which expressed potent thrombin inhibitory properties (see, e.g., U.S. Pat. Nos. 5,371,072; 5,597,804; 5,656,600; and 5,670,479). A large number of variations in the P
2
-P
4
residues as well as P
1
′ residues were investigated which provided a family of active and selective thrombin inhibitors. See, e.g., 3-4 of FIG.
3
B.
In a related class of protease inhibitors, P
1
-ketonorvalinamide peptide derivatives showed high inhibitory activity against a family of intracellular calpains. The calpains are cysteine proteases responsible for neurodegeneration which accompanies either global or focal cerebral ischemia. Such neutral P
1
-ketoamide inhibitors were prepared from 2-hydroxy-3-aminohexanoic acid (3-5 of FIG.
3
C). Several related neutral, lipophilic P
1
-ketoamide derivatives have found application as inhibitors for a broad range of cysteine protease enzymes. See, e.g., 3-6 of FIG.
3
C. (Harbeson et al.,
J. Med. Chem.,
37:2918-2929 (1994)).
There have been reports describing the synthesis of peptidal &agr;-ketoamide derivatives which are useful as enzyme inhibitors. The most widely utilized method of preparation is based upon a conventional multi-step solution phase approach and is outlined in FIG.
4
A/Scheme 1. (See U.S. Pat. Nos. 5,371,072; 5,597,804; 5,656,600; and 5,670,479; Semple et al.,
Bioorg. Med. Chem. Lett.
7:315 (1997); Maryanoff et al.,
J. Am. Chem. Soc.
117:1225 (1995); and Harbeson et al.,
J. Med. Chem.
37:2918 (1994).) A protected amino acid derivative 4-2 (PG denotes protecting group) is elaborated via known methods to the protected &agr;-aminoaldehyde derivative 4-3. The &agr;-hydroxy-&bgr;-amino ester intermediate
Levy Odile E.
Semple Joseph E.
Corvas International Inc.
Low Christopher S. F.
Mohamed Abdel A.
Pillsbury & Winthrop LLP
LandOfFree
Methods for the synthesis of &agr;- hydroxy-&bgr;-amino acid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for the synthesis of &agr;- hydroxy-&bgr;-amino acid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for the synthesis of &agr;- hydroxy-&bgr;-amino acid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2919222