Method for producing peptide compound comprising highly sterically hindered amino acid
It was found that a peptide compound that has an N-substituted-α,α-disubstituted amino acid residue at the N-terminus and containing a dipeptide residue in which the N-substituted-α,α-disubstituted amino acid residue and an N-substituted amino acid residue are linked together, can be efficiently produced by linking an N-unsubstituted-α,α-disubstituted amino acid whose amino group is protected with an electron-withdrawing protecting group to an N-substituted amino acid or a peptide compound having an N-substituted amino acid residue at the N-terminus, and then allowing a substituent-introducing agent to act in the presence of a specific base to selectively introduce a substituent to the amino group at the N-terminus.
1. A method for producing a peptide compound having an N-substituted-α,α-disubstituted amino acid residue at the N-terminus and comprising a dipeptide residue in which the N-substituted-α,α-disubstituted amino acid residue is linked to an N-substituted amino acid residue, a salt thereof, or a solvate of these, the method comprising the following steps of:
Step A: reacting (1) an N-substituted amino acid, a salt thereof, or a solvate of these, or a peptide compound having an N-substituted amino acid residue at the N-terminus, a salt thereof, or a solvate of these, wherein the main-chain amino group of the N-substituted amino acid or the N-substituted amino acid residue is represented by —NHR, wherein R is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted aralkyl, and optionally substituted cycloalkyl, or R represents a carbon chain bonded to the N atom, which together with the carbon atom at the α-position form an optionally substituted ring,
with (2) an α,α-disubstituted amino acid having an amino group protected with an electron-withdrawing protecting group, a salt thereof, a dehydrated product thereof, or a solvate of these, wherein the amino group is the amino group on the main chain of the α,α-disubstituted amino acid and is represented by the formula —NHR′, wherein R′ is the electron-withdrawing protecting group, wherein the electron-withdrawing protecting group is a protecting group with which the pKa in water of the NH group to which the protecting group is bonded is 6 to 11,
in the presence or absence of a condensing reagent to obtain a peptide compound having an α,α-disubstituted amino acid residue having an amino group protected with an electron-withdrawing protecting group at the N-terminus and comprising a dipeptide residue in which the α,α-disubstituted amino acid residue is linked to an N-substituted amino acid residue, a salt thereof, or a solvate of these; and
Step B: introducing a substituent to the amino group of the α,α-disubstituted amino acid residue protected with the electron-withdrawing protecting group at the N-terminus in the presence of a base and a substituent-introducing agent to obtain a peptide compound having an α,α-disubstituted amino acid residue having an amino group on the main chain of the α,α-disubstituted amino acid substituted with the substituent and protected with the electron-withdrawing protecting group at the N-terminus and comprising a dipeptide residue in which the α,α-disubstituted amino acid residue is linked to the N-substituted amino acid residue, a salt thereof, or a solvate of these.
2. The method of claim 1 , wherein the pKa in acetonitrile of the conjugate acid of the base is 18 to 31.
3. The method of claim 1 , wherein the N-substituted amino acid or the peptide compound having an N-substituted amino acid residue at the N-terminus is loaded on a resin for solid-phase synthesis.
4. The method of claim 1 , wherein the N-substituted amino acid or the peptide compound having an N-substituted amino acid residue at the N-terminus is represented by formula (2):
wherein
P 2 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl, or C 7 -C 14 aralkyl;
R 2 is C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 1 -C 6 hydroxyalkyl, C 1 -C 6 alkylsulfonylC 1 -C 6 alkyl, C 2 -C 6 alkynyl, C 1 -C 6 alkoxyC 1 -C 6 alkyl optionally substituted with one or more halogens, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkylC 1 -C 6 alkyl, C 3 -C 8 cycloalkoxyC 1 -C 6 alkyl, or C 7 -C 14 aralkyl;
R 3 is hydroxy, O-PG 2 , an arbitrary amino acid residue, or an arbitrary peptide residue; and
PG 2 is a protecting group for a carboxyl group.
5. The method of claim 1 , wherein the α,α-disubstituted amino acid having an amino group protected with an electron-withdrawing protecting group is represented by formula (3):
wherein
PG 1 is the electron-withdrawing protecting group; and
R 1 and Q 1 are independently selected from C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 1 -C 6 alkoxyC 1 -C 6 alkyl, C 3 -C 8 cycloalkylC 1 -C 6 alkyl, and optionally substituted C 7 -C 14 aralkyl, or
R 1 and Q 1 together with the carbon atom to which they are bonded form a 3- to 8-membered alicyclic ring or a 4- to 7-membered saturated heterocyclic ring.
6. The method of claim 1 , wherein the peptide compound obtained in step A is represented by formula (4):
wherein
PG 1 is the electron-withdrawing protecting group;
R 1 and Q 1 are independently selected from C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 1 -C 6 alkoxyC 1 -C 6 alkyl, C 3 -C 8 cycloalkylC 1 -C 6 alkyl, and optionally substituted C 7 -C 14 aralkyl, or
R 1 and Q 1 together with the carbon atom to which they are bonded form a 3- to 8-membered alicyclic ring or a 4- to 7-membered saturated heterocyclic ring;
P 2 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl, or C 7 -C 14 aralkyl;
R 2 is C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 1 -C 6 hydroxyalkyl, C 1 -C 6 alkylsulfonylC 1 -C 6 alkyl, C 2 -C 6 alkynyl, C 1 -C 6 , alkoxyC 1 -C 6 alkyl optionally substituted with one or more halogens, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkylC 1 -C 6 alkyl, C 3 -C 8 cycloalkoxyC 1 -C 6 alkyl, or C 7 -C 14 aralkyl; and
R 3 is hydroxy, O-PG 2 , an arbitrary amino acid residue, or an arbitrary peptide residue, wherein PG 2 is a protecting group for a carboxyl group.
7. The method of claim 6 , wherein the substituent-introducing agent in step B is P 1 X, wherein P 1 is the same as P 1 in formula (1), and X is a leaving group, and the peptide compound obtained in step B is represented by formula (1):
wherein
P 1 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl, or C 7 -C 14 aralkyl; and
PG 1 , R 1 , Q 1 , P 2 , R 2 , and R 3 are the same as PG 1 , R 1 , Q 1 , P 2 , R 2 , and R 3 in formula (4), respectively.
8. A method for producing a peptide compound comprising a structure in which two amino acid residues are connected as represented by formula (1), a salt thereof, or a solvate of these:
wherein
PG 1 is a protecting group for an amino group;
P 1 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl, or C 7 -C 14 aralkyl;
R 1 and Q 1 am independently selected from C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 1 -C 6 alkoxyC 1 -C 6 alkyl, C 3 -C 8 cycloalkylC 1 -C 6 alkyl, and optionally substituted C 7 -C 14 aralkyl, or
R 1 and Q 1 together with the carbon atom to which they are bonded form a 3- to 8-membered alicyclic ring or a 4- to 7-membered saturated heterocyclic ring;
P 2 is C 1 -C 6 alkyl, C 2 -C 6 alkenyl, or C 7 -C 14 aralkyl;
R 2 is C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 1 -C 6 hydroxyalkyl, C 1 -C 6 alkylsulfonylC 1 -C 6 alkyl, C 2 -C 6 alkynyl, C 1 -C 6 alkoxyC 1 -C 6 alkyl optionally substituted with one or more halogens, C 3 -C 8 cycloalkyl, C 3 -C 8 cycloalkylC 1 -C 6 alkyl, C 3 -C 8 cycloalkoxyC 1 -C 6 alkyl, or C 7 -C 14 aralkyl;
R 3 is hydroxy, O-PG 2 , an arbitrary amino acid residue, or an arbitrary peptide residue; and
PG 2 is a protecting group for a carboxyl group,
the method comprising the following steps of:
Step A: reacting a compound represented by formula (2):
wherein P 2 , R 2 , and R 3 are the same as P 2 , R 2 , and R 3 in formula (1), respectively,
a salt thereof, or a solvate of these and a compound represented by formula (3):
wherein PG 1 , Q 1 , and R 1 are the same as PG 1 , Q 1 , and R 1 in formula (1), respectively,
a salt thereof, a dehydrated product thereof, or a solvate of these with a condensing reagent, or reacting the compound represented by formula (2), a salt thereof, or a solvate of these with a dehydrated product of the compound represented by formula (3), a salt thereof, or a solvate of these to obtain a compound represented by formula (4):
wherein PG 1 , P 2 , Q 1 , and R 1 to R 3 are the same as PG 1 , P 2 , Q 1 , and R 1 to R 3 in formula (1), respectively, wherein the pKa in water of the NH group to which PG 1 is bonded in formula (3) and/or formula (4) is 11 or less,
a salt thereof, or a solvate of these; and
Step B: reacting the compound represented by formula (4), a salt thereof, or a solvate of these with a P 1 -introducing reagent comprising a base to obtain the peptide compound represented by formula (1), a salt thereof, or a solvate of these.
9. The method of claim 5 , wherein
R 1 and Q 1 together with the carbon atom to which they are bonded form a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, or a tetrahydropyran ring; or
R 1 and Q 1 are independently selected from methyl, ethyl, 2-methylpropyl, allyl, methoxymethyl, cyclohexylmethyl, optionally substituted benzyl, or optionally substituted phenethyl.
10. The method of claim 8 , wherein the pKa in water of the NH group to which PG 1 is bonded in formula (3) and/or formula (4) is 6 to 11.
11. The method of claim 5 , wherein PG 1 is C 2 -C 6 haloacyl.
12. The method of claim 11 , wherein C 2 -C 6 haloacyl is trifluoroacetyl, trichloroacetyl, pentafluoropropionyl, 2,3,3,3-tetrafluoro-2-(trifluoromethyl)propionyl, or 3,3,3-trifluoro-2-(trifluoromethyl)propionyl.
13. The method of claim 1 , wherein the dehydrated product is represented by the following formula:
wherein R 1 and Q 1 are independently selected from C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 1 -C 6 alkoxyC 1 -C 6 alkyl, C 3 -C 8 cycloalkylC 1 -C 6 alkyl, and optionally substituted C 7 -C 14 aralkyl, or
R 1 and Q 1 together with the carbon atom to which they are bonded form a 3- to 8-membered alicyclic ring or a 4- to 7-membered saturated heterocyclic ring; and R 4 is C 1 -C 5 haloalkyl.
14. The method of claim 13 , wherein R 1 and Q 1 together with the carbon atom to which they are bonded form a 3- to 8-membered alicyclic ring.
15. The method of claim 13 , wherein R 4 is trifluoromethyl, trichloromethyl, pentafluoroethyl, 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl, or 2,2,2-trifluoro-1-(trifluoromethyl)ethyl.
16. The method of claim 7 , wherein P 1 is methyl, ethyl, n-propyl, i-propyl, allyl, benzyl, or phenethyl.
17. The method of claim 4 , wherein P 2 is methyl, ethyl, n-propyl, i-propyl, allyl, benzyl, or phenethyl.
18. The method of claim 4 , wherein R 3 is an arbitrary amino acid residue or an arbitrary peptide residue loaded on a resin for solid-phase synthesis.
19. The method of claim 3 , wherein the resin for solid-phase synthesis is CTC resin, Wang resin, or SASRIN resin.
20. The method of claim 1 , wherein the condensing reagent is either DIC or EDCI·HCl, or a combination of DIC and Oxyma.
21. The method of claim 8 , wherein the P 1 -introducing reagent is a combination of P 1 X, wherein P 1 is the same as P 1 in formula (1), and X is a leaving group, and the base.
22. The method of claim 21 , wherein pKa in acetonitrile of a conjugate acid of the base is 18 to 31.
23. The method of claim 2 , wherein the base is selected from the group consisting of:
wherein
RB 1 and RB 4 are each independently C 1 -C 4 alkyl, or RB 1 and RB 4 together with the nitrogen atom to which RB 1 is bonded and the carbon atom to which RB 4 is bonded form a 5- to 8-membered ring; and
RB 2 and RB 3 are each independently C 1 -C 4 alkyl, or RB 2 and RB 3 together with the nitrogen atom to which RB 2 is bonded, the nitrogen atom to which RB 3 is bonded, and the carbon atom to which the nitrogen atoms are bonded form a 5- to 8-membered ring;
wherein
RB 6 is hydrogen or C 1 -C 4 alkyl;
RB 5 and RB 7 are each independently C 1 -C 4 alkyl or, together with the respective nitrogen atoms to which they are bonded and the carbon atom to which the respective nitrogen atoms are bonded, form a 5- to 8-membered ring;
RB 5 is C 1 -C 4 alkyl and RB 9 is C 1 -C 4 alkyl or phenyl, or RB 5 and RB 9 together with the respective nitrogen atoms to which they are bonded and the carbon atom to which the respective nitrogen atoms are bonded, form a 5- to 8-membered ring; and
wherein, when RB 9 is phenyl, two benzene rings of the phenyl groups in two B2 may be condensed to form naphthalene;
wherein
RB 10 is C 1 -C 4 alkyl, or RB 10 and RB 11 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 11 except when RB 10 and RB 11 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 11 and RB 12 together with the respective nitrogen atoms to which they are bonded and the phosphorus atom to which the respective nitrogen atoms are bonded form a 5- to 8-membered ring;
RB 12 except when RB 11 and RB 12 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 12 and RB 13 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 13 except when RB 12 and RB 13 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 13 and RB 14 together with the respective nitrogen atoms to which they are bonded and the phosphorus atom to which the respective nitrogen atoms are bonded form a 5- to 8-membered ring;
RB 14 except when RB 13 and RB 14 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 14 and RB 15 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 15 except when RB 14 and RB 15 form a 5- to 8-membered ring is C 1 -C 4 alkyl; and
RB 16 is hydrogen, C 1 -C 5 alkyl, or C 6 -C 10 aryl; and
wherein
RB 17 is independently C 1 -C 4 alkyl, or RB 17 and RB 15 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 15 except when RB 17 and RB 15 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 15 and RB 19 together with the respective nitrogen atoms to which they are bonded and the phosphorus atom to which the respective nitrogen atoms are bonded form a 5- to 8-membered ring;
RB 19 except when RB 15 and RB 19 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 19 and RB 20 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 20 except when RB 19 and RB 20 form a 5- to 8-membered ring is C 1 -C 4 alkyl;
RB 21 is C 1 -C 4 alkyl, or RB 21 and RB 22 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 22 except when RB 21 and RB 22 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 22 and RB 2 together with the respective nitrogen atoms to which they are bonded and the phosphorus atom to which the respective nitrogen atoms are bonded form a 5- to 8-membered ring;
RB 2 except when RB 22 and RB 2 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 2 and RB 24 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 24 except when RB 23 and RB 24 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 24 and RB 25 together with the respective nitrogen atoms to which they are bonded and the phosphorus atom to which the respective nitrogen atoms are bonded form a 5- to 8-membered ring;
RB 25 except when RB 24 and RB 25 form a 5- to 8-membered ring is C 1 -C 4 alkyl, or RB 25 and RB 26 together with the nitrogen atom to which they are bonded form a 5- to 8-membered ring;
RB 26 except when RB 25 and RB 26 form a 5- to 8-membered ring is C 1 -C 4 alkyl; and
RB 27 is C 1 -C 4 alkyl or C 6 -C 10 aryl.
24. The method of claim 2 , wherein the base is selected from the group consisting of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-bis(tetramethylguanidino)naphthalene (TMGN), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 2-tert-butyl-1,1,3,3-tetramethylguanidine (BTMG), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), tert-butylimino-tris(dimethylamino)phosphorane (P 1 -tBu), tert-butylimino-tri(pyrrolidino)phosphorane (P 1 -t-Bu-tris(tetramethylene), BTPP), 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP), tert-octylimino-tris(dimethylamino)phosphorane (P 1 -t-Oct), imino-tris(dimethylamino)phosphorane (HP1(dma)), 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2λ 5 ,4λ 5 -catenadi(phosphazene) (P 2 -t-Bu), and 1-ethyl-2,2,4,4,4-pentakis(dimethylamino)-2λ 5 ,4λ 5 -catenadi(phosphazene) (P 2 -Et).
25. The method of claim 1 , wherein step B is carried out in a solvent selected from the group consisting of DMF, NMP, DMI, tetrahydrofuran, 2-methyltetrahydrofuran, and acetonitrile.
26. A method for producing a peptide compound comprising a dipeptide residue in which an N-substituted-α,α-disubstituted amino acid residue is linked to an N-substituted amino acid residue, a salt thereof, or a solvate of these, the method comprising the method of claim 1 , and further comprising deprotecting an N-terminal protecting group from a peptide compound, a salt thereof, or a solvate of these produced by the method of claim 1 .
27. A method for producing a cyclic peptide compound, a salt thereof, or a solvate of these, the method comprising the steps of:
deprotecting an N-terminal protecting group from a peptide compound, a salt thereof, or a solvate of these produced by the method of claim 1 ;
optionally, elongating a peptide chain; and
cyclizing a group on the C-terminal side and a group on the N-terminal side to form a cyclic moiety,
wherein the cyclic peptide compound comprises 8 to 15 amino acid residues, at least 3 N-substituted amino acid residues, and at least 1 N-unsubstituted amino acid residue, and the cyclic moiety comprises at least 8 amino acid residues.