tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate

C132H168Br2F6N20O24S — CID 158412867

About tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate

tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate (PubChem CID 158412867) has the molecular formula C132H168Br2F6N20O24S and a molecular weight of 2724.77 g/mol. Its IUPAC name is tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate.

Molecular Properties

• Compound Name: tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate
• PubChem CID: 158412867
• Molecular Formula: C132H168Br2F6N20O24S
• Molecular Weight: 2724.77 g/mol
• Exact Mass: 2721.05
• IUPAC Name: tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate
• SMILES: COC(=O)C[C@H](C(=O)N1CN(CC(F)(F)F)C[C@H]1C(=O)OC)C(C)C.COC(=O)C[C@H](C(=O)N1CN(CC(F)(F)F)C[C@H]1C1=NC(c2ccc(Br)cc2)=CC1)C(C)C.COC(=O)C[C@H](C(=O)N1CN(S(C)(=O)=O)C[C@H]1C1=NC(c2ccc(Br)cc2)=CC1)C(C)C.COC(=O)C[C@H](C(=O)N1CN(c2ccccc2)C[C@H]1C1=NC(c2ccc(C)cc2)=CC1)C(C)C.COC(=O)N[C@H](C(=O)N1CCC[C@H]1c1ncc(-c2ccc(-c3ccc(-c4cnc([C@@H]5CN(C(=O)OC(C)(C)C)CN5C(=O)[C@@H](NC(=O)OC)C(C)C)[nH]4)cc3)cc2)[nH]1)C(C)C
• InChI: InChI=1S/C44H57N9O8.C28H33N3O3.C23H27BrF3N3O3.C22H28BrN3O5S.C15H23F3N2O5/c1-25(2)35(49-41(56)59-8)39(54)52-20-10-11-33(52)37-45-21-31(47-37)29-16-12-27(13-17-29)28-14-18-30(19-15-28)32-22-46-38(48-32)34-23-51(43(58)61-44(5,6)7)24-53(34)40(55)36(26(3)4)50-42(57)60-9;1-19(2)23(16-27(32)34-4)28(33)31-18-30(22-8-6-5-7-9-22)17-26(31)25-15-14-24(29-25)21-12-10-20(3)11-13-21;1-14(2)17(10-21(31)33-3)22(32)30-13-29(12-23(25,26)27)11-20(30)19-9-8-18(28-19)15-4-6-16(24)7-5-15;1-14(2)17(11-21(27)31-3)22(28)26-13-25(32(4,29)30)12-20(26)19-10-9-18(24-19)15-5-7-16(23)8-6-15;1-9(2)10(5-12(21)24-3)13(22)20-8-19(7-15(16,17)18)6-11(20)14(23)25-4/h12-19,21-22,25-26,33-36H,10-11,20,23-24H2,1-9H3,(H,45,47)(H,46,48)(H,49,56)(H,50,57);5-14,19,23,26H,15-18H2,1-4H3;4-8,14,17,20H,9-13H2,1-3H3;5-9,14,17,20H,10-13H2,1-4H3;9-11H,5-8H2,1-4H3/t33-,34-,35-,36-;23-,26-;2*17-,20-;10-,11-/m00000/s1
• InChIKey: GZNIUXPZRDKDCV-UTIFNYHHSA-N
• XLogP: 19.76
• TPSA: 501.10 Ų
• H-Bond Donors: 4
• H-Bond Acceptors: 32
• Rotatable Bonds: 38
• Heavy Atoms: 185
• Complexity: —

Lipinski Rule of Five

3 violations

Rule	Value
MW ≤ 500	2724.77
LogP ≤ 5	19.76
H-Bond Donors ≤ 5	4
H-Bond Acceptors ≤ 10	32

Computed Properties (RDKit)

• Structural Alerts: {'alert_name': '>_2_ester_groups', 'substructure': 'N/A'}

Frequently Asked Questions

What is the IUPAC name of tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate?

The IUPAC name of tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate (CID 158412867) is tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate.

What is the SMILES notation for tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate?

The canonical SMILES for tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate is COC(=O)C[C@H](C(=O)N1CN(CC(F)(F)F)C[C@H]1C(=O)OC)C(C)C.COC(=O)C[C@H](C(=O)N1CN(CC(F)(F)F)C[C@H]1C1=NC(c2ccc(Br)cc2)=CC1)C(C)C.COC(=O)C[C@H](C(=O)N1CN(S(C)(=O)=O)C[C@H]1C1=NC(c2ccc(Br)cc2)=CC1)C(C)C.COC(=O)C[C@H](C(=O)N1CN(c2ccccc2)C[C@H]1C1=NC(c2ccc(C)cc2)=CC1)C(C)C.COC(=O)N[C@H](C(=O)N1CCC[C@H]1c1ncc(-c2ccc(-c3ccc(-c4cnc([C@@H]5CN(C(=O)OC(C)(C)C)CN5C(=O)[C@@H](NC(=O)OC)C(C)C)[nH]4)cc3)cc2)[nH]1)C(C)C.

What is the InChIKey of tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate?

The InChIKey is GZNIUXPZRDKDCV-UTIFNYHHSA-N. The full InChI is InChI=1S/C44H57N9O8.C28H33N3O3.C23H27BrF3N3O3.C22H28BrN3O5S.C15H23F3N2O5/c1-25(2)35(49-41(56)59-8)39(54)52-20-10-11-33(52)37-45-21-31(47-37)29-16-12-27(13-17-29)28-14-18-30(19-15-28)32-22-46-38(48-32)34-23-51(43(58)61-44(5,6)7)24-53(34)40(55)36(26(3)4)50-42(57)60-9;1-19(2)23(16-27(32)34-4)28(33)31-18-30(22-8-6-5-7-9-22)17-26(31)25-15-14-24(29-25)21-12-10-20(3)11-13-21;1-14(2)17(10-21(31)33-3)22(32)30-13-29(12-23(25,26)27)11-20(30)19-9-8-18(28-19)15-4-6-16(24)7-5-15;1-14(2)17(11-21(27)31-3)22(28)26-13-25(32(4,29)30)12-20(26)19-10-9-18(24-19)15-5-7-16(23)8-6-15;1-9(2)10(5-12(21)24-3)13(22)20-8-19(7-15(16,17)18)6-11(20)14(23)25-4/h12-19,21-22,25-26,33-36H,10-11,20,23-24H2,1-9H3,(H,45,47)(H,46,48)(H,49,56)(H,50,57);5-14,19,23,26H,15-18H2,1-4H3;4-8,14,17,20H,9-13H2,1-3H3;5-9,14,17,20H,10-13H2,1-4H3;9-11H,5-8H2,1-4H3/t33-,34-,35-,36-;23-,26-;2*17-,20-;10-,11-/m00000/s1.

What are the key properties of tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate?

tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate has a molecular weight of 2724.77 g/mol, XLogP of 19.76, 38 rotatable bonds, 4 hydrogen bond donors, and 32 hydrogen bond acceptors.

Where does this data come from?

All data for tert-butyl (4S)-3-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-4-[5-[4-[4-[2-[(2S)-1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]pyrrolidin-2-yl]-1H-imidazol-5-yl]phenyl]phenyl]-1H-imidazol-2-yl]imidazolidine-1-carboxylate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-methylsulfonylimidazolidine-1-carbonyl]-4-methylpentanoate;methyl (3S)-3-[(5S)-5-[5-(4-bromophenyl)-3H-pyrrol-2-yl]-3-(2,2,2-trifluoroethyl)imidazolidine-1-carbonyl]-4-methylpentanoate;methyl (4S)-3-[(2S)-4-methoxy-4-oxo-2-propan-2-ylbutanoyl]-1-(2,2,2-trifluoroethyl)imidazolidine-4-carboxylate;methyl (3S)-4-methyl-3-[(5S)-5-[5-(4-methylphenyl)-3H-pyrrol-2-yl]-3-phenylimidazolidine-1-carbonyl]pentanoate is sourced from PubChem (CID 158412867), the world's largest open chemistry database maintained by the National Library of Medicine (NIH).