2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole

C272H193F18N29O9 — CID 159216798

About 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole

2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole (PubChem CID 159216798) has the molecular formula C272H193F18N29O9 and a molecular weight of 4353.69 g/mol. Its IUPAC name is 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole.

Molecular Properties

• Compound Name: 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole
• PubChem CID: 159216798
• Molecular Formula: C272H193F18N29O9
• Molecular Weight: 4353.69 g/mol
• Exact Mass: 4350.52
• IUPAC Name: 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole
• SMILES: CC(C)(C)c1ccc(-c2nnc(-c3ccc(-c4ccccc4)cc3)n2-c2ccccc2)cc1.CC(C)(C)c1ccc(-c2nnc(-c3ccc(-c4ccccc4)cc3)o2)cc1.CC(C)(C)c1ccc(-c2nnc(-c3ccc4c(c3)C3(c5ccccc5-4)c4ccccc4-c4ccc(-c5nnc(-c6ccc(C(C)(C)C)cc6)o5)cc43)o2)cc1.CC(c1ccc(Oc2ccc(-c3nc(-c4ccccc4)nc(-c4ccccc4)n3)cc2)cc1)(c1ccc(Oc2ccc(-c3nc(-c4ccccc4)nc(-c4ccccc4)n3)cc2)cc1)C(F)(F)F.Cc1ccc2nc(-c3cc(-c4nc5ccc(C(F)(F)F)cc5nc4-c4ccccc4)cc(-c4nc5ccc(C(F)(F)F)cc5nc4-c4ccccc4)c3)c(-c3ccccc3)nc2c1.Cc1cccc(-c2nnc(-c3ccc(C(c4ccc(-c5nnc(-c6cccc(C(F)(F)F)c6)o5)cc4)(c4ccc(-c5nnc(-c6cccc(C(F)(F)F)c6)o5)cc4)c4ccc(-c5nnc(-c6cccc(C(F)(F)F)c6)o5)cc4)cc3)o2)c1
• InChI: InChI=1S/C61H35F9N8O4.C57H39F3N6O2.C51H30F6N6.C49H40N4O2.C30H27N3.C24H22N2O/c1-34-6-2-7-39(30-34)54-75-71-50(79-54)35-14-22-43(23-15-35)58(44-24-16-36(17-25-44)51-72-76-55(80-51)40-8-3-11-47(31-40)59(62,63)64,45-26-18-37(19-27-45)52-73-77-56(81-52)41-9-4-12-48(32-41)60(65,66)67)46-28-20-38(21-29-46)53-74-78-57(82-53)42-10-5-13-49(33-42)61(68,69)70;1-56(57(58,59)60,44-26-34-48(35-27-44)67-46-30-22-42(23-31-46)54-63-50(38-14-6-2-7-15-38)61-51(64-54)39-16-8-3-9-17-39)45-28-36-49(37-29-45)68-47-32-24-43(25-33-47)55-65-52(40-18-10-4-11-19-40)62-53(66-55)41-20-12-5-13-21-41;1-29-17-20-38-41(23-29)61-44(30-11-5-2-6-12-30)47(58-38)33-24-34(48-45(31-13-7-3-8-14-31)62-42-27-36(50(52,53)54)18-21-39(42)59-48)26-35(25-33)49-46(32-15-9-4-10-16-32)63-43-28-37(51(55,56)57)19-22-40(43)60-49;1-47(2,3)33-21-15-29(16-22-33)43-50-52-45(54-43)31-19-25-37-35-11-7-9-13-39(35)49(41(37)27-31)40-14-10-8-12-36(40)38-26-20-32(28-42(38)49)46-53-51-44(55-46)30-17-23-34(24-18-30)48(4,5)6;1-30(2,3)26-20-18-25(19-21-26)29-32-31-28(33(29)27-12-8-5-9-13-27)24-16-14-23(15-17-24)22-10-6-4-7-11-22;1-24(2,3)21-15-13-20(14-16-21)23-26-25-22(27-23)19-11-9-18(10-12-19)17-7-5-4-6-8-17/h2-33H,1H3;2-37H,1H3;2-28H,1H3;7-28H,1-6H3;4-21H,1-3H3;4-16H,1-3H3
• InChIKey: KREGIJSZYPHTMW-UHFFFAOYSA-N
• XLogP: 70.67
• TPSA: 476.29 Ų
• H-Bond Acceptors: 38
• Rotatable Bonds: 41
• Heavy Atoms: 328
• Complexity: —

Lipinski Rule of Five

3 violations

Rule	Value
MW ≤ 500	4353.69
LogP ≤ 5	70.67
H-Bond Donors ≤ 5	0
H-Bond Acceptors ≤ 10	38

Frequently Asked Questions

What is the IUPAC name of 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole?

The IUPAC name of 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole (CID 159216798) is 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole.

What is the SMILES notation for 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole?

The canonical SMILES for 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole is CC(C)(C)c1ccc(-c2nnc(-c3ccc(-c4ccccc4)cc3)n2-c2ccccc2)cc1.CC(C)(C)c1ccc(-c2nnc(-c3ccc(-c4ccccc4)cc3)o2)cc1.CC(C)(C)c1ccc(-c2nnc(-c3ccc4c(c3)C3(c5ccccc5-4)c4ccccc4-c4ccc(-c5nnc(-c6ccc(C(C)(C)C)cc6)o5)cc43)o2)cc1.CC(c1ccc(Oc2ccc(-c3nc(-c4ccccc4)nc(-c4ccccc4)n3)cc2)cc1)(c1ccc(Oc2ccc(-c3nc(-c4ccccc4)nc(-c4ccccc4)n3)cc2)cc1)C(F)(F)F.Cc1ccc2nc(-c3cc(-c4nc5ccc(C(F)(F)F)cc5nc4-c4ccccc4)cc(-c4nc5ccc(C(F)(F)F)cc5nc4-c4ccccc4)c3)c(-c3ccccc3)nc2c1.Cc1cccc(-c2nnc(-c3ccc(C(c4ccc(-c5nnc(-c6cccc(C(F)(F)F)c6)o5)cc4)(c4ccc(-c5nnc(-c6cccc(C(F)(F)F)c6)o5)cc4)c4ccc(-c5nnc(-c6cccc(C(F)(F)F)c6)o5)cc4)cc3)o2)c1.

What is the InChIKey of 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole?

The InChIKey is KREGIJSZYPHTMW-UHFFFAOYSA-N. The full InChI is InChI=1S/C61H35F9N8O4.C57H39F3N6O2.C51H30F6N6.C49H40N4O2.C30H27N3.C24H22N2O/c1-34-6-2-7-39(30-34)54-75-71-50(79-54)35-14-22-43(23-15-35)58(44-24-16-36(17-25-44)51-72-76-55(80-51)40-8-3-11-47(31-40)59(62,63)64,45-26-18-37(19-27-45)52-73-77-56(81-52)41-9-4-12-48(32-41)60(65,66)67)46-28-20-38(21-29-46)53-74-78-57(82-53)42-10-5-13-49(33-42)61(68,69)70;1-56(57(58,59)60,44-26-34-48(35-27-44)67-46-30-22-42(23-31-46)54-63-50(38-14-6-2-7-15-38)61-51(64-54)39-16-8-3-9-17-39)45-28-36-49(37-29-45)68-47-32-24-43(25-33-47)55-65-52(40-18-10-4-11-19-40)62-53(66-55)41-20-12-5-13-21-41;1-29-17-20-38-41(23-29)61-44(30-11-5-2-6-12-30)47(58-38)33-24-34(48-45(31-13-7-3-8-14-31)62-42-27-36(50(52,53)54)18-21-39(42)59-48)26-35(25-33)49-46(32-15-9-4-10-16-32)63-43-28-37(51(55,56)57)19-22-40(43)60-49;1-47(2,3)33-21-15-29(16-22-33)43-50-52-45(54-43)31-19-25-37-35-11-7-9-13-39(35)49(41(37)27-31)40-14-10-8-12-36(40)38-26-20-32(28-42(38)49)46-53-51-44(55-46)30-17-23-34(24-18-30)48(4,5)6;1-30(2,3)26-20-18-25(19-21-26)29-32-31-28(33(29)27-12-8-5-9-13-27)24-16-14-23(15-17-24)22-10-6-4-7-11-22;1-24(2,3)21-15-13-20(14-16-21)23-26-25-22(27-23)19-11-9-18(10-12-19)17-7-5-4-6-8-17/h2-33H,1H3;2-37H,1H3;2-28H,1H3;7-28H,1-6H3;4-21H,1-3H3;4-16H,1-3H3.

What are the key properties of 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole?

2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole has a molecular weight of 4353.69 g/mol, XLogP of 70.67, 41 rotatable bonds, 0 hydrogen bond donors, and 38 hydrogen bond acceptors.

Where does this data come from?

All data for 2-[3,5-bis[3-phenyl-6-(trifluoromethyl)quinoxalin-2-yl]phenyl]-6-methyl-3-phenylquinoxaline;2-(4-tert-butylphenyl)-5-[2'-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]-9,9'-spirobi[fluorene]-2-yl]-1,3,4-oxadiazole;2-(4-tert-butylphenyl)-5-(4-phenylphenyl)-1,3,4-oxadiazole;3-(4-tert-butylphenyl)-4-phenyl-5-(4-phenylphenyl)-1,2,4-triazole;2-[4-[4-[2-[4-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenoxy]phenyl]-1,1,1-trifluoropropan-2-yl]phenoxy]phenyl]-4,6-diphenyl-1,3,5-triazine;2-(3-methylphenyl)-5-[4-[tris[4-[5-[3-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-yl]phenyl]methyl]phenyl]-1,3,4-oxadiazole is sourced from PubChem (CID 159216798), the world's largest open chemistry database maintained by the National Library of Medicine (NIH).