[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate

C87H129F4N9O53S2 — CID 153001223

About [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate

[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate (PubChem CID 153001223) has the molecular formula C87H129F4N9O53S2 and a molecular weight of 2289.13 g/mol. Its IUPAC name is [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate.

Molecular Properties

• Compound Name: [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate
• PubChem CID: 153001223
• Molecular Formula: C87H129F4N9O53S2
• Molecular Weight: 2289.13 g/mol
• Exact Mass: 2287.71
• IUPAC Name: [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate
• SMILES: CN[C@H](CSCC1O[C@H]2O[C@@H]3C(CO)O[C@H](O[C@@H]4C(CO)O[C@H](O[C@@H]5C(CO)O[C@H](O[C@@H]6C(CSC[C@@H](CC(=O)CCOCCOCCC(C)=O)C(=O)NCCC(=O)OCC(=O)OC[C@H]7O[C@@H](n8ccc(N)nc8=O)C(F)(F)[C@@H]7O)O[C@H](O[C@@H]7C(CO)O[C@@H](O[C@@H]8C(CO)O[C@@H](O[C@H]1[C@H](O)C2O)C(O)[C@H]8O)C(O)[C@H]7O)C(O)[C@H]6O)C(O)[C@H]5O)C(O)[C@H]4O)C(O)[C@H]3O)C(=O)NCCC(=O)OCC(=O)OC[C@H]1O[C@@H](n2ccc(N)nc2=O)C(F)(F)[C@@H]1O
• InChI: InChI=1S/C87H129F4N9O53S2/c1-31(106)7-13-132-15-16-133-14-8-33(107)17-32(73(128)95-9-3-46(108)136-25-48(110)134-23-40-71(126)86(88,89)82(145-40)99-11-5-44(92)97-84(99)130)27-154-29-42-69-55(117)62(124)80(143-42)150-67-38(21-104)139-77(58(120)51(67)113)149-66-37(20-103)142-79(61(123)54(66)116)153-70-43(30-155-28-34(94-2)74(129)96-10-4-47(109)137-26-49(111)135-24-41-72(127)87(90,91)83(146-41)100-12-6-45(93)98-85(100)131)144-81(63(125)56(70)118)151-68-39(22-105)140-76(59(121)52(68)114)147-64-35(18-101)138-75(57(119)50(64)112)148-65-36(19-102)141-78(152-69)60(122)53(65)115/h5-6,11-12,32,34-43,50-72,75-83,94,101-105,112-127H,3-4,7-10,13-30H2,1-2H3,(H,95,128)(H,96,129)(H2,92,97,130)(H2,93,98,131)/t32-,34-,35?,36?,37?,38?,39?,40-,41-,42?,43?,50-,51-,52-,53-,54-,55-,56-,57?,58?,59?,60?,61?,62?,63?,64-,65-,66-,67-,68-,69-,70-,71-,72-,75-,76-,77+,78-,79+,80-,81+,82-,83-/m1/s1
• InChIKey: UYEUKLUKWCYUJT-JHQACAESSA-N
• XLogP: -16.53
• TPSA: 922.36 Ų
• H-Bond Donors: 26
• H-Bond Acceptors: 62
• Rotatable Bonds: 43
• Heavy Atoms: 155
• Complexity: —

Lipinski Rule of Five

3 violations

Rule	Value
MW ≤ 500	2289.13
LogP ≤ 5	-16.53
H-Bond Donors ≤ 5	26
H-Bond Acceptors ≤ 10	62

Computed Properties (RDKit)

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

Frequently Asked Questions

What is the IUPAC name of [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate?

The IUPAC name of [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate (CID 153001223) is [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate.

What is the SMILES notation for [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate?

The canonical SMILES for [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate is CN[C@H](CSCC1O[C@H]2O[C@@H]3C(CO)O[C@H](O[C@@H]4C(CO)O[C@H](O[C@@H]5C(CO)O[C@H](O[C@@H]6C(CSC[C@@H](CC(=O)CCOCCOCCC(C)=O)C(=O)NCCC(=O)OCC(=O)OC[C@H]7O[C@@H](n8ccc(N)nc8=O)C(F)(F)[C@@H]7O)O[C@H](O[C@@H]7C(CO)O[C@@H](O[C@@H]8C(CO)O[C@@H](O[C@H]1[C@H](O)C2O)C(O)[C@H]8O)C(O)[C@H]7O)C(O)[C@H]6O)C(O)[C@H]5O)C(O)[C@H]4O)C(O)[C@H]3O)C(=O)NCCC(=O)OCC(=O)OC[C@H]1O[C@@H](n2ccc(N)nc2=O)C(F)(F)[C@@H]1O.

What is the InChIKey of [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate?

The InChIKey is UYEUKLUKWCYUJT-JHQACAESSA-N. The full InChI is InChI=1S/C87H129F4N9O53S2/c1-31(106)7-13-132-15-16-133-14-8-33(107)17-32(73(128)95-9-3-46(108)136-25-48(110)134-23-40-71(126)86(88,89)82(145-40)99-11-5-44(92)97-84(99)130)27-154-29-42-69-55(117)62(124)80(143-42)150-67-38(21-104)139-77(58(120)51(67)113)149-66-37(20-103)142-79(61(123)54(66)116)153-70-43(30-155-28-34(94-2)74(129)96-10-4-47(109)137-26-49(111)135-24-41-72(127)87(90,91)83(146-41)100-12-6-45(93)98-85(100)131)144-81(63(125)56(70)118)151-68-39(22-105)140-76(59(121)52(68)114)147-64-35(18-101)138-75(57(119)50(64)112)148-65-36(19-102)141-78(152-69)60(122)53(65)115/h5-6,11-12,32,34-43,50-72,75-83,94,101-105,112-127H,3-4,7-10,13-30H2,1-2H3,(H,95,128)(H,96,129)(H2,92,97,130)(H2,93,98,131)/t32-,34-,35?,36?,37?,38?,39?,40-,41-,42?,43?,50-,51-,52-,53-,54-,55-,56-,57?,58?,59?,60?,61?,62?,63?,64-,65-,66-,67-,68-,69-,70-,71-,72-,75-,76-,77+,78-,79+,80-,81+,82-,83-/m1/s1.

What are the key properties of [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate?

[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate has a molecular weight of 2289.13 g/mol, XLogP of -16.53, 43 rotatable bonds, 26 hydrogen bond donors, and 62 hydrogen bond acceptors.

Where does this data come from?

All data for [2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethyl] 3-[[(2S)-2-[[(1S,3S,6S,8R,11S,13R,16S,18R,21S,23R,26S,28S,31S,33S,36R,38R,40R,42R,44R,46R,48R)-25-[[(2S)-3-[[3-[2-[[(2R,3R,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-4,4-difluoro-3-hydroxyoxolan-2-yl]methoxy]-2-oxoethoxy]-3-oxopropyl]amino]-2-(methylamino)-3-oxopropyl]sulfanylmethyl]-36,37,38,39,40,41,42,43,44,45,46,47,48,49-tetradecahydroxy-10,15,20,30,35-pentakis(hydroxymethyl)-2,4,7,9,12,14,17,19,22,24,27,29,32,34-tetradecaoxaoctacyclo[31.2.2.23,6.28,11.213,16.218,21.223,26.228,31]nonatetracontan-5-yl]methylsulfanylmethyl]-4-oxo-6-[2-(3-oxobutoxy)ethoxy]hexanoyl]amino]propanoate is sourced from PubChem (CID 153001223), the world's largest open chemistry database maintained by the National Library of Medicine (NIH).