Chemical Formula: C19H31N5O8
Chemical Formula C19H31N5O8
Found 100 metabolite its formula value is C19H31N5O8
Asp Ile Asn Pro
(2S)-1-[(2S)-2-[(2S,3S)-2-[(2S)-2-amino-3-carboxypropanamido]-3-methylpentanamido]-3-carbamoylpropanoyl]pyrrolidine-2-carboxylic acid
Asp Ile Pro Asn
(3S)-3-amino-3-{[(2S,3S)-1-[(2S)-2-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}pyrrolidin-1-yl]-3-methyl-1-oxopentan-2-yl]carbamoyl}propanoic acid
Asp Leu Asn Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-4-methylpentanamido]-3-carbamoylpropanoyl]pyrrolidine-2-carboxylic acid
Asp Leu Pro Asn
(3S)-3-amino-3-{[(2S)-1-[(2S)-2-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}pyrrolidin-1-yl]-4-methyl-1-oxopentan-2-yl]carbamoyl}propanoic acid
Asp Asn Ile Pro
(2S)-1-[(2S,3S)-2-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-3-carbamoylpropanamido]-3-methylpentanoyl]pyrrolidine-2-carboxylic acid
Asp Asn Leu Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-3-carbamoylpropanamido]-4-methylpentanoyl]pyrrolidine-2-carboxylic acid
Asp Asn Pro Ile
(2S,3S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-3-methylpentanoic acid
Asp Asn Pro Leu
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-4-methylpentanoic acid
Asp Pro Ile Asn
(3S)-3-amino-4-[(2S)-2-{[(1S,2S)-1-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-2-methylbutyl]carbamoyl}pyrrolidin-1-yl]-4-oxobutanoic acid
Asp Pro Leu Asn
(3S)-3-amino-4-[(2S)-2-{[(1S)-1-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-3-methylbutyl]carbamoyl}pyrrolidin-1-yl]-4-oxobutanoic acid
Asp Pro Asn Ile
(2S,3S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carboxypropanoyl]pyrrolidin-2-yl]formamido}-3-carbamoylpropanamido]-3-methylpentanoic acid
Asp Pro Asn Leu
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carboxypropanoyl]pyrrolidin-2-yl]formamido}-3-carbamoylpropanamido]-4-methylpentanoic acid
Asp Pro Gln Val
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carboxypropanoyl]pyrrolidin-2-yl]formamido}-4-carbamoylbutanamido]-3-methylbutanoic acid
Asp Pro Val Gln
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carboxypropanoyl]pyrrolidin-2-yl]formamido}-3-methylbutanamido]-4-carbamoylbutanoic acid
Asp Gln Pro Val
(3S)-3-amino-3-{[(2S)-4-carbamoyl-1-[(2S)-2-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}pyrrolidin-1-yl]-1-oxobutan-2-yl]carbamoyl}propanoic acid
Asp Gln Val Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-4-carbamoylbutanamido]-3-methylbutanoyl]pyrrolidine-2-carboxylic acid
Asp Val Pro Gln
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-3-methylbutanoyl]pyrrolidin-2-yl]formamido}-4-carbamoylbutanoic acid
Asp Val Gln Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carboxypropanamido]-3-methylbutanamido]-4-carbamoylbutanoyl]pyrrolidine-2-carboxylic acid
Glu Asn Pro Val
(4S)-4-amino-4-{[(2S)-3-carbamoyl-1-[(2S)-2-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}pyrrolidin-1-yl]-1-oxopropan-2-yl]carbamoyl}butanoic acid
Glu Asn Val Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-4-carboxybutanamido]-3-carbamoylpropanamido]-3-methylbutanoyl]pyrrolidine-2-carboxylic acid
Glu Pro Asn Val
(4S)-4-amino-5-[(2S)-2-{[(1S)-2-carbamoyl-1-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}ethyl]carbamoyl}pyrrolidin-1-yl]-5-oxopentanoic acid
Glu Pro Val Asn
(4S)-4-amino-5-[(2S)-2-{[(1S)-1-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-2-methylpropyl]carbamoyl}pyrrolidin-1-yl]-5-oxopentanoic acid
Glu Val Asn Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-4-carboxybutanamido]-3-methylbutanamido]-3-carbamoylpropanoyl]pyrrolidine-2-carboxylic acid
Glu Val Pro Asn
(4S)-4-amino-4-{[(2S)-1-[(2S)-2-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}pyrrolidin-1-yl]-3-methyl-1-oxobutan-2-yl]carbamoyl}butanoic acid
Ile Asp Asn Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S,3S)-2-amino-3-methylpentanamido]-3-carboxypropanamido]-3-carbamoylpropanoyl]pyrrolidine-2-carboxylic acid
Ile Asp Pro Asn
(3S)-3-[(2S,3S)-2-amino-3-methylpentanamido]-4-[(2S)-2-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}pyrrolidin-1-yl]-4-oxobutanoic acid
Ile Asn Asp Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S,3S)-2-amino-3-methylpentanamido]-3-carbamoylpropanamido]-3-carboxypropanoyl]pyrrolidine-2-carboxylic acid
Ile Asn Pro Asp
(2S)-2-{[(2S)-1-[(2S)-2-[(2S,3S)-2-amino-3-methylpentanamido]-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}butanedioic acid
Ile Pro Asp Asn
(3S)-3-{[(2S)-1-[(2S,3S)-2-amino-3-methylpentanoyl]pyrrolidin-2-yl]formamido}-3-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}propanoic acid
Ile Pro Asn Asp
(2S)-2-[(2S)-2-{[(2S)-1-[(2S,3S)-2-amino-3-methylpentanoyl]pyrrolidin-2-yl]formamido}-3-carbamoylpropanamido]butanedioic acid
Leu Asp Asn Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-4-methylpentanamido]-3-carboxypropanamido]-3-carbamoylpropanoyl]pyrrolidine-2-carboxylic acid
Leu Asp Pro Asn
(3S)-3-[(2S)-2-amino-4-methylpentanamido]-4-[(2S)-2-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}pyrrolidin-1-yl]-4-oxobutanoic acid
Leu Asn Asp Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-4-methylpentanamido]-3-carbamoylpropanamido]-3-carboxypropanoyl]pyrrolidine-2-carboxylic acid
Leu Asn Pro Asp
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-4-methylpentanamido]-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}butanedioic acid
Leu Pro Asp Asn
(3S)-3-{[(2S)-1-[(2S)-2-amino-4-methylpentanoyl]pyrrolidin-2-yl]formamido}-3-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}propanoic acid
Leu Pro Asn Asp
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-4-methylpentanoyl]pyrrolidin-2-yl]formamido}-3-carbamoylpropanamido]butanedioic acid
Asn Asp Ile Pro
(2S)-1-[(2S,3S)-2-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-carboxypropanamido]-3-methylpentanoyl]pyrrolidine-2-carboxylic acid
Asn Asp Leu Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-carboxypropanamido]-4-methylpentanoyl]pyrrolidine-2-carboxylic acid
Asn Asp Pro Ile
(2S,3S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-carboxypropanoyl]pyrrolidin-2-yl]formamido}-3-methylpentanoic acid
Asn Asp Pro Leu
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-carboxypropanoyl]pyrrolidin-2-yl]formamido}-4-methylpentanoic acid
Asn Glu Pro Val
(4S)-4-[(2S)-2-amino-3-carbamoylpropanamido]-5-[(2S)-2-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}pyrrolidin-1-yl]-5-oxopentanoic acid
Asn Glu Val Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-4-carboxybutanamido]-3-methylbutanoyl]pyrrolidine-2-carboxylic acid
Asn Ile Asp Pro
(2S)-1-[(2S)-2-[(2S,3S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-methylpentanamido]-3-carboxypropanoyl]pyrrolidine-2-carboxylic acid
Asn Ile Pro Asp
(2S)-2-{[(2S)-1-[(2S,3S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-methylpentanoyl]pyrrolidin-2-yl]formamido}butanedioic acid
Asn Leu Asp Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-4-methylpentanamido]-3-carboxypropanoyl]pyrrolidine-2-carboxylic acid
Asn Leu Pro Asp
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-4-methylpentanoyl]pyrrolidin-2-yl]formamido}butanedioic acid
Asn Pro Asp Ile
(2S,3S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-3-carboxypropanamido]-3-methylpentanoic acid
Asn Pro Asp Leu
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-3-carboxypropanamido]-4-methylpentanoic acid
Asn Pro Glu Val
(4S)-4-{[(2S)-1-[(2S)-2-amino-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-4-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}butanoic acid
Asn Pro Ile Asp
(2S)-2-[(2S,3S)-2-{[(2S)-1-[(2S)-2-amino-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-3-methylpentanamido]butanedioic acid
Asn Pro Leu Asp
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-4-methylpentanamido]butanedioic acid
Asn Pro Val Glu
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}-3-methylbutanamido]pentanedioic acid
Asn Val Glu Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-methylbutanamido]-4-carboxybutanoyl]pyrrolidine-2-carboxylic acid
Asn Val Pro Glu
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-carbamoylpropanamido]-3-methylbutanoyl]pyrrolidin-2-yl]formamido}pentanedioic acid
Pro Asp Ile Asn
(3S)-3-{[(1S,2S)-1-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-2-methylbutyl]carbamoyl}-3-[(2S)-pyrrolidin-2-ylformamido]propanoic acid
Pro Asp Leu Asn
(3S)-3-{[(1S)-1-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-3-methylbutyl]carbamoyl}-3-[(2S)-pyrrolidin-2-ylformamido]propanoic acid
Pro Asp Asn Ile
(2S,3S)-2-[(2S)-3-carbamoyl-2-[(2S)-3-carboxy-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]propanamido]-3-methylpentanoic acid
Pro Asp Asn Leu
(2S)-2-[(2S)-3-carbamoyl-2-[(2S)-3-carboxy-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]propanamido]-4-methylpentanoic acid
Pro Asp Gln Val
(2S)-2-[(2S)-4-carbamoyl-2-[(2S)-3-carboxy-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]butanamido]-3-methylbutanoic acid
Pro Asp Val Gln
(2S)-4-carbamoyl-2-[(2S)-2-[(2S)-3-carboxy-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]-3-methylbutanamido]butanoic acid
Pro Glu Asn Val
(4S)-4-{[(1S)-2-carbamoyl-1-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}ethyl]carbamoyl}-4-[(2S)-pyrrolidin-2-ylformamido]butanoic acid
Pro Glu Val Asn
(4S)-4-{[(1S)-1-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-2-methylpropyl]carbamoyl}-4-[(2S)-pyrrolidin-2-ylformamido]butanoic acid
Pro Ile Asp Asn
(3S)-3-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-3-[(2S,3S)-3-methyl-2-[(2S)-pyrrolidin-2-ylformamido]pentanamido]propanoic acid
Pro Ile Asn Asp
(2S)-2-[(2S)-3-carbamoyl-2-[(2S,3S)-3-methyl-2-[(2S)-pyrrolidin-2-ylformamido]pentanamido]propanamido]butanedioic acid
Pro Leu Asp Asn
(3S)-3-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-3-[(2S)-4-methyl-2-[(2S)-pyrrolidin-2-ylformamido]pentanamido]propanoic acid
Pro Leu Asn Asp
(2S)-2-[(2S)-3-carbamoyl-2-[(2S)-4-methyl-2-[(2S)-pyrrolidin-2-ylformamido]pentanamido]propanamido]butanedioic acid
Pro Asn Asp Ile
(2S,3S)-2-[(2S)-2-[(2S)-3-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]-3-carboxypropanamido]-3-methylpentanoic acid
Pro Asn Asp Leu
(2S)-2-[(2S)-2-[(2S)-3-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]-3-carboxypropanamido]-4-methylpentanoic acid
Pro Asn Glu Val
(4S)-4-[(2S)-3-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]-4-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}butanoic acid
Pro Asn Ile Asp
(2S)-2-[(2S,3S)-2-[(2S)-3-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]-3-methylpentanamido]butanedioic acid
Pro Asn Leu Asp
(2S)-2-[(2S)-2-[(2S)-3-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]-4-methylpentanamido]butanedioic acid
Pro Asn Val Glu
(2S)-2-[(2S)-2-[(2S)-3-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]propanamido]-3-methylbutanamido]pentanedioic acid
Pro Gln Asp Val
(2S)-2-[(2S)-2-[(2S)-4-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]butanamido]-3-carboxypropanamido]-3-methylbutanoic acid
Pro Gln Val Asp
(2S)-2-[(2S)-2-[(2S)-4-carbamoyl-2-[(2S)-pyrrolidin-2-ylformamido]butanamido]-3-methylbutanamido]butanedioic acid
Pro Val Asp Gln
(2S)-4-carbamoyl-2-[(2S)-3-carboxy-2-[(2S)-3-methyl-2-[(2S)-pyrrolidin-2-ylformamido]butanamido]propanamido]butanoic acid
Pro Val Glu Asn
(4S)-4-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}-4-[(2S)-3-methyl-2-[(2S)-pyrrolidin-2-ylformamido]butanamido]butanoic acid
Pro Val Asn Glu
(2S)-2-[(2S)-3-carbamoyl-2-[(2S)-3-methyl-2-[(2S)-pyrrolidin-2-ylformamido]butanamido]propanamido]pentanedioic acid
Pro Val Gln Asp
(2S)-2-[(2S)-4-carbamoyl-2-[(2S)-3-methyl-2-[(2S)-pyrrolidin-2-ylformamido]butanamido]butanamido]butanedioic acid
Gln Asp Pro Val
(3S)-3-[(2S)-2-amino-4-carbamoylbutanamido]-4-[(2S)-2-{[(1S)-1-carboxy-2-methylpropyl]carbamoyl}pyrrolidin-1-yl]-4-oxobutanoic acid
Gln Asp Val Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-4-carbamoylbutanamido]-3-carboxypropanamido]-3-methylbutanoyl]pyrrolidine-2-carboxylic acid
Gln Pro Asp Val
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-4-carbamoylbutanoyl]pyrrolidin-2-yl]formamido}-3-carboxypropanamido]-3-methylbutanoic acid
Gln Pro Val Asp
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-4-carbamoylbutanoyl]pyrrolidin-2-yl]formamido}-3-methylbutanamido]butanedioic acid
Gln Val Asp Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-4-carbamoylbutanamido]-3-methylbutanamido]-3-carboxypropanoyl]pyrrolidine-2-carboxylic acid
Gln Val Pro Asp
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-4-carbamoylbutanamido]-3-methylbutanoyl]pyrrolidin-2-yl]formamido}butanedioic acid
Val Asp Pro Gln
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-methylbutanamido]-3-carboxypropanoyl]pyrrolidin-2-yl]formamido}-4-carbamoylbutanoic acid
Val Asp Gln Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-methylbutanamido]-3-carboxypropanamido]-4-carbamoylbutanoyl]pyrrolidine-2-carboxylic acid
Val Glu Asn Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-methylbutanamido]-4-carboxybutanamido]-3-carbamoylpropanoyl]pyrrolidine-2-carboxylic acid
Val Glu Pro Asn
(4S)-4-[(2S)-2-amino-3-methylbutanamido]-5-[(2S)-2-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}pyrrolidin-1-yl]-5-oxopentanoic acid
Val Asn Glu Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-methylbutanamido]-3-carbamoylpropanamido]-4-carboxybutanoyl]pyrrolidine-2-carboxylic acid
Val Asn Pro Glu
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-methylbutanamido]-3-carbamoylpropanoyl]pyrrolidin-2-yl]formamido}pentanedioic acid
Val Pro Asp Gln
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-methylbutanoyl]pyrrolidin-2-yl]formamido}-3-carboxypropanamido]-4-carbamoylbutanoic acid
Val Pro Glu Asn
(4S)-4-{[(2S)-1-[(2S)-2-amino-3-methylbutanoyl]pyrrolidin-2-yl]formamido}-4-{[(1S)-2-carbamoyl-1-carboxyethyl]carbamoyl}butanoic acid
Val Pro Asn Glu
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-methylbutanoyl]pyrrolidin-2-yl]formamido}-3-carbamoylpropanamido]pentanedioic acid
Val Pro Gln Asp
(2S)-2-[(2S)-2-{[(2S)-1-[(2S)-2-amino-3-methylbutanoyl]pyrrolidin-2-yl]formamido}-4-carbamoylbutanamido]butanedioic acid
Val Gln Asp Pro
(2S)-1-[(2S)-2-[(2S)-2-[(2S)-2-amino-3-methylbutanamido]-4-carbamoylbutanamido]-3-carboxypropanoyl]pyrrolidine-2-carboxylic acid
Val Gln Pro Asp
(2S)-2-{[(2S)-1-[(2S)-2-[(2S)-2-amino-3-methylbutanamido]-4-carbamoylbutanoyl]pyrrolidin-2-yl]formamido}butanedioic acid
2-({1-hydroxy-2-isopropyl-2-[methyl({3,6,8-trihydroxy-2-[2-(c-hydroxycarbonimidoyl)ethyl]-2,5,6,7-tetrahydro-1,4-diazocin-5-yl})carbamoyl]ethylidene}amino)propanoic acid
2-({1-hydroxy-2-isopropyl-2-[methyl({3,6,8-trihydroxy-2-[2-(c-hydroxycarbonimidoyl)ethyl]-2,5,6,7-tetrahydro-1,4-diazocin-5-yl})carbamoyl]ethylidene}amino)propanoic acid