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Home , Acetal, Acyl halide, Aminal, Aryl, Azo compound, Cyanate

List of functional groups recognized by checkmol Current program version: v0.5 Norbert Haider, University of Vienna, 2005–2013 http://merian.pch.univie.ac.at/~nhaider/cheminf/cmmm.html For background information and for appropriate citation, please refer tio this article: Haider, N., Functionality Pattern Matching as an Efficient Complementary Structure/Reaction Search Tool: an Open-Source Approach. Molecules, 15, 5079-5092 (2010).

The table below lists the ID number, the English name (as obtained with the –e option), the 8-letter code (as obtained with the –c option [deprecated]) and the structures of the groups recognized by checkmol. The red circles in the structure drawing indicate the “key atoms” which are assigned to each functionality (as listed with the –p option). Wherever possible, a single “key atom” is used to identify and localize a functional group, but in some cases (e.g., for , peroxides, etc.) a pair of connectred atoms serves as a key.

No. functional group name code general structure remarks 001 cation 000000T2 any positive charge 002 anion 000000T1 any negative charge 003 carbonyl compound C2O10000 O or R1 = H, , R2 = H, alkyl, aryl R1 R2 004 aldehyde C2O1H000 O R = H, alkyl, aryl R H 005 ketone C2O1C000 O R1 = alkyl, aryl R2 = alkyl, aryl R1 R2 006 thiocarbonyl compound C2S10000 S or thioaldehyde R1 = H, alkyl, aryl R2 = H, alkyl, aryl R1 R2 007 thioaldehyde C2S1H000 S R = H, alkyl, aryl R H 008 thioketone C2S1C000 S R1 = alkyl, aryl R2 = alkyl, aryl R1 R2 009 C2N10000 R3 N R1 = H, alkyl, aryl 2 1 2 R = H, alkyl, aryl R R R3 = H, alkyl, aryl 010 C2N1N000 R3

N 1 R4 R = H, alkyl, aryl N R2 = H, alkyl, aryl R3 = H, alkyl, aryl R1 R2 R4 = H, alkyl, aryl 011 semicarbazone C2NNC4ON R4

O N R5

1 N 3 R = H, alkyl, aryl R 2 N R = H, alkyl, aryl R3 = H, alkyl, aryl 4 1 2 R = H, alkyl, aryl, R R R5 = H, alkyl, aryl 012 thiosemicarbazone C2NNC4SN R4

S N R5

1 N 3 R = H, alkyl, aryl R 2 N R = H, alkyl, aryl R3 = H, alkyl, aryl 4 1 2 R = H, alkyl, aryl, R R R5 = H, alkyl, aryl 013 C2N1OH00 OH N R1 = H, alkyl, aryl R2 = H, alkyl, aryl R1 R2 014 oxime C2N1OC00 OR3 N R1 = H, alkyl, aryl 2 1 2 R = H, alkyl, aryl R R R3 = alkyl, aryl 015 ketene C3OC0000 O

R1 = H, alkyl, aryl R2 = H, alkyl, aryl R1 R2 016 ketene derivative C3OCC000 X Y R1 = H, alkyl, aryl R2 = H, alkyl, aryl X = any hetero atom 1 2 R R Y = any hetero atom 017 carbonyl hydrate C2O2H200 HO OH R1 = H, alkyl, aryl R2 = H, alkyl, aryl R1 R2 018 C2O2HC00 3 R O OH R1 = H, alkyl, aryl 2 1 2 R = H, alkyl, aryl R R R3 = alkyl, aryl 019 acetal C2O2CC00 R3O OR4 R1 = H, alkyl, aryl R2 = H, alkyl, aryl 3 R1 R2 R = alkyl, aryl R4 = alkyl, aryl 4 3 020 C2NOHC10 R R1 = H, alkyl, aryl in a true hemiaminal, R would be H 3 5 2 R O N R R = H, alkyl, aryl R3 = H, alkyl, aryl 1 2 R4 = H, alkyl, aryl R R R5 = H, alkyl, aryl 1 021 C2N2CC10 R4 R5 R = H, alkyl, aryl R2 = H, alkyl, aryl 3 6 R N N R R3 = H, alkyl, aryl R4 = H, alkyl, aryl 1 2 R R R5 = H, alkyl, aryl R6 = H, alkyl, aryl 4 022 thiohemiaminal C2NSHC10 R R1 = H, alkyl, aryl 3 5 2 R S N R R = H, alkyl, aryl R3 = H, alkyl, aryl 1 2 R4 = H, alkyl, aryl R R R5 = H, alkyl, aryl 023 C2S2CC00 R3S SR4 R1 = H, alkyl, aryl R2 = H, alkyl, aryl 3 R1 R2 R = alkyl, aryl R4 = alkyl, aryl 024 enamine C2CNH000 5 4 R4, R5 = acyl should be types as R R 1 N R = H, acyl, alkyl, aryl enamide R2 = H, acyl, alkyl, aryl 1 3 R 3 R = H, acyl, alkyl, aryl R R4 = H, acyl, alkyl, aryl R2 R5 = H, acyl, alkyl, aryl

025 enol C2COH000 OH 1 R1 = H, acyl, alkyl, aryl R R3 R2 = H, acyl, alkyl, aryl R3 = H, acyl, alkyl, aryl R2 026 enolether C2COC000 OR4 1 1 R = H, acyl, alkyl, aryl 2 R 3 R = H, acyl, alkyl, aryl R R3 = H, acyl, alkyl, aryl R2 R4 = alkyl, aryl 027 hydroxy compound O1H00000 or ROH R = alkyl, aryl

028 alcohol O1H0C000 ROH R = alkyl

029 prim. alcohol O1H1C000 R OH R = alkyl, aryl

030 sec. alcohol O1H2C000 R2 R1 = alkyl, aryl 1 R OH R2 = alkyl, aryl 031 tert. alcohol O1H3C000 2 R3 R R1 = alkyl, aryl 1 R OH R2 = alkyl, aryl R3 = alkyl, aryl 032 1,2- O1H0CO1H HO OH R1 = H, alkyl, aryl 1 3 R2 = H, alkyl, aryl R R 3 R2 R4 R = H, alkyl, aryl R4 = H, alkyl, aryl 1 033 1,2-aminoalcohol O1H0CN1C HO NH2 R = H, alkyl, aryl 1 3 R2 = H, alkyl, aryl R R 3 R2 R4 R = H, alkyl, aryl R4 = H, alkyl, aryl 034 phenol O1H1A000 OH any aromatic or heteroaromatic ring with an OH

035 1,2-diphenol O1H2A000 OH any aromatic or heteroaromatic ring with two adjacent OH (except tautomeric lactams) OH 036 enediol C2COH200 HO OH R1 = H, alkyl, aryl R2 = H, alkyl, aryl R1 R2

037 ether O1C00000 1 1 O 2 R = alkyl, aryl R R R2 = alkyl, aryl 038 dialkylether O1C0CC00 1 1 O 2 R = alkyl R R 2 R = alkyl 039 alkylarylether O1C0CA00 1 1 O 2 R = alkyl R R 2 R = aryl 040 diarylether O1C0AA00 1 1 O 2 R = aryl R R 2 R = aryl 041 thioether S1C00000 1 1 S 2 R = alkyl, aryl R R R2 = alkyl, aryl 042 S1S1C000 2 1 1 S R R = alkyl, aryl R S R2 = alkyl, aryl

043 peroxide O1O1C000 2 1 1 O R R = alkyl, aryl R O R2 = alkyl, aryl 044 O1O1H000 O R = alkyl, aryl R OH 045 derivative N1N10000 2 R R1 = H, acyl, alkyl, aryl 3 R2 = H, acyl, alkyl, aryl 1 N R R N R3 = H, acyl, alkyl, aryl 4 R4 R = H, acyl, alkyl, aryl 046 hydroxylamine N1O1H000 2 R R1 = H, alkyl, aryl 3 R2 = H, alkyl, aryl 1 N R R O R3 = H, alkyl, aryl 3 047 N1C00000 R R1 = alkyl, aryl R2 = H, alkyl, aryl N R1 R2 R3 = H, alkyl, aryl 048 prim. amine N1C10000 RNH R = alkyl, aryl 2 049 prim. aliphat. amine N1C1C000 RNH2 R = alkyl 050 prim. aromat. amine N1C1A000 RNH2 R = aryl 051 sec. amine N1C20000 H R1 = alkyl, aryl N R1 R2 R2 = alkyl, aryl 052 sec. aliphat. amine N1C2CC00 H R1 = alkyl N 1 2 R2 = alkyl R R 053 sec. mixed amine (aryl alkyl) N1C2AC00 H R1 = alkyl N 1 2 R2 = aryl R R 054 sec. aromat. amine N1C2AA00 H R1 = aryl N 1 2 R2 = aryl R R 3 055 tert. amine N1C30000 R R1 = alkyl, aryl R2 = alkyl, aryl N R1 R2 R3 = alkyl, aryl 3 056 tert. aliphat. amine N1C3CC00 R R1 = alkyl R2 = alkyl N 1 2 R3 = alkyl R R 3 057 tert. mixed amine N1C3AC00 R R1 = alkyl R2 = aryl N R1 R2 R3 = alkyl, aryl 3 058 tert. arom_amine N1C3AA00 R R1 = aryl R2 = aryl N 1 2 R3 = aryl R R 059 quaternary ammonium N1C400T2 3 1 4 R R = alkyl, aryl R + R2 = alkyl, aryl N 3 R1 R2 R = alkyl, aryl R4 = alkyl, aryl 060 N-oxide N0O10000 the N-O bond may be formulated as O a O + 1 N + R = alkyl, aryl 2 1 N 3 R = alkyl, aryl R R 3 R2 R = alkyl, aryl

061 deriv. XX000000 RX X = F, Cl, Br, I R = alkyl, alkenyl, aryl 062 alkyl halide XX00C000 RX X = F, Cl, Br, I R = alkyl 063 alkyl fluoride XF00C000 RF R = alkyl

064 alkyl XC00C000 RCl R = alkyl

065 alkyl bromide XB00C000 RBr R = alkyl

066 alkyl iodide XI00C000 RI R = alkyl

067 aryl halide XX00A000 RX X = F, Cl, Br, I R = aryl 068 aryl fluoride XF00A000 RF R = aryl

069 aryl chloride XC00A000 RCl R = aryl

070 aryl bromide XB00A000 RBr R = aryl 071 aryl iodide XI00A000 RI R = aryl

072 organometallic compound 000000MX R M M = any metal R = alkyl, aryl 073 organolithium compound 000000ML RLi R = alkyl, aryl

074 organomagnesium compound 000000MM RMg R = alkyl, aryl

075 carboxylic deriv. C3O20000 O R = H, alkyl, aryl R X X = any hetero atom 076 C3O2H000 O R = H, alkyl, aryl R OH 077 carboxylic acid salt C3O200T1 O R = H, alkyl, aryl R O 078 carboxylic acid C3O2C000 O 2 R1 = H, alkyl, aryl 1 R 2 R O R = alkyl, aryl 079 lactone C3O2CZ00 O a cyclic ester (any ring size)

O

080 carboxylic acid C3ONC000 O 2 R1 = H, alkyl, aryl 1 R 2 R N R = H, alkyl, aryl R3 = H, alkyl, aryl R3 081 carboxylic acid prim. amide C3ONC100 O R = H, alkyl, aryl

R NH2 082 carboxylic acid sec. amide C3ONC200 O 2 R1 = H, alkyl, aryl 1 R 2 R N R = alkyl, aryl H 083 carboxylic acid tert. amide C3ONC300 O 2 R1 = H, alkyl, aryl 1 R 2 R N R = alkyl, aryl R3 = alkyl, aryl R3 084 lactam C3ONCZ00 O a cyclic amide (any ring size) R N R = H, alkyl, aryl

085 carboxylic acid hydrazide C3ONN100 4 O R R1 = H, alkyl, aryl R2 = H, alkyl, aryl 1 N 3 R N R R3 = H, alkyl, aryl 4 2 R = H, alkyl, aryl R 086 carboxylic acid C3ONN200 O R = H, alkyl, aryl + R N N N 087 hydroxamic acid C3ONOH00 O R = H, alkyl, aryl OH R N H 088 carboxylic acid C3N2H000 R4 N R1 = H, alkyl, aryl 3 R2 = H, alkyl, aryl 1 R R N R3 = H, alkyl, aryl 4 2 R = H, alkyl, aryl R 089 carboxylic acid amidrazone C3NNN100 5 R 4 N R R1 = H, alkyl, aryl R2 = H, alkyl, aryl N R1 N R3 R3 = H, alkyl, aryl 4 2 R = H, alkyl, aryl R R5 = H, alkyl, aryl 090 C3N00000 RCN R = H, alkyl, aryl 091 C3OXX000 O R = H, alkyl, aryl R X X = F, Cl, Br, I 092 acyl fluoride C3OXF000 O R = H, alkyl, aryl R F 093 C3OXC000 O R = H, alkyl, aryl R Cl 094 acyl bromide C3OXB000 O R = H, alkyl, aryl R Br 095 acyl iodide C3OXI000 O R = H, alkyl, aryl R I 096 acyl C2OC3N00 O R = H, alkyl, aryl R C N 097 imido ester C3NOC000 R3 N 2 R1 = H, alkyl, aryl 1 R 2 R O R = alkyl, aryl R3 = H, alkyl, aryl 098 imidoyl halide C3NXX000 R2 N R1 = H, alkyl, aryl 1 2 R X R = H, alkyl, aryl X = F, Cl, Br, I 099 deriv. C3SO0000 S R = H, alkyl, aryl R X X = any hetero atom 100 thiocarboxylic acid C3SOH000 S R = H, alkyl, aryl R X X = OH, SH 101 thiocarboxylic acid ester C3SOC000 S 2 R1 = H, alkyl, aryl 1 R 2 R X R = alkyl, aryl X = O, S 102 thiolactone C3SOCZ00 S a cyclic (any ring size) X = O, S X

103 thiocarboxylic acid amide C3SNH000 S 2 R1 = H, alkyl, aryl 1 R 2 R N R = H, alkyl, aryl R3 = H, alkyl, aryl R3 104 thiolactam C3SNCZ00 S R N R = H, alkyl, aryl

105 imidothioester C3NSC000 R3 N 2 R1 = H, alkyl, aryl 1 R 2 R S R = alkyl, aryl R3 = H, alkyl, aryl 106 oxohetarene C3ONAZ00 R any (hetero) with a C=O structure N O R = H, alkyl, aryl 107 thioxohetarene C3SNAZ00 R any (hetero)aromatic compound with a C=S structure N S R = H, alkyl, aryl

108 iminohetarene C3NNAZ00 R1 R2 N N R1 = H, alkyl, aryl R2 = H, alkyl, aryl 109 orthocarboxylic acid deriv. C3O30000 X X R = H, alkyl, aryl X = OH, alkoxy, aryloxy, R X (substituted) amino, etc. 110 carboxylic acid C3O3C000 R2O OR3 R1 = H, alkyl, aryl 1 4 R2, R3, R4 = alkyl, aryl R OR 111 carboxylic acid amide acetal C3O3NC00 R2O OR3 4 R1 = H, alkyl, aryl R R1 N R2, R3 = alkyl, aryl R4, R5 = H, alkyl, aryl R5 112 carboxylic acid anhydride C3O2C3O2 O O R1, R2 = H, alkyl, aryl 1 2 R O R 113 carboxylic acid C3ONC000 O O R1, R2 = H, alkyl, aryl 1 2 R N R R3 = H, alkyl, aryl, ... R3 114 carboxylic acid unsubst. imide C3ONCH10 O O R1, R2 = H, alkyl, aryl 1 2 R N R H 115 carboxylic acid subst. imide C3ONCC10 O O R1, R2 = H, alkyl, aryl 1 2 R N R R3 = anything but H R3 116 CO2 deriv. (general) C4000000 any with 4 valences to hetero atoms (a double bond counts as 2 valences, a as 3 valences) 117 deriv. C4O30000 O output only if none of the more X, Y = any hetero atom specific types apply X Y 118 carbonic acid monoester C4O3C100 O R = alkyl, aryl HO OR 119 carbonic acid diester C4O3C200 O R1, R2 = alkyl, aryl R1O OR2 120 carbonic acid ester halide C4O3CX00 O R = alkyl, aryl X OR X = F, Cl, Br, I 121 thiocarbonic acid deriv. C4SO0000 S X, Y = any hetero atom X Y 122 thiocarbonic acid monoester C4SOC100 S S may be in any other position R = alkyl, aryl (replacing O) HO OR 123 thiocarbonic acid diester C4SOC200 S S may be in any other position R1, R2 = alkyl, aryl (replacing O) R1O OR2 124 thiocarbonic acid ester halide C4SOX_00 S R = alkyl, aryl X OR X = F, Cl, Br, I 125 carbamic acid deriv C4O2N000 O 1 R1, R2 = H, alkyl, aryl R N X X = OH, alkoxy, aryloxy, halogen R2 126 carbamic acid C4O2NH00 O 1 R1, R2 = H, alkyl, aryl R N OH R2 127 carbamic acid ester C4O2NC00 O (urethane) 1 R1, R2 = H, alkyl, aryl R 3 3 N OR R = alkyl, aryl R2 128 carbamic acid halide C4O2NX00 O 1 R1, R2 = H, alkyl, aryl R N X X = F, Cl, Br, I R2 129 thiocarbamic acid deriv. C4SN0000 S 1 R1, R2 = H, alkyl, aryl R N X X = OH, alkoxy, aryloxy, halogen R2 130 thiocarbamic acid C4SNOH00 S also possible: SH instead of OH 1 R1, R2 = H, alkyl, aryl R N OH R2 131 thiocarbamic acid ester C4SNOC00 S 1 R1, R2 = H, alkyl, aryl R 3 3 N OR R = alkyl, aryl R2 132 thiocarbamic acid halide C4SNXX00 S 1 R1, R2 = H, alkyl, aryl R N X X = F, Cl, Br, I R2 133 C4O1N200 O R1 R4 N N R2 R3 R1, R2, R3, R4 = H, alkyl, aryl

134 isourea C4N2O100 R4 O R1 N N R2 R3 R1, R2, R3, R4 = H, alkyl, aryl

135 thiourea C4S1N200 S R1 R4 N N R2 R3 R1, R2, R3, R4 = H, alkyl, aryl

136 isothiourea C4N2S100 R4 S R1 N N R2 R3 R1, R2, R3, R4 = H, alkyl, aryl

137 guanidine C4N30000 R5 N R1 R4 N N R2 R3 R1, R2, R3, R4, R5 = H, alkyl, aryl 5 138 semicarbazide C4ON2N00 O R 1 R N 4 N N R R2 R3 R1, R2, R3, R4, R5 = H, alkyl, aryl

5 139 thiosemicarbazide C4SN2N00 S R 1 R N 4 N N R R2 R3 R1, R2, R3, R4, R5 = H, alkyl, aryl 140 azide N4N20000 + R NNN R = alkyl, aryl

141 N2N10000 1 R N 2 N R R1, R2 = alkyl, aryl 142 diazonium salt N3N100T2 + R NN R = alkyl, aryl

143 isonitrile N3C10000 + R N C R = alkyl, aryl

144 C4NO1000 RO CN R = alkyl, aryl

145 C4NO2000 R NCO R = alkyl, aryl

146 C4NS1000 RS CN R = alkyl, aryl

147 C4NS2000 R NCS R = alkyl, aryl

148 carbodiimide C4N20000 1 2 R NCN R R1, R2 = H, alkyl, aryl

149 compound N2O10000 R NO R = alkyl, aryl 150 N4O20000 O R N R = alkyl, aryl O 151 nitrite N3O20000 RO NO R = alkyl, aryl

152 N4O30000 O RO N R = alkyl, aryl O 153 deriv. S6O00000 O for query purposes only X, Y = any hetero atom X S Y O 154 sulfuric acid S6O4H000 O HO S OH O 155 sulfuric acid monoester S6O4HC00 O R = alkyl, aryl RO S OH O 156 sulfuric acid diester S6O4CC00 O 1 2 1 2 R , R = alkyl, aryl R O S OR O 157 sulfuric acid amide ester S6O3NC00 O 3 R 1 1 R = alkyl, aryl R O S N R2, R3 = H, alkyl, aryl 2 O R 158 sulfuric acid amide S6O3N100 O R2 R1, R2 = H, alkyl, aryl HO S N 1 O R 159 sulfuric acid diamide S6O2N200 R1 O R4 R1, R2, R3, R4 = H, alkyl, aryl N S N 2 3 R O R 160 sulfuryl halide S6O3XX00 O X = F, Cl, Br, I X S Y Y = any hetero atom O 161 deriv. S5O00000 O for query purposes only R = alkyl, aryl R S X X = any hetero atom O 162 sulfonic acid S5O3H000 O R = alkyl, aryl R S OH

O 163 sulfonic acid ester S5O3C000 O 1 2 1 2 R , R = alkyl, aryl R S OR O 164 S5O2N000 O 3 R 1 1 R = alkyl, aryl R S N R2, R3 = H, alkyl, aryl 2 O R 165 S5O2XX00 O R = alkyl, aryl R S X X = F, Cl, Br, I O 166 S4O20000 O 1 2 1 2 R , R = alkyl, aryl R S R O 167 S2O10000 O R1, R2 = alkyl, aryl 1 S 2 R R 168 sulfinic acid deriv. S3O00000 O for query purposes only R = alkyl, aryl R S X X = any hetero atom 169 sulfinic acid S3O2H000 O R = alkyl, aryl S R OH 170 sulfinic acid ester S3O2C000 O R1, R2 = alkyl, aryl R1 S OR2 171 sulfinic acid halide S3O1XX00 O R = alkyl, aryl S X = F, Cl, Br, I R X 172 sulfinic acid amide S3O1N000 O R3 R1 = alkyl, aryl R1 S N R2, R3 = H, alkyl, aryl R2 173 deriv. S1O00000 for query purposes only S R = alkyl, aryl R X X = any hetero atom 174 sulfenic acid S1O1H000 R = alkyl, aryl R S OH

175 sulfenic acid ester S1O1C000 1 2 R1, R2 = alkyl, aryl R S OR

176 sulfenic acid halide S1O0XX00 R = alkyl, aryl R S X X = F, Cl, Br, I 177 sulfenic acid amide S1O0N100 R3 1 S R1 = alkyl, aryl R N R2, R3 = H, alkyl, aryl R2 178 S1H10000 RSH R = alkyl, aryl 179 alkylthiol S1H1C000 RSH R = alkyl 180 arylthiol S1H1A000 RSH R = aryl 181 phosphoric acid deriv. P5O0H000 O for query purposes only X, Y, Z = O, N, Hal residue P X Z Y 182 phosphoric acid P5O4H200 O P HO OH HO 183 phosphoric acid ester P5O4HC00 O R = alkyl, aryl P X OR X, Y = any O, N, Hal residue Y 184 phosphoric acid halide P5O3HX00 O X = F, Cl, Br, I P X Z Y, Z = any O, N, Hal residue Y 185 phosphoric acid amide P5O3HN00 O 1 P R X N 1 2 Y R , R = H, alkyl, aryl R2 X, Y = any O, N, Hal residue 186 thiophosphoric acid deriv. P5O0S000 S for query purposes only X, Y, Z = any O, N, Hal residue P X Z Y 187 thiophosphoric acid P5O3SH00 S P HO OH HO 188 thiophosphoric acid ester P5O3SC00 S R = alkyl, aryl P X OR X, Y = any O, N, Hal residue Y 189 thiophosphoric acid halide P5O2SX00 S X = F, Cl, Br, I P X Z Y, Z = any O, N, Hal residue Y 190 thiophosphoric acid amide P5O2SN00 S 1 P R X N 1 2 Y R , R = H, alkyl, aryl R2 X, Y = any O, N, Hal residue 191 phosphonic acid deriv. P4O30000 O R = alkyl, aryl P R Y X, Y = any O, N, Hal residue X 192 phosphonic acid P4O3H000 O R = alkyl, aryl P R OH OH 193 phosphonic acid ester P4O3C000 O R1, R2 = alkyl, aryl 1 P 2 R OR X = any O, N, Hal residue X 194 P3000000 R3 R1, R2, R3 = alkyl, aryl P R1 R2 195 phosphinoxide P2O00000 O R1, R2, R3 = alkyl, aryl P R1 R3 R2 196 deriv. B2O20000 X R = alkyl, aryl B R Y X, Y = any O, N, Hal residue 197 boronic acid B2O2H000 OH R = alkyl, aryl B R OH 198 boronic acid ester B2O2C000 X R1, R2 = alkyl, aryl 1 B 2 R OR X = any O, N, Hal residue 199 000C2C00 R4 R1 R3 R1, R2, R3, R4 = H, alkyl, aryl R2 200 000C3C00 R1 R2 R1, R2 = H, alkyl, aryl 201 aromatic compound 0000A000 any aromatic carbocyclic or heterocyclic structure, criteria: , including cyclopentadienyl anion, tropylium cation, Hückel’s rule must apply (4n + 2 pi fulvene, tropone, pyridone-type lactams, etc. electrons); planar geometry is not checked 202 heterocyclic compound 0000CZ00 any cyclic structure with at least one non-carbon starting with v0.3b, metal atoms are atom incorporated not accepted as ring members, unless option –M is used 203 alpha-aminoacid C3O2HN1C O 1 R1, R2 = H, alkyl, aryl R OH NH R2 204 alpha-hydroxyacid C3O2HO1H O R = H, alkyl, aryl R OH OH