Penam
{{Chembox
| Name =
| ImageFile = File:Penam.svg
| ImageSize = 150px
| OtherNames = 1-Aza-7-oxo-4-thiabicyclo[3.2.0]heptane
| IUPACName = (5R)-4-thia-1-azabicyclo[3.2.0]heptan-7-one
| SystematicName =
| Section1 = {{Chembox Identifiers
| CASNo = 53908-04-6
| CASNo_Ref = {{Cascite|changed|ChemSpider}}
| PubChem = 9548842
| Beilstein = 4374479
| ChemSpiderID = 7827765
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 35991
| SMILES = C1CSC2N1C(=O)C2
| InChI = 1S/C5H7NOS/c7-4-3-5-6(4)1-2-8-5/h5H,1-3H2/t5-/m1/s1
| InChIKey = WSHJJCPTKWSMRR-RXMQYKEDSA-N
| StdInChI = 1S/C5H7NOS/c7-4-3-5-6(4)1-2-8-5/h5H,1-3H2/t5-/m1/s1
| StdInChIKey = WSHJJCPTKWSMRR-RXMQYKEDSA-N
}}
| Section2 = {{Chembox Properties
| C=5|H=7|N=1|O=1|S=1
| Appearance =
| Density =
| MeltingPtC =
| BoilingPtC =
| Solubility =
}}
| Section3 = {{Chembox Hazards
| ExternalSDS =
| MainHazards =
| FlashPt =
| AutoignitionPt =
}}
| Section4 =
| Section5 =
| Section6 =
| Section8 = {{Chembox Related
| OtherCompounds = clavam
}}
}}
File:Penicillin-G.svg, an example of a penam]]
{{distinguish|penem}}
Penams are the primary skeleton structures that define the penicillin subclass of the broader β-lactam family of antibiotics and related compounds. They are bicyclic ring systems containing a β-lactam moiety fused with a five-member thiazolidine ring. {{Cite journal|last1=Novak|first1=Igor|last2=Chua|first2=Pei Juan|date=2006-09-01|title=Computational Study of Pharmacophores: β-Lactams|journal=The Journal of Physical Chemistry A|volume=110|issue=35|pages=10521–10524|doi=10.1021/jp063162b|pmid=16942059|bibcode=2006JPCA..11010521N|issn=1089-5639}} Due to ring strain and limitations on amide resonance, the structure is unstable and highly susceptible to catalytic cleavage at the amide bond.{{Citation|last=Patrick|first=Graham|title=5. Pharmaceuticals and medicinal chemistry|date=2017-03-23|work=Organic Chemistry: A Very Short Introduction|pages=71–89|publisher=Oxford University Press|doi=10.1093/actrade/9780198759775.003.0005|isbn=978-0-19-875977-5}} Benzylpenicillin (penicillin G) is the natural product parent that contains the penam structure.
Structure
Penams have inflexible structures. The structure is locked in a puckered (i.e. bent) shape due to the pyramidal geometry of the bridgehead nitrogen. The pyramidalization (χ = 54°) and twist of the C-N bond (τ = 18°) is caused by the strain from the lone pair's exclusion from planarity with the cyclic rings and electrostatic repulsion effects. As a result, the distorted C-N bond causes misalignment the orbitals of the carbonyl carbon and the nitrogen lone pair that allow for resonance overlap. The amide C-N bond length is 1.406{{nbsp}}Å and displays greater single bond character than in noncyclic tertiary amides. The C-O bond length is 1.205{{nbsp}}Å which is shorter than C-O bonds in noncyclic tertiary amides.{{Cite journal|last1=Glover|first1=Stephen A.|last2=Rosser|first2=Adam A.|date=2012-06-14|title=Reliable Determination of Amidicity in Acyclic Amides and Lactams|journal=The Journal of Organic Chemistry|volume=77|issue=13|pages=5492–5502|doi=10.1021/jo300347k|pmid=22646836|issn=0022-3263}}
Penams are strained due to the angle strain on the four-member β-lactam ring, whose internal bond angles are 90º.{{Cite journal|last1=Hu|first1=Feng|last2=Lalancette|first2=Roger|last3=Szostak|first3=Michal|date=2016-03-08|title=Structural Characterization of N-Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage|journal=Angewandte Chemie International Edition|volume=55|issue=16|pages=5062–5066|doi=10.1002/anie.201600919|pmid=26953809|issn=1433-7851}} Consequently, penams are susceptible to acid- and base-catalyzed hydrolysis.
References
{{Reflist}}
{{Cell wall disruptive antibiotics}}
Category:Beta-lactamase inhibitors
Category:Nitrogen heterocycles