Molecular Structure of 4-Hydroxypipecolic acid (CAS NO.14228-16-1):

IUPAC Name: 4-Hydroxypiperidine-2-carboxylic acid 
Molecular Formula: C₆H₁₁NO₃
Molecular Weight: 145.16 
Index of Refraction: 1.522
Molar Refractivity: 34.1 cm³
Molar Volume: 111.7 cm³
Surface Tension: 54.8 dyne/cm
Density: 1.299 g/cm³
Flash Point: 163 °C
Enthalpy of Vaporization: 68.34 kJ/mol
Boiling Point: 346 °C at 760 mmHg
Vapour Pressure: 3.72E-06 mmHg at 25 °C
Product Categories: pharmacetical
Canonical SMILES: C1CNC(CC1O)C(=O)O
InChI: InChI=1S/C6H11NO3/c8-4-1-2-7-5(3-4)6(9)10/h4-5,7-8H,1-3H2,(H,9,10)
InChIKey: KRHNXNZBLHHEIU-UHFFFAOYSA-N

 4-Hydroxypipecolic acid (CAS NO.14228-16-1) is used as an N-methyl-D-aspartate receptors agonist.

 4-Hydroxypipecolic acid (CAS NO.14228-16-1), its Synonyms are 4-Hydroxy-2-piperidinecarboxylic acid ; t-Hpis ; trans-4-Hydroxy-(S)-pipecolic acid-4-sulfate ; 2-Piperidinecarboxylic acid, 4-hydroxy- .
 A new method for the determination of naturally occurring imino acids in plants which comprises the formation of dinitrophenyl derivatives and their measurement by HPLC was devised. The determination limits were 100 pmol for 4-Hydroxypipecolic acid (HPA) and proline (Pro) and 10 pmol for pipecolic acid (Pip).