Title:  Pipecolic Acid 
CAS Registry Number:  535-75-1 
CAS Name:  2-Piperidinecarboxylic acid 
Additional Names:  pipecolinic acid;  hexahydropicolinic acid;  homoproline;  dihydrobaikiaine 
Molecular Formula:  C6H11NO2 
Molecular Weight:  129.16 
Percent Composition:  C 55.79%, H 8.58%, N 10.84%, O 24.77% 
Literature References:  The l-form occurs in plants:  Phillips, Chem. Ind. (London) 1953, 127.  Prepn:  A. Ladenburg, Ber. 24, 640 (1891); Stevens, Ellman, J. Biol. Chem. 182, 75 (1950); V. Asher et al., Tetrahedron Lett. 22, 141 (1981).  Synthesis of L-pipecolic acid from L-lysine:  Fujii, Miyoshi, Bull. Chem. Soc. Jpn. 48, 1341 (1975).  Synthesis of racemate:  R. T. Shuman et al., J. Org. Chem. 55, 738 (1990). 
  
Derivative Type:  l-Form  
Properties:  Needles by sublimation, mp 270°.  [a]D25 -34.9°.  Sol in water, dil alcohol.  Sparingly sol in abs alcohol, acetone, chloroform.  Insol in ether. 
Melting point:  mp 270° 
Optical Rotation:  [a]D25 -34.9° 
  
Derivative Type:  d-Form  
Properties:  Platelets from alcohol, mp 270°.  [a]D25 +35.7°.  Sol in water.  Somewhat sol in alcohol. 
Melting point:  mp 270° 
Optical Rotation:  [a]D25 +35.7° 
  
Derivative Type:  dl-Form  
Properties:  Leaflets from water, mp 264°.  Sol in water, boiling alcohol. 
Melting point:  mp 264° 
  
Derivative Type:  dl-Hydrochloride  
Molecular Formula:  C6H11NO2.HCl 
Molecular Weight:  165.62 
Percent Composition:  C 43.51%, H 7.30%, N 8.46%, O 19.32%, Cl 21.41% 
Properties:  Crystals (warts) from alcohol + benzene, mp 258-262°. 
Melting point:  mp 258-262° 
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