Chromic Acid → N-Carbobenzyloxy-4-keto-L-proline

HRID 1106038Notes

Reaction equation

HRID 1106038 reaction equation
[C:1]([N:11]1[CH2:18][CH:17]([OH:19])[CH2:16][C@H:12]1[C:13]([OH:15])=[O:14])([O:3][CH2:4][C:5]1[CH:10]=[CH:9][CH:8]=[CH:7][CH:6]=1)=[O:2].[Cr](O)(O)(=O)=O>CC(C)=O.S(=O)(=O)(O)O>[C:1]([N:11]1[CH2:18][C:17](=[O:19])[CH2:16][C@H:12]1[C:13]([OH:15])=[O:14])([O:3][CH2:4][C:5]1[CH:6]=[CH:7][CH:8]=[CH:9][CH:10]=1)=[O:2]

Participants

5

Reactant 2

HCID 24425Chromic AcidHCID 12731799(2S)-1-((benzyloxy)carbonyl)-4-hydroxypyrrolidine-2-carboxylic acid

Product 1

HCID 11076282N-Carbobenzyloxy-4-keto-L-prolineYield 10.7%

Reagents, catalysts & solvents 2

HCID 180AcetoneSolventHCID 1118Sulfuric AcidSolvent

Procedure

21.5 g (0.81 mole) of N-carbobenzyloxy-4-hydroxy-L-proline is oxidized in 1.2 liters of acetone with 83 ml of 8 N chromic acid in sulfuric acid as described in J.A.C.S. 79, 189 (1957). In order to facilitate the subsequent filtration of chromium salts, 30 g of Celite (diatomaceous earth) is added to the acetone solution before introduction of the oxidizing agent. An air stirrer is employed. The reaction mixture is filtered and the acetone filtrate is concentrated to approximately 300 ml before diluting with 1 liter of chloroform. The solution is washed with 300 ml of saturated sodium chloride (four times), dried (MgSO4), filtered and the solvent evaporated to give N-carbobenzyloxy-4-keto-L-proline (22.8 g) which is crystallized from ether (50 ml)-hexane (150 ml) to obtain 17.2 g (81%) of product, m.p. 99°-101°, [α]D26 +17° (c, 1% in chloroform).

Workup

  1. filtrationthe subsequent filtration of chromium salts, 30 g of Celite (diatomaceous earth)
  2. additionis added to the acetone solution before introduction of the oxidizing agent
  3. customAn air stirrer is employed
  4. filtrationThe reaction mixture is filtered
  5. concentrationthe acetone filtrate is concentrated to approximately 300 ml
  6. additionbefore diluting with 1 liter of chloroform
  7. washThe solution is washed with 300 ml of saturated sodium chloride (four times)
  8. dry with materialdried (MgSO4)
  9. filtrationfiltered
  10. customthe solvent evaporated

Sources & evidence

ORD record
ord-a43e7206c84e4b68b3013cc6f36da823
Source dataset
uspto-grants-1982_01
Patent number
US04311705

Reaction notes

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