Hydroxyproline stereochemistry

The stereochemistry of the hydroxyproline betaines, betonicine and turicine, had not been previously established this has now been done by the use of nonepimerizing methylating conditions on hydroxyprolines of known stereochemistry. 

Two new non-indol dicetopiperazines (166, 167) with a D-cz5-4-hydroxyproline residue were isolated as colorless amorphous solids from the culture broth of the same marine yeast Aureobasidium pullulans (de Bary) Arnaud (Hyphomycetes) from which orcinotriol (156) was isolated. Their structure, including absolute stereochemistry, was determined by spectroscopic and chemical means [186]. 

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