Sentence:  In any case, OXLs from Cα-trisubstituted residues were extensively employed for the preparation of enantiomerically α-amino acid derivatives  and  Cα-tetrasubstituted α-amino acids (in the latter experiments, also in the context of investigations in the prebiotic and <WSD>exobiotic</WSD> fields). 
Meaning of the word marked with <WSD> tags:  From outside of an organism or from the substrate.