Diazirine compounds photoreactions

Fig. 9 Structures of compounds used to compare the photoaffinity labeling of different photoreactive groups, (a) Photoreactive dUTP analogs 84a-d reported by Tate et al. [87]. (b) Photoreactive SAH analogs 85a,b reported by Dalhoff et al. [88]. The insert shows the transfer of the activated methyl group from SAM to nucleophilic positions (Nu) in various substrates by methyltransferases (MTase). A adenosine, (c) Photoreactive metalloprotease probes 86a,b reported by Yao et al. [65]. (d) Diazirine-containing analog of clicked compound 79-80 for labeling of y-secretase, reported by Fuwa et al. [82], (e) Photoreactive peptide vinyl sulfones 88a-c used to probe the 20S proteasome cavity, reported by Geurink et al. [89]...

Due to the complication of alternate pathways involved in the photochemistry of diazo compounds or diazirines, new strategies for carbene generation from non-nitrogenous precursors have been studied. Phenyliodonium ylides" (27) andmethyl-8-chloro-3a,7a-methanoindan-8-carboxylates" (28) are alternative precursors to dicarboethoxycarbene and carbomethoxychlorocarbene, respectively. Photoreactions from these precursors presumably will not be plagued by the excited-state chemistry observed for the diazo compounds and diazirines. 

The most important photoreactions of diazirines are the generation of carbenes and the valence isomerization to linear diazo compounds (Scheme 1). At first glance, these appear to be straightforward processes but under closer scrutiny, several experimental observations introduce complications. 

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