Using photocaging for fast time-resolved structural biology studies.

Careful selection of photocaging approaches is critical to achieve fast and well synchronized reaction initiation and perform successful time-resolved structural biology experiments. This review summarizes the best characterized and most relevant photocaging groups previously described in the literature. It also provides a walkthrough of the essential factors to consider in designing a suitable photocaged molecule to address specific biological questions, focusing on photocaging groups with well characterized spectroscopic properties.

Regioselective 1,4-Conjugate Addition of Grignard Reagents to α,β-γ,δ-Dienones and α,β-γ,δ-Dienyl Thiol Esters.

Alkyl Grignard reagents (Et, Bu, Pr, cyclohexyl), with the exception of BuMgCl, undergo exclusive or exceptionally highly regioselective 1,4-addition reactions to α,β-γ,δ-unsaturated ketones, while aryl and heteroaryl Grignard reagents give mixed results ranging from exclusive 1,4-addition (1-naphthyl, 2-N-methylpyrrolyl) to regioselective 1,2-addition (2-furyl, 2:1). All alkyl, aryl, and heteroaryl Grignard reagents examined gave exclusive 1,4-addition reactions with α,β-γ,δ-unsaturated thiol esters, with the exception of BuMgCl, which gave an 80:20 mixture of 1,4:1,6-addition products. The high chemo- and regioselectivity observed for these reactions is attributed to a radical or radical-like pathway for the alkyl Grignard reagents and possibly a carbanion pathway for aryl Grignard reagents.