New photolabile phosphate protecting group

Baldwin, Jack E.; McConnaughie, Adrian W.; Moloney, Mark G.; Pratt, Andrew J.; Shin, Sung Bo

doi:10.1016/s0040-4020(01)87875-3

Cited by 57 publications

(39 citation statements)

References 22 publications

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“…1) (1). We have used the DMB group to protect phosphates (2), carbamates (3), and carbonates (4), as have other workers (5)(6)(7). This study focuses on the mechanism by which the DMB group is photochemically deprotected.…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Studies on the Photochemical Deprotection of 3′,5′‐Dimethoxybenzoin Esters

Pirrung

Zhang

et al. 2006

Photochem & Photobiology

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Several mechanistic alternatives proposed for the photochemical deprotection of dimethoxybenzoin esters are presented. Both experimental and theoretical evidence suggest the mechanism is heterolysis of the singlet excited state to form a carboxylate and the alpha-ketocation. The alpha-ketocation has been observed by transient spectroscopy. We propose the alpha-ketocation undergoes electrocyclization to an intermediate with extended conjugation, whose deprotonation gives the observed benzofuran product. A Brønsted study of the rates of benzofuran formation with dimethoxybenzoin esters derived from acids of varying pKa shows the rate is independent of the basicity of the leaving group. In this multistep reaction, benzofuran formation by a final deprotonation is slower than alpha-ketocation generation.

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Section: Introductionmentioning

confidence: 99%

“…1) (1). We have used the DMB group to protect phosphates (2), carbamates (3), and carbonates (4), as have other workers (5–7).…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Studies on the Photochemical Deprotection of 3′,5′‐Dimethoxybenzoin Esters

Pirrung

Zhang

et al. 2006

Photochem & Photobiology

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“…With unambiguous syntheses of unsymmetrical benzoin phosphates in hand, we gave further consideration to the properties reported by Baldwin et a1. 2 for the phosphate 23b.…”

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confidence: 99%

Synthetic, mechanistic and photochemical studies of phosphate esters of substituted benzoins

Corrie¹,

Trentham²

1992

J. Chem. Soc., Perkin Trans. 1

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“…c N/A = not available. d Inorganic phosphate released in H 2 O ([ 56 ]), e When internal return is included. f In MeOH, g nr = no reaction (leaving group was acetate).…”

Section: Discussionmentioning

confidence: 99%

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

Senadheera¹,

Yousef²,

Givens³

2014

Beilstein J. Org. Chem.

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SummaryWe have developed a new photoremovable protecting group for caging phosphates in the near UV. Diethyl 2-(4-hydroxy-1-naphthyl)-2-oxoethyl phosphate (14a) quantitatively releases diethyl phosphate upon irradiation in aq MeOH or aq MeCN at 350 nm, with quantum efficiencies ranging from 0.021 to 0.067 depending on the solvent composition. The deprotection reactions originate from the triplet excited state, are robust under ambient conditions and can be carried on to 100% conversion. Similar results were found with diethyl 2-(4-methoxy-1-naphthyl)-2-oxoethyl phosphate (14b), although it was significantly less efficient compared with 14a. A key step in the deprotection reaction in aq MeOH is considered to be a Favorskii rearrangement of the naphthyl ketone motif of 14a,b to naphthylacetate esters 25 and 26. Disruption of the ketone-naphthyl ring conjugation significantly shifts the photoproduct absorption away from the effective incident wavelength for decaging of 14, driving the reaction to completion. The Favorskii rearrangement does not occur in aqueous acetonitrile although diethyl phosphate is released. Other substitution patterns on the naphthyl or quinolin-5-yl core, such as the 2,6-naphthyl 10 or 8-benzyloxyquinolin-5-yl 24 platforms, also do not rearrange by aryl migration upon photolysis and, therefore, do not proceed to completion. The 2,6-naphthyl ketone platform instead remains intact whereas the quinolin-5-yl ketone fragments to a much more complex, highly absorbing reaction mixture that competes for the incident light.

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New photolabile phosphate protecting group

Cited by 57 publications

References 22 publications

Mechanistic Studies on the Photochemical Deprotection of 3′,5′‐Dimethoxybenzoin Esters

Mechanistic Studies on the Photochemical Deprotection of 3′,5′‐Dimethoxybenzoin Esters

Synthetic, mechanistic and photochemical studies of phosphate esters of substituted benzoins

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

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