Mild and Rapid Method for the Generation of <i>ortho</i>-(Naphtho)quinone Methide Intermediates

Mild and Rapid Method for the Generation of <i>ortho</i>-(Naphtho)quinone Methide Intermediate

Mild and Rapid Method for the Generation of <i>ortho</i>-(Naphtho)quinone Methide Intermediates

A new mild method has been devised for generating <i>o</i>-(naphtho)quinone methides via fluoride-induced desilylation of silyl derivatives of <i>o</i>-hydroxybenzyl(or 1-naphthylmethyl) nitrate. The reactive <i>o</i>-(naphtho)quinone methide intermediates were trapped by C, O, N, and S nucleophiles and underwent “inverse electron-demand” hetero-Diels–Alder reaction with dienophiles to give stable adducts. The method has useful potential application in natural product synthesis and drug research

Organocatalytic Domino Reaction of Cyanosulfones: Access to Complex Cyclohexane Systems with Quaternary Carbon Centers

When ε-nitro-α,β-unsaturated esters are added to conjugated cyanosulfones in the presence of a bifunctional thiourea catalyst, a highly stereoselective domino reaction occurs to generate complex cyclohexanes with up to four stereogenic centers, one of which is quaternary in nature. Therefore, it is demonstrated that, like nitro compounds, sulfones can undergo an asymmetric intramolecular conjugate addition to α,β-unsaturated esters in the presence of a bifunctional organocatalyst

Oligonucleotides used.

<p>Oligonucleotides used.</p

Excess enzyme does not lead to 5

<p> <b>hmC deamination.</b> (<b>A</b>) The ssDNA oligonucleotide deamination assay was performed for 15 min at 37° C with increasing amounts of enzyme (0–11.5 pmol AID) and analysed as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043279#pone-0043279-g001" target="_blank">Figure 1</a>. Labels are as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043279#pone-0043279-g001" target="_blank">Figure 1</a>. Triangle indicates a nonspecific cleavage product excluded from quantitation. Each substrate oligo was tested at least 3 times, representative gels are shown. (<b>B</b>) The gels were quantitated, and analysed as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043279#pone-0043279-g001" target="_blank">Figure 1</a> F, with the resulting average 3′ target to 5′target ratio plotted against the inverse vdWv.</p

In vitro deamination of substrates with unmodified (5

<p>′ <b>AGC) and C5 modified cytosines (3</b>′ <b>AGC) by AID.</b> (<b>A</b>) MtMig recognizes only deaminated products of cytosine or cytosine derivatives (U, T, 5FU, 5 hmU) opposite a dG in a double stranded context. Absence of MtMig or cytosine-derivatives did not lead to product formation. (<b>B</b>) Name, vdWv of the C5, and structure of deoxynucleoside derivatives used in the assays are shown on the left of the gels. Oligos were incubated with 1.8 pmol AID for the indicated times and migration of substrate and products are indicated on the right of gels. Bases in brackets are those that have been deaminated by AID and removed by MtMig prior to cleavage. Triangle indicates a nonspecific cleavage product excluded from quantitation. One representative of three independent experiments is shown. (<b>C</b>)<b> </b>Quantitation of the 3′ AGC deamination assays shown in B: 3′ AG-C -(top); 3′ AG-5FC - (middle); 3′ AG-5 mC - (bottom). Although the scales are different on the y-axis, the kinetic profiles do not significantly deviate from one another. (<b>D</b>) Quantitation of the 5′ AGC deamination of (B), indicating that the various modification at the 3′ AGC do not alter the activity of AID towards the 5′ AGC. (<b>E</b>) The average product formation in the linear phase (5 – 30 min) of the reaction from (C) was converted to pmol [P]/ pmol [E]/ min. The values were then plotted against the inverse of the vdWv from (B) for each derivative. The line of best fit and its r² value are shown. The position of the theoretical value of the CH₂OH side chain is indicated on the x-axis by an arrow. (<b>F</b>) The vdWv plotted against the average ratio of the 3′ target to that of the 5′ target for each time point. Analogous to (E), the line of best fit showed extremely high correlation (r² = 0.98) and intersected the x-axis (1/25.96) at a size that is smaller than that of 5 hmC (i.e. a larger value of the inverted vdWv).</p