Gwydion H Churchill

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We propose models for describing replacement rate variation in genes and proteins, in which the profile of relative replacement rates along the length of a given sequence is defined as a function of the site number. We consider here two types of functions, one derived from the cosine Fourier series, and the other from discrete wavelet transforms. The number(More)
A simulation study was used to examine the consequences of karyotypic rearrangements on molecular genetic map construction. Two groups of 50 datasets were created for F2 populations segregating for a reciprocal translocation of chromosomal segments or a reciprocal translocation and inversion. Multiple attempts were made to construct maps for each dataset(More)
A general route to prepare substituted, saturated five-membered heterocycles has been developed. The application of a wide range of starting materials to the osmium-catalyzed oxidative cyclization reaction is described. Diols, hydroxy-amides, hydroxy-sulfonamides, and carbamates all cyclize in moderate to excellent yields to give cis-tetrahydrofurans and(More)
A chiral NHC catalyzes the asymmetric formal [2 + 2] cycloaddition of alkylarylketenes with both electron-deficient benzaldehydes and 2- and 4-pyridinecarboxaldehydes to generate stereodefined β-lactones. In the benzaldehyde series, optimal product diastereo- and enantiocontrol is observed using 2-nitrobenzaldehyde (up to 93:7 dr (syn:anti) and 93% ee).(More)
Stereo- and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N-heterocyclic carbenes, giving selectively either β-lactones (up to 88:12 dr, up to 94 % ee) or α-chloroesters (up to 94 % ee). Either 2-arylsubstitution or an α-branched iPr alkyl substituent within the(More)
N-heterocyclic carbene (NHC)-catalyzed redox asymmetric hetero-Diels-Alder reactions of α-aroyloxyaldehydes with β-trifluoromethyl enones generates synthetically useful dihydropyranones containing a stereogenic trifluoromethyl substituent in good yields (up to 81%) and excellent diastereoselectivity and enantioselectivity (up to >95:5 dr and >99% ee). The(More)
Rhodium complexes based upon chiral sulfinamide-alkene, TADDOL-derived phosphoramidite, or diene ligands catalyze cyclizations of arylboron compounds onto ketones, generating a variety of products containing five-, six-, or seven-membered rings with good yields and high enantioselectivities.
In model studies towards the quaternary centre at the heart of diazonamide A (early structure 2; revised structure 1), cyclisations of the alkene-substituted iodoaryls 4, 13, 18 and 23, under Heck reaction conditions, were shown to lead to the corresponding benzodihydrofuran 5, benzofuranone 14 and the oxindoles 19 and 24 respectively, in 50-80% yield.(More)
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