Pivaloyl deriv

For 2-acetylpyrrole, 2-acetylthiophene, and 2-acetylselenophene, the presence in solution of the preferred X,0-cis conformation, planar or nearly planar, is widely accepted (81RCR336). Low-temperature NMR measurements C C) of 2-CO-alkyl derivatives of thiophene have provided evidence (85JCS(P2)1839) that the S,0-trans conformer, if present, is not detectable (<5%), at least in CHF2CI solution. The LIS method at room temperature gave (85JCS(P2)1839) 15% of this conformer in the case of the COMe derivative and 25% for CO-i-Pr. Better agreement between experimental and calculated LIS values was obtained (85JCS(P2)1839) when planar structures were assumed even for the conformers of the 2-pivaloyl derivative. 

The results of dipole moment and Kerr constant elaboration indicated (84JST(116)377) that in the 2-pivaloyl derivatives of furan and pyrrole the... 

Application of these metalation conditions to a more diverse series of pyrimidines 384, including a 4-A-pivaloyl derivative, with intervention of a TMSC1 quench leads to 5-TMS products 385 in low yields (Scheme 117). 

A recent procedure which utilizes the pivaloyl derivative of o-bromoaniline as one of the fragments is also a type llac approach. The compound is converted to its dilithio derivative at -78 °C. Reaction with a-halo ketones then affords indole hydrates by N-alkylation and reaction of the o-lithiated position with the carbonyl group dehydration subsequently yields indoles (equation 108) (81TL1475). The (V-trifluoroacetyl and N-t-butoxycarbonyl derivatives of o-bromoaniline exhibit similar reactivity. 

Photochemical deoxygenation of the 3-0-pivaloyl derivative 126 was also used for the preparation of the methyl ascaryloside (119) (Scheme 36).205... 

Topaquinone (TPQ), the oxidized form of 2,4,5-trihydroxyphenylalanine (TOPA), is the cofactor of copper-containing amine oxidases. The following model compounds have been prepared in order to understand the catalytic function of TPQ the jV-pivaloyl derivative of 6-hydroxydopamine in aqueous acetonitrile [38] topaquinone hydantoin and a series of 2-hydroxy-5-alkyl-l,4-benzoquinones in anhydrous acetonitrile (o- as well as />-quinones) [39] 2-hydroxy-5-methy 1-1,4-benzoquinone in aqueous system [40] and 2,5-dihydroxy-1,4-benzoquinone [41]. Reaction of model compounds with 3-pyrrolines revealed why copper-quinopro-tein amine oxidases cannot oxidize a secondary N [42], The studies clearly showed that certain model compounds do not require the presence of Cu for benzylamine oxidation whereas TPQ does [38,40] the aminotransferase mechanism proceeds via the -quinone form [39] the 470 nm band can be ascribed to a 71-71 transition of TPQ in />-quinonic form with the C-4 hydroxyl ionized but hydrogen bonded to some residue [40] hydrazines attack at the C-5 carbonyl, forming an adduct in the azo form [41], Electrochemical characterization has been carried out for free TPQ [43],... 

The absolute stereochemistry at C-2 of acyclic 1,2,4,-triol systems can be determined by difference CD spectroscopy. The method has been applied to 1,2,4-tri-O-benzoyl- and 2,4-di-O-benzoyl-l-O-pivaloyl-derivatives. ... 

The tetra-O-pivaloyl derivative of P-D-galactopyranosylamine was employed as a chiral auxiliary in the synthesis of (—)-lasubine II (1342) by... 

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