Chelation between gamma-hydroxy unsaturated nitriles and Grignard reagents promotes an otherwise difficult anionic conjugate addition reaction. The intermediate chelate is readily generated by deprotonation with t-BuMgCl followed by the addition of a second Grignard reagent that triggers an intramolecular conjugate addition. Structurally diverse Grignard reagents add with equal efficiency, providing an intermediate
作者:Fraser F. Fleming、Qunzhao Wang、Zhiyu Zhang、Omar W. Steward
DOI:10.1021/jo0258150
日期:2002.8.1
Grignard and organolithium reagents to gamma-hydroxy-alpha,beta-alkenenitriles promotes efficient conjugateadditions to what are otherwise recalcitrant Michael acceptors. Sequential deprotonation and addition of a modest excess of a second Grignard reagent allows effective conjugate delivery of alkyl groups to cyclic and acyclic alkenenitriles. Mechanistically, conjugateadditions proceed through alkylmagnesium
An efficient transition-metal free C–C bond cleavage/borylation of cycloketone oxime esters has been described. In this reaction, the B2(OH)4 reagent not only served as the boron source but also acted as an electron donor source through formation of a complex with a DMAc-like Lewis base. This complex could be used as an efficient single electron reductant in other ring-opening transformations of cycloketone
Preparation of 2-amino-7-(1-substituted-2-hydroxyethyl)-3,
申请人:Novartis AG
公开号:US06043365A1
公开(公告)日:2000-03-28
The compounds of formula I ##STR1## wherein Ar represents biaryl, carbocyclic or heterocyclic aryl, are prepared, as substantially pure enantiomers, by (a) condensing a compound of the formula ##STR2## as a substantially pure enantiomer, wherein Ar has meaning as defined above and R.sub.6 is on O-protecting group with a lower alkyl ester of formic acid; (b) then condensing the compound so obtained with a compound of the formula ##STR3## wherein R.sub.8 is hydrogen or COOR.sub.3 and R.sub.3 is lower alkyl; (c) then cyclizing the compound so obtained to a compound of the formula ##STR4## as a substantially pure enantiomer; (d) and then condensing the compound so obtained (1) with a carbocyclic aroyl isothiocyanate and treatment of the product so obtained with an alkyl halide followed by anhydrous ammonia; or (2) with cyanamide in acid, optionally followed by treatment with a base.
The invention relates to the 2-amino-7-(1-substituted-2-hydroxyethyl)-3, 5-dihydro-pyrrolo[3,2-d] pyrimidin-4-ones of formula I
and tautomers thereof, wherein Ar represents biaryl, carbocyclic or heterocyclic aryl; pharmaceutically acceptable prodrug ester derivatives; and pharmaceutically acceptable salts thereof, which are particularly useful as potent purine nucleoside phosphorylase (PNP) inhibitors.