General and Scalable Synthesis of 2-Aryl and 2-Alkyl Pyrimidines via an Electronically Tuned SAr Approach.

An efficient SAr approach for generating a wide array of 2-aryl and 2-alkyl pyrimidines in good to high yields was developed. This methodology does not require precious metal catalysts and is compatible with aryl, heteroaryl, and alkyl magnesium halides as nucleophiles. This process is scalable and performed at room temperature well below the temperature of the competing decomposition of the activated 2--butyl sulfonyl pyrimidine electrophile.

Diastereoselective Fluorocyclopropanation of Chiral Allylic Alcohols Using an α-Fluoroiodomethylzinc Carbenoid.

Chiral fluorocyclopropyl carbinols were synthesized in high diastereoselectivities via a zinc mediated cyclopropanation reaction, using sec-allylic alcohols as simple building blocks. An enantioselective version of this transformation was achieved through in situ formation of chiral allylic zinc sec-alkoxides from the requisite aldehydes using Walsh's protocol.

Chemical diversification of sialic acid glycosides by stereospecific, chemoselective deamination.

Late bloomer: Nitrosation of peracetylated sialic acid glycosides followed by treatment with sodium trifluoroethoxide and then a suitable nucleophile enables the late-stage modification of these glycosides with stereospecific replacement of the acetamido group. This method should enable access to many glycoside derivatives with a minimum of synthetic effort.

Dissecting the influence of oxazolidinones and cyclic carbonates in sialic acid chemistry.

At a moment's notice: Thermal equilibration of 1 and mass spectral analysis of sialyl phosphates suggest that the 4O,5N-oxazolidinone and the 4,5-O-carbonate systems influence the anomeric effect and the mechanisms of sialidation by virtue of their dipole moment in the mean plane of the pyranose ring. The electron-withdrawing effect destabilizes 2 and promotes associative glycosylation mechanisms. TEMPO = 2,2,6,6-tetramethylpiperidine N-oxide.

Practical synthesis of 2-keto-3-deoxy-D-glycero-D-galactononulosonic acid (KDN).

Reaction of propargylmagnesium bromide with 2,3;5,6-di-O-isopropylidene-D-mannonolactone followed by highly stereoselective reduction of the so-formed lactol with sodium borohydride gives a syn-diol from which practical syntheses of 2-keto-3-deoxy-D-glycero-D-galactononulosonic acid (KDN) and various partially protected derivatives have been achieved all of which feature the oxidative unmasking of the α-keto acid moiety from the alkyne.

Stereoselective synthesis of alpha-keto-deoxy-D-glycero-D-galacto-nonulosonic acid glycosides by means of the 4,5-O-carbonate protecting group.

[Image: see text] A 1-adamantyl thioglycoside derivative of KDN, derived from -acetylneuraminic acid, carrying a 3,4--carbonate protecting group is a highy efficient and α-selective KDN donor on activation with NIS and TfOH in dichloromethane and acetonitrile at −78 °C. Glycosylations conducted with this protecting group do not suffer from competing glycal formation. Seven examples are given, including the use of galactose 3- and 6-hydroxy groups.