A de novo approach for the rapid construction of orthogonally protected Land D-deoxysugars and analogues is described. A novel and robust silicon-acetal undergoes Prins cyclisations with a series of homoallylic alcohols in high yield and excellent stereocontrol. Modified Tamao–Fleming oxidation of the resulting silyltetrahydropyrans gives direct access to deoxyglycoside analogues and the approa...

Phenacylmalononitrile 1 reacts with dimethylformamide dimethyl acetal to yield an enaminone which could be readily converted into a pyrrole or an aminopyridazine by treating with ammonium acetate and hydrazine hydrate, respectively. Compound 1 reacted with hydrazine hydrate in ethanol at room temperature to yield the dihydropyridazine 9 as a single product. In refluxing ethanol this product fur...

The first total syntheses of (-)-trichorabdal A and (-)-longikaurin E are reported. A unified synthetic strategy is employed that relies on a Pd-mediated oxidative cyclization of a silyl ketene acetal to generate an all-carbon quaternary center and build the bicyclo[3.2.1]octane framework. These studies, taken together with our previous synthesis of (-)-maoecrystal Z, demonstrate that three arc...

The oxidative cleavage of aliphatic acetals of normal aliphatic aldehydes and substituted aliphatic aldehydes with aliphatic as well as aromatic alcohols with lead tetra acetate in acetic acid, aqueous acetic acid and in acetic acid-benzene medium is first order each in [oxidant] and [acetal] and yields the corresponding esters as the main product The rate of oxidation depends upon the dielectr...

Difluoroalkenylzinc reagents prepared from 1-(2'-methoxy-ethoxymethoxy)-2,2,2-trifluoroethane and 1-(N,N-diethylcarbamoyloxy)-2,2,2-trifluoroethane at ice bath temperatures underwent Negishi coupling with a range of aryl halides in a convenient one pot procedure. While significant differences between the enol acetal and carbamate reagents were revealed, the Negishi protocol compared very favour...

Recently, a series of alkyl 2-substituted 3-(dimethylamino)prop-2-enoates and related enaminones have been prepared as versatile reagents for the preparation of various dehydroalanine derivatives, heterocyclic systems, and natural product analogues. In extension, chiral cyclic enamino lactams and lactones, derived from α-amino acids and (+)-camphor have been used in the synthesis of functionali...

Many natural products of biological interest contain [6,5]- and [6,6]-spiroketal moieties that can adopt various configurations, benefiting or not from anomeric conformation stabilizing effects. The spiroketal fragments are often important for the biological activity of the compounds containing them. Most stable spiroketal stereoisomers, including those benefiting from conformational anomeric e...

The determination of the content and distribution of the higher aliphatic aldehydes in tissues have depended on modifications (l-3) of the Feulgen procedure which employs the fuchsin-sulfurous acid reagent. However, several observers, notably Ehrlich et al. (2), have commented on two features of this procedure which make its application difficult: The Schiff reagent reacts with a wide variety o...