Total Synthesis of l-Biopterin from l-Tartaric Acid via 5-Deoxy-l-arabinose

Highly α-selective hydrolysis of α,β-epoxyalcohols using tetrabutylammonium fluoride

We report a simple method for the highly regio- and stereoselective hydrolysis of α,β-epoxyalcohols. Treatment of enantiopure epoxyalcohols derived from Sharpless epoxidation with TBAF/H(2)O resulted in exclusive ring opening at the normally disfavored α-position, providing access to arabino- or lyxo-configured triols with full preservation of stereochemical purity. The method was applied in syntheses of 5-deoxy-l-arabinose (26) and a family of bicyclic acetals based on the insect pheromone hydroxybrevicomin (4).

Studies on the generation of enolate anions from butane-2,3-diacetal protected glycolic acid derivatives and subsequent highly diastereoselective coupling reactions with aldehydes and acid chlorides

Highly diastereoselective coupling reactions of enolates derived from butane-2,3-diacetal protected glycolic acids 1 and 2 and their alkylated derivatives with aldehydes are reported together with their efficient acid-catalysed deprotection to yield enantiopure anti-2,3-dihydroxyesters. A procedure to provide the corresponding syn-2,3-dihydroxyesters is also described in two cases, proceeding via an acylation-reduction sequence. An usual double addition reaction of butane-2,3-diacetal protected glycolic acid to small aliphatic acid chlorides provides a synthetically useful, densely-functionalised lactone after acidic deprotection.

Highly diastereoselective lithium enolate aldol reactions of butane-2,3-diacetal desymmetrized glycolic acid and deprotection to enantiopure anti-2,3-dihydroxy esters

[reaction--see text] The butane-2,3-diacetal (BDA) desymmetrized glycolic acid building block 1 undergoes efficient and highly diastereoselective lithium enolate aldol reactions with both aromatic and aliphatic aldehydes to afford, after an acidic methanolysis deprotection step, the enantiopure anti-2,3-dihydroxy esters in good yield.