Short Synthesis of Enantiopure C₂-Symmetric 1,2:4,5-Diepoxypentane and “Pseudo”-C₂-Symmetric 3-Azido-1,2:4,5-diepoxypentane from Arabitol

Abstract

On the basis of our previously described selective protection of arabitol as its 1,2:4,5-bis-pentylidene acetal 5, we report a straightforward synthesis of the novel "pseudo"-C(2)-symmetric 3-azido-1,2:4,5-diepoxypentane building block 4 in 6 steps from arabitol. Using a similar synthetic route, an improved synthesis of the C(2)-symmetrical 1,2:4,5-bis-epoxypentane building block 1 is described, also in 6 steps from arabitol. Both enantiomers of 1 and 4 are accessible, and all reactions involved are easily amenable for large-scale synthesis.

Parallel Synthesis and Biological Evaluation of Destruxin E Analogs Modified with a Side Chain in the α‐Hydroxycarboxylic Acid Moiety

“…Alkenylation of ( R )‐ 13 using vinylcuprate provided alkene 15 that was converted to a 1:1 diastereomeric mixture of epoxide 16 in 97 % yield via epoxidation with m ‐CPBA and by protecting the resulting alcohol with a TBS group. A hydrolytic kinetic resolution of the epoxide moiety in 16 using the ( S, S )‐Salen‐Co complex resulted in the formation of the diol (2 R , 4 S )‐ 17 (48 % yield) and the remaining epoxide (2 S , 4 S )‐ 16a (41 % yield) as a single diastereomer. The obtained diol (2 R , 4 S )‐ 17 was converted via two steps into the corresponding epoxide (2 S , 4 R )‐ 16b in 72 % yield.…”

Synthesis of the C19-C26 Segment of Amphidinolide H2

“…The secondary alcohol was liberated using HF·pyridine and subsequently transformed into the imidazolyl thiocarbonyl derivative 15. 17 After deoxygenation using tin-free conditions, 18 …”

“…The secondary alcohol was liberated using HF•pyridine and subsequently transformed into the imidazolyl thiocarbonyl derivative 15. 17 After deoxygenation using tin-free conditions, 18 Weinreb amide 16 was synthesized from the corresponding carboxylic acid. Finally, the methyl ketone 8 was obtained upon treatment with MeMgCl (Scheme 4).…”

Enantioselective Synthesis and Selective Monofunctionalization of (4R,6R)-4,6- Dihydroxy-2,8-dioxabicyclo[3.3.0]octane

“…To this end, selective protection of arabitol under kinetic conditions to the 1,2:4,5-diacetal 8 9 was followed by conversion to the triflate 9 and mesylate 10 in high yield (100% and 93%). 10 However, reaction of 9 with NaCN in DMF at room temperature only returned elimination products 12 and 13 in 80% combined yield. The formation of the olefin isomers arises from unselective cyanide attack of the diastereotopic β-protons.…”