Alkoxyallene‐Based De Novo Synthesis of Rare Deoxy Sugars: New Routes to L‐Cymarose, L‐Sarmentose, L‐Diginose and L‐Oleandrose

Abstract

Starting from lithiated methoxyallene and lactaldehyde derivatives, the four rare 2,6-dideoxy-hexoses L-cymarose, Lsarmentose, L-diginose and L-oleandrose were synthesized in a stereodivergent fashion. Key steps towards these four target monosaccharides were the oxidative ring openings of allene-derived 2,5-dihydrofurans, diastereoselective carbonyl

Synthesis of the bis(cyclohexenone) core of (−)-lomaiviticin A

“…29 Several syntheses of oleandrose have been reported. 18,[30][31][32][33][34][35][36][37][38] We developed a new and practical chiral pool approach. Beginning with the commercial reagent 3,4-di-O-acetyl-6deoxy-L-glucal (8; Scheme 2), site-selective C4 deacetylation and benzylation was achieved under biphasic conditions (benzyl bromide, aqueous sodium hydroxide, dichloromethane).…”

Alkoxyallenes as building blocks for organic synthesis

“…22 Dihydrofurans of type 66 are prone to undergo an oxidative ring-opening delivering enediones 67 (Scheme 23) which have been used for the synthesis of the rare carbohydrate L-Cymarose and its stereoisomers starting from L-lactic acid as a chiral pool compound. 23 Other enediones 68 bearing a CH group next to the internal carbonyl group could be converted into cyclopentenone derivatives 69 (Scheme 24). 24 In the course of these studies, it was discovered that goldcatalysis -well known for other allene cyclisations 25 -smoothly converts many of the primary addition products 47 (Scheme 19), obtained from lithiated alkoxyallenes and carbonyl compounds into the corresponding dihydrofuran derivatives 54.…”

Synthesis of the Fully Glycosylated Cyclohexenone Core of Lomaiviticin A

“…As detailed in Scheme , the bis(glycoside) 6 was prepared by sequential glycosylation reactions of the diol 8 with suitably protected N , N -dimethyl- d -pyrrolosamine and l -oleandrose sugar donors. Both d - and l -oleandrose are well-known, and several synthetic routes to each have been described . The 2-deoxyaminosugar N , N -dimethyl- d -pyrrolosamine is less common among natural products, and preparation of pyrrolosamine, bearing the fully alkylated tertiary amine function, has not yet been reported. , …”