The 2- and 3-C-Methyl Derivatives of Methyl 2,3-Dideoxy-α-D-erythro-hex-2-enopyranosid-4-ulose

Abstract

The oxirane rings of carbohydrate 2,3-anhydro sugars are opened stereospecifically by lithium dimethyl cuprate. These reactions go in high yields, without the formation of abberant side products encountered with other organometallic reagents. The alcohols produced are converted via their xanthate esters to olefins in good overall yields. The latter on hydrolysis and oxidation give the title enones.

An approach to the total synthesis of the Prelog–Djerassi lactone

“…A synthesis of the Prelog-Djerassi lactone from the intermediate (4; R = CPh,) has been reported. 2q The C-2 methyl group was introduced by ring opening of the epoxide (6) (according to Fraser-Reid). 6 The epoxide (6) could be prepared in high yield by either of two routes (75% over three steps).…”

“…2q The C-2 methyl group was introduced by ring opening of the epoxide (6) (according to Fraser-Reid). 6 The epoxide (6) could be prepared in high yield by either of two routes (75% over three steps). '** When compound (6) was treated at 0 "C in diethyl ether with lithium dimethylcuprate, formed in situ from methyllithium and copper(1) iodide, two products were isolated, the desired diaxial ring-opened product (7) in 65% yield and the glycal (8) in 9% yield.…”

“…6 The epoxide (6) could be prepared in high yield by either of two routes (75% over three steps). '** When compound (6) was treated at 0 "C in diethyl ether with lithium dimethylcuprate, formed in situ from methyllithium and copper(1) iodide, two products were isolated, the desired diaxial ring-opened product (7) in 65% yield and the glycal (8) in 9% yield. The by-product (8) presumably arises from attack of iodide ion on compound (6) and subsequent elimination.…”

Unusual stereochemistry in the copper-catalysed ring opening of a carbohydrate oxirane with vinylmagnesium bromide

“…"6 In all the cases examined the expected trcms-diaxial ring opening of the oxirane occurred with inversion of configuration.' As part of a projected synthesis of pseudomonic acid C we have examined the nucleophilic opening of the oxirane of 4,6-O-benzylidene-l,5:2,3-dianhydro-~-allitol (1) with various carbon nucleophiles. We now report some observations on the reaction of (1) with various organocuprates and draw attention to the anomolous stereochemistry obtained with vinylmagnesium bromide-CuI.…”

Stereospecific synthesis of (−)-α-multistriatin from D-glucose

“…, y~e l d of the 2-deoxy sugar 4 (7) on treatment with d l m e t h y l l~t h~u~~~ cuprate The alcohol 4 L ! as converted illto the colrespondlng xanthate 5 (7) In 94c0 y~eld and the resulting xanthate u a s deouygenated u ~t h tr~-i?-but) Istannane (8) to y~eld compound 6, [,lDZ8 +82 7 (142 mg ml, ether), rnp 70-72 C. in 90' ; y~eld from 5 The benzyl~dene group 111 6 was hydlolyzed ( 7 ) Conlpoulld 18 u a s also ' 1 crqstall~ne s o l~d , mp 153-154°C. [alD2' +45 4 (74 iiig ml, cliloroforrn)…”