A stereoselective total synthesis of the HCl salts of mycestericins F, G and ent-F

The total synthesis of the HCl salts of two natural sphingolipid-related amino acid derivatives, mycestericins F 4 and G 5 together with unnatural ent-4·HCl, starting from the four crucial scaffolds 6, 8, 9, 11 and utilizing the Wittig reaction to build the C20 backbone, has been achieved. The selection of selective functional group interconversions accompanied with suitable protection–deprotection protocols in the coupling products 20 and 34 gave the desired structures.

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Ethyl (4S)-4-{(4′R)-3′-benzyl-4′-[(1″S)-1″,2″-dihydroxyethyl]-2′-oxooxazolidin-4′-yl}-4-hydroxybutanoateC18H25NO7[α]D20=-23.1 (c 0.76, CHCl3)Source of chirality: d-xyloseAbsolute configuration: (1″S,4′R,4S)

3-[(5′R,6′S)-1′-Benzyl-8′,8′-dimethyl-2′-oxo-3′,7′,9′-trioxa-1′-azaspiro[4′.5′]decan-6′-yl]propanalC18H23NO5[α]D20=+61.6 (c 0.35, CHCl3)Source of chirality: d-xyloseAbsolute configuration: (5′R,6′S)

tert-Butyl {(4S,5S)-4-[10′-(2″-hexyl-1″,3″-dioxolan-2″-yl)decyl]-5-(hydroxymethyl)-2,2-dimethyl-1,3-dioxan-5-yl}carbamateC31H59NO7[α]D20=+22.2 (c 0.52, CHCl3)Source of chirality: d-xyloseAbsolute configuration: (4S,5S)

(2S,3S)-2-Amino-3-hydroxy-2-(hydroxymethyl)-14-oxoicosanoic acid hydrochlorideC21H42ClNO5[α]D20=-3.5 (c 0.18, CH3OH)Source of chirality: d-xyloseAbsolute configuration: (2S,3S)

(2R,3R)-2-Amino-3-hydroxy-2-(hydroxymethyl)-14-oxoicosanoic acid hydrochlorideC21H42ClNO5[α]D20=+4.4 (c 0.16, CH3OH)Source of chirality: d-xyloseAbsolute configuration: (2R,3R)

(4S)-4-[(1′R)-1′-Hydroxy-12′-oxooctadecyl]-4-(hydroxymethyl)oxazolidin-2-oneC22H40NO5[α]D20=+9.3 (c 0.54, CHCl3)Source of chirality: d-xyloseAbsolute configuration: (1′R,4S)

(2S,3R)-2-Amino-3-hydroxy-2-(hydroxymethyl)-14-oxoicosanoic acid hydrochlorideC21H42ClNO5[α]D20=+10.5 (c 0.24, CH3OH)Source of chirality: d-xyloseAbsolute configuration: (2S,3R)