Loroglossine, a characteristic constituent of orchids, is shown to be bis[4-@-~-g1ucopyranosyloxy)-benzyl]-(2 R, 3 S)-2-isobutyl-tartrate (1). Base catalysed hydrolysis and esterification with diazomethane gave 1 mol-equiv. of dimethyl (+ )-2-isobutyl-erythro-tartrate (( + )-3) and 2 mol-equiv. of a glucoside which after acetylation formed 4 identical with a synthetic sample. The structure of (+ )-3 follows from the synthesis of (5)-3 by osmium tetroxide oxidation of isobutyl-maleic acid anhydride and subsequent esterification. The absolute configuration of (+ )-3 was based on Horeau experiments and NMR. data of the diastereomeric mixture of its esters 15 and 16 and pure 15 with (S)-(+)-and (R)-(-)-a-phenyl-butyric acid, respectively.In einer vorlaufigen Mitteilung [2] haben wir iiber die Konstitution und die absolute Konfiguration von Loroglossin (l), einem charakteristischen Inhaltsstoff zahlreicher Orchideen-Arten, berichtet. Bisher wurde Loroglossin (1) in folgenden Pflanzen (alle Orchidaceae) nachgewiesen: A nacamptis pyramidalis (L.) L.C. RICH. (= Orchis pyramidalis L.) [3], Cephalanthera damasonium (MILL.) DRUCE (= C. grandij7ora (SCOP.) S.F. GRAY) [4], Epipactis atrorubens (HOFFM.) SCHLJLTES [3], E. helleborine (L.) Crantz (= E. lutifoliu (L.) ALL.) [3], E. palustris (L.) Crantz [5] [6], Goodyera repens (L.) R. BR. [7], Gymnadenia conopsea (L.) R. BR. (= Orchis conopsea L.) [2] [3], Limodorum abortivum Sw. [7], Listera ovata (L.) R. BR. [5] [6], Loroglossum hircinum (L.) L.C. RICH. (= Himantoglossum hircinum (L.) SPRENGEL) (81, Ophrys apifera H u h . [4], 0. insectifera L. (= 0. muscifera HLJDS.) [3], 0. sphegodes MILL. (= 0. aranifera HUDS.) [4] [9], Orchis incurnata L. [2], 0. latifolia L. [2] [3] [lo], 0. maculata L. (21 (31 [lo], 0. muscula L. [3] [lo], 0. militaris HUDS. 131 [12], 0. morio L. [3], 0. purpurea HUDS. (= 0. fusca JACQ.) [3], 0. simiu LAMK. [4] [9], 0. ustulata L. [7], Platanthera bifolia (L.) L.C. RICH. (= Orchis bifolia L.) [4], Spiranthes spiralis (L.) CHEVALL. (= S. autumnalis L.C. RICH.) [7].