Synthesis of 20S-protopanaxadiol β-D-galactopyranosides
20S-Protopanaxadiol (3β,12β,20S-trihydroxydammar-24-ene) 3-, 12-, and 20-O-β-D-galactopyranosides were synthesized for the first time. Condensation of 12β-acetoxy-3β,20S-dihydroxydammar-24-ene (1) and 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosylbromide (α-acetobromogalactose) (2) under Koenigs–Knorr conditions with subsequent removal of the protecting groups resulted in regio- and stereoselective formation of 20S-protopanaxadiol 3-O-β-D-galactopyranoside, an analog of the natural ginsenoside Rh2. Glycosylation of 12β,20S-dihydroxydammar-24-en-3-one (5) by 2 with subsequent treatment of the reaction products with NaBH4 in isopropanol and deacetylation with NaOMe gave 20S-protopanaxadiol 12- and 20-O-β-Dgalactopyranosides.
Saponins of the Leaves of Panax ginseng C. A. MEYER
From the leaves of Panax ginseng C. A. MEYER, six saponins I, II, III, IV, V, and VI were isolated. Saponins IV, V, and VI were proved to be identical, respectively with ginsenosides-Rg1, -Re, and-Rd, all of which have already been isolated from Ginseng roots. The high contents of these saponins in the leaves indicate significance of the leaves as the source of the dammarane-type saponins and their sapogenins. New saponins I, II, and III designated as ginsenosides-F1, -F2, and-F3 were established to be formulated as 20-O-β-glucopyranosyl-20 (S)-protopanaxatriol, 3, 20-di-O-β-glucopyranosyl-20 (S)-protopanaxadiol, and 20-O-(α-arabinopyranosyl-(1→6)-β-glucopyranosyl)-20 (S)-protopanaxatriol, respectively, on the basis of the enzymatic hydrolysis, mass spectra of their acetates, nuclear magnetic resonance, and chemical evidences.
CAUSES OF FLUCTUATIONS IN R&D EXPENDITURES A QUANTITATIVE ANALYSIS
Introduction 124 The stylised facts of R&D in OECD economies 124 The determinants of business R&D expenditures 127 Modelling R&D expenditures 130 Conclusion 135 Bibliography 137 Annex: The model 138