GLYCOSYLATED INDOLOCARBAZOLE SYNTHESIS
Tertiary alcohols containing the structural features illustrated in 3 or 4 (Scheme I) are prepared by reacting at least one diazo carbonyl compound, (e.g., 1 in Scheme I) and at least one allylic alcohol (e.g., 2 in Scheme I) in a coupling reaction run under conditions that produce carbene or carbenoid intermediates from the diazo-containing substrate such as transition metal catalysis or either thermal or photochemical decomposition. In some preferred embodiments, Rh2(OAc)4 is employed to catalyze the coupling reaction. In Scheme I R represents a substituent comprised of any number and combination of the elements H, C, N, S, Si, O, Cl, Br, I, and F. Indolocarbazoles (e.g., 7 in Scheme II) are prepared by coupling of diazo carbonyl compounds (e.g., 5 Scheme II) and biindoles (e.g., 6 in Scheme II). Indolocarbazoles are furanosylated (e.g., 7 in Scheme II) with acetals (e.g., 8 in Scheme II) or their open chain congeners (e.g., 9 in Scheme II) under conditions known to promote acetal exchange or formation, such as protic or Lewis acids. Furanosylated indolocarbazoles (e.g., 10 in Scheme II) are also prepared via ring contraction of pyranosylated indolocarbazoles (e.g., 11 in Scheme II) under conditions know to effect oxidation and benzylic acid type rearrangements, and pyranosylated indolocarbazoles (e.g., 11 in Scheme II) are prepared via ring expansion of the furanosylated congeners (e.g., 10 in Scheme II).