Of tjipanazole

Comparison of the H-NMR spectrum of tjipanazole G1 (363) with that of tjipanazole Cl (362) indicated the absence of a chlorine atom at C-3 of the aglycon. This was also clear from the H-NMR spectrum by the presence of an additional, mutually ortho-coupled (/=8.4Hz), triplet proton signal at S 7.22, assignable to the C-3 proton. Based on these spectral data and the close structural similarity to tjipanazole Cl (362), the structure 363 was assigned to tjipanazole G1 (329) (Scheme 2.94). 

Comparison of the H-NMR spectrum of tjipanazole G2 (366) with that of tjipanazole G1 (363) showed the presence of a similar structure, except for the difference in the configuration of the 2 -methyl group of the sugar moiety, showing... 

The H-NMR spectrum of tjipanazole FI (371) was very similar to that of tjipanazole Cl (362) (see Scheme 2.94), except for the nature of the sugar unit... 

Gilbert and Van Vranken described the synthesis of tjipanazole F2 (372) by introduction of the halide and the glycosidic substituent at the heterocyclic skeleton without the use of protecting groups and with complete control of regioselectivity... 

In the following year, this method was also applied to the total synthesis of tjipanazole FI (371) (784). For this synthesis, the required bisindole 1444 was obtained starting from 5-chloroindole (1440) in three steps and 47% overall yield. Acylation of 1440 with oxalyl chloride led to the glyoxylic acid chloride 1441. Transmetalation of indolylmagnesium bromide with zinc chloride, followed by addition of the acid chloride, provided the ot-diketone 1443. Exhaustive reduction of 1443 with lithium aluminum hydride (LiAlFl4) afforded the corresponding bisindolylethane 1444. Executing a similar reaction sequence as shown for the synthesis of tjipanazole F2 (372) (see Scheme 5.243), the chloroindoline (+ )-1445 was transformed to tjipanazole FI (371) in two steps and 50% overall yield (784) (Scheme 5.244). 

The same authors also reported the total synthesis of tjipanazole B (369) in 66% overall yield, in two steps, by reacting tjipanazole D (359) with a-D-xylopyranosyl chloride (1503) in a biphasic mixture of MTBE and 45% aqueous KOH and Aliquat 336, followed by hydrogenation with Pd(OH)2 (796). Similarly, reaction of tjipanazole D (359) with a-D-glycopyranosyl chloride (1504) led to tjipanazole E (370) in two steps and 77% overall yield (796) (Scheme 5.257). 

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