Total synthesis of illicidione A and illihendione A

Acylphloroglucinol Derivatives from the South African Helichrysum niveum and Their Biological Activities

“…Other 2D spectra thereby supported the structure of 3 . The absolute configuration at C-3 could not be ascertained directly from the data obtained however, the comparison of the measured specific rotation value ([α]D20 +1.8, ( c 0.04 MeOH)] of 3 with the reported value [reported [α]D20 −1.2 (c 0.029, MeOH) of similar structure containing “identical stereo centre” and similar coupling constant values of H-3 and H-4 [19] indicated 3 S isomer of 3 . Accordingly, the structure of 3 was established as 8-(2-methyl-1-propanone)-3 S ,5,7-trihydroxyl-2,2-dimethylchromane (helinivene C).…”

Bispericyclic Diels–Alder Dimerization of ortho‐Quinols in Natural Product (Bio)Synthesis: Bioinspired Chemical 6‐Step Synthesis of (+)‐Maytenone

“…This enigmatic search has kept organic chemists busy for decades since Wessely's pioneering work on ortho ‐quinol acetates sixty years ago [12] . Over the years, several chemical methods relying on the use of, inter alia, lead(IV)‐, selenium(IV)‐, iodine(III)‐, iodine(V)‐, iodine(VII)‐, and copper(II)‐based reagents have been developed to prepare ortho ‐quinols in either racemic or stereocontrolled formats, [13] and their self‐cyclodimerizing variants were successfully utilized in the chemical synthesis of a number of natural products, including biscarvacrol ( 1 ), [11a, 14] aquaticol ( 2 ), [14b, 15] bacchopetiolone ( 3 ), [16] grandifloracin ( 6 ), [8h, 11a, 17] illihendione A ( 7 ) [18] and bisorbicillinol ( 8 ) [19] (Figure 1). Our own work on (chiral) iodine(V)‐mediated hydroxylative phenol dearomatization (HPD) reactions drove us to accomplish several of these “biomimetic” syntheses, [11a, 14c, 15, 16] and hence to investigate what makes the behavior of those ortho ‐quinols so special in their [4+2] cyclodimerization.…”

Enantioselective Total Synthesis and Assignment of the Absolute Configuration of the Furo[3,2-a]carbazole Alkaloid Furoclausine-B

“…With the phenol 8 , we studied the enantioselective epoxidation using the fructose-derived chiral Shi catalysts (Figure , Scheme ). A sequence of enantioselective epoxidation and intramolecular nucleophilic epoxide opening was successfully applied to similar compounds by Hamada and co-workers as well as by other groups. − The Shi catalyst 13 is readily available from l -fructose. , However, direct epoxidation of 8 using catalyst 13 followed by an in situ 5- exo -tet ring closure provided the dihydrobenzofuran 15 in only poor yield and with low enantiomeric excess (10.5% ee). Obviously, a protection of the hydroxy group was required, and thus, the phenol 8 was transformed to the silyl ether 16 .…”