The Guaianolide 11βH,13-Dihydromicheliolide

Stereoselective Synthesis of (+)-11βH,13-Dihydroestafiatin, (+)-11βH,13-Dihydroludartin, (−)-Compressanolide, and (−)-11βH,13-Dihydromicheliolide from Santonin

“…Regioselective opening of the C 3 −C 4 oxirane ring with PhSeNa/Ti( i -PrO) 4 /DMF followed by hydrogenolysis of the C−Se bond with deactivated Raney Ni gave compound 7 (67% yield for the two steps). The spectral and physical data for 7 were fully coincident with those reported for the synthetic (−)-11β H ,13-dihydromicheliolide, ,, but clearly differ from those for the natural product isolated from Achillea millefolia 21 in the chemical shifts for H-5, H-6, H-11, H-14, and H-15. In our synthetic compound H 5 appears at δ 2.62 and in the natural product at δ 2.36, whereas H 6 , H 11 , H 14 , and H 15 appear at higher field (δ 3.80, 2.24, 1.66, and 1.28, respectively) in comparison with those of the natural product (δ 4.27, 2.69, 1.72, and 1.44, respectively).…”

“…0.5 g) at room temperature. After 30 min the mixture was filtered through a short plug of silica gel (EtOAc) to yield compound 7 (9 mg, 90%): white crystals, mp 124−126 °C (hexanes−EtOAc) [lit 22a. 124−127 °C (CHCl 3 )]; [α] 22 D −4.7° ( c 0.68) [lit .…”

“…collina , Compressanolide ( 6 ) has also been obtained by cyclization of gallicin, and dihydromicheliolide ( 7 ) has been obtained by solvolysis of a 4α-hydroxy-1β-tosyl derivative of vulgarin …”

Natural sesquiterpenoids

“…319 The crystal structure of 11 ,13-dihydromicheliolide has been reported. 320 The absolute configuration of chlorojanerin has been determined by X-ray analysis. 321 The circular dichroism spectra of eight guaianolides, obtained from Centaurea scoparia, have been studied.…”