First Total Synthesis of Grahamimycin A

Baker's Yeast Reduction of β‐Hydroxy Ketones

“…For diol 14 , lipase‐PS‐mediated acetylation also had to be investigated (Scheme ), in order to establish the absolute configurations of the baker's‐yeast‐mediated reduction products. A search in the literature showed that the absolute configuration of the derivative (+)‐ syn ‐ 21 was known,15 and we envisaged the possibility of functionalising the two hydroxy groups of diol 14 with high regioselectivity and enantioselectivity by enzyme‐catalysed tranesterification. When a 1:2 mixture of syn / anti diols 14 , obtained upon NaBH 4 reduction of the corresponding hydroxy ketone, was treated with lipase PS in tert ‐butyl methyl ether solution in the presence of vinyl acetate, the monoacetate (+)‐ anti ‐ 22 could be recovered as a single pure compound, showing de = 99 % and ee = 99 % (GC of the corresponding acetonide on a chiral column).…”

Synthetic Advances in Macrosphelides: Natural Anticancer Agents

“…The hydroxy butyrate 32 was protected and hydrolyzed to produce butyric acid 33 to be converted into hydroxyfuran 28 through esterification and THP deprotection. This alcohol 28 was transformed into dimeric alcohol 36 via esterification/deprotection with carboxylic acid 35 , which were prepared by Horner-Emmons olefination and hydrolysis of the known aldehyde 34 [22]. The furan moiety of alcohol 36 was oxidized with NBS and the Pinnick oxidation sequence to produce seco acid 37 .…”

De novo synthesis of natural products via the asymmetric hydration of polyenes

“…30 There have been several synthetic efforts toward colletodiol 30 , 31 colletol 36 , 32 and grahamimycin A 1 . 33 Surprisingly, there has been only one route to the most biologically active structure, grahamimycin A (colletoketol) 37 , which was completed by Kobayashi in 2000.…”

“…33 Surprisingly, there has been only one route to the most biologically active structure, grahamimycin A (colletoketol) 37 , which was completed by Kobayashi in 2000. 30 …”