1361049-74-2Relevant academic research and scientific papers
Total synthesis of (+)-lactiflorin by an intramolecular [2+2] photocycloaddition
Lu, Ping,Bach, Thorsten
, p. 1261 - 1264 (2012/03/22)
Enlightning synthesis: A light-induced intramolecular [2+2] photocycloaddition reaction (1→2) was the key step in the stereoselective synthesis of (+)-lactiflorin (3) and its triacetate. By comparison with reported analytical data, it was possible to unambiguously elucidate the structure of this natural product, to which three different structures had been previously assigned. Copyright
Intramolecular [2+2] photocycloaddition reactions as an entry to the 2-oxatricyclo[4.2.1.04,9]nonan-3-one skeleton of lactiflorin
Lu, Ping,Herdtweck, Eberhardt,Bach, Thorsten
, p. 1947 - 1958 (2012/09/05)
Two [2+2] photocycloaddition routes were evaluated as possible ways to access the tricyclic core structure found in the terpene monoglycoside lactiflorin. While the first route via γ-substituted cyclopentenones was quickly discarded, the reactions of racemic (5R*)-3-benzyloxy-5-but-3'- enyl-4-methoxycarbonylfuran-2(5H)-ones proceeded in high yields and with perfect diastereoselectivity. However, it turned out that the regioselectivity was strongly dependent on the substitution pattern within the but-3'-enyl chain, which connects the terminal olefinic double bond to the photoexcited butenolide chromophor. If the chain was unsubstituted or if a tert-butyldimethylsilyloxy group was placed at the 2' position in a syn-relationship to the existing stereogenic center (5R*,2'S*), the crossed product prevailed with regioselectivities of 89:11 to 69:31. If the tert-butyldimethylsilyloxy group was positioned at 2' in an anti-relationship to the existing stereogenic center (5R*,2'R*), the desired straight products were obtained in regioselectivities of 74:24 to 55:45 (61-83% yield). Following this route, the aglycon part of lactiflorin was obtained by an intramolecular [2+2] photocycloaddition and a subsequent hydrogenolysis in 53% yield. Its further conversion into the natural product after glycosylation included a methyl addition to the lactone carbonyl group, which was optimized to give the desired key intermediate in a yield of 70%. The further conversion to lactiflorin was achieved in four steps and with an overall yield of 49%.
