A synthesis of (+)-aphidicol-15-ene

Abstract

A stereospecific synthesis of (+)-aphidicol-15-ene is described. Pursuing a concept successfully applied to our total synthesis of stemarin and the stemodane diterpenoids, the C/D ring system was elaborated by functional group manipulation and rearrangement of a 6-hydroxybicyclo[2.2.2]octan-2-one system. RONALD B. KELLY, G. SANKAR LAL, GOPALA GOWDA et RABINDRA N. Rw. Can. J. Chem. 62, 1930Chem. 62, (1984. This concept was an efficient feature of total syntheses of stemarin (1)(1), and of 2-desoxystemodinone (2a) and stemodinol (2b)(2,3); we now wish to describe its application to a stereospecific synthesis of (+)-aphidicol-15-ene (5), a derivative of aphidicolin (3)(4).' This synthesis was undertaken as a model, relative to a projected total synthesis of aphidicolin.The keto alcohol 6, formerly encountered as an intermediate in our synthesis of (+)-2-desoxystemodinone (2a)(3), served also as an intermediate in the present synthesis. This intermediate, prepared from podocarpic acid (3), is the enantiomer represented by 6 and leads to the enantiomer 5 derived from aphidicolin (4).In preparation for the rearrangement of the bicyclic system of 6 to that of 5, it was necessary to reduce the secondary hydroxyl group to a methylene group and convert the keto

(+)-Podocarpic Acid as Chiral Template in the Synthesis of Aphidicolane, Stemodane and Stemarane Diterpenoids †

“…(+)-Podocarpic acid (4) was then used for obtaining (+)-stemod-12-ene (31) and (+)-2-deoxystemodinone (2d), thus confirming the absolute configuration attributed to the stemodane diterpenoids on the basis of ORD and CD studies [50]. (+)-Podocarpic acid (4) was also converted into (+)-aphidicol-15-ene (36) [51] and into the Stemodia chilensis tetracyclic diterpenoid (+)-19-acetoxystemodan-12-ol (2f) allowing confirmation of the structure attributed to the latter only on the basis of NMR experiments [54]. (+)-Podocarpic acid (4) was then extensively used in the work which led to the synthesis of (+)-stemar-13-ene (57) and (+)-18-deoxystemarin (3b) [55,56,59,60,62].…”

“…Reduction of the latter with tri-n-butyltin hydride followed by saponification gave 47. The conversion of 47 into (+)-36 [51] paralleled that of 42a into (+)-31 [50] (see Section 8.4). …”

“…In the following years the Kelly group focused its attention on stemodane and aphidicolane diterpenoids. In this frame the syntheses of (+)-stemod-12-ene (31), (+)-2-deoxystemodinone (2d) [50] and (+)-aphidicol-15-ene (36) [51] from (+)-podocarpic acid (4) were achieved.…”

Stemodane Diterpenes and Diterpenoids: Isolation, Structure Elucidation, Biogenesis, Biosynthesis, Biological Activity, Biotransformations, Metabolites and Derivatives Biological Activity, Rearrangements

“…This goal was achieved by locating, in a substituted bicyclo[2.2.2]octane system, at a specific position, a suitably configurated leaving group the departure of which promoted the migration of the antiperiplanar C-C bond. Remarkable examples of such specificity were reported in the past in the frame of biogenetic syntheses of stemodane [4,5,9,[29][30][31][32][33], aphidicolane [30,31,[34][35][36][37][38] and stemarane [39][40][41][42][43][44], diterpenes and diterpenoids. As can be seen (Scheme 4), the bonds indicated by a green arrow migrate in one case (entry a) through the lower face of the molecule, while in entry b, the same bond migrates through the lower face owing to the different location of the leaving group.…”

Electrochemical pore etching in Ge

“…[1], there are only 5 more recent studies on pore etching [2 -5] and no macropores were found so far by pure anodic etching. While Ge today plays only a marginal role in semiconductor technology, pore formation in Ge could be of interest for applications like photonic crystals [6], sensors or filters. In this letter anodically etched Ge macropores and their morphological features are reported for the first time.…”