By L.A. Paquette
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The 1st NATO technology discussion board was once held in Biarritz in September 1990. This Taormina convention is the second one in a sequence that we want to be a protracted one and that i think that it has equalled the good fortune of its predecessor. In establishing those conferences the NATO technological know-how Committee desired to assemble top specialists to study fields of robust current curiosity.
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When triene 508 was treated with p-toluenesulfonylacetylene, highly stereoselective addition from the endo surface occurred to deliver an adduct which was directly epoxidized (Scheme XLI). The proximity of the two bonds in 509 allows for ready photocyclization. Oxidative cleavage of 510 afforded 82 J Peristylanes diketone 511 which was desulfonylated after bisketalization. Stepwise reduction of 512 furnished the desired 499. MCPBA(leq) CH3COCH3 " ~ Ts 508 Ts 509 510 I HIO CH30H,H20 1. H30+ TS 499 512 511 Scheme X L I A synthesis of a dimethyl derivative of 501 has also recently been announced by Hirao, et al.
The possible importance of this compound in the elaboration of lac resin by insects has been pointed out. 85 VI NaturalProductsChemistry ~ " HO. R 03' Si02. ~. MoO t 5 4b 1 H 536 " . ~.... L t H -----[ t , H 1, H 538 Scheme X L H H O. / ~-(CH2)7 H \(CH2)5-CH2OH OH~"~f'/~",l/COOH H 539 ~CH20H 540 The action of activated manganese dioxide on 541 gives the oxo-ether 542 as a single product in quantitative yield. On the other hand, 543 leads under analogous conditions to a mixture of six products szs) The configurations of shellolic (544) and laccishelloic acids (545) have been correlated by conversion of the Cl3-hydroxymethyl function of the former into the methyl group of the latter via two routes involving reduction of an intermediate thioacetal and an iodo derivative, respectively 324).
Flash vacuum pyrolysis at 600 °C resulted in further isomerization and formation of 493 and 494 282~. More recently, two improved syntheses of 490 have been realized in Rees' laboratory 283,2s4). The main features of these approaches are summarized in Scheme XL. 2, N o% A ~ [ ~ 0 Me 3. HOAc, H20 •/•. CH3I Me? 0 MeO ~ O M e 1. LDA,PhSeCl 2" H202 :3. 2_MHC~ TsOH ~ CH2C,2 ~OMe ~ 1. -Bu )2AIH o.. o ~ '~. (PhO)3PCH~ I 4. NoOH,H20 OMe 490 Scheme X L The intermediate tricyclic ketones 495 and 496 have been transformed to the methoxy-substituted derivative 497 284,285).