A Concise, Protection-Free and Divergent Approach for the Enantioselective Syntheses of Two Pheromonal Epoxide Components of the Fall Webworm Moth and Other Species

Abstract

On the basis of Zhou's modified Sharpless asymmetric epoxidation, sequential coupling reactions, and a divergent strategy, the protection-free syntheses of two main pheromonal components 1 and 5, found in the fall webworm moth, Hyphantria cunea, and other species have been accomplished in 10 steps (for two compounds). The overall yields are 31% for 1, 28% for 5, and 25% for both 1 and 5, respectively. The ee values of the final products 1 and 5 are at least 99%.

Are Alkyne Reductions Chemo-, Regio-, and Stereoselective Enough To Provide Pure (Z)-Olefins in Polyfunctionalized Bioactive Molecules?

“…Actually, the presence of a significant amount of under-reduced structures is all the more surprising, since the authors did not report the use of any reagent to poison the palladium surface. The reaction conditions are compatible with the presence of many functional groups, including methyl ester, 315,316,320,354,355 conjugated ester, 356,357 OBO ester, 340,358 carboxylic acid function, 324,359,360 free hydroxyl groups, 314,315,317,319,322, 324,326,329,341 epoxide, 319,327,328,335,349 acetate, 361 acetal, 356 M O M , 3 1 4 m o n o m e t h o x y t r i t y l , 3 0 7 N -t o s y l , 3 4 0 THP, 318,325,343,362−364 benzoyl, 351,365,366 and allylic benzoyl 321 groups, but also sulfides, 367 OTES, 323 OTBDMS, 320,335,368 OTBPS, 307,332,340,343,355,361 PMB, 356,369 quinone moiety, 324 chlorine atom, 345 and 1,3-dioxolane, 342 1,2-dioxolane, 370 or 1,2-dithiolanes, 360 thiazolidin-2-one 1, 356 and cyclopropane.…”

“…Lindlar hydrogenation reactions were carried out in various solvents from nonpolar to protic polar. The solvents most commonly reported in the literature are benzene, − n -hexane, − ethyl acetate, , methanol − or ethanol, , but also toluene, cyclohexane, heptane, petroleum ether, dichloromethane, Et 2 O, EtOAc-EtOH (2/1), or Et 2 O-THF or dry acetone–THF or a CH 2 Cl 2 –hexane (1/1) mixture were also used.…”

Synthesis of Stereochemically and Skeletally Diverse Fused Ring Systems from Functionalized C-Glycosides

“…Ultimately, this was overcome by using the triflate derived from ( R )-or ( S )-glycidol ( 17 ) 19 (Scheme 4). Liberation of the primary alcohol by TBDPS deprotection gave monocyclic compound 19 , the precursor to the epoxide-opening/ring closing reaction.…”

“…Initially, alkylation of sulfonamide 15a – d with epichlorohydrin proved difficult when using the all syn stereoisomer, presumably due to steric hindrance. Ultimately, this was overcome using the ( R )- or ( S )-glycidol triflates ( 17 ) (Scheme ). Liberation of the primary alcohol by TBDPS deprotection gave compound 19 , the precursor to the epoxide-opening/ring-closing reaction.…”

The Handy Use of Brown’s P2‐Ni Catalyst for a Skipped Diyne Deuteration: Application to the Synthesis of a [D4]‐Labeled F4t‐Neuroprostane

“…Based on a literature survey, Lindlars palladium catalyst [23] (5 % Pd/CaCO 3 poisoned with lead) was revealed to be a good candidate for the stereoselective semihydrogenation of skipped diynes as indicated in many successful substrates. [24] The results of these experiments, summarized in Table 1, clearly showed that the regio-and stereochemical outcome of the reaction strongly depends on the solvent and catalyst loading. No conversion was observed when using 13 % of Lindlars catalyst, irrespective of the solvents employed (Table 1, entries 1-3).…”