Studies on the Synthesis of Reidispongiolide A: Stereoselective Synthesis of the C(22)-C(36) Fragment

A highly stereoselective synthesis of the C(22)-C(36) fragment 2 of reidispongiolide A is described. This synthesis features the highly stereoselective mismatched double asymmetric crotylboration reaction of the aldehyde derived from 5 and the new chiral reagent (S)-(E)-7 that provides 12 with >15:1 dr. Subsequent coupling of the derived vinyl iodide 3 with aldehyde 16 provided allylic alcohol 17, that was elaborated by three steps into the targeted reidispongiolide fragment 2.     

Kinetic deconjugation: a gateway to the synthesis of Xxx-Gly (E)-alkene dipeptide isosteres

A new method for the preparation of Xxx-Gly (E)-alkene dipeptide isosteres (EADIs), using LDA deprotonation followed by 1 N HCl quench, was explored. The method, named kinetic deconjugation, enabled the synthesis of Tyr-Gly, Gly-Gly, Ser-Gly, Pro-Gly, and Phe-Gly EADIs, as well as one Tyr-Gly trisubstituted alkene dipeptide isostere (TADI). Overall, this method, based on commercially available materials, leads to high yields, requires few synthetic steps and works on the gram scale in the synthesis of a wide variety of EADIs.     

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

A variety of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans were easily synthesized in good yields under mild conditions by a domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylethylidene)- and 2-(1-phenylpropylidene)malononitriles. In the latter case, intermediate 7-amino-10-methyl-10-nitro-9-phenyl-6-(trifluoromethyl)-10,10a-dihydro-6H-benzo[c]chromene-8-carbonitriles were isolated as a result of a rare [1,5] sigmatropic shift of the nitro group.     

Mild and practical stereoselective synthesis of (Z)- and (E)-allyl bromides from Baylis-Hillman adducts using Appel agents (PPh3/CBr4): a facile synthesis of semiplenamides C and E

Appel agents (PPh₃/CBr₄) have been utilized for high-yielding stereoselective synthesis of (Z)- and (E)-allyl bromides from Baylis-Hillman adducts at room temperature. The method has been applied for the synthesis of naturally occurring bioactive fatty acid amides, semiplenamides C and E.     

A simple synthesis of 4E,7Z-tridecadien-1-yl acetate,a component of the sex pheromone of the potato mothPhtorimaea operculella (Lepidoptera:Gelehiidae)

A simple, five-step synthesis of the title compound was developed starting from commercially available 2,4-nonadienal. The overall yield of the pheromone is 29%, and the geometric purity of the ⁴ and ⁷ double bonds is 95%. TheZ configuration of the ⁷ bond results from the 1,4-cis-hydrogenation of the intermediate 1,4,6-undecatrien-3-ol in the presence of an (arene)chromium tricarbonyl complex, while theE configuration of the ⁴ bond arises in the Claisen-Johnson rearrangement occuring in the reaction of 1,5Z-undecadien-3-ol with trimethyl orthoacetate.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2350–2353, September, 1996.     

Pheromone synthesis. Part 244: Synthesis of the racemate and enantiomers of (11Z,19Z)-CH503 (3-acetoxy-11,19-octacosadien-1-ol), a new sex pheromone of male Drosophila melanogaster to show its (S)-isomer and racemate as bioactive

The enantiomers of (11Z,19Z)-3-acetoxy-11,19-octacosadien-1-ol were synthesized from the enantiomers of 3,4-epoxy-1-butanol PMB ether. Its racemate was also synthesized. Its (S)-isomer and racemate were shown to possess the same pheromone activity as CH503, a long-lived inhibitor of male courtship in Drosophila melanogaster, although the racemate was less active.     

Synthesis and structural characterization of a dichloro zinc complex of N,N′-bis-(2,6-dichloro-benzyl)-(R,R)-1,2-diaminocyclohexane: Application to ring opening polymerization of rac-lactide

A novel dichloro zinc complex (L¹)ZnCl₂, where L¹ is N,N′-bis-(2,6-dichloro-benzyl)-(R,R)-1,2-diaminocyclohexane, has been synthesized and characterized. The dimethyl derivatives, generated in situ from the well characterized dichloro zinc complexes (L¹)ZnCl₂ and (L²)ZnCl₂, where L² is N,N′-bis-(benzyl)-(R,R)-1,2-diaminocyclohexane, were employed as initiators for the ring opening polymerization (ROP) of rac-lactide (rac-LA). The complexes were found to be highly efficient initiators yielding the polylactide (PLA) with a narrow molecular weight distribution. The catalytic activity and heterotactic selectivity of the Zn(II) complexes were affected by the substituents on the phenyl groups of benzyl moieties in (R,R)-1,2-diaminocyclohexane. The dimethyl derivative of (L²)ZnCl₂ produced highly stereocontrolled PLA with P_r = 0.75 at −25 °C.     

A convenient and new approach to the synthesis of ω-heterocyclic amino acids from carboxy lactams through ring-chain-transformation. Part 2: Synthesis of (2R)-/(2S)-2-aminomethyl-3-(1-aryl-/1,5-diaryl-1H-pyrazol-3-yl)-propionic acid

Making use of amide activation, a convenient and short path synthesis of optically pure ω-heterocyclic-β-amino acids has been achieved from (1R,3R)- and (1R,3S)-5-oxo-1-(1-phenyl-ethyl)-pyrrolidine-3-carboxylic acid methyl ester. The key step of the synthesis involves a regiospecific ring-chain-transformation of the enaminones when subjected to 1,2-binucleophilic attacks. The method is illustrated by the synthesis of (2R)-/(2S)-2-aminomethyl-3-(1-aryl-/1,5-diaryl-1H-pyrazol-3-yl)-propionic acid.