Paraconic Acids—The Natural Products from Lichen Symbiont

Catalytic Conversion of Furans and Pyrroles to Natural Products and Analogues Utilizing Donor‐Acceptor Substituted Cyclopropanes as Key Intermediates

“…The substitution pattern of the butyrolactones generated by the above strategy provided an opportunity for the further elaboration towards natural products. Various paraconic acids 28 , showing broad biological activities, such as antibiotic, antitumor, or growth‐regulating properties, can be obtained from 25a (Scheme ): utilizing cross‐metathesis reactions as a key step allowed the installation of different lengths of alkyl chains in the 5‐position typically found in this compound class. Oxidation of the aldehyde or acetal moiety to the corresponding carboxylic acid and methylation or methylenation via enolization of the lactone allowed the completion of the synthesis of (−)‐roccelaric acid ( 28a ), (−)‐nephrosteranic acid ( 28b ), (−)‐protopraesorediosic acid ( 29a ), and (−)‐protolichesterinic acid ( 29b ), while (−)‐methylenolactocin was directly accessible from 25d …”

Enantioselective, Catalytic One‐Pot Synthesis of γ‐Butyrolactone‐Based Fragrances

“…Various synthesis approaches are described in literature and a selection is depicted in Figure : One of the synthesis routes is the oxidative cyclisation of β,γ ‐unsaturated carboxylic acids using a chiral selenium catalyst (route a). Chiral γ ‐butenolides are formed, which can be further modified and reduced to the desired γ ‐butyrolactones ,,. Another method is the copper‐catalysed cyclopropanation of furanes followed by ozonolysis (route b) ,,.…”

“…Chiral γ ‐butenolides are formed, which can be further modified and reduced to the desired γ ‐butyrolactones ,,. Another method is the copper‐catalysed cyclopropanation of furanes followed by ozonolysis (route b) ,,. Also, [4+2]‐, [3+2]‐, or [2+2]‐cycloadditions are known to yield the title compound (route c) ,.…”

“…The aldol reaction using a chiral auxiliary X c represents another common synthesis route (route d). The homo aldol reaction is more challenging due to self‐condensation, but it was also utilized in some cases,,, as was the halo lactonisation (route e) ,. Transition metal catalysed ring closing metathesis is also applied leading to γ ‐butenolides, which then can be further transformed to yield γ ‐butyrolactones like quercus lactone or cognac lactone ,.…”

Palladium‐Catalyzed Asymmetric Allylic Alkylation of 4‐Substituted Isoxazolidin‐5‐ones: Straightforward Access to β2,2‐Amino Acids

“…[10] In this context, we recently applied the palladium-catalyzed asymmetric allylic alkylation [11] (Pd-AAA)t o two new classes of prochiral substrates, namely allyl dienol [12,13] and allyl enol [14] carbonates. This method provided ah ighly enantioselective access to aw ide variety of chiral butenolides and butyrolactonesb earing an all carbon a-quaternary stereogenic center.I tw as also used as ak ey step in the total synthesis of (À)-nephrosteranica cid and (À)-roccellaric acid, two members of the paraconic acid family of natural products, [15] whiche xhibiti nteresting antibiotic properties. In view of these results, we envisionedt hat aP d-AAAcould potentially be applied to 4-substitutedi soxazolidin-5-ones to afford the corresponding a,a-disubstituted products, which could in turn be readily converted to b 2, 2 -amino acids after subsequentr eductive NÀOb ond cleavage( Figure 1B).…”