Catalytic Enantioselective Total Synthesis of (+)–Lycoperdic Acid

Abstract

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Asymmetric Synthesis of Enantiopure Pyrrolidines by C(sp3)−H Amination of Hydrocarbons

“…Importantly, this sequence of two consecutive stereoselective C(sp 3 )ÀH amination reactions led us to synthesize a variety of new 2,5-disubstituted pyrrolidines for which the preparative methods are scarce. These methods rely on the lengthy elaboration of 1,4-dicarbonyl compounds, [24] the derivatization of pyroglutamic acid, [25] or the direct functionalization of preformed pyrrolidines. [26] Also worth of mention are the bridged nitrogen heterocycles 9 e and 9 p accessible in two steps from dibenzosuberane and cycloheptane, which are simplified analogues of the NMDA receptor antagonist MK-801 and tropane alkaloids, respectively.…”

Asymmetric Syntheses of Enantioenriched 2,5-Disubstituted Pyrrolidines

“…This strategy was further applied by the group of Pihko to the synthesis of symmetrical and nonsymmetrical 2,5-diarylpyrrolidine organocatalysts. 40,41 Later, the group of Yamada reported a complementary catalytic system based on a chiral β-ketoiminato cobalt(II) complex for the reduction of several diketones (Scheme 16) to 43 Both R-and S-selective transaminases were identified for the first step, fully converting 1,4-diketones into enantiopure dihydropyrroles 76. Then a R-selective reductive aminase enabled stereoselective reduction of the obtained dihydropyrroles to the corresponding pyrrolidines in the same pot.…”

“…Interestingly, they could also apply this protocol for the asymmetric reduction of the homologated diketone to access the corresponding C 2 -symmetrical piperidine. This strategy was further applied by the group of Pihko to the synthesis of symmetrical and nonsymmetrical 2,5-diarylpyrrolidine organocatalysts. , Later, the group of Yamada reported a complementary catalytic system based on a chiral β-ketoiminato cobalt­(II) complex for the reduction of several diketones (Scheme ) to access the corresponding C 2 -symmetrical azetidines, pyrrolidines, and piperidines …”

Enzymatic Synthesis of Noncanonical α‐Amino Acids Containing γ‐Tertiary Alcohols

“…However, the existing routes require multiple steps of protecting group manipulation and lack efficiency because these ncAAs contain multiple functional groups and stereogenic centers (Figure 1b). [11] Pihko et al developed an enantioselective organocatalytic total synthesis route for (+)-lycoperdic acid and exploited an iminium-catalyzed asymmetric Mukaiyama À Michael reaction to install the key tertiary stereogenic center. Shi et al utilized a sequential CÀ H activation strategy for the synthesis of maremycins A and B, in which the steps to install tertiary stereogenic centers were not selective, resulting in a mixture of 1 : 1 diastereomers.…”

“…Shi et al utilized a sequential CÀ H activation strategy for the synthesis of maremycins A and B, in which the steps to install tertiary stereogenic centers were not selective, resulting in a mixture of 1 : 1 diastereomers. [11] Enzymatic processes are privileged tools to produce ncAAs because they proceed with high stereocontrol and avoid protecting group manipulations. [12] Nonetheless, the existing enzymatic methods for accessing multifunctionalized ncAAs with tertiary alcohols are currently scarce and incompetent, often resulting in a mixture of diastereoisomers.…”