By Iwao Ojima, Edison S. Zuniga (auth.), Bimal K. Banik (eds.)
I. Ojima • E. S. Zuniga • J. D. Seitz: Advances within the Use of Enantiopure β-Lactams for the Synthesis of Biologically energetic Compounds of Medicinal Interests.- I. Fernández • Miguel A. Sierra: β -Lactams from Fischer Carbene Complexes: Scope, boundaries, and response Mechanism.- Bablee Mandal • Basudeb Basu: Synthesis of β-Lactams via Alkyne–Nitrone Cycloadditions.- T. T. Tidwell: instruction of Bis-β-Lactams by means of Ketene–Imine Cycloadditions.- Edward Turos: The Chemistry and Biology of N-Thiolated β-Lactams.- Indrani Banik • Bimal ok. Banik: Synthesis of β-Lactams and Their Chemical Manipulations through Microwave-Induced Reactions.
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Extra info for β-Lactams: Unique Structures of Distinction for Novel Molecules
The synthesis of cryptophycin-24 (Arenastatin A) is illustrated in Scheme 76, as a representative total synthesis of this class of compounds . The b-lactam key intermediate 263 was prepared through the coupling of 261, obtained from 259 and 260 in four steps, with N-(p-MeO-Phe)-b-lactam 262. The macrolactonization of 263 was achieved through cyanide-initiated b-lactam ring opening using Bu4NCN and subsequent lactonization. The attempted use of NaH and NaHMDS as base for direct ringopening coupling was unsuccessful, presumably due to the instability of 263 to basic conditions.
However, the conventional ester formation encountered a serious epimerization problem  and thus efficient coupling methods needed to be developed. Then, the b-lactam synthon method provided an exceptionally practical solution, featuring the highly efficient ring-opening coupling of N-acyl-b-lactam with a baccatin III derivative [6, 7, 60, 131]. (3S,4R)-1-Benzoyl-3-EEO-4-phenyl-b-lactam 249a (EE ¼ 1-ethoxylethyl) was prepared from (3S,4R)-3-TIPSO-4-phenyl-b-lactam 247 (98% ee) directly obtained through highly efficient chiral ester enolate – N-TMS–imine cyclocondensation (Scheme 72) (vide supra) [6, 60].
Thus, Type 1 alkylation with MeI took place at the C3 position of Advances in the Use of Enantiopure b-Lactams for the Synthesis of. . Ph Ph O O N Ph N O 1 R ii. R2X H N O N (S)-206 (R)-205 Ph Ph O CO2t-Bu O O N i. LiHMDS O i. LiHMDS ii. R1X Ph 39 Ph H i. TFA R2 1 ii. Li/NH3 H2N R R2 R1 CO-NH CO2H (S,S)-207 CO2t-Bu Priority: R1 > R2 N O CO2t-Bu 204 i. LiHMDS ii. R2X Ph Ph O O N Ph N i. LiHMDS O O R2 ii. R2X H N O Ph N O CO2t-Bu (R)-205 H i. TFA R1 HN R2 ii. Li/NH3 2 Ph R1 R2 CO-NH CO2H (S,R)-207 CO2t-Bu (R)-206 Scheme 60 Synthesis of (S,S)-and (S,R)-dipeptides via sequential Type 2 dialkylation Ph Ph O Ph O N O Ph N O 204 i.