Chiral spiro-β-lactams from 6-diazopenicillanates

An efficient synthesis of spiro- β-lactams having sulfenyl, sulfinyl and sulfonyl moiety

“…7 Although a great deal of functionalized monocyclic β-lactams has been reported, relativly few reports have been devoted to the synthesis of spiro-β-lactams. [8][9][10][11] Among the different strategies developed for the construction of β-lactams, 12 the reaction of acid chlorides with imines i.e., Staudinger reaction 13 constitutes one of the most popular procedures. In view of the ever growing applications of spiro-β-lactams, ranging * For correspondence from their biological activity to their utility as synthetic intermediates in organic synthesis, we extended our work on C-3 alkylation of 3-methylthio-β-lactams to the synthesis of spiro-β-lactams.…”

Lithium Chloride Catalyzed Asymmetric Domino Aza‐Michael Addition/[3 + 2] Cycloaddition Reactions for the Synthesis of Spiro‐ and Bicyclic α,β,γ‐Triamino Acid Derivatives

“…Tricyclic scaffolds 7a and 9a containing the 1‐pyrazoline unit are not only precursors for triamino acid derivatives but are also β‐amino acid surrogates by extrusion of molecular nitrogen. Irradiation of both compounds by a high pressure mercury lamp furnished angularly fused and peri‐fused cyclopropanes 37 and 39 , respectively, in good yields as single diastereomers (Scheme ) . Removal of the phenylethyl groups by hydrogenolysis over Pearlman's catalyst provided conformationally constrained tricyclic β‐amino acids 38 and 40 reminiscent of alkaloid structures, which exemplify the potential applicability of the method toward natural product synthesis and also for the preparation of β‐peptide foldamers or pharmaceutical analogs.…”

Synthesis of Chiral Spirocyclopentenyl‐β‐lactams through Phosphane‐Catalyzed [3+2] Annulation of Allenoates with 6‐Alkylidenepenicillanates

“…An approach to new penicillin analogues is to explore the reactivity of 6‐diazopenicillanates or 6‐alkylidenepenicillanates for the functionalization at C‐6, keeping the penicillanate nucleus. In fact, chiral spiro‐2‐pyrazolinepenicillanates can be obtained from the 1,3‐dipolar cycloaddition of 6‐diazopenicillanates 3a,3b,5. Our own contribution5 established that cycloaddition with dipolarophiles such as acrylonitrile, acrylates or methyl vinyl ketone affords spiro‐2‐pyrazoline‐β‐lactams, whereas with N ‐substituted maleimides, spiro‐1‐pyrazoline‐β‐lactams are obtained.…”

“…In fact, chiral spiro‐2‐pyrazolinepenicillanates can be obtained from the 1,3‐dipolar cycloaddition of 6‐diazopenicillanates 3a,3b,5. Our own contribution5 established that cycloaddition with dipolarophiles such as acrylonitrile, acrylates or methyl vinyl ketone affords spiro‐2‐pyrazoline‐β‐lactams, whereas with N ‐substituted maleimides, spiro‐1‐pyrazoline‐β‐lactams are obtained. Microwave‐induced denitrogenation of these spiro‐1‐pyrazoline‐β‐lactams allows the stereoselective synthesis of novel spirocyclopropyl‐β‐lactams.…”

“…Microwave‐induced denitrogenation of these spiro‐1‐pyrazoline‐β‐lactams allows the stereoselective synthesis of novel spirocyclopropyl‐β‐lactams. 6‐Diazopenicillanates also react with electron‐deficient alkynes to give the corresponding spiro‐3 H ‐pyrazole‐β‐lactam as a single product 5. The observed stereoselectivity can be explained by considering that the major product results from addition to the sterically less hindered α‐side of the β‐lactam.…”