Azetidinones bicyclic

Azetidin-2-one, l-benzyl-3,3,4-triphenyl-, 7, 249 Azetidin-2-one, l-(2-bromophenyl)-X-ray crystallography, 7, 247 Azetidin-2-one, 3-carboxy-synthesis, 7, 262 Azetidin-2-one, 3-halo-synthesis, 7, 77 ring contraction, 7, 81-82 Azetidin-2-one, 4-imino-IR spectroscopy, 7, 248 Azetidin-2-one, 1-phenyl-irradiation, 7, 255 Azetidin-2-one, 4-phenyl-reductive ring cleavage, 7, 252 Azetidin-2-one, 4-thio-IR spectroscopy, 7, 248 Azetidinones bicyclic, 7, 348-356 C NMR, 7, 348 H NMR, 7, 348 reactivity, 7, 356-358 spectroscopy, 7, 357 structure, 7, 349 synthesis, 7, 358-359 fused ring... 

The diazo function in compound 4 can be regarded as a latent carbene. Transition metal catalyzed decomposition of a diazo keto ester, such as 4, could conceivably lead to the formation of an electron-deficient carbene (see intermediate 3) which could then insert into the proximal N-H bond. If successful, this attractive transition metal induced ring closure would accomplish the formation of the targeted carbapenem bicyclic nucleus. Support for this idea came from a model study12 in which the Merck group found that rhodi-um(n) acetate is particularly well suited as a catalyst for the carbe-noid-mediated cyclization of a diazo azetidinone closely related to 4. Indeed, when a solution of intermediate 4 in either benzene or toluene is heated to 80 °C in the presence of a catalytic amount of rhodium(n) acetate (substrate catalyst, ca. 1000 1), the processes... 

Lactam antibiotics are bicyclic or monocyclic azetidinone ring-containing compounds (Fig. 1). They kill bacteria by preventing the assembly of (4-3) peptidoglycans. These covalently closed net-like polymers form the matrix of the cell wall by which the bacteria can divide and multiply, despite their high internal osmotic pressure. 

Monocyclic azetidinones are useful building blocks in organic synthesis. Besides the wide use in the syntheses of monobactam antibiotics and nuclear analogues of natural bicyclic p-lactam antibiotics,1 2 3 new applications have appeared with the syntheses of unnatural a-amino acids, amino sugars4 and inhibitors of elastase.5 ... 

Extensive and 13CNMR studies on bicyclic azetidinones have been reported (B-82MI51205, B-82MI51206, B-72MI51200). Data on acetylthienamycin (56), epithienamycin A... 

Table 4 Structural Properties of some Bicyclic Azetidinones...

IR, UV and mass spectral properties of bicyclic azetidinones, other than penicillins and cephalosporins, have received thorough treatment (B-82MI51201). 

As a result of the intense interest in exploitation of the biological properties of the /3-lactam antibiotics a large number of nuclear analogs of the various naturally occurring structures have been synthesized. In addition to the carbapenems and oxapenams already described (Sections 5.12.3.4.2 and 5.12.3.4.3) a number of other novel bicyclic azetidinones have been reported. Examples of many of these are listed in Table 6. The methods used to synthesize these compounds are too varied to list in any systematic way. 

X-ray crystallographic examination of bicyclic azetidinone (106) indicates that the azetidinone ring is essentially planar (73JA4647). Selected bond angles and distances are listed in Table 7. H NMR and IR properties for several bicyclic azetidinones are given in Table 8. Theoretical calculation (79T1499) and CD studies (78JOC4438) for the 1-azabicyclo[3.2.0]heptane system have been reported. 

Under appropriate thermal conditions bicyclic azetidinones can undergo valence bond tautomerism in a behavior similar to that described for bicyclic azetidines in Section 5.12.2.2.1. Thus, the position of equilibrium illustrated in equation (4) strongly favors the... 

The majority of transformations carried out at ring substituents of bicyclic azetidinones were described in Section 5.12.3.3.2 for azetidinones related to cephalosporins and penicillins. Nucleophilic displacement reactions of 7-halo-l-azabicyclo[4.2.0]octan-8-ones with thallium phthalimide and hydrazine have been reported (76ACS(B)318). 

In contrast to the synthesis of bicyclic azetidinones containing a carboxyl group on the atom adjacent to the lactam nitrogen (see Section 5.12.3.4), few examples are reported in which bicyclic azetidinones without this carboxyl group are prepared from azetidinone precursors. One unique approach, however, utilized a free radical ring closure to obtain 6-oxa-l-azabicyclo[5.2.0]nonan-9-one (116) in modest yield (81TL2689). 

There appear to be no applications of commercial importance for the types of bicyclic azetidinone described in this section. 

Table 8 Spectroscopic Properties of Selected Bicyclic Azetidinones Structure sCH) (p.p.m.) 7(1ff-1ff) (Hz) v(C—0) (cm-1) Ref.

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