Lactam substituted

A Hungarian research group observed a nonexpected formation of a tetrazolo[l,5- ]derivative <2001J(P 1) 1131 >. These authors found that treatment of the /3-lactam-substituted tetrazolylmethyl ketone 135 with lead tetraacetate results in a ring closure to pyridine ring fused to tetrazole, and product 136 was formed as a mixture of diastereomers in low yield (Scheme 33). 

Lactams substituted only in the 3 position cannot be prepared by the present procedure, since the lactam formed has the nitrogen of the chlorosulfonyl isocyanate attached to the more highly substituted carbon atom of the olefinic double bond in Markownikoff fashion. 2-Azetidinones substituted in the 3 position only have been prepared by Grignard reagent-catalyzed cyclizations of esters of appropriately substituted /3-amino acids.4,5... 

In 2003, Cainelli and coworkers have shown that monocyclic [3-lactams substituted at the C-3, the C-4, and the N-l positions are the most active in inhibiting LE and gelatinases MMP-2 and MMP-9 [340], They have also reported that C-4 unsaturation on the [3-lactam ring raised the inhibitory activity towards these proteases, with selectivity over LE by 3- 1 -(A/V-butyldi methyl si lyloxvjethyl] derivatives, and over the gelatinase MMP-2 by C-3-unsubstituted 4-[l-ethoxycarbonyl]... 

For N-alkyl or N-aryl /3-lactams, substitution at the 4-position must involve either elimination-addition via an azetinone containing a 3.4 carbon-carbon double bond (7—>8—>9) or direct displacement by SN2 (7— 9) or SN1 (7—>10—>9) mechanisms. The elimination-addition pathway would again presumably occur by an ElcB mechanism, but with anion formation now occurring at the 3- rather than the I-position (90JOC3244). 

Scheme VI/19. Ring enlargement reactions of /3-lactams substituted at 3-position, a) 20° b) reflux in C6H5OCHv...

Use of the dihydroxylation procedure with the P-lactam-substituted alkenes 16 showed a matched-mismatched phenomenon (Scheme 3.15). Use of an achiral reagent showed little facial bias. With an alkyl or ester group rather than aryl as the other alkene substituent (R1), the selectivity diminished [311]. 

Recently, Jacobsen developed a new strategy for inducing enantioselectivity in reactions of protio-iminium ions, wherein a chiral urea 95 interacts with the highly reactive intermediate through a network of noncovalent interactions. This interaction leads to an attenuation of the reactivity of the iminium ion and allows high enantioselectivity in the Povarov reaction, giving lactam-substituted tetrahydroquinoline derivatives 98 in excellent enantioselectivities and diastereoselectivities. ... 

This chapter will be concerned with the anionic polymerization reactions of five specific types of monomers, including both 3-lactones and 3-lactams substituted in either the a- or 3-positions or both, as shown in Figure 1. 

Tire reaction mechanisms can be very complex since they are functions of both the initiating system and the lactam substitution. Among the various mechanisms, the polymerization initiated by protic inorganic adds, such as hydrogen chloride or bromide, will be those mainly considered and described in detail in the present section. 

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