Open-chained amides

In solution 1550-1510 Amide II found in open-chain amides only... 

The broadband at 3270 cm-1 is due to the O-H stretching vibration of the hydroxyl group. Moreover, the N-H stretching vibration absorption for open-chain amides occurs near 3270 cm-1 in the niclosamide solid state. 

Phenyl-[l,3]dioxane 32 has been reported to bind the 0X2 receptor with a pX of 8.3 and a pXb of 7.9, and is 600-fold selective for 0X2 over 0X1 [85,86]. JNJ-10268752 (no specific structure has been disclosed) has been described as a selective 0X2 receptor antagonist (X, 0X1 /OX2 = 18/2, 500 nM, respectively) [87]. Compounds exemplified by 33 have been reported as 0X2 receptor antagonists (IC5o = 9nM) selective versus 0X1 (IC50 = 1870 nM) [88]. Recently, open chain amide 34, sulfonamide compound 35 [89,82], and spirocyclic sulfonamide 36 [90]... 

Most important are quantitative solid-state reactions of cyclic carbonic acid derivatives with gaseous or solid amines. These give open-chain amides that can be recyclized in various cases to new products of preparative interest. 

The water initiated polymerization of lactams represents the classical, industrially widely used process and, therefore, a large effort has been devoted to the investigation of the kinetics and mechanism of the individual reactions. In order to establish the accepted reaction mechanism, the concentration of all components involved in the complex set of reactions had to be followed during polymerization and determined at equilibrium. Thorough studies by Hermans, Heikens, Kruissink, Reimschuessel, Staverman and by van der Want as well as by Wiloth elucidated the complex scheme of equilibrium reactions involving water, cyclic and open chain amide groups, amine and carboxyl groups [1, 2, 4, 5, 12, 13, 15, 22, 23,177, 214-235]. 

Penicillin (and, for that matter cephalosporin) antibiotics are cyclic amides and are very prone to hydrolysis. Normal amide bonds are more resistant to hydrolysis than are esters, but in penicillins the amide is cyclised into a four-membered P-lactam ring. The bond angles in this ring are close to 90°, in contrast to an open-chain amide in which the bond angle is 120° (sp2 hybridised carbon). This unnatural bond angle in the P-lactam ring means that the ring is very easily opened by nucleophiles, particularly water. 

Amidation of electron-deficient alkenes.2 In the presence of CI2(CH3CN)2Pd and CuCI (1 1) amides react with I-alkenes bearing COOR, COR, CHO, or CONR2 groups to form (H)-enamidcs in generally good yield. Cyclic amides arc more reactive than open-chain amides. Carbamates are particularly reactive. 

The 2-oxazolin-4-one ring is readily opened under mild hydrolytic conditions to yield open-chain amides.127 132 The alkoxy and phenoxy groups in 53 are cleaved rapidly by water in organic solvents, whereas the amino derivative (53, R = NPhj) requires mild acid catalysis. 

LeBel and Whang182 obtained a tetrahydro-l,3-oxazine (66) and an open-chain amide by irradiating (2537 A) the fused isoxazolidine 39b. The yield of 66 is increased if the reaction is photosensitized with benzo-phenone or fluorenone. 

CI sH, NO4, Mr 281.27 or C iftH 13NO5, Mr 299.28, amorphous powder. Main phytoalexin isolated in the form of the acetate from leaves of oat (Avena sativa) after infection with the rust fungus Puccinia coronata. According to Lit. the natural product exists in the form of the open chain amide avenanthramide A. at. Physiol. Plant Pathol. 19, 217-226 (1981). 1. Agric. Food Chem. 37, 60 (1989) Tetrahedron Lett. 31, 2647—2648 (1990). - [CAS 78164-38-2 (A.) 108605-70-5 (avenanthra-mide A)]... 

The reaction between tri-O-acetyl-D-glucal 7 and chlorosulfonyl isocyanate has been studied in the past, but neither formation of a cycloadduct nor of a rearranged product has been observed. Isocyanate acted only as acid catalyst causing decomposition of sugar material. On the other hand, [2+2]cycloaddition of active isocyanates to dihydro-2H-pyran and to its derivatives has been widely investigated, under a variety of conditions. The reaction of tosyl isocyanate with dihydro-2H-pyran 1 at low temperature (0 ) led to the formation of bicyclic p-lactam 2. Elevation of the cyclization temperature resulted in the rearrangement of the four-membered ring to the open-chain amide 3 (Scheme 4). 

Trichloroacetyl isocyanate reacted with glycals 21 producing [2+2]cycloadducts 23, [4+2]adducts 24 and the open-chain amide 25. The initial proportion of the adducts 23 and 24 changed slowly, resulting in the predominance of 24. In all cases, both bicyclic intermediates slowly rearranged to amide 25. 

A minor revision of the structure of the aglycone portion of bleomycin and phleomycin has been proposed, a )3-lactam ring being replaced by a corresponding open-chain amide unit. ... 

Cyclic lactams with ring sizes of seven or less behave [12, 154] like normal cis amides in dilute solutions [6,10,16], and absorb near 3420 cm". However, in the condensed phase the band near 3280 cm" is not shown, but is replaced by another at 3175 cm". In solution this band occurs at 3220 cm", and the frequency is independent of concentration [75], except of course at very high dilutions when the monomer is released. This suggests that only a dimeric species is present normally. These materials also show the 3080 cm" band, which is usually more intense than in open-chain amides. The differences between the NH frequencies of these two... 

Tertiary urethanes absorb close to 1685 cm in chloroform [159], rising to 1710 cm in carbon tetrachloride [148]. Urethane itself absorbs at 1618 cm , corresponding to the amide II absorption of an unsubstituted amide, whilst the iViV-di-substituted products show no band in this region. The simple A/ -mono-substituted urethanes [5] and carbamates show their NH stretching absorption for the solid products in the 3300—3250 cm region, which is normal for open-chain amides. 

The NH stretching absorptions are normal for open-chain amides and occur near 3270 cm (solid), but the identification of any... 

The main relationship in lactam polymerization is the equilibrium established between the monomer and the open-chain amide groups [2] ... 

Open-chain amides are nearly always trans and exhibit the 1550 cm band. 

While open-chain amides are predominantly tmns, small ring lactams exist as the cz s-form below about octanelactam at which point transoid forms start to enter [2], the former category containing all of the many aromatic amides whose tautomer ratios have been investigated [3-5]. Curiously, no attempt has been made to determine whether this difference in conformation has consequences for tautomer ratio. In fact, a quite simple argument can be applied. 

Figure 2.1a, sets out the four-way relationship between the trans-la and cis-Ib conformers of a simple open-chain amide and their corresponding iminols, 2a and 2b. By Hine s Principle of Least Motion [6], proton transfers take place much faster than those of the molecular skeleton, 2a and 2b are discrete species that may interconvert or otherwise react in subsequent steps but not till the first stage is complete. For Af-methylacetamide (1, = Me), quantitative data exist for... 

Evidence for and also against oxygen protonation in acid media is drawn from structure-basicity data. Huisgen and Brade (190) made a careful study of the basicities of open chain amides and lactams in acetic acid solution and found the latter to exhibit an entirely different relation between basicity and ring size than do the cyclic imines. Furthermore, the basicity constants for the 1,2-benzlactams do not correlate with their bromination rates as would be the case if protonation took place on nitrogen (191). 

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