Synthesis and Preliminary Pharmacological Evaluation of New 6-cyano-2,3-dihydro-5<I>H</I>-oxazolo[3,2-<I>a</I>]pyrimidin-5-ones and 2-ethyl(methylenecyanoacetate)-2-iminooxazolidines

Abstract

One‐step ring‐annulation of 5‐substituted 2‐amino‐2‐oxazolines with diethyl ethoxymethy‐lenemalonate yielded 2‐substituted 6‐carboethoxy‐2,3‐dihydro‐5H‐oxazolo[3,2‐a]pyrimidin‐5‐ones. Under the same conditions 2‐substituted 6‐cyano‐2,3‐dihydro‐5H‐oxazolo[3,2‐a]‐pyrimidin‐5‐ones and the corresponding 2‐ethyl(methylenecyanoacetate)‐2‐iminooxazo‐lidines were obtained from ethyl ethoxymethylenecyanoacetate. Some of these compounds were evaluated in mice for antiparasitic activity.

Synthesis and in vitro cytostatic activity of new β - d -arabino furan[1′,2′:4,5]oxazolo- and arabino-pyrimidinone derivatives

“…Moreover, the 13 C NMR spectrum of 5 showed one signal around 98.4 ppm specific for the enamine alkene bond (]C(Me)NH 2 ). In the structure of 5, the pucker is C(14) endo differing from that observed in previously described uracil-b-D-arabinofuranoside [16] where the pucker is C(14) endo making impossible an intramolecular hydrogen bond between O (20) and O (17). There is an intramolecular hydrogen bond between N(9)-H(9A) and O (7) where the N(9)-O(7) distance is 2.673(2) &angst.…”

“…2). Moreover, N(9) is hydrogen bonded to O (11) of the molecule at (x À 1,Ày À 1, þz) with N(9)-H(9B)-O(11) ¼ 2.814(3) Å; other hydrogen bond are found between O (18) and N(5) of the molecule (x, y, z À 1) where the distance is 2.823(2) Å, and O (20) and O (17) of the molecule (xÀ1, y þ 1, z) with O (20).O(17) ¼ 2.813(2) &angst. Moreover, the 13 C NMR spectrum of 5 showed one signal around 98.4 ppm specific for the enamine alkene bond (]C(Me)NH 2 ).…”

“…Diethyl ethoxymethylene malonate (DEEM) is a well-known bis-electrophile reagent used for heterocyclic ring annelation [9,17]. Diethyl ethoxymethylene malonate (DEEM) is a well-known bis-electrophile reagent used for heterocyclic ring annelation [9,17].…”

An easy route to 2‐substituted‐2,3‐dihydro‐5(7)H‐oxazolo[3,2‐a]pyrimidin‐5‐ones and 7‐ones starting from the corresponding 2‐amino‐2‐oxazolines

“…This conformation could explain the relative stability of 5a-b,6a towards an ulterior intramolecular cyclization involving the second nucleophilic nitrogen atom [14]. A comparable behavior of related amidines towards other biselectrophiles was previously described [15][16][17].…”

“…Both structures were determined by direct methods using MULTAN 80 [18]. The Jul-Aug 2001 825 (14) 1093 (2) 1561 (1) 10380 (2) 41(1) N (15) 1383 (1) -848 (1) 11284 (2) 40(1) C (16) 1336 (1) -901 (1) 13121 (2) 40 (1) C(17) 1222 (2) -157 (1) 14154 (2) 45(1) C (18) 1131 (2) 752 (1) 13413 (2) 43(1) C (19) 1432 (2) -1853 (2) 13885 (3) 60 (1) O(20) 1014 (2) 1481 (1) 14186 (2) 66(1) Table 3 Bond lengths (Å) and Angles (°) for Compound 3a (13) scattering factors were taken from [19]. C, N and O Atoms were refined anisotropically.…”