Study of a diastereoisomeric dihydrothiophene derivative at 150 K

The crystal and molecular structure of (4R,5R)-4-(1',2',3',4',5'-penta-O-ac etyl-D-manno-pentitol-1-yl)-5-[N-(4-methoxyphenyl)carbamoyl]-2-(N-methylben zylamino)-3-nitro-5-phenyl-4, 5-dihydrothiophene {IUPAC name: 1-(2R,3R)-5-( N-benzyl-N-methylamino)-2-[N-(4-methoxyphenyl)carbamoyl]-4-nitro-2-phenyl-2 ,3-dihydro-3-thienyl]-1,2,3,4, 5-penta-O-acetyl-D-manno-pentitol}, C41H45N3 O14S, has been investigated at 150 K, The analysis of the crystal structure allows the definition of the absolute configuration of the products of the cycloaddition reaction between 3,5-di-phenyl-2-(N-methylbenzylamine)-1,3-t hiazolium-7-olate and (E)-3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-C-nitro-D- manno-hept-1-enitol, where only one of the two diastereoisomeric dihydrothi ophenes could be isolated. The configurations at the new C4 and C5 stereoce ntres, with respect to that known at C6, are R,R. Except for a slight overa ll contraction and a slightly altered geometry of the terminal acetyl group , the structure is virtually the same as at room temperature.