The reduction of y-nitro-carbonyl compounds to give A'-pyrroline l-oxides is described and the reactions of several such N-oxides are reported. THE corrin nucleus, parent of the macrocyclic component of the vitamin B,, molecule, is at an oxidation level between that of the pyrroles and the Al-pyrrolines and, in our synthetical studies in this field, it became apparent that the Af-pyrroline l-oxides might offer a flexibility in synthesis somewhat greater than the parent Schiff bases.The A1-pyrroline l-oxides (I) are cyclic nitrones derivable by oxidation of hydroxylamines (11) or by cyclisation of a y-hydroxyamino-carbonyl compound (111). As R4 R4 R4 R4 . ; I J -J R S = ;:rJ +/ RS -;rio.R5 -.;I!O.R

Structures for vitamin B,, (I) and its hexacarboxylic acid degradation product (11) containing six rather than five conjugated double bonds are adopted and reactions bearing on this point are considered. With mild alkali in the presence of oxygen the acetamide side-chain of ring B of the vitamin undergoes cyclisation, to give dehydrovitamin BIB, a 7-lactam, whereas with an equivalent of a halogenating agent the same side-chain is converted into a y-lactone ; mechanisms for these cyclisations are considered. The reaction of vitamin B,, with more than one equivalent of halogenating agent has a marked effect on the chromophore ; under analogous conditions, dehydrovitamin B,, gives a crystalline monohalogeno-derivative.

Acid Hydrolysis of 2' : 3'-isoPropyZidene Oa : 5'-cycloCytidine Toluene-p-sulphonate.-2' : 3'-bso-Propylidene 0 2 : 6'-cydocytidine toluene-p-sulphonate (24.6 mg.) was dissolved in water (1 c.c.) and sulphuric acid added (1 C.C. ; N.). The clear solution was heated on the steam-bath for 2 hours and ethanol (10 c.c.) added. The solution was evaporated to a small bulk (1 c.c.), and acetone (5 c.c.) added. When the mixture was kept at 0" overnight, colourless needle-like prisms separated (10.3 mg.). These were collected and washed with acetone: they had m. p. 218-219" (Kofler block), undepressed on admixture with an authentic specimen of cytidine sulphate.Paper chromatography (Whatman No. 1) of the hydrolysis product with tevL-butanoI-ammoniawater (80 : 4 : 18) confirmed its homogeneity and established the presence of sulphate ion and cytidine (RF = 0.25 ; reference cytidine spot, RF = 0.25).

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2087 422. Experiments towards the Synthesis of Corrins. Part I. The A Novel Proline Preparation and Reactions of Some A1-Pyrrolines. Synthesis.

Koordinationspolyedern. Diese Forderung erfullen z. B. Elemente der B-Gruppen des Peroidensystems. Nach Orgel [81]

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(13)C n.m.r. spectra have been obtained for aqueous solutions of histones F2a(1) and F2a(2), for the group F2a, for the appropriate amino acid mixturesand for the corresponding hydrolysates. These, when compared with computer simulated spectra give good agreement for secondary structure with that calculated from the known primary structure of the proteins. Evidence based on the spectra obtained at various salt concentrations leads to the conclusion that F2a is not a simple mixture but an interacting heterologous group of histones F2a(1) and F2a(2).