The chemical ionization mass spectra of 21 of the 23 free "natural" amino acids have been measured. All give quasimolecular ions and simple fragmentation patterns which can be rationalized as arising from decomposition of the molecule protonated at several sites. We have recently reported3 the chemical ionization (Cl) mass spectra of a series of natural products, in particular alkaloids4 whose high proton affinity makes them especially susceptible to protonation by the strong acids CHS + and C2H5 + formed by electron bombbardment of methane at pressures of the order of 1 Torr.5This paper deals with the results obtained when this technique is applied to free amino acids. Earlier work in the area of electron impact (El) mass spectrometry of free amino acids,6-8 revealed that satisfactory spectra could be obtained with no contribution from diketopiperazines if either a direct insertion probe6,8 or a crucible ion source7 is used. In general however, the high ionizing energies led to mass spectra in which the molecular ion (M+) was often of very low abundance (< 1 % except for methionine, phenylalanine, and tryptophan) and in which many rearrangements and much homolysis were occurring. Even when recourse is made to ester derivatives,9-11 the molecular ion intensities are only 0.05-0.2% of the base peak except in the cases of methionine and the aromatic amino acids.As an adjunct to our work on the problem of peptide sequencing by Cl mass spectrometry12 we have studied the Cl mass spectra, with methane as the reactant gas, of all the common naturally occurring amino acids.These spectra have been measured on an MS-902 mass spectrometer equipped with the source described pre-viously8 91011using a direct insertion probe. Thus the high temperatures (~200-250°) required to vaporize the free amino acids have not been avoided but since ion formation is now carried out by protonation rather than the (1) Part III:

Fractions 12-21 (0.155 g) when worked up in the same manner yielded the analytical sample of Illb, mp 121-123°. The mass spectrum showed a molecular ion at mje 274; ir (KBr) 6.65,

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results shown were obtained. The number of patterns incorrectly classified is very small, but the number of patterns which were not classified because of their scalars falling in the dead zone was substantial.

The cyclodimerization of p-toluenesulfonamide and 3-chloro-2-(chloromethyl)-1-propene to prepare N,N'-bis(p-toluenesulfonyl)-3,7-bis(methylene)-1,5-diazacyclooctane (1a) and its ozonation to the corresponding 3,7-dione 2a are reported. Unusual transannular cyclizations initiated by lithium aluminum hydride treatment or bromination of 1a and oxidative coupling of the dioxime derived from 2a are described. These reactions lead, respectively, to the following derivatives of the little-studied 3,7-diazabicyclo[3.3.0]octane ring system: 1,5-dimethyl-3,7-diazabicyclo[3.3.0]octane (5), N,N'-bis(p-toluenesulfonyl)-1,5-bis(bromomethyl)-3,7-diazabicyclo[3.3.0]octane (8), and N,N'-bis(p-toluenesulfonyl)-1,5-dinitro-3,7-diazabicyclo[3.3.0]octane, (12). Acid-catalyzed hydration of 1a, in contrast, gives the expected 5-methyl-3,7-diazabicyclo[3.3.1]nonan-1-ol (10). Reaction of the dibromide 8 with the nucleophiles, sodium sulfide, sodium oxide, and sodium p-toluenesulfonamide conveniently delivers the corresponding novel 3,7,10-triheterocyclic [3.3.3]propellanes.