California Sea Grant College Program

Part one of this Dissertation describes development of the o-nitrophenylselenium substituent for vinyl group protection and its application in the syntheses of tetrapyrrole derivatives. These derivatives, 5-meso-methylhemin chloride and 3,8-divinylchlorin-e6 trimethyl ester, should be useful in the investigation of heme catabolism and chlorophyll a biosynthetic mechanisms.

Chapter one introduces two biologically important tetrapyrroles, heme and chlorophyll a. The theories of heme breakdown and the multiple biosynthetic routes of chlorophyll a are presented.

Chapter 2 describes the development of the 2-o-nitrophenylseleoethyl vinyl protecting group and demonstrates its use in the Vilsmeier formylation reaction which has been shown to adversely affect unmodified vinyl groups in tetrapyrrole systems. The X­ ray crystal structure for 3-(o-nitrophenylselenoethyl)chlorin-e6 trimethyl ester is illustrated.

The application of the 2-o-nitrophenylselenoethyl vinyl protecting group in the syntheses of 5-meso-methylhemin chloride and 3,8-divinylchlorin-e6 trimethyl ester is discussed in Chapter three. Deprotection under non-basic conditions allows this organoselenium substituent to be a more successful protecting group than the 2-chloroethyl functionality in the synthesis of these base sensitive tetrapyrrole derivatives.

The second part of this Dissertation describes isolation and partial synthesis of secondary metabolites from the marine sponges, Xestospongia sp. and Dysidea herbacea. An introduction to marine natural products is discussed in Chapter four.

Chapter five describes the isolation of three new brominated fatty acids, (5E, 11E. 15E, 19E) 20-bromoeicosa-5,11,15,19-tetraene-9,17-diynoic acid, (5Z, 11E, 15e, 19E) 6,20-dibromoeicosa-5,11,15,19-tetraene-9,17-diynoic acid, and methyl (Z,E)-14,14- dibromo-4,6, 13-tetradecatrienoate, from Xestospongia sp. These novel acids contain unencountered carbon numbers; C20 and C14.

The partial synthesis of polychlorinated amino acid derivatives from the marine sponge Dysidea herbacea is examined in Chapter six. These unique polychlorinated metabolites are notable for their 5,5,5-trichloroleucine functionality. Four chlorinated amino nitrile diastereomers were synthesized from an asymmetric Strecker reaction and serve as key intermediates toward the synthesis of stereospecifically labeled leucine at carbon-S with deuterium atoms.