List of Abbreviations ........................................... 4
1 Stereoselective Synthesis of Cholesterol Derivatives ......... 7
1.1 Introduction ............................................ 7
1.2 Caenorhabditis elegans: a brief introduction ............ 9
1.3 Cholesterol (1) in C. elegans .......................... 10
1.4 Motivation ............................................. 11
1.5 Objective .............................................. 12
2 Synthesis of 4α-Bromocholestan-3β-ol ........................ 13
2.1 Introduction ........................................... 13
2.2 Attempts towards the Synthesis of
4α-Bromocholestanols ................................... 14
2.3 Hormonal Activities of 4α-Bromo-5α-cholestan-3β-ol
(10) ................................................... 17
2.4 Summary and Outlook .................................... 17
3 Synthesis of Dafachronic Acids .............................. 18
3.1 Dafachronic Acid v/s Gamravali ......................... 18
3.2 Objective .............................................. 19
3.3 Existing synthetic approaches for DAs in the
literature ............................................. 20
3.3.1 COREY'S approach ................................ 21
3.3.2 KNÖLKER's approach .............................. 22
3.3.3 PELLICIARI's approach ........................... 24
3.4 Attempts towards Synthesis of (255)-Dafachronic Acids .. 25
3.4.1 Synthesis of Precursor 41 ....................... 25
3.4.2 Synthesis of (25S)-Δ1,7-Dafachronic Acid (22) ... 28
3.4.3 Synthesis of (25S)-Δ8(14)-Dafachronic Acid
(23) ............................................ 32
3.4.4 Synthesis of (25S)-Δ1,4-Dafachronic Acid (24) ... 36
3.4.5 Synthesis of (25S)-Δ1-Dafachronic Acid (26) ..... 42
3.4.6 Synthesis of (25S)-Δ5,7-Dafachronie Acid (27) ... 44
3.4.7 Synthesis of Hydroxy Acid Derivatives of
Steroids ........................................ 65
3.4.8 Summary and Outlook ............................. 68
3.4.9 Hormonal Activities of Dafachronic Acids ........ 69
4 Synthesis of Desmosterol Derivatives ........................ 72
4.1 Introduction ........................................... 72
4.2 Objective .............................................. 72
4.3 Synthesis of the 24E (95a), 24Z-26-hydroxydesmosterol
(95b) .................................................. 73
4.4 Summary and Outlook .................................... 80
5 Synthesis of Natural Products from Corals ................... 81
5.1 Introduction ........................................... 81
5.2 Objective .............................................. 82
5.3 First Total Synthesis of the Griffmisterone E (103) .... 82
5.4 Total Synthesis of Griffinisterone I (104) ............. 95
5.4.1 Synthesis plan A ................................ 97
5.4.2 Synthesis plan B ................................ 98
5.5 Summary and outlook .................................... 99
6 Experimental section ....................................... 101
6.1 General ............................................... 101
6.2 Synthesis of Synthesis of 4α-Bromo-cholestan-3β-ol .... 103
6.3 Synthesis of Dafachronic Acids ........................ 106
6.2.1 Synthesis of (25S)-Δ1,7-Dafachronic Acid ....... 106
6.2.2 Synthesis of (25S)-Δ8(14)-Dafachronic Acid ..... 118
6.2.3 Synthesis of (25S)-Δ1,4-Dafachronic Acid ....... 121
6.2.4 Synthesis of (25S)-Δ1-Dafachronic Acid ......... 128
6.2.5 Synthesis of (25S)-Δ5,7-Dafachronic Acid ....... 132
6.2.6 Synthesis of Hydroxyacids ...................... 147
6.2.1 Abbreviations
6.4 Synthesis of Desmosterol Drivatives ................... 150
6.5 Synthesis of Griffinisterone Derivatives .............. 156
6.6 Crystallographic data ................................. 177
7 Literature ................................................. 185
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