stereochemistry of gamma-amino-beta-hydroxy acids of natural and synthetic origin a dissertation ...

228 Pages·2012·5.65 MB·English

by  Alejandro Preciado

STEREOCHEMISTRY OF GAMMA-AMINO-BETA-HYDROXY ACIDS OF
NATURAL AND SYNTHETIC ORIGIN

A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE
UNIVERSITY OF HAWAI‘I IN PARTIAL FULFILMENT OF THE
REQUIREMENTS FOR THE DEGREE
DOCTOR OF PHILOSOPHY

IN

CHEMISTRY

May 2012

By
Alejandro B. Preciado

Dissertation Committee Members:
Philip G. Williams, Chairperson
Thomas K. Hemscheidt
Marcus A. Tius
Oscar Navarro
Joe Ramos
ii
ACKNOWLEDGMENTS

I would like to thank many people that have provided me support throughout my
academic development. First, to my friends and colleagues at the University of Hawaii-
Manoa whom have been a pleasure to work with. Especially Dr. Jingqui Dai and Wesley
Yoshida for many helpful discussions and encouragement. I would like to thank
Professors Dan Little (UCSB) and Marcus Tius (UH) for sharing their passion and
enthusiasm for chemistry. I would like to extend my appreciation to Professor Thomas
Hemscheidt for his assistance beyond the call of refereeing my dissertation. I would like
to thank my research mentor, Professor Philip Williams, for his helpful insights and
continual encouragement. I would like to thank Professor Joe Ramos and Florian
Sulzmaier, our collaborators at the Hawaii Cancer Center, for bioactivity screening of
compounds. Finally, I would like to extend sincere gratitude to my wife Terra, to mother
Mary and to grandmother Emma for their valuable support.
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ABSTRACT
STEREOCHEMISTRY OF GAMMA-AMINO-BETA-HYDROXY ACIDS OF
NATURAL AND SYNTHETIC ORIGIN

By
Alejandro B. Preciado

The following dissertation will discuss my contribution to research in the area of
structure elucidation, specifically dealing with the configurational assignment of γ-
amino-β-hydroxy acid derivatives. Our investigations have unveiled a simple 1H NMR
methodology useful for assigning the relative configuration of the intact moiety. In an
effort to validate a general method for the complete configurational assignment of statine
derivatives, we have performed an extensive time course study on the hydrolysis rates of
the statine derivatives. These investigations have led us to propose a reliable, general and
optimal approach for complete configurational assignment of the most common naturally
occurring statine derivatives. Finally, a total synthesis of the stictamide A and B and
evaluation of biological activities are presented. The synthesis of these natural products
provides evidence to support of the originally proposed structures and expands the scope
of the 1H NMR methodology useful for assigning the configuration of statine derivatives.
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Table of Contents
Acknowledgments..............................................................................................................ii
Abstract..............................................................................................................................iii
List of Appendices............................................................................................................vii
List of Figures/Illustrations..............................................................................................viii
List of Abbreviations..........................................................................................................x
Chapter 1: Introduction.......................................................................................................1
Background.....................................................................................................................1
Methods for structure assignment of statine derivatives................................................6
Chapter 2: 1H NMR method for determining the relative stereochemistry of statine
derivatives.........................................................................................................................12
Background...................................................................................................................12
Synthesis of statine derivatives.....................................................................................13
Results...........................................................................................................................20
Discussion.....................................................................................................................26
Chapter 3: Quantification of C-3 epimerization under acid hydrolysis conditions..........35
Background...................................................................................................................35
Results...........................................................................................................................38
Discussion.....................................................................................................................52
Chapter 4 - Solid phase synthesis of stictamides and derivatives.....................................61
Background...................................................................................................................61
Materials.......................................................................................................................64
Synthesis of stictamide B..............................................................................................68
Synthesis of stictamide A and epimers.........................................................................71
Stictamide A structural modifications..........................................................................77
Biological evaluation....................................................................................................86
v
Conclusion........................................................................................................................91
Experimental section.........................................................................................................92
General experimental procedures.................................................................................92
General chemical procedures........................................................................................93
Physical data...............................................................................................................102
References.......................................................................................................................205
vi

List of Tables
Table Page
Table 1.1. Natural products containing γ-amino-β-hydroxy acids.....................................5
Table 2.1. 1H NMR data for H -2 ABX system of statine derivatives.............................24
2
Table 2.2. Relevant literature examples of 1H NMR for H -2 ABX system of synthetic
2
statine derivatives.............................................................................................................29
Table 2.3. Solvent effects on H -2 ABX system..............................................................30
2
Table 3.1. Averaged hydrolysate composition of selected statine derivatives examined at
the 24 hour time interval...................................................................................................50
Table 3.2. Relative abundance of selected α,β-unsaturated derivatives after 18 hours
hydration...........................................................................................................................52
Table 3.3. Averaged hydrolysate composition of statine tripeptides 3.23a and 3.24a
examined at 18 and 24 hour time intervals.......................................................................56
Table A. Analytical HPLC separation conditions for statine Sanger’s derivatives........189
Table B. Analytical separation conditions for α,β-dehydro statine Marfey’s derivatives.
........................................................................................................................................190
vii
List of Appendices
Appendix Page
Appendix A: HPLC separation conditions for selected statine Sanger’s derivatives.....189
Appendix B: HPLC separation conditions for selected statine Marfey’s derivatives....190
Appendix C: acid hydrolysate composition for alanine statine Sanger’s derivative......191
Appendix D: acid hydrolysate composition for arginine statine Sanger’s derivative...192
Appendix E: acid hydrolysate Sanger’s for isoleucine statine Sanger’s derivative
(evaporative light scattering detection)...........................................................................193
Appendix F: acid hydrolysate composition for L-allo-isoleucine statine Sanger’s
derivative........................................................................................................................194
Appendix G: acid hydrolysate composition for leucine statine Sanger’s derivative......195
Appendix H: acid hydrolysate composition for lysine statine Sanger’s derivative.......196
Appendix I: acid hydrolysate composition for phenylalanine statine Sanger’s derivative
........................................................................................................................................197
Appendix J: acid hydrolysate composition for valine statine Sanger’s derivative.........198
Appendix K: acid hydrolysate composition for serine statine Sanger’s derivative........199
Appendix L: acid hydrolysate composition for threonine statine Sanger’s derivative...200
Appendix M: acid hydrolysate composition for valine statine Sanger’s derivative.......201
Appendix N: Mass spectrum response curve for isostatine............................................202
Appendix O: Mass spectrum response curve for AHPPA..............................................203
Appendix P: IC curve and progress curves for inhibition of MMP-12 (initial screening
50
result)..............................................................................................................................204
viii
List of Figures/Illustrations
Figure

 Page
Scheme 1.1 Biosynthesis of statine (R= sec-Bu)................................................................3
Scheme 1.3 Classical hydrolysis for the isolation and relative stereochemical analysis of
the statine moiety................................................................................................................8
Scheme 2.1 General procedure used to derive synthetic statine analogs..........................15
Figure 2.1 Chelation-controlled reduction of β-keto esters favoring the syn 2.5b statine
derivative..........................................................................................................................18
Scheme 2.2 Conversion to the oxazolidine or oxazolidinone for 3J analysis............19
H4,H3
Figure 2.4 Expansion of 1H NMR ABX pattern of alanine and lysine statine derivatives at
300 and 800 MHz.............................................................................................................25
Figure 2.5 Authentic and simulated spectra for the lysine statine derivative at 300 MHz.
..........................................................................................................................................26
Figure 2.6 Proposed conformational models for statine derivatives in CDCl .................33
3
Scheme 3.1 Analysis of isostatine hydrolysate mixtures as Sanger’s derivatives............40
Scheme 3.3 Chemical dehydration of selected statine derivatives...................................48
Scheme 3.6 Marfey’s analysis of selected α,β-unsaturated derivatives...........................57
Figure 3.4 Proposed conformations of the L- and D- dehydro statine derivatives during
separation by Marfey’s method........................................................................................58
Figure 4.1 Retrosynthetic analysis for the synthesis of stictamide B...............................63
Scheme 4.1 Synthesis of α-Fmoc-N,N’-bis-Boc protected D-arginine compound 4.8.....64
Scheme 4.2 Synthesis of phenyl butanoic acid and derivatives.......................................65
Scheme 4.3 Synthesis of prenylated S-methylisothiourea 4.17.7.....................................66
ix
Figure 4.2 Model accounting for steroselective reduction of N-substituted tetramic acids.
..........................................................................................................................................67
Scheme 4.4 Synthesis of (3S,4S) phenylalanine derivative (Ahppa)................................68
Scheme 4.5 First generation Fmoc solid-phase synthesis of stictamide B 4.2 and methyl
derivative 4.2.1.................................................................................................................69
Figure 4.3 13C difference plot (Δδ in ppm) of stictamide B natural product vs. synthetic.
..........................................................................................................................................69
Scheme 4.6 Failed attempts to prepare the γ-N-substituted dimethyl allyl arginine.........72
Scheme 4.7 Fmoc solid-phase synthesis of stictamide A 4.1, epi-C-12-stictamide A 4.1.1
and epi-C-22-stictamide A 4.1.2.......................................................................................74
Figure 4.4 13C difference plot of stictamide A natural product vs. synthetic stictamides.77
Scheme 4.8 Fmoc solid-phase synthesis of N-terminus stictamide A derivatives...........79
Figure 4.5 Synthetic stictamide derivatives including carbon-numbering designations..80
Figure 4.7 Possible isomeric structure for the dimethyl allyl guanidine functionality of
stictamide A......................................................................................................................84
Figure 4.8 Activity of synthetic stictamides in glioma invasion and cell viability..........89
x

List of Abbreviations
Å ångström
[α]T specific optical rotation at 589 nm and temperature T in °C
D
Ac acetyl
€
Ahppa 4-amino-3-hydroxy-5-phenylpentanoic acid
Amu atomic mass units
Boc tert-butyloxycarbonyl
Bn benzyl
br broad
c concentration in g/100 mL
°C degrees Celsius
C octyl
8
C octadecyl
18
calcein-AM acetomethoxy derivate of calcein
Cbz Carbobenzyloxyl
COSY correlation spectroscopy
C-terminus carboxyl terminus
d doublet
D configurational descriptor (Fisher system)
L configurational descriptor (Fisher system)
δ chemical shift (in ppm)
DIC N,N-diisopropylcarbodiimide