title: The synthesis and metal ion catalysed hydrolysis of methyl 4,5-diaminopentanoate

authors: Beresford, Geoffrey Derrick

abstract: The diamino acid ester, methyl 4, 5-diaminopentanoate has been prepared for the first time. The successful five step synthesis starting from 4-hydroxybutanoic acid lactone, and two other possible pathways via ethyl 3-formylpropanoate, are described. 
pKₐ values for 4,5-diaminopentanoic acid dihydrochloride and its a methyl ester dihydrochloride (determined by potentiometric titration at 25°C and I= 0.10molℓ⁻¹) are discussed in relation to those for other 1,2-diamines.
Stability constants of Cu(II) complexes of 4,5-diaminopentanoic acid and its methyl ester were evaluated from potentiometric titration data by the program SCOGS on a PDP 11/70 computer. Both compounds form high stability constant 1:1 and 1:2 complexes with Cu(II). (For 4,5-diaminopentanoic acid log K₁ = 10.94, log K₂ = 9.40 and for methyl 4,5-diaminopentanoate log K₁ = 9.84, log K₂ = 8.51, at 25°C and I= 0.10molℓ⁻¹). A variety of protonated complexes were also present at lower pH. 
pH-stat and spectrophotometric investigations showed that in the alkaline hydrolysis of methyl 4,5-diaminopentanoate, the simple Bᴀс2 reaction is slow and masked by a competing, extremely rapid, pair of intramolecular aminolysis (lactamisation) reactions. These involve competition between five and six membered lactam ring closure. Overall constants of the order 10³ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹ are observed.
The Cu(II) catalysed hydrolysis of methyl 4,5-diaminopentanoate was studied at constant pH using a pH-stat. The kinetics of hydrolysis of solutions containing a 1:2 mole ratio of Cu(II): ester are consistent with the two consecutive second order (pseudo-first-order at constant pH) reactions (1) and (2) (where E is the ester and A⁻ the anion, of 4 ,5-diaminopentanoic acid).
CuE₂²⁺ + OH⁻ → CuEA⁺ + CH₃OH 	1
CuEA⁺ + OH⁻ → CUA₂ + CH₃OH 		2
The relative values for the two rate constants obtained (k (CuE₂²⁺) = 2.41ℓmol⁻¹s⁻¹ and k (CuEA⁺) = 0.80ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹) can be explained by charge and statistical effects. The value of k(CuEA⁺) was confirmed independently from studies on solutions containing a 2.5:1:4 mole ratio of Cu(II): ester: acid. The value of k(CuEen²⁺) = 0.96ℓmol⁻¹s⁻¹ obtained from solutions containing Cu(II): ester: 1,2-diaminoethane = 2.5:1:4 is approximately k(CuE₂²⁺)/2 as expected statistically. 1:1 Solutions of Cu(II) and methyl 4,5-diaminopentanoate disproportionate, so no values for k(CuE²⁺) could be measured.
The absolute values for the Cu(II) catalysed rate constants are discussed in comparison with those for methyl 2,3-diaminopropanoate and other diamino acid esters. The results for methyl 4,5-diaminopentanoate can be explained by the attenuation of inductive and positive charge effects of the metal ion by the additional methylene groups of the methyl 4,5-diaminopentanoate alkyl chain. Direct methoxycarbonyl-metal ion interaction, presumably absent in methyl 4,5-diaminopentanoate must, therefore, be unimportant in the Cu(II) catalysed hydrolysis of methyl 2,3-diarninopropanoate.

text: The synthesis and metal ion catalysed hydrolysis of methyl 4,5-diaminopentanoate The diamino acid ester, methyl 4, 5-diaminopentanoate has been prepared for the first time. The successful five step synthesis starting from 4-hydroxybutanoic acid lactone, and two other possible pathways via ethyl 3-formylpropanoate, are described. 
pKₐ values for 4,5-diaminopentanoic acid dihydrochloride and its a methyl ester dihydrochloride (determined by potentiometric titration at 25°C and I= 0.10molℓ⁻¹) are discussed in relation to those for other 1,2-diamines.
Stability constants of Cu(II) complexes of 4,5-diaminopentanoic acid and its methyl ester were evaluated from potentiometric titration data by the program SCOGS on a PDP 11/70 computer. Both compounds form high stability constant 1:1 and 1:2 complexes with Cu(II). (For 4,5-diaminopentanoic acid log K₁ = 10.94, log K₂ = 9.40 and for methyl 4,5-diaminopentanoate log K₁ = 9.84, log K₂ = 8.51, at 25°C and I= 0.10molℓ⁻¹). A variety of protonated complexes were also present at lower pH. 
pH-stat and spectrophotometric investigations showed that in the alkaline hydrolysis of methyl 4,5-diaminopentanoate, the simple Bᴀс2 reaction is slow and masked by a competing, extremely rapid, pair of intramolecular aminolysis (lactamisation) reactions. These involve competition between five and six membered lactam ring closure. Overall constants of the order 10³ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹ are observed.
The Cu(II) catalysed hydrolysis of methyl 4,5-diaminopentanoate was studied at constant pH using a pH-stat. The kinetics of hydrolysis of solutions containing a 1:2 mole ratio of Cu(II): ester are consistent with the two consecutive second order (pseudo-first-order at constant pH) reactions (1) and (2) (where E is the ester and A⁻ the anion, of 4 ,5-diaminopentanoic acid).
CuE₂²⁺ + OH⁻ → CuEA⁺ + CH₃OH 	1
CuEA⁺ + OH⁻ → CUA₂ + CH₃OH 		2
The relative values for the two rate constants obtained (k (CuE₂²⁺) = 2.41ℓmol⁻¹s⁻¹ and k (CuEA⁺) = 0.80ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹) can be explained by charge and statistical effects. The value of k(CuEA⁺) was confirmed independently from studies on solutions containing a 2.5:1:4 mole ratio of Cu(II): ester: acid. The value of k(CuEen²⁺) = 0.96ℓmol⁻¹s⁻¹ obtained from solutions containing Cu(II): ester: 1,2-diaminoethane = 2.5:1:4 is approximately k(CuE₂²⁺)/2 as expected statistically. 1:1 Solutions of Cu(II) and methyl 4,5-diaminopentanoate disproportionate, so no values for k(CuE²⁺) could be measured.
The absolute values for the Cu(II) catalysed rate constants are discussed in comparison with those for methyl 2,3-diaminopropanoate and other diamino acid esters. The results for methyl 4,5-diaminopentanoate can be explained by the attenuation of inductive and positive charge effects of the metal ion by the additional methylene groups of the methyl 4,5-diaminopentanoate alkyl chain. Direct methoxycarbonyl-metal ion interaction, presumably absent in methyl 4,5-diaminopentanoate must, therefore, be unimportant in the Cu(II) catalysed hydrolysis of methyl 2,3-diarninopropanoate.

year: 1977

title: High precision traffic measurement by the WAND research group

authors: Cleary, John G.

subjects: computer science

abstract: Over recent years the size and capacity of the Internet has continued its exponential growth driven by new applications and improving network technology. These changes are particularly significant in the New Zealand context where the high costs of trans-Pacific traffic has mandated that traffic be charged for by volume. This has also lead to a significant focus within the New Zealand Internet community on issues of caching and of careful planning for capacity. 
Approximately three years ago the WAND research group began with a program to measure ATM traffic. We were sharply constrained by cost and decided to start by reprogramming some ATM NIC cards. This paper is largely based on our experience as we have broadened this work to include IP-based non-ATM networks and the construction of our own hardware. We have learned a number of lessons in this work, rediscovering along the way some of the hard discipline that all observation scientists must submit to.

text: High precision traffic measurement by the WAND research group Over recent years the size and capacity of the Internet has continued its exponential growth driven by new applications and improving network technology. These changes are particularly significant in the New Zealand context where the high costs of trans-Pacific traffic has mandated that traffic be charged for by volume. This has also lead to a significant focus within the New Zealand Internet community on issues of caching and of careful planning for capacity. 
Approximately three years ago the WAND research group began with a program to measure ATM traffic. We were sharply constrained by cost and decided to start by reprogramming some ATM NIC cards. This paper is largely based on our experience as we have broadened this work to include IP-based non-ATM networks and the construction of our own hardware. We have learned a number of lessons in this work, rediscovering along the way some of the hard discipline that all observation scientists must submit to.

year: 1999-12

title: Is there a lack of science resources and specialists for kaiako at Kura reo o Waikato?

authors: Hopkins, Aareka

subjects: Kura kaupapa

abstract: The New Zealand debates on culture and science education for Maaori are grounded in the concern for the under-achievement of tauira in science. In 1995, a lack of subject experts, specialists and resources to implement the Ministry of Education’s science curriculum was identified. I investigated the concept of a mobile science laboratory to provide subject experts, specialists and resources to Kura Reo o Tainui as a way of improving and enhancing tauira literacy and engagement in puutaiao. This study used a semi-structured survey to elicit the whakaaro and perceptions of kaiako puutaiao from four Wharekura, three Kura Kaupapa Maaori, and three Rumaki Total Immersion classes in Waikato-Tainui, using registered participants in the inaugural Kura Reo o Tainui Waananga in 2008 to select survey participants.

text: Is there a lack of science resources and specialists for kaiako at Kura reo o Waikato? The New Zealand debates on culture and science education for Maaori are grounded in the concern for the under-achievement of tauira in science. In 1995, a lack of subject experts, specialists and resources to implement the Ministry of Education’s science curriculum was identified. I investigated the concept of a mobile science laboratory to provide subject experts, specialists and resources to Kura Reo o Tainui as a way of improving and enhancing tauira literacy and engagement in puutaiao. This study used a semi-structured survey to elicit the whakaaro and perceptions of kaiako puutaiao from four Wharekura, three Kura Kaupapa Maaori, and three Rumaki Total Immersion classes in Waikato-Tainui, using registered participants in the inaugural Kura Reo o Tainui Waananga in 2008 to select survey participants.

year: 2010-08