Provided is a head-up display apparatus that is excellent in viewability when a display screen is viewed through a pair of polarized sunglasses, and is excellent in heat resistance. The head-up display apparatus includes: a display unit configured to output projection light; at least one reflector configured to reflect the projection light; a housing, which has an opening portion, and is configured to store the display unit and the reflector therein; a cover member configured to cover the opening portion; and a polarizing plate arranged on a housing inner side of the cover member. The cover member has an in-plane retardation Re(550) of 3,000 nm or more. The head-up display apparatus is configured so that an angle of reflection of the projection light output from the housing through the opening portion with respect to a windshield is 30 or less, or is 40 or more.

A method for esterification of one or more carboxylic acid groups in a compound containing one or more carboxylic acid groups wherein the esterification reagent is a diazo-compound of formula:

##STR00001##

wherein the R.sub.1 and R.sub.2 groups of the diazo compound are selected such that the corresponding organic compound of formula:

##STR00002##

exhibits a CH pKa value between 18 and 29 as measured in DMSO. Specific reagents and methods for esterification are provided. The esterification reagents provided exhibit high selectivity for esterification of carboxylic acid groups over reaction with amine, alcohol or thiol groups in the compound containing one or more carboxylic acid groups. The method can be used to selectively esterify carboxylic acid groups in peptides or proteins.

A method for esterification of one or more carboxylic acid groups in a compound containing one or more carboxylic acid groups wherein the esterification reagent is a diazo-compound of formula:

##STR00001##

wherein the R.sub.1 and R.sub.2 groups of the diazo compound are selected such that the corresponding organic compound of formula:

##STR00002##

exhibits a CH pKa value between 18 and 29 as measured in DMSO. Specific reagents and methods for esterification are provided. The esterification reagents provided exhibit high selectivity for esterification of carboxylic acid groups over reaction with amine, alcohol or thiol groups in the compound containing one or more carboxylic acid groups. The method can be used to selectively esterify carboxylic acid groups in peptides or proteins.

A method for esterification of one or more carboxylic acid groups in a compound containing one or more carboxylic acid groups wherein the esterification reagent is a diazo-compound of formula: ##STR00001##
wherein the R.sub.1 and R.sub.2 groups of the diazo compound are selected such that the corresponding organic compound of formula: ##STR00002##
exhibits a CH pKa value between 18 and 29 as measured in DMSO. Specific reagents and methods for esterification are provided. The esterification reagents provided exhibit high selectivity for esterification of carboxylic acid groups over reaction with amine, alcohol or thiol groups in the compound containing one or more carboxylic acid groups. The method can be used to selectively esterify carboxylic acid groups in peptides or proteins.

A method for esterification of one or more carboxylic acid groups in a compound containing one or more carboxylic acid groups wherein the esterification reagent is a diazo-compound of formula: ##STR00001##
wherein the R.sub.1 and R.sub.2 groups of the diazo compound are selected such that the corresponding organic compound of formula: ##STR00002##
exhibits a CH pKa value between 18 and 29 as measured in DMSO. Specific reagents and methods for esterification are provided. The esterification reagents provided exhibit high selectivity for esterification of carboxylic acid groups over reaction with amine, alcohol or thiol groups in the compound containing one or more carboxylic acid groups. The method can be used to selectively esterify carboxylic acid groups in peptides or proteins.

A method for esterification of one or more carboxylic acid groups in a compound containing one or more carboxylic acid groups wherein the esterification reagent is a diazo-compound of formula: ##STR00001##
wherein the R.sub.1 and R.sub.2 groups of the diazo compound are selected such that the corresponding organic compound of formula: ##STR00002##
exhibits a CH pKa value between 18 and 29 as measured in DMSO. Specific reagents and methods for esterification are provided. The esterification reagents provided exhibit high selectivity for esterification of carboxylic acid groups over reaction with amine, alcohol or thiol groups in the compound containing one or more carboxylic acid groups. The method can be used to selectively esterify carboxylic acid groups in peptides or proteins.

A method for esterification of one or more carboxylic acid groups in a compound containing one or more carboxylic acid groups wherein the esterification reagent is a diazo-compound of formula: ##STR00001##
wherein the R.sub.1 and R.sub.2 groups of the diazo compound are selected such that the corresponding organic compound of formula: ##STR00002##
exhibits a CH pKa value between 18 and 29 as measured in DMSO. Specific reagents and methods for esterification are provided. The esterification reagents provided exhibit high selectivity for esterification of carboxylic acid groups over reaction with amine, alcohol or thiol groups in the compound containing one or more carboxylic acid groups. The method can be used to selectively esterify carboxylic acid groups in peptides or proteins.

A new synthetic route to a 2,2-dimethyl-4,4-diiodoazobenzene compound using homo-oxidative cross-coupling of an aryl diazonium salt using a Cu-catalyzed Sandmeyer-style reaction.

A new synthetic route to a 2,2-dimethyl-4,4-diiodoazobenzene compound using homo-oxidative cross-coupling of an aryl diazonium salt using a Cu-catalyzed Sandmeyer-style reaction.

A reversible photo-switchable isomerization of novel sterically hindered 2,2,6,6-tetraisopropyl-4,4-diethynylazobenzene and its synthesis.