While using the "HTTP Basic Authentication Connector" there is a special syntax that needs to be followed when chaining with other Connectors.
    

All Supported Platforms

 1. In the Endpont's Call Transformations page, in "Processing Adapter" field, enter the following:   
com.mashery.proxy.customer.generic.http-basic-auth
Note: Even though only this single connector name is used, the adapter is “smart” enough to allow the chaining of other Connectors

 2. Enable the Perform Pre-Processing field

 3. Add the "HTTP Basic Authentication Connector" mandatory property in the pre-processing section and in the subsequent lines, put the names of the connector with the configuration field followed by the configuration data for the the additional connectors that will form the chain.
   
   processors:PROCESSOR1,PROCESSOR22.
   PROCCESSOR1.parameter:value
   PROCCESSOR2.parameter:value

   For example, if you wanted to chain the HTTP Basic Authentication Connector with the HTTP Header Injection of Static Values you would use the following in the “Data to make available for pre-processing” field:
 

processors:com.mashery.proxy.core.add-headers-processor
Keep_Mashery_Default_Response_Code:true    
com.mashery.proxy.core.add-headers-processor.x-api-platform:mashery
com.mashery.proxy.core.add-headers-processor.testKey:testValue

This article provides inputs on how to use "HTTP Basic Authentication Connector" in order to be chained with other Connectors in APIM & APIM-LE